Temperature Requirements of Pistachio (Pistacia vera L. cv. Kerman) and Identification of Suitable Cultivation Areas in Semi-Arid Central-Western Argentina

Temperature Requirements of Pistachio (Pistacia vera L. cv. Kerman) and Identification of Suitable Cultivation Areas in Semi-Arid Central-Western Argentina | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Temperature Requirements of Pistachio (Pistacia vera L. cv. Kerman) and Identification of Suitable Cultivation Areas in Semi-Arid Central-Western Argentina Franco E Calvo, Paolo Sartor, Gonzalo Sánchez Cañete, Javier Chaar, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7857977/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract In recent years, interest in pistachio production has increased significantly in Argentina, although cultivation remains largely confined to specific regions. The objectives of this study were: i) to determine the specific thermal requirements of cv. Kerman for optimal flowering and fruit development under semi-arid conditions, and ii) to use GIS-based modelling to identify suitable land for its expansion. To this end, phenological observations were collected from a commercial orchard in San Juan Province between 2013 and 2022. Thermal requirements for flowering and fruit ripening were calculated using hourly temperature data through the Dynamic Model (chill portions, CP) and Growing Degree Hours (GDH) and Days (GDD). Partial Least Squares (PLS) regression was applied to identify chilling and forcing periods. These parameters were then extrapolated to 72 weather stations across Argentina to evaluate regional suitability. Results indicated that a minimum of 47 CP, 4,150 GDH, and 2,200 GDD are required for optimal flowering and fruit maturation. GIS-based modelling classified land as suitable, marginally suitable, or unsuitable based on these thermal thresholds. Highly suitable areas were identified in the central-western regions. Additional factors, such as late spring frosts and rainfall during flowering and ripening, were integrated to refine the suitability map. The resulting global suitability map identified approximately 64,411 km² as optimal for pistachio cultivation, coinciding with regions of low frost and rainfall risk. This study highlights the potential for expanding pistachio production in Argentina’s semi-arid zones, with considerations for climate trends, frost exposure, and water availability. dormancy chilling forcing phenology climate change Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction The consumption of pistachios, whether as snacks or as ingredients in food products, has steadily increased worldwide over the past two decades (Amico Roxas et al., 2020 ; Ripari Garrido et al., 2024 ). This growth is primarily driven by increased consumer awareness of their nutritional properties and recognition as a healthy food. Recent studies have confirmed the nutritional value of pistachios, highlighting their protein, unsaturated fatty acid, fiber, and antioxidant content (Rabadán et al., 2017 ). Native to arid and semi-arid regions, the pistachio tree exhibits remarkable tolerance to water scarcity and saline soils, allowing its cultivation in areas unsuitable for other crops (García-Tejero et al., 2017 ). Achieving high yields depends on growing the crop under specific environmental conditions, particularly regarding winter chilling accumulation and thermal requirements for flowering and fruit ripening. These constraints currently limit pistachio cultivation to a few regions worldwide. Similar to other deciduous fruit trees, the pistachio tree enters a period of endodormancy after leaf fall in autumn. During this phase, buds remain dormant even under favorable thermal conditions (Lang et al., 1987 ). Overcoming endodormancy requires exposure to sufficient winter chilling. Subsequently, the tree enters ecodormancy, a phase in which buds gradually acquire the ability to resume growth in response to heat accumulation. Previous studies on pistachio in Tunisia (Elloumi et al., 2013 ; Benmoussa et al., 2017 ) and the USA (Pope et al., 2015) have shown that high temperatures during endodormancy can delay or inhibit flowering. In addition, insufficient chilling during endodormancy is associated with increased bud drop, asynchrony between male and female flowering, and irregular flowering, which can result in reduced or null yields. After fruit set, pistachio trees require warm summers to produce nuts of high commercial quality. Warm temperatures promote cell elongation and metabolic activity, determining the rate of fruit and kernel development (Olsen, 2010), and favor the natural splitting of the endocarp (Nuñez et al., 2024), a valuable commercial trait. The kernel filling period depends on adequate thermal accumulation during embryo growth to reach optimal nut size (Aydin et al., 2019). Conversely, cool summers increase the proportion of empty and closed shells (Rahemi and Pakkish, 2009 ). Endocarp lignification, which protects the seed, requires temperatures above 25°C. Poorly lignified endocarps increase the risk of aflatoxin contamination due to mechanical damage during harvest (Mahoney and Molyneux, 1998 ). Other environmental factors also influence the suitability of land for pistachio cultivation. Rainfall during pollination or prior to harvest can negatively affect productivity and seed health (Yarahmadi and Amini, 2021 ). Although pistachio trees are resistant to low mid-winter temperatures (surviving below − 20°C; Marino and Marra, 2019 ), their sensitivity to frost increases during flowering and fruit set. Temperatures between − 2 and − 4°C during these stages can significantly reduce yields (Pakkish et al., 2011 ; Hokmabadi, 2010 ; Sáez-Sánchez, 2017 ). While various strategies exist to mitigate frost damage, the safest and most sustainable approach is to cultivate the crop in areas with a low probability of late frosts. Pistachio cultivation in Argentina has expanded remarkably over the past decade, particularly in the arid and semi-arid central-western regions. The total area currently under cultivation exceeds 8,600 hectares, 96% of which is concentrated in southern San Juan Province and northern Mendoza Province. In recent years, strong interest has emerged in expanding cultivation beyond these traditional areas, raising questions about the agronomic and economic viability of the crop in new locations. Previous studies in the USA (Zhang et al., 2021 ), Tunisia (Benmoussa et al., 2017 ), Australia (Zhang and Taylor, 2011 ), Azerbaijan (Yarahmadi and Amini, 2021 ), and Iran (Ahmadi et al., 2021 ) have determined the agroclimatic requirements of pistachio, providing a basis for identifying suitable land. However, these findings are not always directly applicable due to the specific thermal characteristics of continental climates in western Argentina. Factors such as spatial and temporal variability in chilling accumulation, the frequency of late frosts, thermal conditions during flowering and ripening, and rainfall during harvest can strongly limit the productive potential of new plantations. Classical chilling accumulation models (e.g., Chill Hours or Chill Units) often over- or underestimate requirements in climates with irregular or warm winters (Fernandez et al., 2020 ). Therefore, dynamic models—such as the Dynamic Model, which estimates chill portions (CP)—are recommended, as they are more reliable under these conditions (Erez et al., 1989 ). Ignoring local adaptation may result in the selection of areas that, although superficially appearing suitable based on general literature, ultimately fail to meet critical requirements in practice. Previous studies have employed agroclimatic models and geographic information systems (GIS) to assess land suitability for pistachio cultivation by integrating phenological, meteorological, and topographic data (e.g., Yarahmadi and Amini, 2021 ). These approaches have enabled the development of suitability maps that classify territories according to their potential for cultivation, supporting decision-making by growers and planners. The objectives of this study were to determine the specific thermal requirements of the Kerman (female) pistachio cultivar under the semi-arid conditions of central-western Argentina and to apply GIS-based modelling to identify suitable, marginally suitable, and unsuitable areas for high-productivity pistachio cultivation in the country. The results provide technical criteria for territorial planning and contribute to the sustainable development of fruit production in Argentina’s arid regions. To determine the local floral requirements of the Kerman pistachio cultivar, phenological data—including the beginning, full, and end of flowering, as well as harvest dates—were collected from the main pistachio-producing region of Argentina between 2013 and 2022. Observations were made in a representative commercial orchard (31°50′ S, 68°30′ W; Fig. 1 ) located in Pocito, San Juan Province, Argentina. The orchard, established in 2001, was planted at 5 m × 5 m spacing with female Kerman and male Peters cultivars in an 8:1 ratio. Both cultivars were grafted onto Pioneer Gold I rootstocks. Pistachio yields during the study period ranged from 0.7 to 5.5 t ha⁻¹. Phenological observations were conducted twice per week following the BBCH scale recently proposed by Sánchez Cañete et al. (manuscript under review). The most representative phenological stages were recorded on four tagged shoots from ten trees randomly selected within a plot located in the orchard’s most productive area. Hourly air temperature data were obtained from the San Juan Aero weather station (ICAN SANU) of the Argentinian National Meteorological Service (SMN), located 45 km from the phenological observation site. Hourly temperature records from April 1 to November 1 were processed in the R environment using the ChillR package to calculate chill portions (CP) according to the Dynamic Model (Fishman et al., 1987 ) and Growing Degree Hours (GDH) using a base temperature (Tb) of 4.5°C (Ashcroft et al., 1977 ). The onset and end of the winter chilling period (endodormancy) and the subsequent forcing period (ecodormancy) were determined using Partial Least Squares (PLS) regression applied to 15-day blocks, following methods similar to those described by Luedeling and Gassner ( 2012 ) and Benmoussa et al. ( 2017 ). CP and GDH blocks with Variable Importance in Projection (VIP) values > 0.8 were associated with chilling and forcing phases, respectively. Based on previous studies, we assumed that: (1) the intercept of the mean CP accumulation at the end of the endodormancy period represents the chilling requirement, and (2) the mean accumulated GDH between the beginning of the forcing period and the mean bloom date represents the end of the forcing phase. The post–fruit set thermal requirement to reach harvest maturity was estimated as the mean Growing Degree Days (GDD) accumulated between full bloom and harvest, using a Tb of 7°C. 1.1. Spatial data analysis of environmental suitability and adverse weather Once the flowering requirements were determined, chill and heat inputs were estimated at 72 weather stations of the Argentinian National Meteorological Service (SMN), located between 27° and 41° S (Fig. 1 ). Data on bioclimatic indicators (CP, GDH, and GDD) and weather variables (frost and precipitation) were integrated into a Geographic Information System (GIS). Spatial analysis consisted of using points with known values to estimate those at unknown locations through the Inverse Distance Weighted (IDW) interpolation method. In this approach, the influence of a sample point decreases with increasing distance from the point being estimated. For each bioclimatic indicator (CP, GDH, and GDD), the interpolated values were classified into three suitability categories (Table 1 ): suitable, marginally suitable, and unsuitable. Table 1 Agroclimatic requirements of pistachio cv. Kerman in Argentina. Variable Suitable Marginally-suitable Unsuitable Chilling (Chill Portions) > 47 CP 47 − 40 CP 4150 GDH 4150 − 3675 GDH 2200 GDD 2200 − 1900 GDD < 1900 GDD Severe spring frost events (probability) 30% Effective rainfall events during flowering and ripening stages 3 events 3–5 events > 5 events Effective rainfall accumulated during flowering and ripening stages (mm) 75 mm Because the fulfillment of thermal requirements for flowering is not the sole factor determining production, we also analyzed the risk of severe frosts ( 12 mm), and the average accumulated effective rainfall, calculated as (daily rainfall > 12 mm → daily rainfall – 12 × 0.8), during the critical flowering and ripening periods. Following the same procedure as for the bioclimatic indicators, frost and precipitation data were interpolated and each variable was classified into three categories to identify areas with low risk of adverse weather conditions. Finally, the maps generated from the spatial interpolation of climatic suitability were overlaid with those indicating low-risk areas to delineate the primary recommended zones for pistachio cultivation in Argentina. All geoprocessing and data interpolation procedures were performed using Quantum GIS v. 3.30.3. 2. Results 3.1. Chilling and heat requirements The onset and end of the chilling and forcing periods for the Kerman variety up to flowering were determined based on blocks showing a negative correlation with VIP > 0.8 (Fig. 2 ). The chilling period (Fig. 2 a) began on Julian day 123 (3 May) and ended on day 227 (15 August), during which an average of 47 CP were accumulated (Fig. 3 a). The forcing period (Fig. 3 a), in turn, started on Julian day 235 (23 August) and ended on day 256 (15 September), with an average accumulation of 4,990 GDH (Fig. 3 b). Finally, between full bloom and harvest, a total of 2,200 GDD accumulated during the 2012–2022 period (Fig. 4 ). 3.2. Chilling and heat temperature maps Figure 5 a shows the areas classified as suitable, marginally suitable, or unsuitable according to the chill portion requirement determined for pistachio cultivation. The suitable area is located in southern Argentina, extending from approximately the 32nd to the 36th parallel from north to south. The unsuitable lands occupy northern Argentina, extending southward to around the 30th parallel in the northwest—where altitude is higher—and to the 33rd parallel in central and eastern regions. A narrow band of marginally suitable land extends west to east across the center of the country, separating the suitable from the unsuitable zones. Figure 5 b depicts the distribution of areas meeting the GDH requirements necessary for proper flowering intensity, synchronicity, and timing. Across the study area, GDH accumulation was generally not a limiting factor for pistachio cultivation. Only a small sector in the southwestern region (at higher elevations) was identified as unsuitable, along with isolated areas in the center-west that are also restricted by altitude. Figure 5 c shows the distribution of areas that meet the GDD requirements for optimal fruit ripening. Suitable land represents a large proportion of the study area, extending from north to south up to approximately 34°S and 36°S in the west and east, respectively. Unsuitable areas are located in the southern part of the region, including the central–southern sectors of Neuquén and Río Negro provinces. It is worth noting the extensive marginally suitable area in the central–eastern part of the study region (Buenos Aires province), where maritime influence results in summers with thermal limitations for pistachio cultivation. The overall thermal suitability map for pistachio cultivation (Fig. 6 ) was generated by superimposing the spatial layers shown in Figs. 5 a, 5 b, and 5 c for the study area in Argentina. Lands fully meeting the thermal suitability requirements are confined to a narrow band beginning in western Argentina at approximately 32°S, extending southward to 36–38°S, and then continuing eastward across the country near 36°S. The marginally suitable area is broader and covers much of the central part of the study region. Lands to the north and south of the 29–33°S and 37–40°S parallels, respectively, were classified as unsuitable for Kerman pistachio production. The total area analyzed comprises 2,379,594 km², of which 10.5% was classified as suitable, 47% as marginally suitable, and 43% as unsuitable based on thermal constraints for pistachio cultivation. 3.3. Adverse weather maps In this study, we examined the pollination period between 21 September and 10 October. Precipitation events during flowering can drastically reduce pollen transport efficiency, as wet pollen grains tend to settle, hindering their arrival at receptive stigmas. Moreover, rainfall increases relative humidity, promoting fungal growth that can damage flowers, reduce fruit set, and increase the proportion of empty or defective nuts. Land suitability was classified (Table 1 ) based on the number of rainfall events (Fig. 7 a) and the average accumulated effective precipitation during this critical period (Fig. 7 b). Based on the number of effective rainfall events (greater than 12 mm) during flowering, an area in northwestern Argentina was identified as suitable for pistachio cultivation, while marginal and unsuitable zones extend from west to east. When the spatial distribution of accumulated effective rainfall during flowering was analyzed, much of western Argentina appeared suitable for pistachio cultivation, whereas eastern Argentina contained mostly marginal or unsuitable areas. Flowering is highly sensitive to frost damage. Figure 7 c shows the probability of frost during the pistachio flowering period. The distribution of land according to late frost risk exhibits a clear gradient, with low probability in the north and high probability in the south. Frost is more likely in western regions due to higher altitudes associated with proximity to the Andes mountain range. The physiological and harvest maturity of pistachio depends on endocarp dehiscence (the opening of the shells by internal mechanical forces caused by seed growth) and the ripening of the mesocarp (husk). Both processes are influenced by accumulated temperature (Fig. 5 c) and relative humidity during the post–fruit set period. High rainfall during the ripening period (January–February in the Southern Hemisphere) increases relative humidity, which can limit seed growth, delay ripening, reduce husk opening, and increase the risk of shell staining and phytosanitary problems. These effects ultimately constrain the ability to harvest efficiently and in a timely manner. Considering the frequency of effective rainfall (< 5 events) and low accumulated effective precipitation (< 50 mm) during the ripening period, suitable areas for pistachio cultivation are mainly located in the western part of the country. In contrast, eastern regions are more humid and experience higher summer rainfall, creating conditions unsuitable for pistachio production. 3.4. Land suitable for pistachio The global map of pistachio suitability (Fig. 9 ) was generated by superimposing the thermal suitability map (Fig. 6 ) with maps of meteorological constraints, including frost and precipitation (Figs. 7 and 8 ). Areas suitable for pistachio cultivation with minimal meteorological restrictions are confined to a narrow strip in western Argentina, beginning near the 32°S parallel and extending south to approximately the 36°S parallel, covering only 3% (64,411 km²) of the total study area. Marginally suitable areas are limited to small regions immediately east of the highly suitable land. Additionally, a narrow strip in southeastern Buenos Aires meets the criteria for marginal suitability for pistachio production in Argentina. The marginally suitable area represents approximately 4% (96,860 km²) of the total study area. 3. Discussion In Argentina, as in other regions of the world, agricultural incentive policies have been implemented with the aim of developing areas traditionally considered marginally productive. A major limitation of such policies is that they often fail to align the crops promoted with the environmental conditions and biological requirements of the species (Meza et al., 2022). A clear example is Argentina’s Tax Deferral Law, which sought to stimulate agro-industrial production through tax reductions in selected regions. In this context, during the 1980s and 1990s, the cultivated area for olives and grapevines expanded significantly in regions now recognized as sub-optimal for these crops (Gómez del Campo et al., 2010). Three decades later, this has resulted in farms with yields and product quality below commercial standards, forcing producers either to reconvert their operations or to change their agricultural activity entirely. Due to its specific environmental requirements—including cold winters, warm springs and summers, low relative humidity, and limited rainfall—pistachio cultivation is restricted to a few regions worldwide (Açar, 2024 ). Consequently, three countries account for approximately 90% of global production (FAOSTAT, 2023). These strict environmental demands, combined with strong international demand for tree nuts—particularly pistachios—make it a crop of interest for semi-arid regions around the world. In Argentina, pistachio production is concentrated almost entirely in San Juan Province, a region that does not precisely match the climatic conditions of other major production areas (e.g., it accumulates fewer chill portions than California or Iran) (Pope et al., 2015), yet it still achieves high yields of internationally recognized quality. Argentina is also the leading pistachio producer in the Southern Hemisphere, providing a notable competitive advantage due to counter-seasonality relative to major consumer markets in the Northern Hemisphere. Comparisons of similar studies on the Kerman variety, using the Dynamic Model to determine chilling requirements for successful flowering, reveal significant environmental variability. In California (USA), the estimated requirement was 69 CP (Pope et al., 2015); in Sfax (Tunisia), it was 32.4 CP; and in the present study, 47 CP. These findings highlight that extrapolating Dynamic Model outcomes to climates with divergent thermal patterns is limited, underscoring the need for localized studies. The main limitation to pistachio expansion is the availability of sufficient winter chilling, which must be complemented by high temperatures during spring and summer. In Argentina, the central region is classified as warm temperate, with virtually no thermal constraints during the summer, while winters become more severe in the west due to a marked reduction in maritime influence. The south of San Juan Province, the primary area of pistachio production in Argentina, exhibits these climatic characteristics. It is also important to note that certain cultivation techniques can facilitate pistachio expansion into suboptimal areas; however, such chemical management practices have significant environmental implications, potentially affecting local flora and fauna, in addition to their high economic cost. Although Kerman is currently the main variety cultivated in Argentina, other cultivars—such as Golden Hills and Lost Hills, primarily from California—have lower chilling requirements (Nuñez et al., 2024). The introduction of these varieties could be crucial for expanding cultivation into northwestern regions of the country. The area of interest for pistachio cultivation in Argentina (Fig. 9 ), where zones meeting the thermal requirements for flowering and fruit maturity (Fig. 6 ) overlap with areas of limited risk of adverse weather during critical phenological stages (Figs. 7 and 8 ), encompasses approximately 64,411 km². Within this region, the main crops are olive, grapevine, and walnut, with water availability representing the primary constraint for agricultural expansion and a key point of competition between local communities and the productive sector. Compared with these crops, pistachio is less water-intensive and is intrinsically associated with higher economic water productivity (Calvo et al., 2023 ). Given the rapid expansion of the cultivated area—a 500% increase over the last five years—and strong economic incentives driven by high international demand, the area under pistachio cultivation could reach 15,000 hectares in the near future. However, the main limitation to stable pistachio production—or to reducing yield alternation—in Argentina is the gradual decline in winter chill accumulation, coupled with an increased frequency of summer heat waves—both trends that have become more pronounced in recent decades (Açar, 2024 ). In addition, the entire central-western region of Argentina is strongly influenced by the El Niño–Southern Oscillation (ENSO), which increases the occurrence of Zonda wind events during winter and spring. These events raise atmospheric temperatures over large areas, thereby reducing chill accumulation. Furthermore, Zonda episodes are often followed by polar air incursions that can result in severe frost events, particularly during the flowering period (Norte, 2015 ). While this study focuses on agroclimatic requirements, the sustainable expansion of pistachio cultivation in Argentina also depends on broader agronomic, economic, and social factors. Key considerations include secure access to irrigation water, competition with other land uses and conservation priorities, availability of processing infrastructure, land prices, and market proximity (Meza et al., 2022). Integrated land-use planning and robust policy frameworks will therefore be essential to balance crop expansion with ecosystem preservation and equitable water use, helping to avoid repeating past experiences in Argentina, where agricultural promotion encouraged cultivation in suboptimal environments, resulting in adverse economic and environmental outcomes. 4. Conclusion The central-western region of Argentina offers agroclimatic conditions suitable for the cultivation of the Kerman pistachio variety across a large area with proven agricultural potential. Further expansion will depend on the identification and adoption of sustainable practices under changing climatic scenarios, mitigation of adverse weather events, and the potential introduction of new cultivars with lower chilling requirements. Future research should focus on micro-zoning using digital elevation models within the identified area of interest, assessing cultivar performance, and modelling the long-term impacts of climate change on crop productivity. Declarations Acknowledgements The authors gratefully acknowledge Maximiliano Ighani of Pisté SRL for granting access to the pistachio orchard where phenological data were collected. We also thank Georgina Lémole for her technical support and Mónica Colipe for maintaining the portal www.redfrutosecos.com. F. Calvo holds a postdoctoral fellowship from CONICET, and G. Sánchez is the recipient of a predoctoral fellowship from CONICET. This work is dedicated to the memory of Alem Barrionuevo. Author contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by P.S. and F.S The first draft of the manuscript was written by F.C. and E.T. and all authors commented on previous versions of the manuscript. All authors read and approved of the final manuscript. Funding information This research was supported by grants from the National Institute of Agricultural Technology (INTA), Argentina (PE-I005 2023-2025). Data availability The datasets generated during the current study are available from the corresponding author on reasonable request. Ethics approval : Not applicable. Consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: T he authors have no relevant financial or non-financial interests to disclose. References Açar İ (2024) Possible effects of climate change on pistachio cultivation. In S. Türker, H. Gözel, H. Çetinkaya, Y. Haspolat. (Eds), Climate change and fruit farming (pp. 1–13). Orient Publications. 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HortScience 56(7), 769–779. https://doi.org/10.21273/HORTSCI15722-21 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 16 Nov, 2025 Reviewers invited by journal 06 Nov, 2025 Editor assigned by journal 16 Oct, 2025 First submitted to journal 15 Oct, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7857977","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":541134463,"identity":"debc718e-8a53-46ac-ba74-c2bd44402de2","order_by":0,"name":"Franco E Calvo","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Franco","middleName":"E","lastName":"Calvo","suffix":""},{"id":541134464,"identity":"420457b2-c5d1-4555-9d73-dec89aaac251","order_by":1,"name":"Paolo 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07:33:41","extension":"html","order_by":24,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":97469,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/59401867b7e255eb3cd233ec.html"},{"id":96081260,"identity":"61a88589-0933-4e85-af9d-594d636cb9f5","added_by":"auto","created_at":"2025-11-17 11:37:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":459558,"visible":true,"origin":"","legend":"\u003cp\u003eGeographical distribution of weather stations used to estimate areas with varying suitability for pistachio cultivation in Argentina. The Carpintería locality in San Juan Province, where phenological observations were conducted, is indicated by a yellow circle.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/1fb15fbd84ae3e2ea02d78c7.png"},{"id":96081262,"identity":"cb67f456-e56d-4e28-a6f1-ead9a4f9dbe8","added_by":"auto","created_at":"2025-11-17 11:37:38","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":245659,"visible":true,"origin":"","legend":"\u003cp\u003ePartial least squares (PLS) regression model coefficients for the chilling (a) and forcing (b) periods required to achieve flowering in Kerman pistachios in Carpintería, San Jua n, Argentina.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/8594d05890ed7dfdffdd1fdc.png"},{"id":96081275,"identity":"2884ab2a-478d-4805-8a3e-000958509b30","added_by":"auto","created_at":"2025-11-17 11:37:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":249744,"visible":true,"origin":"","legend":"\u003cp\u003eAverage accumulated chill portions (a) and Growing Degree Hours (b) during the 2013–2023 period in San Juan, Argentina. Error bars represent the range between daily minimum and maximum values for each variable within the evaluated period.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/1701b6b460a4509c46c1a031.png"},{"id":96246621,"identity":"4741bd09-a358-4b30-97a9-3cb8f9c96544","added_by":"auto","created_at":"2025-11-19 07:26:22","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":393450,"visible":true,"origin":"","legend":"\u003cp\u003eAverage accumulated Growing Degree Days (b) during the 2013–2023 period in San Juan, Argentina.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/0aedf9dc447e13d0706001ee.png"},{"id":96081266,"identity":"8bb54ab9-e746-45f7-853f-2908598148ec","added_by":"auto","created_at":"2025-11-17 11:37:38","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":315036,"visible":true,"origin":"","legend":"\u003cp\u003eGeographical distribution of areas in Argentina with varying suitability for pistachio cultivation, based on chilling portion (CP) accumulation during the endodormancy period (panel a), Growing Degree Hours (GDH) during ecodormancy (panel b), and Growing Degree Days (GDD) during fruit development (panel c).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/1557ef9f02a89d0bbdc2c572.png"},{"id":96248278,"identity":"c8540c9d-8715-42af-94f5-320430ecc6f5","added_by":"auto","created_at":"2025-11-19 07:28:16","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":445819,"visible":true,"origin":"","legend":"\u003cp\u003eMap obtained by superimposing the chill portions (CP), Growing Degree Hours (GDH), and Growing Degree Days (GDD) layers.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/e36e71705716a21d8d61464f.png"},{"id":96081271,"identity":"db26d87c-1e9e-4f14-8970-869b59be2721","added_by":"auto","created_at":"2025-11-17 11:37:38","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":310227,"visible":true,"origin":"","legend":"\u003cp\u003eGeographical distribution of areas in Argentina with varying suitability for pistachio cultivation based on adverse weather conditions during the flowering period. Panel (a) shows the number of effective precipitation events, panel (b) shows accumulated precipitation, and panel (c) shows the probability of critical frosts (temperatures below –3°C).\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/f2427e78652ef983f280d06f.png"},{"id":96249282,"identity":"359a5c6e-cb4f-4d36-92a9-9ddb01184810","added_by":"auto","created_at":"2025-11-19 07:32:51","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":349564,"visible":true,"origin":"","legend":"\u003cp\u003eGeographical distribution of areas in Argentina with varying suitability for pistachio cultivation based on adverse weather conditions during the pre-harvest period. Panel (a) shows the number of effective precipitation events, and panel (b) shows accumulated precipitation.\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/a7bfd3bf0df70d62353fcf3f.png"},{"id":96081278,"identity":"0952bcc9-0f49-4bb1-a68e-70efbbe676e9","added_by":"auto","created_at":"2025-11-17 11:37:39","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":438093,"visible":true,"origin":"","legend":"\u003cp\u003eMap obtained by superimposing the global thermal map (Fig. 6) and the adverse weather maps during flowering (Fig. 7) and pre-harvest (Fig. 8) periods.\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/8f0d95295dd16b152230761a.png"},{"id":96256314,"identity":"78f45e7b-42ee-40f8-8de2-f2640a28854a","added_by":"auto","created_at":"2025-11-19 07:49:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3848193,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7857977/v1/b6af478e-f38a-4ba0-b984-8b93aeb1904a.pdf"}],"financialInterests":"","formattedTitle":"Temperature Requirements of Pistachio (Pistacia vera L. cv. Kerman) and Identification of Suitable Cultivation Areas in Semi-Arid Central-Western Argentina","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe consumption of pistachios, whether as snacks or as ingredients in food products, has steadily increased worldwide over the past two decades (Amico Roxas et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Ripari Garrido et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This growth is primarily driven by increased consumer awareness of their nutritional properties and recognition as a healthy food. Recent studies have confirmed the nutritional value of pistachios, highlighting their protein, unsaturated fatty acid, fiber, and antioxidant content (Rabad\u0026aacute;n et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Native to arid and semi-arid regions, the pistachio tree exhibits remarkable tolerance to water scarcity and saline soils, allowing its cultivation in areas unsuitable for other crops (Garc\u0026iacute;a-Tejero et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Achieving high yields depends on growing the crop under specific environmental conditions, particularly regarding winter chilling accumulation and thermal requirements for flowering and fruit ripening. These constraints currently limit pistachio cultivation to a few regions worldwide.\u003c/p\u003e\u003cp\u003eSimilar to other deciduous fruit trees, the pistachio tree enters a period of endodormancy after leaf fall in autumn. During this phase, buds remain dormant even under favorable thermal conditions (Lang et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e1987\u003c/span\u003e). Overcoming endodormancy requires exposure to sufficient winter chilling. Subsequently, the tree enters ecodormancy, a phase in which buds gradually acquire the ability to resume growth in response to heat accumulation. Previous studies on pistachio in Tunisia (Elloumi et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Benmoussa et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) and the USA (Pope et al., 2015) have shown that high temperatures during endodormancy can delay or inhibit flowering. In addition, insufficient chilling during endodormancy is associated with increased bud drop, asynchrony between male and female flowering, and irregular flowering, which can result in reduced or null yields.\u003c/p\u003e\u003cp\u003eAfter fruit set, \u003cb\u003epistachio trees\u003c/b\u003e require warm summers to produce nuts of high commercial quality. Warm temperatures promote cell elongation and metabolic activity, determining the rate of fruit and kernel development (Olsen, 2010), and favor the natural splitting of the endocarp (Nu\u0026ntilde;ez et al., 2024), a valuable commercial trait. The kernel filling period depends on adequate thermal accumulation during embryo growth to reach optimal nut size (Aydin et al., 2019). Conversely, cool summers increase the proportion of empty and closed shells (Rahemi and Pakkish, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Endocarp lignification, which protects the seed, requires temperatures above 25\u0026deg;C. Poorly lignified endocarps increase the risk of aflatoxin contamination due to mechanical damage during harvest (Mahoney and Molyneux, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1998\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOther environmental factors also influence the suitability of land for pistachio cultivation. Rainfall during pollination or prior to harvest can negatively affect productivity and seed health (Yarahmadi and Amini, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Although pistachio trees are resistant to low mid-winter temperatures (surviving below \u0026minus;\u0026thinsp;20\u0026deg;C; Marino and Marra, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), their sensitivity to frost increases during flowering and fruit set. Temperatures between \u0026minus;\u0026thinsp;2 and \u0026minus;\u0026thinsp;4\u0026deg;C during these stages can significantly reduce yields (Pakkish et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Hokmabadi, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; S\u0026aacute;ez-S\u0026aacute;nchez, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). While various strategies exist to mitigate frost damage, the safest and most sustainable approach is to cultivate the crop in areas with a low probability of late frosts.\u003c/p\u003e\u003cp\u003ePistachio cultivation in Argentina has expanded remarkably over the past decade, particularly in the arid and semi-arid central-western regions. The total area currently under cultivation exceeds 8,600 hectares, 96% of which is concentrated in southern San Juan Province and northern Mendoza Province. In recent years, strong interest has emerged in expanding cultivation beyond these traditional areas, raising questions about the agronomic and economic viability of the crop in new locations. Previous studies in the USA (Zhang et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), Tunisia (Benmoussa et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), Australia (Zhang and Taylor, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), Azerbaijan (Yarahmadi and Amini, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), and Iran (Ahmadi et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) have determined the agroclimatic requirements of pistachio, providing a basis for identifying suitable land. However, these findings are not always directly applicable due to the specific thermal characteristics of continental climates in western Argentina. Factors such as spatial and temporal variability in chilling accumulation, the frequency of late frosts, thermal conditions during flowering and ripening, and rainfall during harvest can strongly limit the productive potential of new plantations. Classical chilling accumulation models (e.g., Chill Hours or Chill Units) often over- or underestimate requirements in climates with irregular or warm winters (Fernandez et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Therefore, dynamic models\u0026mdash;such as the Dynamic Model, which estimates chill portions (CP)\u0026mdash;are recommended, as they are more reliable under these conditions (Erez et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Ignoring local adaptation may result in the selection of areas that, although superficially appearing suitable based on general literature, ultimately fail to meet critical requirements in practice.\u003c/p\u003e\u003cp\u003ePrevious studies have employed agroclimatic models and geographic information systems (GIS) to assess land suitability for pistachio cultivation by integrating phenological, meteorological, and topographic data (e.g., Yarahmadi and Amini, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). These approaches have enabled the development of suitability maps that classify territories according to their potential for cultivation, supporting decision-making by growers and planners. The objectives of this study were to determine the specific thermal requirements of the Kerman (female) pistachio cultivar under the semi-arid conditions of central-western Argentina and to apply GIS-based modelling to identify suitable, marginally suitable, and unsuitable areas for high-productivity pistachio cultivation in the country. The results provide technical criteria for territorial planning and contribute to the sustainable development of fruit production in Argentina\u0026rsquo;s arid regions.\u003c/p\u003e\u003cp\u003eTo determine the local floral requirements of the Kerman pistachio cultivar, phenological data\u0026mdash;including the beginning, full, and end of flowering, as well as harvest dates\u0026mdash;were collected from the main pistachio-producing region of Argentina between 2013 and 2022. Observations were made in a representative commercial orchard (31\u0026deg;50\u0026prime; S, 68\u0026deg;30\u0026prime; W; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) located in Pocito, San Juan Province, Argentina. The orchard, established in 2001, was planted at 5 m \u0026times; 5 m spacing with female Kerman and male Peters cultivars in an 8:1 ratio. Both cultivars were grafted onto Pioneer Gold I rootstocks. Pistachio yields during the study period ranged from 0.7 to 5.5 t ha⁻\u0026sup1;.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003ePhenological observations were conducted twice per week following the BBCH scale recently proposed by S\u0026aacute;nchez Ca\u0026ntilde;ete et al. (manuscript under review). The most representative phenological stages were recorded on four tagged shoots from ten trees randomly selected within a plot located in the orchard\u0026rsquo;s most productive area.\u003c/p\u003e\u003cp\u003eHourly air temperature data were obtained from the San Juan Aero weather station (ICAN SANU) of the Argentinian National Meteorological Service (SMN), located 45 km from the phenological observation site. Hourly temperature records from April 1 to November 1 were processed in the R environment using the ChillR package to calculate chill portions (CP) according to the Dynamic Model (Fishman et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1987\u003c/span\u003e) and Growing Degree Hours (GDH) using a base temperature (Tb) of 4.5\u0026deg;C (Ashcroft et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1977\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe onset and end of the winter chilling period (endodormancy) and the subsequent forcing period (ecodormancy) were determined using Partial Least Squares (PLS) regression applied to 15-day blocks, following methods similar to those described by Luedeling and Gassner (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) and Benmoussa et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). CP and GDH blocks with Variable Importance in Projection (VIP) values\u0026thinsp;\u0026gt;\u0026thinsp;0.8 were associated with chilling and forcing phases, respectively.\u003c/p\u003e\u003cp\u003eBased on previous studies, we assumed that: (1) the intercept of the mean CP accumulation at the end of the endodormancy period represents the chilling requirement, and (2) the mean accumulated GDH between the beginning of the forcing period and the mean bloom date represents the end of the forcing phase. The post\u0026ndash;fruit set thermal requirement to reach harvest maturity was estimated as the mean Growing Degree Days (GDD) accumulated between full bloom and harvest, using a Tb of 7\u0026deg;C.\u003c/p\u003e\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e\u003ch2\u003e1.1. Spatial data analysis of environmental suitability and adverse weather\u003c/h2\u003e\u003cp\u003eOnce the flowering requirements were determined, chill and heat inputs were estimated at 72 weather stations of the Argentinian National Meteorological Service (SMN), located between 27\u0026deg; and 41\u0026deg; S (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Data on bioclimatic indicators (CP, GDH, and GDD) and weather variables (frost and precipitation) were integrated into a Geographic Information System (GIS).\u003c/p\u003e\u003cp\u003eSpatial analysis consisted of using points with known values to estimate those at unknown locations through the Inverse Distance Weighted (IDW) interpolation method. In this approach, the influence of a sample point decreases with increasing distance from the point being estimated. For each bioclimatic indicator (CP, GDH, and GDD), the interpolated values were classified into three suitability categories (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e): suitable, marginally suitable, and unsuitable.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAgroclimatic requirements of pistachio cv. Kerman in Argentina.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSuitable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMarginally-suitable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eUnsuitable\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eChilling \u003c/p\u003e\u003cp\u003e(Chill Portions)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;47 CP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e47\u0026thinsp;\u0026minus;\u0026thinsp;40 CP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;40 CP\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpring heat requirements (Growing Degree Hours)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;4150 GDH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4150\u0026thinsp;\u0026minus;\u0026thinsp;3675 GDH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;3675 GDH\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSummer heat \u003c/p\u003e\u003cp\u003e(Growing Degree Days)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;2200 GDD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2200\u0026thinsp;\u0026minus;\u0026thinsp;1900 GDD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;1900 GDD\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSevere spring frost events (probability)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;10%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10\u0026ndash;30%\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;30%\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEffective rainfall events during flowering and ripening stages\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3 events\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3\u0026ndash;5 events\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;5 events\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEffective rainfall accumulated during flowering and ripening stages (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;50 mm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50\u0026ndash;75 mm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;75 mm\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eBecause the fulfillment of thermal requirements for flowering is not the sole factor determining production, we also analyzed the risk of severe frosts (\u0026lt; \u0026minus;\u0026thinsp;3\u0026deg;C), the number of effective rainfall events (daily rainfall\u0026thinsp;\u0026gt;\u0026thinsp;12 mm), and the average accumulated effective rainfall, calculated as (daily rainfall\u0026thinsp;\u0026gt;\u0026thinsp;12 mm \u0026rarr; daily rainfall \u0026ndash; 12 \u0026times; 0.8), during the critical flowering and ripening periods. Following the same procedure as for the bioclimatic indicators, frost and precipitation data were interpolated and each variable was classified into three categories to identify areas with low risk of adverse weather conditions.\u003c/p\u003e\u003cp\u003eFinally, the maps generated from the spatial interpolation of climatic suitability were overlaid with those indicating low-risk areas to delineate the primary recommended zones for pistachio cultivation in Argentina. All geoprocessing and data interpolation procedures were performed using Quantum GIS v. 3.30.3.\u003c/p\u003e\u003c/div\u003e"},{"header":"2. Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Chilling and heat requirements\u003c/h2\u003e\u003cp\u003eThe onset and end of the chilling and forcing periods for the Kerman variety up to flowering were determined based on blocks showing a negative correlation with VIP\u0026thinsp;\u0026gt;\u0026thinsp;0.8 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The chilling period (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) began on Julian day 123 (3 May) and ended on day 227 (15 August), during which an average of 47 CP were accumulated (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). The forcing period (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea), in turn, started on Julian day 235 (23 August) and ended on day 256 (15 September), with an average accumulation of 4,990 GDH (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). Finally, between full bloom and harvest, a total of 2,200 GDD accumulated during the 2012\u0026ndash;2022 period (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Chilling and heat temperature maps\u003c/h2\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows the areas classified as suitable, marginally suitable, or unsuitable according to the chill portion requirement determined for pistachio cultivation. The suitable area is located in southern Argentina, extending from approximately the 32nd to the 36th parallel from north to south. The unsuitable lands occupy northern Argentina, extending southward to around the 30th parallel in the northwest\u0026mdash;where altitude is higher\u0026mdash;and to the 33rd parallel in central and eastern regions. A narrow band of marginally suitable land extends west to east across the center of the country, separating the suitable from the unsuitable zones.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb depicts the distribution of areas meeting the GDH requirements necessary for proper flowering intensity, synchronicity, and timing. Across the study area, GDH accumulation was generally not a limiting factor for pistachio cultivation. Only a small sector in the southwestern region (at higher elevations) was identified as unsuitable, along with isolated areas in the center-west that are also restricted by altitude.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec shows the distribution of areas that meet the GDD requirements for optimal fruit ripening. Suitable land represents a large proportion of the study area, extending from north to south up to approximately 34\u0026deg;S and 36\u0026deg;S in the west and east, respectively. Unsuitable areas are located in the southern part of the region, including the central\u0026ndash;southern sectors of Neuqu\u0026eacute;n and R\u0026iacute;o Negro provinces. It is worth noting the extensive marginally suitable area in the central\u0026ndash;eastern part of the study region (Buenos Aires province), where maritime influence results in summers with thermal limitations for pistachio cultivation.\u003c/p\u003e\u003cp\u003eThe overall thermal suitability map for pistachio cultivation (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) was generated by superimposing the spatial layers shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec for the study area in Argentina. Lands fully meeting the thermal suitability requirements are confined to a narrow band beginning in western Argentina at approximately 32\u0026deg;S, extending southward to 36\u0026ndash;38\u0026deg;S, and then continuing eastward across the country near 36\u0026deg;S. The marginally suitable area is broader and covers much of the central part of the study region. Lands to the north and south of the 29\u0026ndash;33\u0026deg;S and 37\u0026ndash;40\u0026deg;S parallels, respectively, were classified as unsuitable for Kerman pistachio production. The total area analyzed comprises 2,379,594 km\u0026sup2;, of which 10.5% was classified as suitable, 47% as marginally suitable, and 43% as unsuitable based on thermal constraints for pistachio cultivation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Adverse weather maps\u003c/h2\u003e\u003cp\u003eIn this study, we examined the pollination period between 21 September and 10 October. Precipitation events during flowering can drastically reduce pollen transport efficiency, as wet pollen grains tend to settle, hindering their arrival at receptive stigmas. Moreover, rainfall increases relative humidity, promoting fungal growth that can damage flowers, reduce fruit set, and increase the proportion of empty or defective nuts.\u003c/p\u003e\u003cp\u003eLand suitability was classified (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) based on the number of rainfall events (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea) and the average accumulated effective precipitation during this critical period (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). Based on the number of effective rainfall events (greater than 12 mm) during flowering, an area in northwestern Argentina was identified as suitable for pistachio cultivation, while marginal and unsuitable zones extend from west to east. When the spatial distribution of accumulated effective rainfall during flowering was analyzed, much of western Argentina appeared suitable for pistachio cultivation, whereas eastern Argentina contained mostly marginal or unsuitable areas.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFlowering is highly sensitive to frost damage. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ec shows the probability of frost during the pistachio flowering period. The distribution of land according to late frost risk exhibits a clear gradient, with low probability in the north and high probability in the south. Frost is more likely in western regions due to higher altitudes associated with proximity to the Andes mountain range.\u003c/p\u003e\u003cp\u003eThe physiological and harvest maturity of pistachio depends on endocarp dehiscence (the opening of the shells by internal mechanical forces caused by seed growth) and the ripening of the mesocarp (husk). Both processes are influenced by accumulated temperature (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec) and relative humidity during the post\u0026ndash;fruit set period. High rainfall during the ripening period (January\u0026ndash;February in the Southern Hemisphere) increases relative humidity, which can limit seed growth, delay ripening, reduce husk opening, and increase the risk of shell staining and phytosanitary problems. These effects ultimately constrain the ability to harvest efficiently and in a timely manner.\u003c/p\u003e\u003cp\u003eConsidering the frequency of effective rainfall (\u0026lt;\u0026thinsp;5 events) and low accumulated effective precipitation (\u0026lt;\u0026thinsp;50 mm) during the ripening period, suitable areas for pistachio cultivation are mainly located in the western part of the country. In contrast, eastern regions are more humid and experience higher summer rainfall, creating conditions unsuitable for pistachio production.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Land suitable for pistachio\u003c/h2\u003e\u003cp\u003eThe global map of pistachio suitability (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e) was generated by superimposing the thermal suitability map (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) with maps of meteorological constraints, including frost and precipitation (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Areas suitable for pistachio cultivation with minimal meteorological restrictions are confined to a narrow strip in western Argentina, beginning near the 32\u0026deg;S parallel and extending south to approximately the 36\u0026deg;S parallel, covering only 3% (64,411 km\u0026sup2;) of the total study area.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eMarginally suitable areas are limited to small regions immediately east of the highly suitable land. Additionally, a narrow strip in southeastern Buenos Aires meets the criteria for marginal suitability for pistachio production in Argentina. The marginally suitable area represents approximately 4% (96,860 km\u0026sup2;) of the total study area.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Discussion","content":"\u003cp\u003eIn Argentina, as in other regions of the world, agricultural incentive policies have been implemented with the aim of developing areas traditionally considered marginally productive. A major limitation of such policies is that they often fail to align the crops promoted with the environmental conditions and biological requirements of the species (Meza et al., 2022). A clear example is Argentina\u0026rsquo;s Tax Deferral Law, which sought to stimulate agro-industrial production through tax reductions in selected regions. In this context, during the 1980s and 1990s, the cultivated area for olives and grapevines expanded significantly in regions now recognized as sub-optimal for these crops (G\u0026oacute;mez del Campo et al., 2010). Three decades later, this has resulted in farms with yields and product quality below commercial standards, forcing producers either to reconvert their operations or to change their agricultural activity entirely.\u003c/p\u003e\u003cp\u003eDue to its specific environmental requirements\u0026mdash;including cold winters, warm springs and summers, low relative humidity, and limited rainfall\u0026mdash;pistachio cultivation is restricted to a few regions worldwide (A\u0026ccedil;ar, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Consequently, three countries account for approximately 90% of global production (FAOSTAT, 2023). These strict environmental demands, combined with strong international demand for tree nuts\u0026mdash;particularly pistachios\u0026mdash;make it a crop of interest for semi-arid regions around the world.\u003c/p\u003e\u003cp\u003eIn Argentina, pistachio production is concentrated almost entirely in San Juan Province, a region that does not precisely match the climatic conditions of other major production areas (e.g., it accumulates fewer chill portions than California or Iran) (Pope et al., 2015), yet it still achieves high yields of internationally recognized quality. Argentina is also the leading pistachio producer in the Southern Hemisphere, providing a notable competitive advantage due to counter-seasonality relative to major consumer markets in the Northern Hemisphere.\u003c/p\u003e\u003cp\u003eComparisons of similar studies on the Kerman variety, using the Dynamic Model to determine chilling requirements for successful flowering, reveal significant environmental variability. In California (USA), the estimated requirement was 69 CP (Pope et al., 2015); in Sfax (Tunisia), it was 32.4 CP; and in the present study, 47 CP. These findings highlight that extrapolating Dynamic Model outcomes to climates with divergent thermal patterns is limited, underscoring the need for localized studies.\u003c/p\u003e\u003cp\u003eThe main limitation to pistachio expansion is the availability of sufficient winter chilling, which must be complemented by high temperatures during spring and summer. In Argentina, the central region is classified as warm temperate, with virtually no thermal constraints during the summer, while winters become more severe in the west due to a marked reduction in maritime influence. The south of San Juan Province, the primary area of pistachio production in Argentina, exhibits these climatic characteristics.\u003c/p\u003e\u003cp\u003eIt is also important to note that certain cultivation techniques can facilitate pistachio expansion into suboptimal areas; however, such chemical management practices have significant environmental implications, potentially affecting local flora and fauna, in addition to their high economic cost. Although Kerman is currently the main variety cultivated in Argentina, other cultivars\u0026mdash;such as Golden Hills and Lost Hills, primarily from California\u0026mdash;have lower chilling requirements (Nu\u0026ntilde;ez et al., 2024). The introduction of these varieties could be crucial for expanding cultivation into northwestern regions of the country.\u003c/p\u003e\u003cp\u003eThe area of interest for pistachio cultivation in Argentina (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e), where zones meeting the thermal requirements for flowering and fruit maturity (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e) overlap with areas of limited risk of adverse weather during critical phenological stages (Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e), encompasses approximately 64,411 km\u0026sup2;. Within this region, the main crops are olive, grapevine, and walnut, with water availability representing the primary constraint for agricultural expansion and a key point of competition between local communities and the productive sector. Compared with these crops, pistachio is less water-intensive and is intrinsically associated with higher economic water productivity (Calvo et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Given the rapid expansion of the cultivated area\u0026mdash;a 500% increase over the last five years\u0026mdash;and strong economic incentives driven by high international demand, the area under pistachio cultivation could reach 15,000 hectares in the near future.\u003c/p\u003e\u003cp\u003eHowever, the main limitation to stable pistachio production\u0026mdash;or to reducing yield alternation\u0026mdash;in Argentina is the gradual decline in winter chill accumulation, coupled with an increased frequency of summer heat waves\u0026mdash;both trends that have become more pronounced in recent decades (A\u0026ccedil;ar, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In addition, the entire central-western region of Argentina is strongly influenced by the El Ni\u0026ntilde;o\u0026ndash;Southern Oscillation (ENSO), which increases the occurrence of Zonda wind events during winter and spring. These events raise atmospheric temperatures over large areas, thereby reducing chill accumulation. Furthermore, Zonda episodes are often followed by polar air incursions that can result in severe frost events, particularly during the flowering period (Norte, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWhile this study focuses on agroclimatic requirements, the sustainable expansion of pistachio cultivation in Argentina also depends on broader agronomic, economic, and social factors. Key considerations include secure access to irrigation water, competition with other land uses and conservation priorities, availability of processing infrastructure, land prices, and market proximity (Meza et al., 2022). Integrated land-use planning and robust policy frameworks will therefore be essential to balance crop expansion with ecosystem preservation and equitable water use, helping to avoid repeating past experiences in Argentina, where agricultural promotion encouraged cultivation in suboptimal environments, resulting in adverse economic and environmental outcomes.\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThe central-western region of Argentina offers agroclimatic conditions suitable for the cultivation of the Kerman pistachio variety across a large area with proven agricultural potential. Further expansion will depend on the identification and adoption of sustainable practices under changing climatic scenarios, mitigation of adverse weather events, and the potential introduction of new cultivars with lower chilling requirements. Future research should focus on micro-zoning using digital elevation models within the identified area of interest, assessing cultivar performance, and modelling the long-term impacts of climate change on crop productivity.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge Maximiliano Ighani of Pist\u0026eacute; SRL for granting access to the pistachio orchard where phenological data were collected. We also thank Georgina L\u0026eacute;mole for her technical support and M\u0026oacute;nica Colipe for maintaining the portal www.redfrutosecos.com. F. Calvo holds a postdoctoral fellowship from CONICET, and G. S\u0026aacute;nchez is the recipient of a predoctoral fellowship from CONICET. This work is dedicated to the memory of Alem Barrionuevo.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e \u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by P.S. and F.S The first draft of the manuscript was written by F.C. and E.T. and all authors commented on previous versions of the manuscript. All authors read and approved of the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding information \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by grants from the National Institute of Agricultural Technology (INTA), Argentina (PE-I005 2023-2025).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval\u003c/strong\u003e: Not applicable. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate:\u003c/strong\u003e Not applicable. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e Not applicable. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests: T\u003c/strong\u003ehe authors have no relevant financial or non-financial interests to disclose.\u003cbr\u003e \u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eA\u0026ccedil;ar İ (2024) Possible effects of climate change on pistachio cultivation. 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(2023) Assessing temperature‐based adaptation limits to climate change of temperate perennial fruit crops. \u003cem\u003eGCS \u003c/em\u003e29(9), 2557-2571. https://doi.org/10.1111/gcb.16601 \u003c/li\u003e\n\u003cli\u003eNorte FA (2015) Understanding and Forecasting Zonda Wind (Andean Foehn) in Argentina: A Review. \u003cem\u003eACS\u003c/em\u003e 5, 163-193. http://dx.doi.org/10.4236/acs.2015.53012 \u003c/li\u003e\n\u003cli\u003eN\u0026uacute;\u0026ntilde;ez L, Mart\u0026iacute;n H, Mir\u0026aacute;s-Avalos JM, \u0026Aacute;lvarez S (2024) Pistachio Phenology and Yield in a Cold-Winter Region of Spain: The Status of the Cultivation and Performance of Three Cultivars. \u003cem\u003eHorticulturae\u003c/em\u003e 10(12), 1235. https://doi.org/10.3390/horticulturae10121235 \u003c/li\u003e\n\u003cli\u003ePakkish Z, Rahemi M, Panahi B (2011) Low temperature resistance of developing flower buds of pistachio (\u003cem\u003ePistacia vera\u003c/em\u003e L.) cultivars. \u003cem\u003eJEBS\u003c/em\u003e 5(15), 153-157.\u003c/li\u003e\n\u003cli\u003ePopeKS, Dose V, Da Silva D, Brown PH, DeJong TM (2015) Nut crop yield records show that budbreak-based chilling requirements may not reflect yield decline chill thresholds. \u003cem\u003eInt J Biometeorol\u003c/em\u003e 59, 707-715. https://doi.org/10.1007/s00484-014-0881-x \u003c/li\u003e\n\u003cli\u003eRabad\u0026aacute;n A, \u0026Aacute;lvarez-Ort\u0026iacute; M, Pardo JE, G\u0026oacute;mez R, Pardo-Gim\u0026eacute;nez A, Olmeda M (2017) A comprehensive approach to pistachio oil production. \u003cem\u003eBFJ\u003c/em\u003e 119(4), 921-933. https://doi.org/10.1108/BFJ-08-2016-0373 \u003c/li\u003e\n\u003cli\u003eRahemi M, Pakkish Z (2009) Determination of chilling and heat requirements of pistachio (Pistacia vera L.) cultivars. \u003cem\u003eAgr Sci China\u003c/em\u003e 8(7), 803-807. https://doi.org/10.1016/S1671-2927(08)60281-3 \u003c/li\u003e\n\u003cli\u003eRipari Garrido J, Patrignani M, Puppo MC, Salinas MV (2024) Nutritional and bioactive characterization of pistachio\u0026mdash;a review with special focus on health. \u003cem\u003eEFF\u003c/em\u003e 2, 363-390. https://doi.org/10.37349/eff.2024.00042 \u003c/li\u003e\n\u003cli\u003eS\u0026aacute;ez-S\u0026aacute;nchez I (2017) El cultivo del pistacho. Ja\u0026eacute;n, Espa\u0026ntilde;a: Degusta Ja\u0026eacute;n.\u003c/li\u003e\n\u003cli\u003eYarahmadi J, Amini A (2021) Determining land suitability for pistachio cultivation development based on climate variables to adapt to drought. \u003cem\u003eTheor Appl Climatol\u003c/em\u003e 143(3), 1631-1642. https://doi.org/10.1007/s00704-020-03499-4 \u003c/li\u003e\n\u003cli\u003eZhang J, Taylor C (2011) The dynamic model provides the best description of the chill process on \u0026lsquo;Sirora\u0026rsquo;pistachio trees in Australia. \u003cem\u003eHortScience\u003c/em\u003e 46(3), 420-425. http://dx.doi.org/10.21273/HORTSCI.46.3.420 \u003c/li\u003e\n\u003cli\u003eZhang L, Laca E, Allan CJ, Mahvelati NM, Ferguson L (2021) Nonlinear Model Selection for Fruit and Kernel Development as a Function of Heat in Pistachio. \u003cem\u003eHortScience\u003c/em\u003e 56(7), 769\u0026ndash;779. https://doi.org/10.21273/HORTSCI15722-21\u003cbr\u003e \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-biometeorology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ijbm","sideBox":"Learn more about [International Journal of Biometeorology](http://link.springer.com/journal/484)","snPcode":"484","submissionUrl":"https://www.editorialmanager.com/ijbm/default2.aspx","title":"International Journal of Biometeorology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"dormancy, chilling, forcing, phenology, climate change","lastPublishedDoi":"10.21203/rs.3.rs-7857977/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7857977/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn recent years, interest in pistachio production has increased significantly in Argentina, although cultivation remains largely confined to specific regions. The objectives of this study were: i) to determine the specific thermal requirements of cv. Kerman for optimal flowering and fruit development under semi-arid conditions, and ii) to use GIS-based modelling to identify suitable land for its expansion. To this end, phenological observations were collected from a commercial orchard in San Juan Province between 2013 and 2022. Thermal requirements for flowering and fruit ripening were calculated using hourly temperature data through the Dynamic Model (chill portions, CP) and Growing Degree Hours (GDH) and Days (GDD). Partial Least Squares (PLS) regression was applied to identify chilling and forcing periods. These parameters were then extrapolated to 72 weather stations across Argentina to evaluate regional suitability. Results indicated that a minimum of 47 CP, 4,150 GDH, and 2,200 GDD are required for optimal flowering and fruit maturation. GIS-based modelling classified land as suitable, marginally suitable, or unsuitable based on these thermal thresholds. Highly suitable areas were identified in the central-western regions. Additional factors, such as late spring frosts and rainfall during flowering and ripening, were integrated to refine the suitability map. The resulting global suitability map identified approximately 64,411 km\u0026sup2; as optimal for pistachio cultivation, coinciding with regions of low frost and rainfall risk. This study highlights the potential for expanding pistachio production in Argentina\u0026rsquo;s semi-arid zones, with considerations for climate trends, frost exposure, and water availability.\u003c/p\u003e","manuscriptTitle":"Temperature Requirements of Pistachio (Pistacia vera L. cv. Kerman) and Identification of Suitable Cultivation Areas in Semi-Arid Central-Western Argentina","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-17 11:37:34","doi":"10.21203/rs.3.rs-7857977/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-11-16T09:00:03+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-06T16:56:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-16T08:17:08+00:00","index":"","fulltext":""},{"type":"submitted","content":"International Journal of Biometeorology","date":"2025-10-15T07:06:04+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-biometeorology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ijbm","sideBox":"Learn more about [International Journal of Biometeorology](http://link.springer.com/journal/484)","snPcode":"484","submissionUrl":"https://www.editorialmanager.com/ijbm/default2.aspx","title":"International Journal of Biometeorology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"59c6e2d6-2e53-4810-b490-d08a8f7c387a","owner":[],"postedDate":"November 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-11-17T11:37:34+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-17 11:37:34","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7857977","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7857977","identity":"rs-7857977","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}