Drivers of Carbon Flux in Drip Irrigation Maize Fields in Northwest China
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Abstract Background: Under the escalating threat to sustainable development from the global increase in carbon dioxide concentrations, the variations in carbon flux in the farmland ecosystem and their influencing factors have attracted global attention. Over the past few decades, with the development of eddy covariance technology, the carbon fluxes of forests and grasslands have been determined in many countries. However, studies are very limited for the arid regions in northwestern China, which covers a large area where a mixed mode of agriculture and grazing is practiced. Results: To study the effects of drip irrigation on the net ecosystem productivity (NEE), ecosystem respiration (ER), gross primary production (GPP) and net biome productivity (NBP) in the arid regions of northwestern China, we measured the carbon flux annually from 2014 to 2018 using an eddy covariance system. Our results showed that the maize field carbon flux exhibited single-peak seasonal patterns during the growing seasons. During 2014-2018, the NEE, ER and GPP of the drip-irrigated maize field ranged between -407~-729 g C m-2, 485.46~975.46 g C m-2, and 1068.23~1705.30 g C m-2. In four of the five study years, the ER released back to the atmosphere was just over half of the carbon fixed by photosynthesis. The mean daily NEE, ER and GPP were significantly correlated with the net radiation (Rn), air temperature (Ta), leaf area index (LAI) and soil moisture (SWC). The results of path analysis showed that leaf area index is the main driving force of seasonal variation of carbon flux. When harvested removals were considered, the annual NBP was -234 g C m-2, and the drip-irrigated maize field was a carbon source. Conclusions: This study shows the variation and influencing factors of NEE, ER and GPP in the growth period of spring maize under film drip irrigation in arid areas of northwest China. The ecosystem was a carbon sink before maize harvest, but it was converted into a carbon source considering the carbon emissions after harvest. The variation of carbon flux was influenced by both environmental and vegetation factors, and its leaf area index was the main driver that affects the seasonal variation of carbon flux.
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Drivers of Carbon Flux in Drip Irrigation Maize Fields in Northwest China | 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 Drivers of Carbon Flux in Drip Irrigation Maize Fields in Northwest China Hui Guo, Sien Li, Fuk-Ling Wong, Shujing Qin, Yahui Wang, Danni Yang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-101488/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 30 Apr, 2021 Read the published version in Carbon Balance and Management → Version 1 posted 9 You are reading this latest preprint version Abstract Background: Under the escalating threat to sustainable development from the global increase in carbon dioxide concentrations, the variations in carbon flux in the farmland ecosystem and their influencing factors have attracted global attention. Over the past few decades, with the development of eddy covariance technology, the carbon fluxes of forests and grasslands have been determined in many countries. However, studies are very limited for the arid regions in northwestern China, which covers a large area where a mixed mode of agriculture and grazing is practiced. Results: To study the effects of drip irrigation on the net ecosystem productivity (NEE), ecosystem respiration (ER), gross primary production (GPP) and net biome productivity (NBP) in the arid regions of northwestern China, we measured the carbon flux annually from 2014 to 2018 using an eddy covariance system. Our results showed that the maize field carbon flux exhibited single-peak seasonal patterns during the growing seasons. During 2014-2018, the NEE, ER and GPP of the drip-irrigated maize field ranged between -407~-729 g C m -2 , 485.46~975.46 g C m -2 , and 1068.23~1705.30 g C m -2 . In four of the five study years, the ER released back to the atmosphere was just over half of the carbon fixed by photosynthesis. The mean daily NEE, ER and GPP were significantly correlated with the net radiation (Rn), air temperature (Ta), leaf area index (LAI) and soil moisture (SWC). The results of path analysis showed that leaf area index is the main driving force of seasonal variation of carbon flux. When harvested removals were considered, the annual NBP was -234 g C m -2 , and the drip-irrigated maize field was a carbon source. Conclusions: This study shows the variation and influencing factors of NEE, ER and GPP in the growth period of spring maize under film drip irrigation in arid areas of northwest China. The ecosystem was a carbon sink before maize harvest, but it was converted into a carbon source considering the carbon emissions after harvest. The variation of carbon flux was influenced by both environmental and vegetation factors, and its leaf area index was the main driver that affects the seasonal variation of carbon flux. Environmental Policy carbon flux drip-irrigated maize field gross primary productivity net ecosystem productivity ecosystem respiration net biome productivity Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Full Text Tables Table 1 The details of irrigation in maize field from 2014 to 2018 Date Irrigation (mm) Date Irrigation (mm) Date Irrigation (mm) Date Irrigation (mm) Date Irrigation (mm) 2014/6/6 50.00 2015/6/1 50.00 2016/4/24 51.00 2017/4/23 35.10 2018/5/1 50.77 2014/6/23 50.00 2015/6/13 50.00 2016/6/10 45.47 2017/6/14 68.02 2018/6/7 53.08 2014/6/28 50.00 2015/6/26 50.00 2016/6/25 49.82 2017/6/25 64.79 2018/6/18 40.58 2014/7/7 50.00 2015/7/10 50.00 2016/7/3 54.26 2017/7/10 62.07 2018/6/30 49.62 2014/7/18 50.00 2015/7/24 50.00 2016/7/15 65.09 2017/7/22 57.45 2018/7/11 55.38 2014/7/28 50.00 2015/8/7 50.00 2016/7/27 54.45 2017/8/8 53.76 2018/7/22 50.96 2014/8/22 50.00 2015/8/20 50.00 2016/8/7 53.53 2017/8/22 27.09 2018/8/1 68.27 2015/8/31 50.00 2016/8/22 53.19 2018/8/14 53.27 Table 2 The details of fertilization in maize field from 2014 to 2018 Year Date (NH4) 2 HPO 4 (kg hm -1 ) Urea (kg hm -1 ) Compound fertilizer (kg hm -1 ) 2014 10-Apr (base fertilizer) 275.00 42.00 8-Jun 150.00 5-Jul 120.00 2015 12-Apr (base fertilizer) 262.50 37.50 30-May 63.00 9.00 11-Jun 78.75 11.25 25-Jun 168.00 24.00 9-Jul 126.00 18.00 27-Jul 105.00 15.00 2016 5-Apr (base fertilizer) 300.00 225.00 27-Jun 300.00 15-Jul 150.00 2017 26-Mar (base fertilizer) 375.00 375.00 15-Jun 270.00 30-Jun 180.00 2018 26-Mar (base fertilizer) 375.00 375.00 7-Jun 225.00 18-Jun 150.00 30-Jun 75.00 Table 3 Dry grain (D g ), dry cob (D c ), dry leaf (D l ), dry stem (D s ) and exported carbon (C e ) in the spring maize field during 2014-2018 Year D g (g m -2 ) D c (g m -2 ) D l (g m -2 ) D s (g m -2 ) C e (g C m -2 ) 2014 904 126.43 314.70 502.63 795.75 2015 997 139.44 310.42 724.63 931.98 2016 1095 153.15 432.91 596.09 979.73 2017 529 73.99 192.40 614.35 599.27 2018 792 110.77 372.28 492.23 757.55 AVG 863.40 120.76 324.54 585.99 812.86 Table 4 Growing season sums of net ecosystem exchange (NEE), ecosystem respiration (ER) and gross primary productivity (GPP)，NEE max is the peak of NEE in the growing season, ER max is the maximum value of ecosystem respiration in the growing season, GPP max is the maximum value of GPP in the growing seasons Year Growing days NEE ER GPP NEE max ER max GPP max (Day) (g C m -2 ) (g C m -2 ) (g C m -2 ) (g C m -2 ) (g C m -2 ) (g C m -2 ) 2014 134 -630.13 485.46 1115.54 -14.32 7.6 20.83 2015 132 -729.89 975.46 1705.3 -18.69 14.67 26.79 2016 144 -601.18 825.81 1427.05 -13.67 9.98 21.31 2017 142 -406.76 661.84 1068.63 -10.98 8.77 18.99 2018 146 -527.47 724.94 1252.35 -11.42 9.14 17.94 Mean 139.6 -579.09 734.7 1313.77 -13.82 10.03 21.17 SD 5.57 107.89 163.58 232.07 2.75 2.44 3.06 CV 0.04 -0.19 0.22 0.18 -0.20 0.24 0.14 SD is the standard deviation. CV is coefficient of variation. Table 5 Partial correlation coefficients between environmental variables and net ecosystem exchange (NEE), ecosystem respiration (ER) and gross primary productivity (GPP) Carbon flux Year Rn Ta VPD SWC IP LAI NEE 2014 -0.47** -0.320** 0.153 -0.303** -0.176* -0.817** 2015 -0.390** -0.470** 0.044 -0.148 -0.146 -0.806** 2016 -0.625** -0.666** -0.407** -0.266** -0.175* -0.497** 2017 -0.581** -0.638** -0.449** -0.148 -0.109 -0.749** 2018 -0.480** -0.666** -0.11 -0.293** -0.188* -0.765** ER 2014 0.448** 0.395** -0.037 0.231** -0.013 0.775** 2015 0.258** 0.733** 0.350** 0.339** 0.034 0.742** 2016 0.313** 0.675** 0.217** 0.111 0.05 0.471** 2017 0.329** 0.770** 0.432** 0.272** 0.114 0.878** 2018 0.338** 0.618** -0.202* 0.384** 0.154 0.929** GPP 2014 0.499** 0.365** -0.132 0.303** 0.137 0.859** 2015 0.376** 0.619** 0.106 0.237** 0.117 0.858** 2016 0.596** 0.748** 0.393** 0.247** 0.154 0.547** 2017 0.523** 0.727** 0.470** 0.204* 0.118 0.845** 2018 0.455** 0.687** 0.001 0.344** 0.186* 0.892** ** Significantly correlated at the 0.01 level (bilateral) and * significantly correlated at the 0.05 level (bilateral). ER: ecosystem respiration; NEE: net ecosystem exchange; GPP: gross primary productivity; Rn: net radiation; Ta: air temperature; VPD:vapor pressure deficit; SWC: soil water content; IP: the sum of precipitation and irrigation and LAI: leaf area index. Table 6 Regression results of multi-factor liner model between daily carbon flux (NEE, ER and GPP) and environmental variables and LAI, selected according to significant level p<0.01 C arbon flux Year Multi-factor liner model R 2 p NEE 2014 NEE=-0.02Rn-0.05Ta-24.87SWC-1.50LAI+8.03 0.73 <0.01 2015 NEE=-0.04Rn-0.05Ta-1.83LAI+7.29 0.78 <0.01 2016 NEE=-0.03Rn-0.30Ta-1.17VPD-10.19SWC-0.41LAI+10.22 0.72 <0.01 2017 NEE=-0.03Rn-0.07Ta-0.44VPD-1.42LAI+5.07 0.74 <0.01 2018 NEE=-0.01Rn-0.24Ta+3.44SWC-1.22LAI+5.59 0.76 <0.01 Total NEE=-1.03LAI-0.029Rn-1.67Ta-0.03IP+5.72SWC 0..79 <0.01 ER 2014 ER=0.01Rn+0.06Ta+10.06SWC+0.54LAI-1.50 0.79 <0.01 2015 ER=0.004Rn+0.27Ta+1.60VPD+3.36SWC+0.85LAI-4.38 0.78 <0.01 2016 ER=0.003Rn+0.47Ta-2.09VPD-0.09LAI-1.16 0.76 <0.01 2017 ER=-0.002Rn+0.23Ta+0.03VPD+1.15SWC+0.83LAI-1.32 0.90 <0.01 2018 ER=0.002Rn+0.09Ta-0.74SWC+0.87LAI+0.77 0.89 <0.01 Total ER=0.52LAI+0.17Ta+0.01Rn+5.04SWC 0.71 <0.01 GPP 2014 GPP=-0.01Rn+0.04Ta+17.39SWC+2.69LAI-3.36 0.85 <0.01 2015 GPP=0.05Rn+0.53Ta-34.61SWC+2.70LAI-6.04 0.90 <0.01 2016 GPP=0.04Rn+0.77Ta-1.91VPD+8.70SWC+0.33LAI-11.09 0.70 <0.01 2017 GPP=0.02Rn+0.29Ta+0.45VPD+2.26LAI-6.10 0.86 <0.01 2018 GPP=0.02Rn+0.33Ta-4.17SWC+2.09LAI-4.82 0.89 <0.01 Total GPP=1.54LAI+0.03Rn+0.34Ta+0.02IP 0.89 <0.01 Cite Share Download PDF Status: Published Journal Publication published 30 Apr, 2021 Read the published version in Carbon Balance and Management → Version 1 posted Review # 2 received at journal 01 Mar, 2021 Review # 1 received at journal 27 Feb, 2021 Reviewer # 2 agreed at journal 17 Feb, 2021 Reviewer # 1 agreed at journal 14 Feb, 2021 Reviewers invited by journal 02 Dec, 2020 Editor assigned by journal 05 Nov, 2020 Editor invited by journal 05 Nov, 2020 Submission checks completed at journal 01 Nov, 2020 First submitted to journal 29 Oct, 2020 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. 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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-101488","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research","associatedPublications":[],"authors":[{"id":4460126,"identity":"dd8ac29e-8f2f-48b4-bad0-d1207a71bbe1","order_by":0,"name":"Hui Guo","email":"","orcid":"","institution":"China Agricultural University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Guo","suffix":""},{"id":4460127,"identity":"45897088-b0fd-452c-8946-28f55185cc5b","order_by":1,"name":"Sien 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University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Danni","middleName":"","lastName":"Yang","suffix":""},{"id":4460132,"identity":"edee21d7-e05d-4797-9ce5-5f2f82e11c36","order_by":6,"name":"Hon-Ming Lam","email":"","orcid":"","institution":"chinese university of Hong Kong","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hon-Ming","middleName":"","lastName":"Lam","suffix":""}],"badges":[],"createdAt":"2020-11-01 16:48:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-101488/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-101488/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s13021-021-00176-5","type":"published","date":"2021-04-30T21:02:34+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":3521948,"identity":"36ab6f29-fb37-44c9-87bf-5756eb797867","added_by":"auto","created_at":"2020-11-11 22:03:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":54600,"visible":true,"origin":"","legend":"Mean daily values of meteorological factors measured at the experimental sites in growing seasons during 2014-2018: (a) net radiation (Rn), (b) air temperature (Ta), (c) saturated vapor pressure deficit (VPD), (d) soil water content (SWC) and precipitation and irrigation (P+I)","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1/95c891338c11f2fa65977e3b.png"},{"id":3521949,"identity":"80c098fa-0113-400c-9cf1-214aa9ec0bfb","added_by":"auto","created_at":"2020-11-11 22:03:46","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":19746,"visible":true,"origin":"","legend":"Variations in the leaf area index (LAI) of maize during the growing seasons, 2014-2018","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1/16a8a857c7ed6a60d8551607.png"},{"id":3521950,"identity":"d9f63a14-312c-47d1-98be-8bf52e5ef784","added_by":"auto","created_at":"2020-11-11 22:03:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":31110,"visible":true,"origin":"","legend":"Seasonal fluctuations in daily average (a) net ecosystem exchange (NEE), ecosystem respiration (ER) and gross primary productivity (GPP), (b) the cumulative NEE, ER and GPP over the period of 2014-2018.","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1/29844cc8dbe0ce4d7110e7f2.png"},{"id":3521951,"identity":"22337e5c-253e-4a88-8d44-661e82fa0062","added_by":"auto","created_at":"2020-11-11 22:03:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":34017,"visible":true,"origin":"","legend":"The variation of the ratio of ER/GPP in different growing stages during 2014-2018","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1/514d92a3d60040daae834b5e.png"},{"id":3521952,"identity":"9b9b3bda-a17a-461a-8a59-22a94d9bc0ca","added_by":"auto","created_at":"2020-11-11 22:03:46","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":24218,"visible":true,"origin":"","legend":"The seasonal variation in ecosystem respiration (ER) and net ecosystem exchange (NEE) in response to gross primary productivity (GPP) during 2014-2018. * represents a significant level (p \u003c 0.001).","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1/7b011ac413693e76271ce495.png"},{"id":3521953,"identity":"ad846af7-539c-4262-aad5-baabd63babb3","added_by":"auto","created_at":"2020-11-11 22:03:46","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":18323,"visible":true,"origin":"","legend":"The variation of net biome productivity (NBP) in growing seasons during 2014-2018","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1/ffd6887b86396242eaeb4051.png"},{"id":3521954,"identity":"3e893f6d-6940-4de5-9759-c677171b3ff5","added_by":"auto","created_at":"2020-11-11 22:03:46","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":131240,"visible":true,"origin":"","legend":"Structural equation models for daily net ecosystem echange (NEE). ecosystem respiration (ER) and gross primary production (GPP) during the growing season in 2014–2018.","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1/114d2c9e4beab2551616fb02.png"},{"id":13555027,"identity":"91d972d4-fca9-406e-a613-fa0e55dab7a9","added_by":"auto","created_at":"2021-09-17 02:43:25","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":513426,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1_covered.pdf"},{"id":3521955,"identity":"a7b4f09b-27d5-4979-a342-1f15af37040b","added_by":"auto","created_at":"2020-11-11 22:03:50","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1011169,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript1.pdf","url":"https://assets-eu.researchsquare.com/files/rs-101488/v1_stamped.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eDrivers of Carbon Flux in Drip Irrigation Maize Fields in Northwest China\u003c/p\u003e","fulltext":[{"header":"Full Text","content":"\u003cp\u003eThis preprint is available for \u003ca href='/article/rs-101488/latest.pdf' target='_blank'\u003edownload as a PDF\u003c/a\u003e.\u003c/p\u003e"},{"header":"Tables","content":"\n\u003cp\u003eTable 1 The details of irrigation in maize field from 2014 to 2018\u003c/p\u003e\n\u003ctable border=\"1\" width=\"100%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003eDate\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003eIrrigation\u003c/p\u003e\n\u003cp\u003e(mm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003eDate\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003eIrrigation\u003c/p\u003e\n\u003cp\u003e(mm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003eDate\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003eIrrigation\u003c/p\u003e\n\u003cp\u003e(mm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003eDate\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003eIrrigation\u003c/p\u003e\n\u003cp\u003e(mm)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003eDate\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003eIrrigation\u003c/p\u003e\n\u003cp\u003e(mm)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e2014/6/6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2015/6/1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2016/4/24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e51.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2017/4/23\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e35.10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2018/5/1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.77\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e2014/6/23\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2015/6/13\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2016/6/10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e45.47\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2017/6/14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e68.02\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2018/6/7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e53.08\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e2014/6/28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2015/6/26\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2016/6/25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e49.82\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2017/6/25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e64.79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2018/6/18\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e40.58\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e2014/7/7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2015/7/10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2016/7/3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e54.26\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2017/7/10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e62.07\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2018/6/30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e49.62\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e2014/7/18\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2015/7/24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2016/7/15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e65.09\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2017/7/22\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e57.45\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2018/7/11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e55.38\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e2014/7/28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2015/8/7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2016/7/27\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e54.45\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2017/8/8\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e53.76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2018/7/22\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.96\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e2014/8/22\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2015/8/20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2016/8/7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e53.53\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2017/8/22\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e27.09\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2018/8/1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e68.27\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e2015/8/31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e50.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2016/8/22\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e53.19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"10%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"11%\"\u003e\n\u003cp\u003e2018/8/14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"9%\"\u003e\n\u003cp\u003e53.27\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 2 The details of fertilization in maize field from 2014 to 2018\u003c/p\u003e\n\u003ctable border=\"1\" width=\"99%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"8%\"\u003e\n\u003cp\u003eYear\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003eDate\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e(NH4)\u003csub\u003e2\u003c/sub\u003eHPO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003e(kg hm\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003eUrea\u003c/p\u003e\n\u003cp\u003e(kg hm\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003eCompound fertilizer\u003c/p\u003e\n\u003cp\u003e(kg hm\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"3\" width=\"8%\"\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e10-Apr (base fertilizer)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e275.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e42.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e8-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e150.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e5-Jul\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e120.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"6\" width=\"8%\"\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e12-Apr (base fertilizer)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e262.50\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e37.50\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e30-May\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e63.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e9.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e11-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e78.75\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e11.25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e25-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e168.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e24.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e9-Jul\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e126.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e18.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e27-Jul\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e105.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e15.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"3\" width=\"8%\"\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e5-Apr (base fertilizer)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e300.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e225.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e27-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e300.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e15-Jul\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e150.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"3\" width=\"8%\"\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e26-Mar (base fertilizer)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e375.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e375.00\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e15-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e270.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e30-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e180.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"4\" width=\"8%\"\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e26-Mar (base fertilizer)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e375.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e375.00\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e7-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e225.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e18-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e150.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"27%\"\u003e\n\u003cp\u003e30-Jun\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"21%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"22%\"\u003e\n\u003cp\u003e75.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"19%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 3 Dry grain (D\u003csub\u003eg\u003c/sub\u003e), dry cob (D\u003csub\u003ec\u003c/sub\u003e), dry leaf (D\u003csub\u003el\u003c/sub\u003e), dry stem (D\u003csub\u003es\u003c/sub\u003e) and exported carbon (C\u003csub\u003ee\u003c/sub\u003e) in the spring maize field during 2014-2018\u003c/p\u003e\n\u003ctable border=\"1\" width=\"99%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e\u003cstrong\u003eYear\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e\u003cstrong\u003eD\u003csub\u003eg\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(g m\u003csup\u003e-2\u003c/sup\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"20%\"\u003e\n\u003cp\u003e\u003cstrong\u003eD\u003csub\u003ec\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(g m\u003cspan style=\"text-decoration: line-through;\"\u003e\u003csup\u003e-2\u003c/sup\u003e\u003c/span\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e\u003cstrong\u003eD\u003csub\u003el\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(g m\u003csup\u003e-2\u003c/sup\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e\u003cstrong\u003eD\u003csub\u003es\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(g m\u003csup\u003e-2\u003c/sup\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"20%\"\u003e\n\u003cp\u003e\u003cstrong\u003eC\u003csub\u003ee\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e(g C m\u003csup\u003e-2\u003c/sup\u003e)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e904\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"20%\"\u003e\n\u003cp\u003e126.43\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e314.70\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e502.63\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"146\"\u003e\n\u003cp\u003e795.75\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e997\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"20%\"\u003e\n\u003cp\u003e139.44\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e310.42\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e724.63\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"146\"\u003e\n\u003cp\u003e931.98\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e1095\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"20%\"\u003e\n\u003cp\u003e153.15\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"104\"\u003e\n\u003cp\u003e432.91\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"104\"\u003e\n\u003cp\u003e596.09\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"146\"\u003e\n\u003cp\u003e979.73\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e529\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"20%\"\u003e\n\u003cp\u003e73.99\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e192.40\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e614.35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"146\"\u003e\n\u003cp\u003e599.27\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e792\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"20%\"\u003e\n\u003cp\u003e110.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e372.28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e492.23\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"146\"\u003e\n\u003cp\u003e757.55\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e\u003cstrong\u003eAVG\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"104\"\u003e\n\u003cp\u003e\u003cstrong\u003e863.40 \u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"146\"\u003e\n\u003cp\u003e\u003cstrong\u003e120.76 \u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"104\"\u003e\n\u003cp\u003e\u003cstrong\u003e324.54 \u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"104\"\u003e\n\u003cp\u003e\u003cstrong\u003e585.99 \u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"146\"\u003e\n\u003cp\u003e\u003cstrong\u003e812.86 \u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 4 Growing season sums of net ecosystem exchange (NEE), ecosystem respiration (ER) and gross primary productivity (GPP)，NEE\u003csub\u003emax\u003c/sub\u003e is the peak of NEE in the growing season, ER\u003csub\u003emax\u003c/sub\u003e is the maximum value of ecosystem respiration in the growing season, GPP\u003csub\u003emax\u003c/sub\u003e is the maximum value of GPP in the growing seasons\u003c/p\u003e\n\u003ctable border=\"1\" width=\"99%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"2\" width=\"7%\"\u003e\n\u003cp\u003e\u003cstrong\u003eYear\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e\u003cstrong\u003eGrowing days\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eNEE\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eER\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eGPP\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eNEE\u003csub\u003emax\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eER\u003csub\u003emax\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003eGPP\u003csub\u003emax\u003c/sub\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e\u003cstrong\u003e(Day)\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e(g C m\u003csup\u003e-2\u003c/sup\u003e\u003c/strong\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e(g C m\u003csup\u003e-2\u003c/sup\u003e\u003c/strong\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e(g C m\u003csup\u003e-2\u003c/sup\u003e\u003c/strong\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e(g C m\u003csup\u003e-2\u003c/sup\u003e\u003c/strong\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e(g C m\u003csup\u003e-2\u003c/sup\u003e\u003c/strong\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e(g C m\u003csup\u003e-2\u003c/sup\u003e\u003c/strong\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"7%\"\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e134\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-630.13\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e485.46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e1115.54\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-14.32\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e7.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e20.83\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"7%\"\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e132\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-729.89\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e975.46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e1705.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-18.69\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e14.67\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e26.79\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"7%\"\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e144\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-601.18\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e825.81\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e1427.05\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-13.67\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e9.98\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e21.31\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"7%\"\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e142\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-406.76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e661.84\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e1068.63\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-10.98\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e8.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e18.99\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"7%\"\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e146\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-527.47\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e724.94\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e1252.35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-11.42\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e9.14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e17.94\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"7%\"\u003e\n\u003cp\u003e\u003cstrong\u003eMean\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e\u003cstrong\u003e139.6\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e-579.09\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e734.7\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e1313.77\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e\u003cstrong\u003e-13.82\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e10.03\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e21.17\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"7%\"\u003e\n\u003cp\u003e\u003cstrong\u003eSD\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e\u003cstrong\u003e5.57\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e107.89\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e163.58\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e232.07\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e2.75\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e2.44\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e3.06\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"7%\"\u003e\n\u003cp\u003e\u003cstrong\u003eCV\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"18%\"\u003e\n\u003cp\u003e\u003cstrong\u003e0.04\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-0.19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e0.22\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e0.18\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e-0.20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e0.24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"12%\"\u003e\n\u003cp\u003e0.14\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eSD is the standard deviation.\u003c/p\u003e\n\u003cp\u003eCV is coefficient of variation.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 5 Partial correlation coefficients between environmental variables and net ecosystem exchange (NEE), ecosystem respiration (ER) and gross primary productivity (GPP)\u003c/p\u003e\n\u003ctable border=\"1\" width=\"0\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"102\"\u003e\n\u003cp\u003e\u003cstrong\u003eCarbon flux\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"72\"\u003e\n\u003cp\u003e\u003cstrong\u003eYear\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"106\"\u003e\n\u003cp\u003e\u003cstrong\u003eRn\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"72\"\u003e\n\u003cp\u003e\u003cstrong\u003eTa\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"72\"\u003e\n\u003cp\u003e\u003cstrong\u003eVPD\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"72\"\u003e\n\u003cp\u003e\u003cstrong\u003eSWC\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"72\"\u003e\n\u003cp\u003e\u003cstrong\u003eIP\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"91\"\u003e\n\u003cp\u003e\u003cstrong\u003eLAI\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"5\"\u003e\n\u003cp\u003eNEE\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.47**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.320**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.153\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.303**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.176*\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.817**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.390**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.470**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.044\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.148\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.146\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.806**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.625**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.666**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.407**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.266**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.175*\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.497**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.581**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.638**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.449**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.148\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.109\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.749**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.480**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.666**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.293**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.188*\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.765**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"5\"\u003e\n\u003cp\u003eER\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.448**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.395**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.037\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.231**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.013\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.775**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.258**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.733**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.350**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.339**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.034\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.742**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.313**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.675**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.217**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.111\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.05\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.471**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.329**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.770**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.432**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.272**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.114\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.878**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.338**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.618**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.202*\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.384**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.154\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.929**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"5\"\u003e\n\u003cp\u003eGPP\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.499**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.365**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e-0.132\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.303**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.137\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.859**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.376**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.619**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.106\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.237**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.117\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.858**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.596**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.748**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.393**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.247**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.154\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.547**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.523**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.727**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.470**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.204*\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.118\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.845**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.455**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.687**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.001\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.344**\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.186*\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd\u003e\n\u003cp\u003e0.892**\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e** Significantly correlated at the 0.01 level (bilateral) and * significantly correlated at the 0.05 level (bilateral).\u003c/p\u003e\n\u003cp\u003eER: ecosystem respiration; NEE: net ecosystem exchange; GPP: gross primary productivity; Rn: net radiation; Ta: air temperature; VPD:vapor pressure deficit; SWC: soil water content; IP: the sum of precipitation and irrigation and LAI: leaf area index.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 6 \u003c/strong\u003eRegression results of multi-factor liner model between daily carbon flux (NEE, ER and GPP) and environmental variables and LAI, selected according to significant level p\u0026lt;0.01\u003c/p\u003e\n\u003ctable border=\"1\" width=\"99%\"\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e\u003cstrong\u003eC\u003c/strong\u003earbon flux\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u003cstrong\u003eYear\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003e\u003cstrong\u003eMulti-factor liner model\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e\u003cstrong\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u003cstrong\u003ep\u003c/strong\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"5\" width=\"14%\"\u003e\n\u003cp\u003eNEE\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eNEE=-0.02Rn-0.05Ta-24.87SWC-1.50LAI+8.03\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.73\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eNEE=-0.04Rn-0.05Ta-1.83LAI+7.29\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.78\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eNEE=-0.03Rn-0.30Ta-1.17VPD-10.19SWC-0.41LAI+10.22\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.72\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eNEE=-0.03Rn-0.07Ta-0.44VPD-1.42LAI+5.07\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.74\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eNEE=-0.01Rn-0.24Ta+3.44SWC-1.22LAI+5.59\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"14%\"\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003eTotal\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eNEE=-1.03LAI-0.029Rn-1.67Ta-0.03IP+5.72SWC\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0..79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"6\" width=\"14%\"\u003e\n\u003cp\u003eER\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eER=0.01Rn+0.06Ta+10.06SWC+0.54LAI-1.50\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eER=0.004Rn+0.27Ta+1.60VPD+3.36SWC+0.85LAI-4.38\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.78\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eER=0.003Rn+0.47Ta-2.09VPD-0.09LAI-1.16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eER=-0.002Rn+0.23Ta+0.03VPD+1.15SWC+0.83LAI-1.32\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.90\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eER=0.002Rn+0.09Ta-0.74SWC+0.87LAI+0.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.89\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003eTotal\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eER=0.52LAI+0.17Ta+0.01Rn+5.04SWC\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.71\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd rowspan=\"6\" width=\"14%\"\u003e\n\u003cp\u003eGPP\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2014\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eGPP=-0.01Rn+0.04Ta+17.39SWC+2.69LAI-3.36\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.85\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2015\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eGPP=0.05Rn+0.53Ta-34.61SWC+2.70LAI-6.04\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.90\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2016\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eGPP=0.04Rn+0.77Ta-1.91VPD+8.70SWC+0.33LAI-11.09\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.70\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2017\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eGPP=0.02Rn+0.29Ta+0.45VPD+2.26LAI-6.10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.86\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e2018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eGPP=0.02Rn+0.33Ta-4.17SWC+2.09LAI-4.82\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.89\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003eTotal\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"67%\"\u003e\n\u003cp\u003eGPP=1.54LAI+0.03Rn+0.34Ta+0.02IP\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"5%\"\u003e\n\u003cp\u003e0.89\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd width=\"6%\"\u003e\n\u003cp\u003e\u0026lt;0.01\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"carbon-balance-and-management","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cbam","sideBox":"Learn more about [Carbon Balance and Management](https://cbmjournal.biomedcentral.com/)","snPcode":"13021","submissionUrl":"https://submission.nature.com/new-submission/13021/3","title":"Carbon Balance and Management","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"carbon flux, drip-irrigated maize field, gross primary productivity, net ecosystem productivity, ecosystem respiration, net biome productivity","lastPublishedDoi":"10.21203/rs.3.rs-101488/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-101488/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eUnder the escalating threat to sustainable development from the global increase in carbon dioxide concentrations, the variations in carbon flux in the farmland ecosystem and their influencing factors have attracted global attention. Over the past few decades, with the development of eddy covariance technology, the carbon fluxes of forests and grasslands have been determined in many countries. However, studies are very limited for the arid regions in northwestern China, which covers a large area where a mixed mode of agriculture and grazing is practiced. \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e To study the effects of drip irrigation on the net ecosystem productivity (NEE), ecosystem respiration (ER), gross primary production (GPP) and net biome productivity (NBP) in the arid regions of northwestern China, we measured the carbon flux annually from 2014 to 2018 using an eddy covariance system. Our results showed that the maize field carbon flux exhibited single-peak seasonal patterns during the growing seasons. During 2014-2018, the NEE, ER and GPP of the drip-irrigated maize field ranged between -407~-729 g C m\u003csup\u003e-2\u003c/sup\u003e, 485.46~975.46 g C m\u003csup\u003e-2\u003c/sup\u003e, and 1068.23~1705.30 g C m\u003csup\u003e-2\u003c/sup\u003e. In four of the five study years, the ER released back to the atmosphere was just over half of the carbon fixed by photosynthesis. The mean daily NEE, ER and GPP were significantly correlated with the net radiation (Rn), air temperature (Ta), leaf area index (LAI) and soil moisture (SWC). The results of path analysis showed that leaf area index is the main driving force of seasonal variation of carbon flux. When harvested removals were considered, the annual NBP was -234 g C m\u003csup\u003e-2\u003c/sup\u003e, and the drip-irrigated maize field was a carbon source. \u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConclusions: \u003c/strong\u003eThis study shows the variation and influencing factors of NEE, ER and GPP in the growth period of spring maize under film drip irrigation in arid areas of northwest China. The ecosystem was a carbon sink before maize harvest, but it was converted into a carbon source considering the carbon emissions after harvest. The variation of carbon flux was influenced by both environmental and vegetation factors, and its leaf area index was the main driver that affects the seasonal variation of carbon flux.\u003c/p\u003e","manuscriptTitle":"Drivers of Carbon Flux in Drip Irrigation Maize Fields in Northwest China","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2020-11-11 22:03:44","doi":"10.21203/rs.3.rs-101488/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2021-03-02T00:00:00+00:00","index":2,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"editorInvitedReview","content":"","date":"2021-02-28T00:00:00+00:00","index":1,"fulltext":"Recommendation: Reviewer's comments unavailable due to the journal's policy.\n"},{"type":"reviewerAgreed","content":"","date":"2021-02-18T00:00:00+00:00","index":2,"fulltext":""},{"type":"reviewerAgreed","content":"","date":"2021-02-15T00:00:00+00:00","index":1,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2020-12-03T00:00:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2020-11-06T00:00:00+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2020-11-05T23:00:00+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2020-11-01T16:48:05+00:00","index":"","fulltext":""},{"type":"submitted","content":"","date":"2020-10-30T00:00:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"carbon-balance-and-management","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cbam","sideBox":"Learn more about [Carbon Balance and Management](https://cbmjournal.biomedcentral.com/)","snPcode":"13021","submissionUrl":"https://submission.nature.com/new-submission/13021/3","title":"Carbon Balance and Management","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7ce90153-f4eb-4b52-bebf-ff55b5a3f2fe","owner":[],"postedDate":"November 11th, 2020","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":1027275,"name":"Environmental Policy"}],"tags":[],"updatedAt":"2021-07-27T21:02:34+00:00","versionOfRecord":{"articleIdentity":"rs-101488","link":"https://doi.org/10.1186/s13021-021-00176-5","journal":{"identity":"carbon-balance-and-management","isVorOnly":false,"title":"Carbon Balance and Management"},"publishedOn":"2021-04-30 21:02:34","publishedOnDateReadable":"April 30th, 2021"},"versionCreatedAt":"2020-11-11 22:03:44","video":"","vorDoi":"10.1186/s13021-021-00176-5","vorDoiUrl":"https://doi.org/10.1186/s13021-021-00176-5","workflowStages":[]},"version":"v1","identity":"rs-101488","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-101488","identity":"rs-101488","version":["v1"]},"buildId":"WrCJVZZCHTDjtuVLN7oU0","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}
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