Fertile island effects across soil depths in drylands of the Tibetan Plateau

Abstract Background and aims In arid regions, patches of vegetation serve a vital function in carbon and nutrient sequestration, fostering the emergence of 'fertile islands' within the soil beneath their canopies. However, the variation in the fertile island effects across soil depth remains an open question. Methods To explore this, we sampled soils from two different layers (0-30 cm and 30-50 cm) within perennial vegetation patches and open areas across 54 drylands dispersed across the Tibetan Plateau. Our study focused on six key soil variables related to carbon, nitrogen, and phosphorus stocks, allowing us to assess the differences in fertile island effects at these varying depths. Results Among six soil fertility parameters, organic carbon exhibited the most pronounced fertile island effect at both soil depths.. In the surface soil, the influence of vegetation in soil carbon content intensified with increasing precipitation seasonality and precipitation in the wettest quarter but declined with increasing temperature during the driest quarter. Conversely, in the deeper soil layer, the fertile island effect for nitrogen and phosphorus intensified with greater soil sand content and vegetation greenness. Conclusions The fertile island effects responded differently to environmental factors at these two depths. These findings offer fresh and valuable insights into the interplay between environmental drivers and fertile island effects, a critical aspect of dryland ecosystems worldwide.