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<p>Amid global precipitation changes, it remains unclear whether hydrological niche separation (HNS) mechanisms apply to herbaceous plant communities in desert steppes are severely affected by seasonal drought. How these plants access limited water and tolerate drought to coexist also remains unverified. In this study, we employed stable isotope techniques to examine water acquisition and drought adaptation in coexisting species of the desert steppe in northern China under five precipitation treatments, i.e., decreased 50%, decreased 30%, ambient, increased 30%, and increased 50% precipitation. The following results showed that: (1) water sources of coexisting species shifted with changes in precipitation amount and timing, i.e., all coexisting plants exhibited preferential utilization of surface soil moisture. When surface soil moisture was scarce, they shifted to deeper water sources, and when deep water sources remained scarce, they were forced to compete more intensely for surface water sources; (2) community’s HNS was affected by precipitation amount but not by timing, i.e., with adequate soil moisture, plant water source ranges expanded, reducing overlap and enhancing HNS, whereas under extreme drought, the range contracted and increased the overlap, although HNS remained stable; and (3) water acquisition strategies of coexisting species differed along hydrological niche axis defined by water stress adaptability (i.e., stable carbon isotope composition and proline content). <i>Convolvulus ammannii</i> Desr. had the strongest drought adaptation, although its strategy showed a weak correlation with water uptake. <i>Stipa breviflora</i> Griseb., with moderate drought resistance, adopted a water-conserving strategy that was suitable for extreme drought. <i>Leymus secalinus</i> (Georgi) Tzvelev, <i>Polygala tenuifolia</i> Willd., and <i>Larix potaninii</i> Batalin showed resource-dependent and flexible water strategies, thriving in wetter soils but struggling under extreme drought. Our findings indicated that herbaceous species in desert steppes adapted their water uptake and drought tolerance strategies according to changes in precipitation amount and timing. As a core regulatory mechanism, HNS (under increasing precipitation variability due to climate change) not only supports species coexistence by reducing interspecific competition, but also promotes efficient soil moisture use. This mechanism enhances community drought resistance and contributes to ecosystem stability. Overall, this study provides key ecological evidence for understanding plant community adaptation in arid and semi-arid areas facing the influence of global climate change.</p>

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Spatiotemporal niche separation mechanisms of water utilization strategies in the desert steppe plant communities, northern China

  • 期刊论文

  • 发表日期：

    2025年12月18日

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  • Kechen Song,
  • Haiying Hu,
  • Hao Zhang,
  • Siyu Guan,
  • Wenhui Deng,
  • Jiayi Yong,
  • Xiaona Zhao,
  • Xing Wang

摘要

Amid global precipitation changes, it remains unclear whether hydrological niche separation (HNS) mechanisms apply to herbaceous plant communities in desert steppes are severely affected by seasonal drought. How these plants access limited water and tolerate drought to coexist also remains unverified. In this study, we employed stable isotope techniques to examine water acquisition and drought adaptation in coexisting species of the desert steppe in northern China under five precipitation treatments, i.e., decreased 50%, decreased 30%, ambient, increased 30%, and increased 50% precipitation. The following results showed that: (1) water sources of coexisting species shifted with changes in precipitation amount and timing, i.e., all coexisting plants exhibited preferential utilization of surface soil moisture. When surface soil moisture was scarce, they shifted to deeper water sources, and when deep water sources remained scarce, they were forced to compete more intensely for surface water sources; (2) community’s HNS was affected by precipitation amount but not by timing, i.e., with adequate soil moisture, plant water source ranges expanded, reducing overlap and enhancing HNS, whereas under extreme drought, the range contracted and increased the overlap, although HNS remained stable; and (3) water acquisition strategies of coexisting species differed along hydrological niche axis defined by water stress adaptability (i.e., stable carbon isotope composition and proline content). Convolvulus ammannii Desr. had the strongest drought adaptation, although its strategy showed a weak correlation with water uptake. Stipa breviflora Griseb., with moderate drought resistance, adopted a water-conserving strategy that was suitable for extreme drought. Leymus secalinus (Georgi) Tzvelev, Polygala tenuifolia Willd., and Larix potaninii Batalin showed resource-dependent and flexible water strategies, thriving in wetter soils but struggling under extreme drought. Our findings indicated that herbaceous species in desert steppes adapted their water uptake and drought tolerance strategies according to changes in precipitation amount and timing. As a core regulatory mechanism, HNS (under increasing precipitation variability due to climate change) not only supports species coexistence by reducing interspecific competition, but also promotes efficient soil moisture use. This mechanism enhances community drought resistance and contributes to ecosystem stability. Overall, this study provides key ecological evidence for understanding plant community adaptation in arid and semi-arid areas facing the influence of global climate change.