The role of root-zone soil moisture in delaying vegetation responses to drought: Comparative insights from karst and non-karst areas

IF 6.3 1区地球科学 Q1 ENGINEERING, CIVIL

Journal of Hydrology Pub Date : 2025-09-06 DOI:10.1016/j.jhydrol.2025.134216

Yeye Liu, Jinjiao Lian, Yunpeng Nie, Kelin Wang, Hongsong Chen

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Abstract

Vegetation loss occurs when soil moisture falls below a critical threshold, above which vegetation can withstand drought stress. Root-zone soil moisture (SM_root) is crucial for enhancing drought resistance and sustaining ecosystem stability, yet its role in shaping drought thresholds and how these thresholds differ between karst and non-karst regions remains poorly understood. Here, we quantified drought thresholds (T_SM) from both surface soil moisture (SM_surf) and SM_root across contrasting lithologies to evaluate how geological settings modulates vegetation drought responses. We found pronounced spatial heterogeneity in T_SM, with higher values in the peak forest plain (14.7th percentile) and basins, reflecting heightened atmospheric demand and greater drought vulnerability, whereas lower values in the karst plateau and gorge (10.3rd percentile) indicated stronger drought resistance. T_SM exhibited a significant increasing trend during 2001–2018, implying a gradual decline in drought resistance. SM_root-based thresholds (11.3rd percentile) were consistently lower than those derived from SM_surf (12.9th percentile), highlighting the role of SM_root in delaying the onset of drought stress. Karst ecosystems exhibited lower T_SM than non-karst systems, especially in croplands and forests, indicating that vegetation in karst landscapes operates under drier conditions yet maintains higher drought tolerance. However, projections under future climate scenarios reveal greater drought risks in karst ecosystems, particularly under strong warming. Furthermore, climatic controls on T_SM also differed between lithologies: in non-karst regions, thresholds responded coherently to plant-available water, whereas in karst regions, correlations with plant-available water alternated between positive and negative. This contrasting behavior suggests that karst vegetation flexibly shifts between shallow soil moisture and deeper bedrock water. These findings underscore the critical role of SM_root in mitigating drought impacts and reveal that geological settings shape ecosystem drought resilience under changing climates.

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根区土壤水分在延缓植被对干旱响应中的作用：喀斯特和非喀斯特地区的比较见解

当土壤湿度低于一个临界阈值时，植被就会损失，超过这个阈值植被就能承受干旱胁迫。根区土壤水分（SMroot）对增强抗旱性和维持生态系统稳定性至关重要，但其在形成干旱阈值中的作用以及这些阈值在喀斯特和非喀斯特地区之间的差异尚不清楚。在这里，我们量化了不同岩性的地表土壤湿度（SMsurf）和地表土壤湿度（SMroot）的干旱阈值（TSM），以评估地质环境如何调节植被干旱响应。研究发现，峰顶森林平原和流域的TSM值较高（14.7个百分位），反映了大气需求增加和干旱脆弱性，而喀斯特高原和峡谷的TSM值较低（10.3个百分位）表明抗旱性较强。2001-2018年，TSM呈显著上升趋势，抗旱性逐渐下降。基于SMroot的阈值（11.3百分位数）始终低于SMsurf的阈值（12.9百分位数），这突出了SMroot在延迟干旱胁迫发生中的作用。喀斯特生态系统的TSM低于非喀斯特生态系统，尤其是农田和森林，说明喀斯特生态系统的植被在干旱条件下仍保持着较高的耐旱性。然而，对未来气候情景的预测表明，喀斯特生态系统的干旱风险更大，特别是在强变暖的情况下。此外，不同岩性对TSM的气候控制也不同：在非喀斯特地区，阈值对植物有效水分的响应一致，而在喀斯特地区，与植物有效水分的相关性在正负之间交替。这种对比行为表明喀斯特植被在浅层土壤水分和深层基岩水分之间灵活转换。这些发现强调了SMroot在缓解干旱影响中的关键作用，并揭示了地质环境对气候变化下生态系统干旱恢复能力的影响。

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来源期刊

Journal of Hydrology 地学-地球科学综合

CiteScore

11.00

自引率

12.50%

发文量

1309

审稿时长

7.5 months

期刊介绍： The Journal of Hydrology publishes original research papers and comprehensive reviews in all the subfields of the hydrological sciences including water based management and policy issues that impact on economics and society. These comprise, but are not limited to the physical, chemical, biogeochemical, stochastic and systems aspects of surface and groundwater hydrology, hydrometeorology and hydrogeology. Relevant topics incorporating the insights and methodologies of disciplines such as climatology, water resource systems, hydraulics, agrohydrology, geomorphology, soil science, instrumentation and remote sensing, civil and environmental engineering are included. Social science perspectives on hydrological problems such as resource and ecological economics, environmental sociology, psychology and behavioural science, management and policy analysis are also invited. Multi-and interdisciplinary analyses of hydrological problems are within scope. The science published in the Journal of Hydrology is relevant to catchment scales rather than exclusively to a local scale or site.