Mechanisms underlying the impacts of extreme temperatures on carbon and energy fluxes in dryland ecosystems

IF 5.7 1区农林科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Catena Pub Date : 2025-08-28 DOI:10.1016/j.catena.2025.109401

Simin Zhang , Tingxi Liu , Limin Duan , Yongzhi Bao , Lina Hao , Xin Tong , V.P. Singh

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Abstract

Under global climate change, the increasing frequency and intensity of extreme temperature events have significantly affected carbon and energy fluxes in dryland ecosystems. However, the underlying response mechanisms and the regulatory role of water availability remain insufficiently quantified. Based on long-term growing-season observations (2013–2024) in the Horqin Sandy Land, this study quantitatively characterized the impacts of extreme low-temperature (ELT) and extreme high-temperature (EHT) events on carbon (NEE, Reco, GPP) and energy (Rn, LE, H) fluxes in dune and meadow ecosystems, from the dual perspectives of flux anomalies and change rates, while incorporating soil moisture gradients (VWC ± ). The results showed that during the study period, EHT&VWC + events increased significantly (by 65 % in dunes and 37 % in meadows), while ELT&VWC − events sharply declined (by 89 % in dunes and 63 % in meadows). Carbon fluxes in dunes were highly sensitive to soil moisture conditions, with drought-induced carbon release reversible to a carbon sink upon water supplementation. In contrast, meadows exhibited stronger temperature adaptability, maintaining a stable carbon sink function (−0.20/-0.25 g C m^–2d^–1) under high-temperature drought regardless of soil water variation, likely due to their deeper root systems and higher evaporative cooling capacity, which buffer heat stress and sustain photosynthetic activity. The two ecosystems exhibited distinct energy allocation strategies: dunes dissipated energy primarily by enhancing sensible heat flux (H sensitivity = 0.90), whereas meadows prioritized the regulation of latent heat flux (LE sensitivity = 0.84). This study proposed an “event frequency–water regulation–flux response” framework, which provided methodological support and empirical basis for the resilience assessment of dryland ecosystems to climate extremes and the optimization of management strategies.

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极端温度对旱地生态系统碳和能量通量影响的机制

在全球气候变化背景下，极端温度事件的频率和强度不断增加，显著影响了旱地生态系统的碳和能量通量。然而，潜在的反应机制和水供应的调节作用仍然没有充分量化。基于2013-2024年科尔沁沙地长期生长季观测数据，结合土壤水分梯度（VWC±），从通量异常和变化率的双重视角，定量表征了极端低温（ELT）和极端高温（EHT）事件对沙丘和草甸生态系统碳（NEE、Reco、GPP）和能量（Rn、LE、H）通量的影响。结果表明：研究期间，eht&vwc +事件显著增加（沙丘增加65%，草甸增加37%），elt&vwc−事件急剧减少（沙丘减少89%，草甸减少63%）。沙丘的碳通量对土壤湿度条件高度敏感，干旱引起的碳释放在补充水分后可逆地转化为碳汇。相比之下，草甸表现出更强的温度适应性，在高温干旱条件下保持稳定的碳汇功能（- 0.20/-0.25 g C m-2d-1），无论土壤水分变化如何，这可能是由于草甸根系较深，蒸发冷却能力较强，可以缓冲热胁迫，维持光合活性。两个生态系统的能量分配策略不同，沙丘主要通过增强感热通量来耗散能量（H敏感性= 0.90），草甸则优先调节潜热通量（LE敏感性= 0.84）。本研究提出了“事件频率-水量调节-通量响应”框架，为旱地生态系统对极端气候的适应能力评估和管理策略优化提供了方法支持和经验依据。

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来源期刊

Catena 环境科学-地球科学综合

CiteScore

10.50

自引率

9.70%

发文量

816

审稿时长

54 days

期刊介绍： Catena publishes papers describing original field and laboratory investigations and reviews on geoecology and landscape evolution with emphasis on interdisciplinary aspects of soil science, hydrology and geomorphology. It aims to disseminate new knowledge and foster better understanding of the physical environment, of evolutionary sequences that have resulted in past and current landscapes, and of the natural processes that are likely to determine the fate of our terrestrial environment. Papers within any one of the above topics are welcome provided they are of sufficiently wide interest and relevance.