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南方科技大学公共卫生及应急管理学院2026级博士研究生招生报考通知（长期有效）

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[交流] [优秀文章推荐]中科院揭示冻土碳循环对气候变暖响应已有2人参与

野外增温实验发现气候变暖仅促进生长季前期总初级生产力

　　中国科学院植物研究所获悉，该所研究员杨元合研究组的最新一项研究揭示了气候变暖对冻土碳循环的直接效应及其调控因素。相关研究论文近日在线发表在《生态学（Ecology）》杂志上。

　　冻土区储存着大量有机碳，同时也经历了显著的气候变暖。大量研究显示，冻土生态系统碳循环对气候变暖十分敏感。这是因为一方面，温度上升会提高土壤微生物活性，进而加速生态系统碳释放；另一方面，气候变暖也会促进土壤氮磷矿化，促进植物生长，进而增加生态系统碳固定。然而，学术界迄今仍不清楚增温引起的养分变化究竟如何调控冻土生态系统碳交换过程。

生长季前期总初级生产力对增温的响应受温度和植被指数的共同影响（a-b），而生长季后期的响应则受植物养分的调控（c-d）

　　为了解决上述科学问题，中国科学院植物研究所杨元合研究组选择青藏高原多年冻土区内的高寒沼泽化草甸这一类特殊的生态系统，避免了以往增温实验中“温度上升引起土壤含水量下降”的缺陷，进而揭示了气候变暖对冻土碳循环的直接效应及其调控因素。通过2014年至2016年连续3个生长季的野外监测，研究人员发现温度上升增加了生长季前期生态系统碳固定，但这种促进效应在生长季后期消失，这一现象主要与植物提前衰老引起的叶片氮磷浓度下降有关。上述结果表明，增温引起的植物养分变化并没有增加生态系统的碳固定，反而抑制了增温对生态系统碳固定的促进效应。

　　该研究为认识气候变暖背景下生态系统碳-氮-磷交互作用提供了新视角，对理解冻土碳循环与气候变暖之间的反馈关系具有重要启示。相关结果并不支持学术界关于“气候变暖引起的养分变化有利于生态系统碳固定”的传统认识，意味着气候变暖情景下养分对生态系统碳交换的调控比以往预想的更为复杂。

　　Large uncertainties exist in carbon (C)-climate feedback in permafrost regions, partly due to an insufficient understanding of warming effects on nutrient availabilities and their subsequent impacts on vegetation C sequestration. Although a warming climate may promote a substantial release of soil C to the atmosphere, a warming-induced increase in soil nutrient availability may enhance plant productivity, thus offsetting C loss from microbial respiration. Here, we present evidence that the positive temperature effect on carbon dioxide (CO2) fluxes may be weakened by reduced plant nitrogen (N) and phosphorous (P) concentrations in a Tibetan permafrost ecosystem. Although experimental warming initially enhanced ecosystem CO2 uptake, the increased rate disappeared after the period of peak plant growth during the early growing season, even though soil moisture was not a limiting factor in this swamp meadow ecosystem. We observed that warming did not significantly affect soil extractable N or P during the period of peak growth, but decreased both N and P concentrations in the leaves of dominant plant species, likely caused by accelerated plant senescence in the warmed plots. The attenuated warming effect on CO2 assimilation during the late growing season was associated with lowered leaf N and P concentrations. These findings suggest that warming-mediated nutrient changes may not always benefit ecosystem C uptake in permafrost regions, making our ability to predict the C balance in these warming-sensitive ecosystems more challenging than previously thought.

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