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Drought and heat wave impacts on grassland carbon cycling across hierarchical levels.
Plant, Cell & Environment ( IF 7.3 ) Pub Date : 2020-04-19 , DOI: 10.1111/pce.13767
Linfeng Li 1, 2 , Zhenzhen Zheng 1 , Joel A Biederman 3 , Ruyan Qian 1 , Qinwei Ran 1 , Biao Zhang 1 , Cong Xu 1 , Fang Wang 1, 2 , Shutong Zhou 1 , Rongxiao Che 4 , Junfu Dong 1 , Zhihong Xu 2 , Xiaoyong Cui 1, 5 , Yanbin Hao 1, 5 , Yanfen Wang 1, 5
Affiliation  

Droughts and heat waves are increasing in magnitude and frequency, altering the carbon cycle. However, understanding of the underlying response mechanisms remains poor, especially for the combination (hot drought). We conducted a 4-year field experiment to examine both individual and interactive effects of drought and heat wave on carbon cycling of a semiarid grassland across individual, functional group, community and ecosystem levels. Drought did not change below-ground biomass (BGB) or above-ground biomass (AGB) due to compensation effects between grass and non-grass functional groups. However, consistently decreased BGB under heat waves limited such compensation effects, resulting in reduced AGB. Ecosystem CO2 fluxes were suppressed by droughts, attributed to stomatal closure-induced reductions in leaf photosynthesis and decreased AGB of grasses, while CO2 fluxes were little affected by heat waves. Overall the hot drought produced the lowest leaf photosynthesis, AGB and ecosystem CO2 fluxes although the interactions between heat wave and drought were usually not significant. Our results highlight that the functional group compensatory effects that maintain community-level AGB rely on feedback of root system responses, and that plant adjustments at the individual level, together with shifts in composition at the functional group level, co-regulate ecosystem carbon sink strength under climate extremes.

中文翻译:

干旱和热浪对草地碳循环的跨层次影响。

干旱和热浪的强度和频率都在增加,改变了碳循环。然而,对潜在响应机制的理解仍然很差,特别是对于组合(热干旱)。我们进行了一项为期 4 年的田间试验,以研究干旱和热浪对半干旱草地碳循环的个体和交互影响,跨越个体、功能群、社区和生态系统。由于草和非草功能组之间的补偿效应,干旱没有改变地下生物量 (BGB) 或地上生物量 (AGB)。然而,在热浪下持续降低 BGB 限制了这种补偿效果,导致 AGB 降低。生态系统 CO2 通量受到干旱抑制,归因于气孔关闭引起的叶片光合作用减少和草的 AGB 减少,而 CO2 通量几乎不受热浪的影响。总体而言,尽管热浪和干旱之间的相互作用通常不显着,但热干旱产生的叶片光合作用、AGB 和生态系统 CO2 通量最低。我们的研究结果强调,维持群落水平 AGB 的功能群补偿效应依赖于根系反应的反馈,个体水平的植物调整,以及功能群水平的组成变化,共同调节生态系统碳汇强度在极端气候条件下。AGB 和生态系统 CO2 通量,尽管热浪和干旱之间的相互作用通常不显着。我们的研究结果强调,维持群落水平 AGB 的功能群补偿效应依赖于根系反应的反馈,个体水平的植物调整,以及功能群水平的组成变化,共同调节生态系统碳汇强度在极端气候条件下。AGB 和生态系统 CO2 通量,尽管热浪和干旱之间的相互作用通常不显着。我们的研究结果强调,维持群落水平 AGB 的功能群补偿效应依赖于根系反应的反馈,个体水平的植物调整,以及功能群水平的组成变化,共同调节生态系统碳汇强度在极端气候条件下。
更新日期:2020-04-19
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