Li Xiangyun, Zuo Xiaoan, Yue Ping, Zhao Xueyong, Hu Ya, Guo Xinxin, Guo Aixia, Xu Chong, Yu Qiang
Urat Desert-Grassland Research Station, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Science, Lanzhou, 730000, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
BMC Ecol Evol. 2021 Jun 1;21(1):106. doi: 10.1186/s12862-021-01842-5.
Increasing drought induced by global climate changes is altering the structure and function of grassland ecosystems. However, there is a lack of understanding of how drought affects the trade-off of above- and belowground biomass in desert steppe. We conducted a four-year (2015-2018) drought experiment to examine the responses of community above-and belowground biomass (AGB and BGB) to manipulated drought and natural drought in the early period of growing season (from March to June) in a desert steppe. We compared the associations of drought with species diversity (species richness and density), community-weighted means (CWM) of five traits, and soil factors (soil Water, soil carbon content, and soil nitrogen content) for grass communities. Meanwhile, we used the structural equation modeling (SEM) to elucidate whether drought affects AGB and BGB by altering species diversity, functional traits, or soil factors.
We found that manipulated drought affected soil water content, but not on soil carbon and nitrogen content. Experimental drought reduced the species richness, and species modified the CWM of traits to cope with a natural drought of an early time in the growing season. We also found that the experimental and natural drought decreased AGB, while natural drought increased BGB. AGB was positively correlated with species richness, density, CWM of plant height, and soil water. BGB was negatively correlated with CWM of plant height, CWM of leaf dry matter content, and soil nitrogen content, while was positively correlated with CWM of specific leaf area, CWM of leaf nitrogen content, soil water, and soil carbon content. The SEM results indicated that the experimental and natural drought indirectly decreased AGB by reducing species richness and plant height, while natural drought and soil nitrogen content directly affected BGB.
These results suggest that species richness and functional traits can modulate the effects of drought on AGB, however natural drought and soil nitrogen determine BGB. Our findings demonstrate that the long-term observation and experiment are necessary to understand the underlying mechanism of the allocation and trade-off of community above-and belowground biomass.
全球气候变化导致干旱加剧，正在改变草原生态系统的结构和功能。然而，对于干旱如何影响荒漠草原地上和地下生物量的权衡，人们还缺乏了解。我们进行了一项为期四年（2015 - 2018年）的干旱实验，以研究荒漠草原生长季早期（3月至6月），群落地上和地下生物量（AGB和BGB）对人工控制干旱和自然干旱的响应。我们比较了干旱与草本群落物种多样性（物种丰富度和密度）、五个性状的群落加权均值（CWM）以及土壤因子（土壤水分、土壤碳含量和土壤氮含量）之间的关系。同时，我们使用结构方程模型（SEM）来阐明干旱是否通过改变物种多样性、功能性状或土壤因子来影响AGB和BGB。
我们发现人工控制干旱影响了土壤含水量，但对土壤碳和氮含量没有影响。实验性干旱降低了物种丰富度，物种改变了性状的CWM以应对生长季早期的自然干旱。我们还发现实验性干旱和自然干旱均降低了AGB，而自然干旱增加了BGB。AGB与物种丰富度、密度、株高CWM和土壤水分呈正相关。BGB与株高CWM、叶干物质含量CWM和土壤氮含量呈负相关，而与比叶面积CWM、叶氮含量CWM、土壤水分和土壤碳含量呈正相关。SEM结果表明，实验性干旱和自然干旱通过降低物种丰富度和株高间接降低了AGB，而自然干旱和土壤氮含量直接影响BGB。
这些结果表明，物种丰富度和功能性状可以调节干旱对AGB的影响，然而自然干旱和土壤氮决定了BGB。我们的研究结果表明，需要进行长期观测和实验，以了解群落地上和地下生物量分配与权衡的潜在机制。
