Journal of Plant Ecology ›› 2021, Vol. 14 ›› Issue (6): 1158-1174.DOI: 10.1093/jpe/rtab062

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  • 收稿日期:2020-12-19 修回日期:2021-02-07 接受日期:2021-05-22 出版日期:2021-12-01 发布日期:2021-06-11

Dominant roles but distinct effects of groundwater depth on regulating leaf and fine-root N, P and N:P ratios of plant communities

Yin Wang1,2, Jianming Wang1,2,3, Xiaolin Wang1,2, Yicheng He1,2, Guanjun Li1,2 and Jingwen Li1,2,*   

  1. 1 School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China, 2 Ejina Institute of Populus euphratica, Beijing Forestry University, Inner Mongolia 735400, China, 3 Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

    *Corresponding author. E-mail: Lijingwenhy@bjfu.edu.cn
  • Received:2020-12-19 Revised:2021-02-07 Accepted:2021-05-22 Online:2021-12-01 Published:2021-06-11

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摘要： 地下水位对植物群落叶片与细根氮磷化学计量特征的调控作用不同但影响显著
地下水作为干旱区水资源可利用性的决定因素，在调节植被分布和生态系统过程中具有至关重要的作用。尽管近年来在环境胁迫与群落水平性状的关系方面取得了较大的研究进展，但对于干旱区地下水变化所引起的水分胁迫如何影响植物群落水平化学计量比仍知之甚少。本研究的目的是评估植物群落地上地下部分化学计量比对地下水变化的不同响应。我们通过对典型干旱内陆河流域的110个样方进行调查，测定叶片和细根的氮磷含量，利用生物量加权法计算其化学计量比，并试图探究沿地下水位梯度，群落水平的化学计量比的变化模式及其关键驱动因素。研究结果表明，在群落水平上，地下水、植被类型以及物种组成是影响叶片与细根氮、磷与氮磷比的主要因素，其中地下水位起着主导性作用。地下水的作用主要表现为间接作用，其主要通过调控植被类型和物种组成来影响群落水平的氮磷化学计量比。植被类型和物种组成均对群落水平的氮磷化学计量比具有显著的直接作用。此外，在群落水平上，地下水对叶片与细根氮磷化学计量比的作用不同。地下水通过影响植被类型进而降低叶片氮、磷含量，以及增加叶片氮磷比与细根氮含量。地下水通过影响物种组成进而增加细根磷含量，降低细根氮磷比。综上所述，地下水而不是气候有效的调控了群落水平的氮磷化学计量比。此外，植物群落地上地下部分氮磷化学计量比对地下水位变化具有不同的响应。

关键词: 生态化学计量比, 地下水位, 氮磷比, 细根, 叶片, 干旱内陆河流域

Abstract:

Aims

As the determinant of water availability in drylands, groundwater plays a fundamental role in regulating vegetation distribution and ecosystem processes. Although considerable progress has been made over the past years in the relationship between environment stress and plant community-level traits, the potential influence of water stress induced by groundwater changes on plant community-level stoichiometry remains largely unclear. Here, we examined whether belowground and aboveground community-level stoichiometry responded differently to groundwater changes.

Methods

We measured nitrogen (N) and phosphorus (P) concentrations in plant leaves and fine-roots of 110 plots under a broad range of groundwater depths in a typical arid inland river basin. We examined the spatial patterns and drivers of community-level N:P stoichiometry in leaves and fine-roots.

Important Findings

Community-level leaf and fine-root N, P and N:P ratios were mainly determined by groundwater, vegetation types and species composition, among which groundwater played a dominant role. Groundwater indirectly regulated community-level N:P stoichiometry through affecting vegetation types and species composition. Vegetation types and species composition had significant direct influences on community-level N:P stoichiometry. Furthermore, groundwater depth had opposite influences on community-level leaf and fine-root N:P stoichiometry. Groundwater depth regulated vegetation types and further decreased leaf N, P but increased leaf N:P ratios and fine-root N. Groundwater depth had a positive indirect impact on fine-root P but a negative indirect impact on fine-root N:P ratios primarily by affecting species composition. Our findings indicate that groundwater rather than climate conditions effectively regulates community-level N:P stoichiometry, and below- and aboveground N:P stoichiometry has opposite responses to groundwater.

Key words: ecological stoichiometry, groundwater depth, N:P ratio, fine-root, leaf, arid inland river basin

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