Responses of hydraulics at the whole-plant level to simulated nitrogen deposition of different levels in Fraxinus mandshurica
Responses of hydraulics at the whole-plant level to simulated nitrogen deposition of different levels in Fraxinus mandshurica
复制标题
水曲柳全株水力学对不同水平氮沉降模拟的响应
DOI：
10.1093/treephys/tpw048
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发表时间：
2016
期刊：
影响因子：
4
通讯作者：
Guang-You Hao
中科院分区：
文献类型：
--
作者：
Ai-Ying Wang;Miao Wang;Da Yang;Jia Song;Wei-Wei Zhang;Shi-Jie Han;Guang-You Hao
氮沉降通过影响植物与环境的相互作用对森林生态系统产生重大影响，其中之一就是通过改变植物的水力结构来影响植物的水分关系。然而，有一个令人惊讶的是缺乏综合研究树木水力结构响应氮沉降，特别是在整个植物水平。在本研究中，我们使用了一个5年的N添加实验来模拟6个不同水平的N沉降（20-120 kg ha− 1 year −1）对优势树种（水曲柳）生长和全株导水率的影响。 来自中国东北典型的温带森林。结果表明，通过中等浓度的施肥（20-80 kg ha− 1 year −1）缓解氮限制促进了植物生长，但在阈值水平之上进一步增加氮对植物生长产生负面影响。 F.不同浓度的氮素处理均伴随着全株导水率的相应变化，生长速率越高，全株导水率（Kplant）越低，叶片水分利用效率越高。通过对全株水分运输途径各组分导水率的详细分析，发现根和叶导水率的变化是影响钾肥对氮肥反应的主要因素，而茎导水率的变化不是影响钾肥对氮肥反应的主要因素。植物生长和水力结构对增加氮添加水平的反应都不是线性的，即，氮素有效性与各测定参数的相关性呈钟形曲线，在中等施氮水平下达到峰值。在本研究中发现，在响应施肥的水力结构的变化可能是一个重要的潜在机制，通常观察到的变化与水有关的树的性能，在响应氮沉降。
Nitrogen (N) deposition is expected to have great impact on forest ecosystems by affecting many aspects of plant–environmental interactions, one of which involves its influences on plant water relations through modifications of plant hydraulic architecture. However, there is a surprising lack of integrative study on tree hydraulic architecture responses to N deposition, especially at the whole-plant level. In the present study, we used a 5-year N addition experiment to simulate the effects of six different levels of N deposition (20–120 kg ha−1year−1) on growth and whole-plant hydraulic conductance of a dominant tree species (Fraxinus mandshuricaRupr.) from the typical temperate forest of NE China. The results showed that alleviation of N limitation by moderate concentrations of fertilization (20–80 kg ha−1year−1) promoted plant growth, but further N additions on top of the threshold level showed negative effects on plant growth. Growth responses ofF. mandshuricaseedlings to N addition of different concentrations were accompanied by corresponding changes in whole-plant hydraulic conductance; higher growth rate was accompanied by reduced whole-plant hydraulic conductance (Kplant) and higher leaf water-use efficiency. A detailed analysis on hydraulic conductance of different components of the whole-plant water transport pathway revealed that changes in root and leaf hydraulic conductance, rather than that of the stem, were responsible forKplantresponses to N fertilization. Both plant growth and hydraulic architecture responses to increasing levels of N addition were not linear, i.e., the correlation between measured parameters and N availability exhibited bell-shaped curves with peak values observed at medium levels of N fertilization. Changes in hydraulic architecture in response to fertilization found in the present study may represent an important underlying mechanism for the commonly observed changes in water-related tree performances in response to N deposition.