Xie Dong, Wu Zhigang, Chen Han Y H, Wang Zhong, Wang Qiang, Yu Dan
The National Field Station of Freshwater Ecosystem in Liangzi Lake, College of Life Sciences, Wuhan University, Wuhan, China.
Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, China.
Front Plant Sci. 2018 Aug 2;9:1129. doi: 10.3389/fpls.2018.01129. eCollection 2018.
Temperature comprises a major driver for species distribution and physiological processes in alpine plants. For all terrestrial plant species tested to date, elevation associated decreases in temperature have been observed to influence the balance between carbon acquisition and usage; restricting the upper limit of most alpine trees (i.e., treeline). However, such a carbon source-sink balance has not been tested in any alpine aquatic plants, which is an important component of the alpine aquatic ecosystem. The species inhabits a broad range of habitats across the high-altitude plateau. Three species (, , and ) from 12 water bodies at elevational gradients between 2766 and 5111 m were collected in the Qinghai-Tibetan Plateau. The late growing seasonal concentrations of non-structural carbohydrates (NSC) in the leaves were measured to find how high-altitude conditions influence the carbon balance in aquatic plants. Regression tree analysis separated the 12 water bodies into two groups according to water turbidity (seven water bodies with high turbidity and five water bodies with low turbidity). Overall, leaf NSC concentrations (primarily starch) decreased significantly with increasing elevation in widely distributed and . Regression tree analysis indicated that water turbidity (i.e., shady environment) was a strong determinant of leaf NSC. In the low turbidity group (<3.5 NTU), leaf NSC concentrations decreased with increasing elevation; however, in the high turbidity group (>3.5 NTU), leaf NSC concentrations were low and had no association with elevation. Unlike most recent studies in tree species, which show low temperatures limited growth at high-elevations, our results demonstrated that carbon gain limitation is the primary mechanism for the elevational distribution limit of species in the Qinghai-Tibetan Plateau. Moreover, water turbidity moderated the effects of low temperature by masking the expected carbon limitation trend. Therefore, at least two environmental factors (i.e., temperature and light availability) induced photosynthesis decreases might explain the NSC responses for aquatic plants in response to elevation.
温度是高山植物物种分布和生理过程的主要驱动因素。对于迄今为止测试的所有陆地植物物种，已观察到海拔升高导致的温度降低会影响碳获取与利用之间的平衡；限制了大多数高山树木的上限（即树线）。然而，这种碳源 - 汇平衡尚未在任何高山水生植物中得到测试，而高山水生植物是高山水生生态系统的重要组成部分。该物种栖息于高海拔高原的广泛栖息地。在青藏高原海拔2766至5111米的海拔梯度上，从12个水体中采集了3个物种（、和）。测量了叶片中非结构性碳水化合物（NSC）在生长后期的浓度，以了解高海拔条件如何影响水生植物的碳平衡。回归树分析根据水体浊度将12个水体分为两组（7个高浊度水体和5个低浊度水体）。总体而言，广泛分布的和中叶片NSC浓度（主要是淀粉）随海拔升高显著降低。回归树分析表明，水体浊度（即阴暗环境）是叶片NSC的一个重要决定因素。在低浊度组（<3.5 NTU）中，叶片NSC浓度随海拔升高而降低；然而，在高浊度组（>3.5 NTU）中，叶片NSC浓度较低且与海拔无关。与最近大多数关于树种的研究不同，那些研究表明低温限制了高海拔地区的生长，我们的结果表明，碳获取限制是青藏高原物种海拔分布限制的主要机制。此外，水体浊度通过掩盖预期的碳限制趋势来缓和低温的影响。因此，至少两个环境因素（即温度和光照可用性）导致的光合作用下降可能解释了水生植物对海拔升高的NSC响应。
