青藏高原高寒草地植物的群落性状和功能在降水梯度上调控了生物量的分配权衡

了解在不同生态系统中植物生物量分配的调控机制是阐明植物适应性策略的重要理论基础。目前,虽然生境条件对植物生物量分配的影响已被广泛研究,但对植物群落性状和功能(plant community traits and functions,PCTF)如何调控生物量分配,特别是在高寒草地生态系统中的研究却较少。本研究计算了在群落水平上的5种叶片功能性状的群落加权平均值(community-weighted means,CWM),并利用相关分析、方差分解分析和结构方程模型探讨了PCTF与生物量权衡之间的关系。研究结果发现,高寒草甸(alpine meadow,AM)和高寒草原(alpine steppe,AS)的权衡值都大于零,但两者存在显著差异,AM的权衡值(0.203)明显高于AS(0.088)。此外,决定AS生物量分配的关键因素是物种丰富度(0.69)和叶片干物质含量(CWM_(LDMC),0.42),而在AM中,关键因素是叶片干物质含量(CWM_(LDMC),0.48)和叶片碳含量(CWM_(LC)-0.45)。值得注意的是,无论AS中的CWM_(LDMC)和物种丰富度,还是AM中的CWM_(LDMC)和CWM_(LC)都主要受气候因素中的降水调节。总而言之,降水往往通过对PCTF的影响来调控高寒草地的生物量分配,因此强调了PCTF在调节降水梯度上植物生物量分配策略的重要性。

Climate Signals from Tree Ring Chronologies of the Upper and Lower Treelines in the Dulan Region of the Northeastern Qinghai-Tibetan Plateau

The radial growth of trees In mountainous areas is subject to environmental conditions associated with changes In elevation. To assess the sensitivity of tree-ring growth to climate variation over a wide range of elevations, we compared the chronological characteristics of Sabina przewalskii Kom. and their relationships with climatic variables at the upper and lower treellnes In the Dulan region of the northeastern Qlnghal-Tlbetan Plateau. It was found that the radial growth in this region was controlled primarily by precipitation in late spring and early summer （from May to June）. In addition, a higher temperature from April to June could Intensify drought stress and lead to narrow tree rings. The significant similarity In climate-tree growth relationships at both the upper and lower treellnes Indicated that tree rings of S. przewalskU In this region are able to provide common regional climate information. However, the chronologies at the lower forest limits showed a higher standard deviation and more significant correlations with climatic factors, suggesting that the radial growth there was more significantly Influenced by climate variation. The first principal component of the four chronologies showed a common growth response to local climate. The second principal component showed a contrasting growth response between different sampling sites. The third principal component revealed different growth patterns In response to altitudinal variation. Further analysis Indicated that the precipitation In late spring and early summer controlled the growth of S. przewalskii on a regional scale and that other factors, such as mlcroenvlronment at the sampling sites, also affected the strength of the climatic response of tree growth.