ABSTRACT

Habitat loss of forest tree species distributed in cold temperate and alpine zones is a serious issue in the context of global warming. Considering that intraspecific variation is essential for adaptation to changing environments, intraspecific variation in seed weight, leaf traits, and sapling size of a sub-alpine broad-leaved tree species, Betula ermanii, was examined in this study using seeds collected from 11 populations across its natural distribution. Seeds were sown in seed beds, and containerized seedlings were grown in a greenhouse with a uniform environment (a common garden experiment). The effects of four climate variables, i.e. warmth index (WI), minimum temperature of the coldest month (TMC), summer precipitation (PRS), and maximum snow depth (MSD) were evaluated on seed weight, leaf functional traits, and sapling size using a generalized linear mixed model (GLMM). Positive latitudinal clines were detected for seed weight, whereas negative clines were detected for both specific leaf area and leaf nitrogen. These clines were not consistent with the general trends observed in previous studies. The reasons might be partly explained by geographic variation in climatic variables and nutrient availability. The findings obtained from this study should be useful for conservation of mountainous forest ecosystems in the age of climate change.

摘要

在全球变暖的背景下，分布在寒温带和高山地区的森林树种的栖息地丧失是一个严重的问题。考虑到种内变异对于适应不断变化的环境、种内变异在亚高山阔叶树种Betula ermanii 的种子重量、叶片性状和树苗大小方面至关重要，在本研究中使用从其自然分布的 11 个种群收集的种子进行了检查。将种子播种在苗床中，容器化的幼苗在环境均匀的温室中生长（常见的花园实验）。评估了四个气候变量，即温暖指数 (WI)、最冷月最低温度 (TMC)、夏季降水 (PRS) 和最大积雪深度 (MSD) 对种子重量、叶片功能性状和树苗大小的影响使用广义线性混合模型 (GLMM)。检测到种子重量的正纬度基因，而检测特定叶面积和叶氮的负基因。这些基因与先前研究中观察到的总体趋势不一致。部分原因可能是气候变量和养分供应的地理差异。从这项研究中获得的结果应该有助于在气候变化时代保护山地森林生态系统。