太白山森林群落和林下草本物种变化的环境解释

Environmental Interpretation of Variations on Forest Community and Understory Herbaceous in Taibai Mountain,Shaanxi,China

采用典范对应分析(CCA)、Pearson相关分析、冗余分析(RDA)分别研究了不同环境因子对太白山森林群落及林下草本物种组成、多样性、功能性状等方面的影响。结果表明:(1)9种环境因子对于群落及林下草本物种的组成变化的解释程度不高,分别为23.9%和21.1%,但与海拔和土壤含水量紧密相关的CCA 1轴能大致区分高、中、低海拔样方的群落所有物种和草本植物的组成差异。(2)沿海拔梯度,群落所有物种的α多样性先增加后降低,林下草本物种α多样性沿海拔梯度有下降趋势,但二者都与坡度(Slope)及木本层盖度(WCD)无关。(3)海拔是决定森林群落及林下草本层物种功能性状值变化的主要因子,与海拔密切相关的RDA1轴能解释森林群落和林下草本物种性状值变化的71.2%和54.7%,林下草本植物与群落的最大株高(Hmax)变化模式不一致。

Our study aimed to determine the relationship between the environment factors and these varia tion patterns. Also,we examined the difference of variation patterns between forest community and under- story herb layer only. The canonical correspondence analysis （CCA） was used for testing the relationship between 9 environment factors and species composition data. A correlation test was determined the rela- tionship between environment factors and species ~ diversity. Redundancy analysis （RDA） was used to ana- lyze the importance of environment factors on plant functional traits. We also tested the Pearson correlation coefficient of community ~ diversity and functional traits between forest community and understory herb layer. We found that：l） 9 environment factors had a poor power to explain the change of both forest corn munity and understory herb layer. However,the axis 1 of CCA could distinguish the altitude range of each plot in both modes. 2） Along the elevation, the Shannon-Wiener index of forest community at first in- creased and then decreased while the Shannon Wiener index of understory herb layer decreased monoton- ously. 3）The Shannon-Wiener index of both community and herb layer was independence to slope and woody species layer cover degree（WCD）. The axis 1 of RDA which related to altitude could explain 71.2 of total trait variation for forest community and 54.7 % for understory herb layer. The variation pattern of plant max height value （H ） of forest community and herb layer was different.