宝天曼国家级自然保护区木本植物多样性及土壤养分的海拔梯度格局

Altitudinal Gradient Pattern of Woody Species Diversity and Soil Nutrients in Baotianman National Nature Reserve

为了探究宝天曼国家级自然保护区内不同海拔梯度对木本植物多样性及土壤养分的影响,采用野外调查、样品采集和统计分析相结合的方法,揭示该保护区海拔1 000~1 700 m山地的木本植物多样性和土壤养分的垂直分布格局。沿海拔梯度每隔100 m设置3个样方(20 m×20 m),8个海拔高度共设置24个样方,调查样方内所有木本植物的物种名称、胸径(DBH≥1 cm)、树高、坐标等,并对每个样地的土壤进行采样。计算不同样地木本植物的Simpson指数、Shannon-Wiener指数和Pielou均匀度,以及各样地之间的Cody指数,测定土壤全氮、有机质、速效钾、速效磷质量分数等土壤指标。采用单因素方差分析法、皮尔逊(Pearson)相关性分析法以及冗余分析(RDA)法分析pH、速效磷、速效钾、全氮、有机质和海拔等因素与物种多样性之间的相关性。结果表明:(1)Simpson多样性指数、Shannon-Wiener指数、Pielou均匀度指数沿海拔梯度呈现下降趋势,且均在海拔1 300~1 400 m范围内出现波动,Cody指数在1 400 m海拔和1 000 m处达到峰值;(2)土壤养分随海拔的增加呈现出下降的趋势,但速效磷、速效钾、全氮质量分数的最低值都出现在海拔1 300 m;(3)Pielou均匀度指数与土壤理化性质显著相关,与pH极显著相关,Simpson指数、Shannon-Wiener指数则与土壤速效磷、速效钾质量分数呈现显著相关;(4)海拔变化对物种多样性的解释度最大(61.6%),土壤养分中速效磷对物种多样性解释度最高为12.8%。随着海拔的增加,物种多样性指数和土壤养分整体呈现下降趋势。

In order to explore the influence of different altitude gradients on woody plant diversity and soil nutrients in Baotianman National Nature Reserve, the sample method was used to analyze the species diversity and the vertical distribution pattern of soil nutrients in the 1 000-1 700 m mountains in the reserve. Three plots (20 m×20 m) were set every 100 m along the altitude gradient. A total of 24 plots (20 m×20 m) were selected with 8 altitudinal gradients. Species names, diameter at breast height (DBH), tree height and coordinates of all woody plants (DBH≥1 cm) were registered and the soil in each sample plot was sampled and analyzed. The Simpson index, Shannon-Wiener index and Pielou index of woody plants for different plots, and Cody index between different plots were calculated. The contents of total nitrogen (TN), soil organic matter (SOM), available potassium (AK), available phosphorus (AP), and other soil indexes were also measured and analyzed. One-Way ANOVA, Pearson correlation analysis and redundancy analysis were used to analyze the correlations between pH, AP, AK, TN, SOM and altitudinal with species diversity. The results showed that: (1) The Simpson index, Shannon-Wiener index, Pielou index were all negatively correlated with altitudinal gradient change with a fluctuation at the elevations of 1 300-1 400 m. The Cody indexwas peaking between 1 400 and 1 000 m altitudinal (18.78). (2) Soil nutrients were negatively correlated with elevation change while the minimum content of AP, AK, and TN were found in the 1 300 m elevation transect. (3) Pielou index was significantly correlated with soil physicochemical properties, and the correlation with pH reached a very significant level, whereas Simpson index and Shannon-Wiener index showed more correlation with AK and AP. (4) Among all the environmental factors, altitudinal factors showed the correlation with species diversity (61.6%). In soil nutrient factors, the readily available nutrient of soil explained more species diversity (12.8%). As a whole, the species diversity index and soil nutrients showed a downward trend with increasing elevation.