摘要
Structure, species composition, and soil properties of a subtropical evergreen broad-leaved forest in Okinawa, Japan, were examined by establishment of plots at thirty sites. The forest was characterized by a relatively low canopy and a large number of small-diameter trees. Mean canopy height for this forest was 10 m and stands contained an average of 5400 stems-ha^-1 （ -〉 3.0 cm DBH）; 64% of those stems were smaller than 10 cm DBH. The total basal area was 54.4 m^2-ha^-1, of which Castanopsis sieboldii contributed 48%. The forest showed high species diversity of trees. 80 tree species （≥ 3.0 cm DBH） from 31 families was identified in the thirty sampling plots. C. sieboldii and Schima wallichii were the dominant and subdominant species in terms of importance value. The mean tree species diversity indices for the plots were, 3.36 for Diversity index （H＇）, 0.71 for Equitability index （J＇） and 4.72 for Species richness index （S＇）, all of which strongly declined with the increase of importance value of the dominant, C. sieboldii. Measures of soil nutrients indicated low fertility, extreme heterogeneity and possible A1 toxicity. Regression analysis showed that stem density and the dominant tree height were significantly correlated with soil pH. There was a significant positive relationship between species diversity index and soil exchangeable K^＋, Ca^2＋, and Ca^2＋/Al^3- ratio （all p values 〈0.001） and a negative relationship with N, C and P. The results suggest that soil property is a major factor influencing forest composition and structure within the subtropical forest in Okinawa.
采用样地调查法,对日本冲绳岛北部的亚热带常绿阔叶林的林分结构,树种组成以及土壤特性等进行了调查分析。结果表明,该亚热带林具有林冠低矮、小径木多等特点。林分的平均林冠高度仅10m,平均立木密度达5400株·hm2(≥3.0cmDBH),其中胸径小于10cm的立木占64%。林分胸高断面积为54.4m2·hm-2。30个调查样地共出现树种数(≥3.0cmDBH)达80种,分属31个科。根据树种的重要值,Castanopsis sieboldii和Schima wallichii分别为优势树种和亚优势树种。树种多样性指数(H’)平均达3.63,均衡度指数(J’)为0.71,丰富度指数(S’)为4.72。这些多样性指数都随着优势树种重要值的增加而显著降低。土壤养分测定结果表明,该森林的土壤肥力低,异质性大,并可能存在Al毒害。由相关分析知,林分密度和优势树高均与土壤pH值呈显著正相关关系;多样性指数则与土壤交换性K+,Ca2+以及Ca2+/Al3+比呈显著的正相关,而与土壤有机碳,全氮和磷呈显著的负相关。这些结果说明土壤性质是影响冲绳亚热带常绿阔叶林林分结构和树种组成多样性的重要因素。图3表4参38。
基金
supported by National Natural Science Foundation of China (No.30471386)
Japanese Society for Promotion of Sciences (15P03118)
