黄土高原四种乡土牧草群落种—面积曲线拟合及最小面积的确定

Fitting and assessment of species-area curves of four native pasture communities on Loess Plateau

探讨了黄土高原4种乡土牧草的种-面积曲线应遵从的基本条件,分别对7个经典模型进行拟合,从中确定以下4个模型作为研究方法,S=b+alnA、S=aln(bA+1)、S=aAb、S=aA/(1+bA),采用了SAS8.1、MATLAB6.5系统对其分别进行拟合求解及作图,以F值检验结果作为评价指标,检验后淘汰前三个模型,以曲线S=aA/(1+bA)作为标准,提出求取该曲线的二阶导数,以其二阶导数趋于0的点为群落的最小面积的新方法,并得出达乌里胡枝子、无芒隐子草、冰草、白羊草的群落最小面积分别为3.4、4.1、1.4、4.8m2。由于4个群落都符合该模型故可以认为它是黄土高原草本植物群落的种-面积曲线的最优模型。

According to the investigation scale and the research purpose, the basic conditions for species-area curves on Loess Plateau have been analyzed. Four typical models were adopted in the study: (S=b+alnA,) S=aln(bA+1), S=aA^b, S=aA/(1+bA) . With the aid of SAS8.1 and MATLAB6.5 system, the first three models were fallen into disuse according to the F value of fitting curves. The model S=aA/(1+bA) was regarded as the standard curve to get second derivative species-area for the communities of Lespedeza davurica (Laxm.) Schindl, Cleistogenes songorica (Roshev) Ohwi, Agropyron cristatum (L.) Gaertn,and Bothriochioa ischaemum (L.) Keng, that is, 3.4 m^2, 4.1 m^2, 1.4 m^2 and 4.8 m^2. Since this model fitted all the communities well, it was considered as the best species-area model for the herbage plant communities on Loess plateau.