Studies on the stability of different communities in Nonggang karst region of Guangxi

Five aspects of nine stability evaluating index such as coverage of local species and local species diversity are selected to constitute index system. And then, the stability of the Southwest Guangxi karst communities are evaluated and analyzed comprehensively by means of principal components analysis and grey relational analysis. Correspondingly, three grades(highly, moderately and lowly stable community)of stableness are classified according to classification formula of stability. The results show that: the communities such as Cephalomappa sinensis + Bischofia polycarpa - Drypetes perreticulata- Ophiopogon dracaenoides community, have higher stability index, while the com munities such as Eupatorium odoratum+ Pueraria phaseoloides community have lower stability index. The community Cephalomappa sinensis+ Bischofia polycarpa- Drypetes perreticulata- Ophiopogon dracaenoides and other seven com munities are classified as the highly stable community; the community Melia azedarach+ Zeniain signis- Mallotus japonicus- Microstegium fasciculatum+ Eupatorium odoratum and other three communities are classified as the moderately stable community; the community Eupatorium odoratum+ Pueraria phaseoloides, Trigonostemon lutescens+ litsea glutinosa- Eupatorium odoratum and other thirteen com munities are classified as lowly stable community. The order of vegetation stability, native forests> secondary natural forest> shrub/ plantation> grass, reflects the stability of the law of succession, i.e. community stability increases as the succession goes on.