[Interspecific association between understory species in a southern highland plantation].

Based upon 2 x 2 contingency table, chi2 test and association coefficient were used to determine the interspecific association between understory species in a southern highland plantation, and to analyze the restoration degree and the stability of southern highland vegetations originated from plantation. The Qianyanzhou in Taihe County of Jiangxi Province, a typical sample of southern highland plantation, was chosen to make the study. The results showed that both in shrub layer and in herb layer, species pair with chi2 reaching significant level (P <0.05) was few in number. In shrub layer, 12 species pairs' association was highly significant (P < 0.01), 19 pairs' was significant (P < 0.05), and other 200 pairs' was nonsignificant, while in herb layer, 11 pairs' was highly significant, 11 pairs' was significant and other 83 pairs' was nonsignificant. According to interspecific association and correlation, shrub layer was divided into two species groups: Group I . Adinandra bockiana, Syzygiumn grijsii, Vaccinium bracteatunm, Ilex aculeolata, Smilax ferox, Eurya muricata and Group II . Lespedeza davidii, Serissa serissoides, Vitex negundo var. cannabifolia. Many species in Group I had a significantly negative association with the species in Group II, and dominant species always played a key role in the relationships among species. The three dominant species in herb layer, Wooduardia japonica, Dryopteris atrata and Adiantun flabellulaturn, had a highly significant positive correlation between each other, and moreover, had a significant or highly significant positive association with many other herbaceous species. Similarily, dominant species in shrub layer played a key role on the interspecific association in the two species groups. The ratios of positive and negative association indicating the species compositions of the two layers were fluctuating, which was 125/106 in shrub layer and 42/63 in herb layer. Several shortcomings of interspecific association method were pointed out, with some proposals put forward.