Influences of Conservation for Regeneration on Plant Diversity of Ecological Cunninghamia lanceolata Forest at Different Development Stage in Zhejiang

Ecological Cunninghamia lanceolata forest was divided into three development stages(≤10-year as young, 11-20-year as half-mature and > 20-year as mature) and two forest types(pure C. lanceolata forest and mixed forest with C. lanceolata) in Zhejiang province. 67 sample plots in 23 counties were established for monitoring plant diversities at tree, shrub and herb layer in different forest types. The results showed that at tree layer of pure C. lanceolata forest, plant diversity index increased slowly (<15%), and heterogeneity and homogeneity was higher than that at herb layer in mature forest, while at shrub layer, plant diversity index of pure C. lanceolata forest was not high at young stage, species numbers and heterogeneity increased slowly (<5%). Gleason index at herb layer decreased from 2.62 to 1.68 because of the increase of closure. Mixed young forest had the highest plant diversity index at shrub layer, half-mature one had the lowest species numbers and heterogeneity. Plant diversity index at different layer in different development stages was ordered by shrub layer>tree layer> herb layer, Gleason index of herb layer was an exception. Plant diversity at tree and shrub layer of pure C. lanceolata forest with different development stage was lower than mixed forest. Species richness, heterogeneity and evenness index of herb layer in pure young C. lanceolata forest was higher than that in mixed forest, and got close in half-mature one, but lower in mature than that in mixed forest. The study found that plant diversity of pure C. lanceolata forest was lower than that of mixed forest in the same developmental stage