Diversity of understory herbs in Picea forests with different stand densities.

To explain the relevance of stand density and understory vegetation diversity in cold, temperate coniferous forests, the Picea(spruce) forests in the Pangquangou Nature Reserve of Guandi Mountain, Shanxi Province were selected as a representative study. In the experiment, twenty seven sample plots were set in stands with nine stand densities(475, 500, 525, 675, 700, 800, 900, 925 and 1 000 trees·hm-2) and three replicates. The sample plot area is 400 m2( 20 m × 20 m). Species composition of understory herbaceous plants was determined in all replicates and the relevance between stand density and diversity index was analyzed using Simpson, Shannon-Wiener Diversity, Pielou Evenness Indexes and Richness. Results showed(1)37 species of herbs belonging to 35 genera in 18 families.(2) The diversity indexes of herbaceous plants decreased with an increase in stand density: with a stand density of 475 trees·hm-2the Simpson Index was0.82, the Shannon-Wiener Index was 1.97, and the Pielou Index was 0.71; whereas, at 1 000 trees·hm-2the Simpson Index was 0.54, the Shannon-Wiener Index was 1.18, and the Pielou Index was 0.39.(3) With different stand densities, the Richness of herbaceous plants ranged from 14 to 23. Thus, in cold, temperate coniferous forests with Picea as the main species, the diversity index of understory herbs decreased with a stand density increase.