Biodiv Sci ›› 2004, Vol. 12 ›› Issue (3): 354-360.DOI: 10.17520/biods.2004043
• 论文 •
QIN Lin, YU Shi-Xiao*
The complexity of a forest community is defined as having the average amount of its information by eliminating the uncertainties of species and layers of a tree individual randomly selected from all trees in the forest community. The joint entropy H(X,Y) is proposed to measure the complexity of a forest community H(X,Y)=H(X)+H(Y|X), in which H(X)=-∑[DD(]Si=1[DD)][SX(]niN[SX)]log2([SX(]niN[SX)]) and H(Y|X)=-∑[DD(]Si=1[DD)][SX(]niN[SX)]∑[DD(]4j=1[DD)][SX(]nijni[SX)]log2([SX(]nijni[SX)]), where S stands for the number of tree species (X), N for the total number of individuals in the forest community, ni for the number of the ith tree species, and nij ?for the number of the ith tree species in the jth layer. H(X) is defined as the compositional complexity of tree species and H(Y|X) as the structural complexity of tree species. The higher the H(X,Y) value, the greater the complexity in the forest community. A case study is presented based on the survey data from three types of forest communities in Heishiding Nature Reserve, Guangdong Province. Three sampling plots were established, each with a size of 60 m×60 m, representing coniferous forest, mixed coniferous broadleaved forest and evergreen broadleaved forest. Each plot was divided into 36 quadrats with a size of 10 m×10 m. The data for all trees with DBH1 cm were gathered, including their coordinates in the sampling plots. Tree sizes were divided into four categories based on their DBH: DBH1, 5, 10, and 30 cm. Using computer simulation, 13 types of quadrat sizes (12 m×12 m, 16 m×16 m, …, 60 m×60 m) within a plot were objectively selected based on the method of nested quadrat sampling. The results show that the order of H(X,Y) of three typical forest types is as follows: evergreen broadleaved forest > mixed coniferous broadleaved forest > coniferous forest. At the same time, the fractal relationships between H(X,Y) and sampling size among the three forest types reveal that H(X,Y) has a statistical selfsimilarity feature.
QIN Lin, YU Shi-Xiao. Complexity of forest communities:a case study of three different forest types in Heishiding Nature Reserve, Guangdong[J]. Biodiv Sci, 2004, 12(3): 354-360.
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