The dynamic changes of species diversity of Eucalyptus urophylla × E. grandis and Acacia mangium plantations in Gaoyao, Guangdong.

Three permanent plots in Eucalyptus urophylla × E.grandis and Acacia mangium plantations were set up in Gaoyao,Guangdong province to measure the species diversities of the understory and herbage layers,with the employment of four diversity indexes: species abundance,Shannon-Wiener diversity,Simpson diversity and Pielou evenness indexes.Investigations were carried out in 2004 and 2007.The results are as follows:(1) The number of species decreased in the understory layer of E.urophylla×E.grandis plantation from 25 in 2004 to 22 in 2007,while the number of species increased greatly in the herbage layer from 31 in 2004 to 47 in 2007;while all of Shannon-Wiener,Simpson diversity indexes and Pielou evenness index increased in these two layers.And the number of disappeared species in the understory layer was more than that of the newly appeared species in 2007,which was contrary to the herbage layer.(2) The number of species decreased in both the understory and the herbage layers of A.mangium plantation,while Shannon-Wiener,Simpson diversity indexes and Pielou evenness index decreased or changed a little.The numbers of disappeared species were more than that of the newly appeared species in both the understory and the herbage layers in 2007.