Impact of Cutting Intensity on Forest Stand Growth and Understand Species Diversity of the Mixed Plantations of Cunninghamia lanceolata and Broadleaved Trees

The objective of this study was to explore the impact of cutting intensity on forest growth and plant diversity in mixed plantation of Cunninghamia lanceolata and broadleaved trees and provide a scientific basis for improving forest quality and species diversity. Taking the mixed plantation of Cunninghamia lanceolata and broadleaved trees in northern Fujian Province in China as the research object, different cutting intensities were treated as experimental conditions in August 2011. Selected cutting intensity was medium intensity（MI） 34.6%, high intensity（HI） 48.6%, extra-high intensity（EHI） 67.6%, respectively, and non-cutting（NC） was used as the control. Based on track survey data in the year after cutting, 3, 5 and 10 years after cutting, the impact of cutting intensity on standing growth and plant diversity of the forest were analyzed. The results showed the average annual growth of mean diameter at breast height（DBH） from large to small was MI, HI, EHI, NC, and the parameter MI was 17. 2% higher than NC. There were no significant differences among the various cutting intensity（P＞0. 05）. The average annual growth of the tree height of the stand was slightly lower than that of NC and there were no significant differences（P＞0. 05）. The annual growth of the sectional area at breast height of the single plant from large to small was MI, EHI, HI, NC, and the parameter in MI was 84. 8% higher than NC. The annual growth of the stock volume of single plant from large to small was MI, EHI, HI, NC, and the parameter in MI was 82. 6% high-er than NC. MI, HI and EHI were significantly higher than NC. The species richness, diversity and evenness of the shrub layer from large to small were EHI, HI, MI, NC, and EHI was significantly higher than NC（P＞0. 05）, which were 1. 76 times, 1. 43 times and 1. 13 times of NC. The species richness and diversity of herbal layer from large to small were EHI, HI, MI, NC, and EHI was signifi-cantly higher than NC（P＜0. 05）, which were 2. 17 times and 1. 92 times of NC. However, there was no significant difference in the species evenness of herb layer among all the cutting intensities（P＞0. 05）. It could be concluded that selective cutting can effectively promote the stand growth and the species diversity of understory shrub and herb layers in the mixed plantation of Cunninghamia lanceolata and broadleaved trees in northern Fujian Province in short term. Selective cutting at medium intensity were beneficial to acceler-ate the growth of stand and selective cutting at extra high intensity can increase the species diversity of understory shrub layer and herb layer.