Effects of thinning on growth and vegetation diversity of Pinus massoniana plantation

In order to find out the optimum thinning intensity,the influences of thinning intensity on the stand-diameter structure,growth and the plants diversity were studied by selecting the planted Pinus massoniana pure forest of 12-year-old as tested objects.The results show that(1) The breast height and single tree volume increased with the increase of thinning,there was significantly different among thinning treatments.The tree height and the unit area stand volume increased first and then decreased,and there was no significantly different among thinning intensities.(2)The analysis on the trees number of different diameter classes indicated that differences were very significant or significant at various treatments except 18,20,22 three diameter classes.With the increases of thinning intensity,the number of plant growth to larger diameter class increased,and the rate of smaller diameter class gradually declined.(3)With the increase of thinning intensity,the number of species,the Simpson index,the Shannon-Wiener index,richness and uniformity increased first and then decreased.Species diversity was highest at medium thinning,and it decreased with heavy thinning.