Effect Of Thinning On Plantation Of Pinus Tabulaeformis And Platycladus Orientalis In Low Mountainous Areas Of North Beijing

The Platycladus orientalis plantation and Pinus tabulaeformis plantation,which cover an a rea of 60,106 hm2 and 59,816.8 hm2,count for 20% of the total non-commercial forests respectively, are major non-commercial plantation in Beijing mountainous aeras and im-porving quality of the stand is the key stone of ecological construction in Beijing. Discussing the effect of thinning on Platycladus orientalis and Pinus tabulaeformis plantation,which provide theoretical basis for forest ecosystem management,in order to play a variety of benefits of non-commercial plantation in Beijing mountainous aeras.This test selected Platycladus orientalis plantation on sunny slope with thick soi,shady slope with thick soil,sunny slope with thin soil and Pinus tabulaeformis plantation on shady slope with thick soil with light,medium and heavy thinning in Shui zhang village of miyun and longsha,hanbaoshan of changping in 2004.The growing of stand,the undergrowth diversity,the soil improvement and hydrological effects of litter were investigated and analyzed in 2009 in the basis of the results of Jia Zhong kui in 2005. The data was analysed by principale component analysis with spss 16.0 in order to evaluate the different effects of thinning.The results showed:(1) The effect of thinning on the litter amount and water retention is obvious.After thinning, Contrasted with the control,the litter amount increased 19.0%-268.3% maximal litter water retention rate increased 2.9%-28.7%, maximal litter water retention increased 24.3%-379.3%, The effect of medium thinning was the most obvious.(2) The soil bulk density was reduced, the soil total porosity and soil infiltration were increased after thinning,the improvement of 0-10cm was better than 10-20cm obviously.In the depth of 0-10cm, the soil bulk density of Platycladus orientalis with different sites decreased 18.9% at most, the soil total porosity increased 19.1%at most, the soil bulk density of Pinus tabulaeformis decreased 3.9%-7.9%, the soil total porosity increased 2.9%-7.3%;After 5 years of thinning,the water conservation and the total water-holding capacity increased significantly, the effect of medium thinning was the most effective measure. The water conservation and the total water-holding capacity increased 37.1% and 14.3% respectively at most of Platycladus orientalis, increased 47.8% and 7.7% respectively at most of Pinus tabulaeformis which indicated that thinning measure could improve soil water conservation;The soil nutrient,organic matter and enzyme activity increased in different extent,but the effect of thinning on the soil catalase was not significant in some stand.In total,the thinning had a significant effect on the soil improvement. The principale component analysis of the soil improvement showed that the medium thinning measure was suitable for the Platycladus orientalis plantation on sunny slope with thick soil,while the heavy thinning measure wsas suitable for other three stands.(3) The species of the undergrowth were all increased after different extent thinning. Shannon-Wiener index was sensitive toward thinning intensity, Contrasted with the control,the Shannon-Wiener index of bush and herbal increased 25.2%-74.8% and 15.8%-109.7% respectively.The total biomass of the undergrowth incresed obviously and 1.5-4.3 times more than the control.(4) Thinning was benefit for promoting the growth of the stand and the effect was different to different growth index of different stands.In total, the thinning had a great effect on the DBH,crown and individual volume,while the effect on the height and the total volume was not obvious.After thinning,the average annual growth amount of DBH,height,crown and individual volume was 126.9%,40.9%,9.4 times and 105.9% more than the control respectively.(5) The principale component analysis of different stands showed that the heavy thinning was suitable for Platycladus orientalis plantation on shady slope with thick soil,Platycladus orientalis plantation on sunny slope with thin soil and Pinus tabulaeformis plantation on shady slope with thick soil, the medium thinning was suitable for Platycladus orientalis plantation on sunny slope with thick soil.In conclusion, thinning was benefit for promoting the growth of the stand,improving the function of water conservation of the litter,increasing the soil water conservation and soil fertility,increasing diversity of the undergrowth, improving stability of the stand. Therefore, resonable thinning measures shoud be adopted to control the density of the stand acording to the evaluation results,so as to comprehensive benefits of forests.