| Larix principis-rupprechtii Mayr.is the main forest ecological tree species,which distributes widely and accumulates superlatively in North Hebei Mountain area.It plays an irreplaceable role in aspects of water conservation and windbreak and sand fixatio,forming and maintaining ecosystem of forests areas;it relieves sandstorm invasion from Inner Mongolia Plateau Hunshadake Sandy Land to Beijing-Tianjin area;Meanwhile,it purifies the water quality of Luanhe fiver upstream,so it is green Barrier of ecological security of Beijing-Tianjin area.As a main management objective tree species in Mulan Forest Bureau, its quality is directly related to ecological construction in Beijing-Tianjin area.This thesis studied on growth of trees and change of floristic diversity under different retention density after tending of Larix principis-rupprechtii Mayr.systematically and analyzed tending effect synthetically,which will provide theoretical basis to determine reasonable management density and specific tending measure,main results are as follows:1 After tending of the Larix principis-rupprechtii Mayr.on semi-shady slope,shade slope and high mountain flatland,the DBH,height,crown of the tending group were higher than that of the control group.Compared with the control,the reserve density of semi-shady slope increased by 15.2%～50.0%,shade slope increased by 8.2%～44.8%in Ba Yingzhuang forest farm;High mountain flatland increased by 7.3%～72.2%.Compared with the control,crown of the tending group increased by14.6%～46.4%,8.7%～40.4%, 21.2%-50.9%;average stands height of the tending group increased by 9.7%-26.2%, 4.1%～21.2%,2.5%～52.5%;individual volume of the tending group increased by 17.7%～37.4%,11.7%～25.4%,7.3%～47.7%.2 Larix principis-rupprechtii Mayr.stand volume was lower temporarily by intermediate cutting.But the growth rate of the cutting stand was higher than before.When the reserve density decreased,the accumulation average growth rate would increase.After a period,the volume of the tending stand would be close to the stand with the reserve density increasing.The volume growth of stands semi-shady slope were 6.3,6.4,8.0,8.6, 9.2m~3/hm~2,the volume growth rate of stands semi-shady slope were 8.6%,7.9%,7.8%, 7.0%,6.1%.Shade slope were 5.9,5.3,7.4,8.1,8.6 m~3/hm~2,the volume growth rate was 8.3%,7.3%,7.2%,6.5%,6.1%.High mountain flatland was 6.0,6.8,7.1,8.0,8.5 m~3/hm~2, the volume growth rate was 13.1%,13.2%,10.6%,9.6%,8.9%.3 When the stand experienced the cutting,the higher light level made the most of mutual species's importance value reduced and showed the negative reaction.Species number of the negative reaction species increased with the reserve density's decreasing. Compared with the control,species number of stands semi-shady slope and shade slope increased by 13,10,7,6 and 11,10,6,4 the control stands.Species number of high mountain flatland increased by 9,11,5,3.By bringing up the site after the thinning under different conditions to retain density in Larix principis-rupprechtii Mayr.plantation forest herbs important changes in the value of the study,obtained:on semi-shady slope understory herbs,positive species and negative species with the number of species to retain the density decreases,the show generally increasing trend in 600 / hm~2 stand in the positive and negative reaction to the largest number of species 20,12;shade slope various herbal and understory.The positive response of plant species with the number of reservations about the density decreases with the increase in 500 / hm~2 stand in the response is to maximize the number of species 15;high mountain flatland forest understory herbs are the kinds of responses with the number of species density of reservations has also reduced the general trend of increasing.4 Tending to retain density thinning different understory herbs plantation in Larix principis-rupprechtii Mayr.plantation species richness index,diversity and species evenness show with reservations reduce the density of the increasing trend.Diversity index of half negative slope and shady slope were as follows:500 strains/hm~2＞600 strains/hm~2＞700 strains/hm~2＞800 strains/hm~Z＞the control of 1100 strains/hm~2;Compared with all indexes of the same reserve density,shady slope was better than half negative slope.Herb diversity showed that 500 strains/hm~2＞400 strains/hm~2＞600 strains/hm~2＞700 strains/hm~2＞the control of 900 strains/hm~2 of high mountain flatland.5 For increasing the growth and diversity of undergrowth,the heavy tending has the best effect;the appropriate stand density for the Larix principis-rupprechtii Mayr.is 500 truncks/hm2.on 37～39 semi-shady slope,shade slope and an original density of 1100 trunks/hm~2,and effects of tending thinning were as follows high mountain flatland＞semi-shady slope＞shade slope.In conclusion,tending has significant effects on the forest environment,stand growth and undergrowth diversity of the Larix principis-rupprechtii Mayr.plantation in North Hebei Mountain area.Reasonable tending methods should be applied to control the stand density,so as to make the plantation growing in a healthy and sustainable way.
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