Study On Community Features And Productivity Of Larix Principis-rupprechtii Mayr. In Yanshan Mountainous Regions

Larix principis-rupprechtii Mayr. is the main eclolgical tree species with widestdistribution and maximal cumulation in Yanshan mountainous regions. It is most importantfor protecting riverhead, keeping natural environment, forming and maintaining ecosystemof forests areas. Also, it is the main tree planted with purpose managed by Magnolia ForestManagement Bureau. This paper studied Larix principis-rupprechtii Mayr. of MagnoliaForest Management Bureau, including community structure, species diversity, growthprocess, biomass and productivity by investigation outdoors and experimentation indoors.Some conclusions were as follows:(1) The upright structure of Larix principis-rupprechtii Mayr. manmade pure forestswere simple. Basically, they were devided into two arbor layers and one herbage layers.Larix principis-rupprechtii Mayr., populus tremuloides, birch theropencedrymion, poplarand birch kargeleaf mixed forest form four extinct layers with different height from bottomto top. In the community level structures, individual density of herbage was the largest,which showes that the soil conditions here were better, and there was plenty of water.Individual density of arbor layer was larger than shrub layer, which showed that shrublayer was affected by arbor layer, its growth and propagation was restricted and the amountof plants were less. The rank structre of species size was direct pyramid type. There weredirect pyramid types in all rank. From the living curve, Larix principis-rupprechtii Mayr.belonged to Deevey-Ⅲtype, namely, increasing species.(2) The biological diversity indices of larix principis-rupprechtii Mayr. manmade pureforests accorded with bias normal distribution along with the change trends of stand agesand canopy density limits. The results indicated that altitude, gradient, exposure, slopelocation, density, canopy, mixed proportion were significant factors influencing the speciesdiversity in the regions. The maximum of every index in shrub layer was in spot 19, whilethe minimum was in spot 10, 22, and 24. The maximum index of herbage layer was in spotNo33, while the minimum one was in spots 19.The maximum index of larixprincipis-rupprechtii Mayr., populus tremuloides, birch theropencedrymion and shrublayer were in spots 13 and of herbage layer were in spots 16. In the mixed forest composedof Larix principis-rupprechtii Mayr., populus tremuloides and birch theropencedrymion,the maximum index of shrub layer is in spot 13, while of herbage layer is in spot 16. Theminimum indices of them were both in spot 31.(3) The diameter, height and volume total increment of larix principis-rupprechtiiMayr. rised constaintly along with the growth of stand age. Current annual increment andaverage increment was increasing with the growth of stand age, but the former one was faster, which value was larger. In the curve, time current annual increment achieving thepeak was earlier than the one of average growth capacity. After achieving the peak, currentannual increment gradually intersect with average growth capacity. Then, the value ofcurrent annual increment was small than average one. The peak of current annualincrement of diameter at breast height was longer haul than the one of tree height, whilethe peak of volume inside bark was later than the ones above. Capacities in successiveyears of diameter at breast height,height and volume were fluctuant.(4) The productivity of larix principis-rupprechtii Mayr. was increasing along with theaugment of diameter class. The distribution order of every organ's biomass in arbor layerwas trunks, branchs, leaves and fruits from large to small. Trunks' proportion betweenbiomass and total ones was increasing along with stand age. Biomass in arbor layer mainlyaccumulates in thinks and branches, and biomasses in former were far bigger than thelatter, which indicates that the whole branches of larix principis-rupprechtii Mayr. weregood and trunks were productive. Also, it indicates that the living condition of larixprincipis-rupprechtii Mayr.manmade pure trees was good. Good management measureswere taken, accelerating the growth. In the community biomass of arbor layer and litterlayer take the most propotion. Spots 10, 22, 24 and 30 were larix principis-rupprechtiiMayr.manmade pure trees without shrub layer. In spots 9, 13, 8 and 31, the biomass inherbage layer has a little propotion in the total. Spot 11 has the largest Biomass, which wasup to 122.028t·hm-~2. Thereinto, the total number of Biomass in arbor layer and litter layerwas up to 99.96%. There was no Biomass in shrub layer, and herbage layer only has apercentage of 0.04%.(5) Biological diversity in larix principis-rupprechtii Mayr., populus tremuloides,birch theropencedrymion with the same age or near was higher than larixprincipis-rupprechtii Mayr. manmade pure trees, but the latter has the larger productivity.So in the course of forest management, microenvironment mixing or mixing in sight scaleshould be done for commonweal trees in protect areas. To increasing spots productivity,giving priority to developing pure trees, adjusting spot density and paying attention tomixing in sight scale should be done, which will be propitious to the protection ofbiological diversity, and improve the stability of forest ecosystem in the course ofincreasing community productivity.(6) Notability analysis between total biomass, productivity and habitat factor, standfactor:y=(y1,y2,y3,y4,y5) were divided into three groups (cluster)multiple linear regressionas follows.screened multiple linear regression in the first group were: y1=-45.50+4.05x1+0.09x4-1.88x3+12.32x6; y2=2.92+0.04x1-0.01x4-0.02x3-0.11x6; y3=0.13-0.004x1-0.0004x4+0.001x3+0.003x6.screened multiple linear regression in thesecond group was: y4=1.3+0.62x8-2.10x5.screened multiple linear regression the thirdgroup was: y5=0.095+0.16x8-0.05x7.Known by y=(y1,y2,y3,y4,y5), community biomass, arbor layer's productivity, and shrub layer's productivity were influenced notably by thesame independent variable collection, such as stand age, density, slope and exposure, butnot influenced notably by other factors. Herbage layer's productivity was influencednotably by canopy density and mixed proportion, litter productivity of community wasinfluenced notably by slope location and mixed proportion.