Effects Of Different Stand Densities On The Biomass Of Larix Principis-rupprechtii Forest And Floristic Diversity

This article takes larix principis-rupprechtii forests as research object, we have set20sample plots with different stand densities in Bei-gou Forest farm of Mulan forestadministration of Chengde, we studied biomass of each organ of larixprincipis-rupprechtii and undergrowth vegetation diversity, and analysed influence ofdifferent stand densities on biomass of each organ and undergrowth vegetation diversity.We want to learn biomass distribution laws of each organ of larix principis-rupprechtii aswell as correlation of diversity indexes under influence of stand densities, the researchresults are:(1) Biomass distribution of each organ of single plant of larix principis-rupprechtiishow: trunk> tree root> tree branch> leaf, and only few sample plots show: trunk> treebranch> tree root> leaf, this means that biomass accumulation of woods is mainly intrunk, trunk has supporting effect to trees, and the allocation proportion is maximum,but biomass accumulation of leaves is lesser. In forest stands of919/hm2～1636/hm2,there are certain proportional relations between biomass allocation of organs of larixprincipis-rupprechtii mayr, the distribution ratio of organs are: mean value of biomassof trunk is59.64%(45.26%～70.29%), mean value of biomass of tree root is17.42%(12.76%～26.36%), mean value of biomass of leaf is7.59%(2.11%～18.19%).Allocation proportion of trunk biomass has trend of gradually drop along withaccretion of stand density, but when stand density is1242/hm2, allocation proportion oftrunk biomass reaches lowest, variation trend of allocation proportion of tree branch,tree root and leaf are not very obvious.(2) Taking DBH(D), D2H as independent variables, biomass of single plant andeach organ as dependent variables, we built biomass model of larix principis-rupprechtiimayr single plant and each organ. The regression model can be used to forecast biomassof single plant and each organ as prediction model, and it has statistical significance. Butfor forecast of biomass of tree root, tree branch and leaf, we can choose better model toforecast. For biomass forecast of single plant and trunk, we can choose any fittingequation, and the applicability are both higher.(3) As accretion of stand density, the species and importance values are lessened, and only in forest stand of1616/hm2, the importance values of dominant tree species areall increased. In larix principis-rupprechtii mayr forest stands of different densities,Carex rigescens is main dominant species, it has largest importance value, and takesabsolute predominance. Saussurea Pectinata Korsh,Rhizoma Polygonati Odorati,Rhizoma Atractylodis, Thalictrum aquilegifolium L. var. sibiricum Regel, Bidensbipinnata, Herba Potentillae Chinensis and so on are associated species in forest standsof different densities. As accretion of stand density, Artemisia gmelinii develops intoassociated species from dominant species. As accretion of stand density, light conditionin forests becomes worse and worse, most masculine and semi-masculine herbaceousplants have been replaced by minority feminine herbaceous plants.(4) After Person analysis to stand density and diversity indexes, we can get thefollowing conclusion: stand density N and diversity index S have highly significantnegative correlation relation with Shannon-Wiener diversity index H, and havesignificant negative correlation relationship with Simpson diversity index D, have nocorrelativity with evenness index Jsi based on Simpson diversity index and evennessindex Jsw based on Shannon-Wiener diversity index; species richness index S has highlysignificant positive correlation relationship with evenness index Jsi based on Simpsondiversity index, and has significant positive correlation relationship with Simpsondiversity index D and Shannon-Wiener diversity index H; Simpson diversity index D andShannon-Wiener diversity index H have highly significant positive correlationrelationship, D,Jsi and Jsw also have significant positive correlation relationship；Shannon-Wiener diversity index H has highly significant correlation relationship with Jsiand Jsw.(5) Analysis about impact of stand density on species richness, species diversity,species evenness shows that: stand density has great impacts on species richness andspecies diversity, they have significant correlativity, but influence on species evenness isnot obvious.