Study On Spatial Distribution Pattern Of The Biomass And Plant Diversity In Larix Princicpis-rupprechtii Mayr. Plantation In Yanshan Mountainous Regions

Larix principis-rupprechtii Mayr. is the main eclolgical tree species, one of the widest distribution maximal cumulation in Yanshan mountainous regions. It has played an irreplaceable role in conserving water, mainting soil, forming and maintaining ecosystem of forests areas. Based on the data of the field investigation, we studied the plantation community structure, species diversity, spatial distribution pattern of the biomass of four different age stand in Larix principis-rupprechtii Mayr. plantation. The main results are as follows.(1) From the view of floristic composition, the quantity of species was most in the 6-year-old Larix princicpis-rupprechtii Mayr. plantation, in which the 37 specieces belonged to 19 families and 33 genera respectively. The quantity of species was least in the 12-year-old Larix princicpis-rupprechtii Mayr. plantation, in which the 28 specieces belonged to 17 families and 23 genera respectively. There were 33 species in 22-year-old Larix princicpis-rupprechtii Mayr. plantation, and they belonged to 15 families and 28 genera. There were 34 species in 32-year-old Larix princicpis-rupprechtii Mayr. plantation, and they belonged to 20 families and 29 genera. It indicated that with the age increase of Larix princicpis-rupprechtii Mayr. plantation, the richness floristic composition decreased at first and then increased.(2) The plantation showed stratification obviously in the different age stand of Larix princicpis-rupprechtii Mayr. plantation, which can be divided into arbor layer, shrublayer as well as herb laye, and the coverage of each layer was different in different age stand. In the shrub layer and the herb layer, the species composition and important value of the dominant species and accompanying species were significantly different with the age increasing of the stand of Larix princicpis-rupprechtii Mayr. plantation, the community similarity decreased.(3) The studies on species diversity in the shrub layer and the herb layer in Larix princicpis-rupprechtii Mayr. plantation showed that: Margarlef richness index in the shrub layer decreased slowly with the increasing stand age, but Margarlef richness index in the herb layer appeared fluctuation variation, with the increasing stand age. In the shrub layer, Shannon-Wiener index appeared fluctuation variation, with the increasing stand age. But Shannon-Wiener index in the herb layer increased at first and then decreased with the increasing stand age. Pielou evenness index in the shrub layer appeared fluctuation variation, with the increasing stand age, but Pielou evenness indexin the herb layer increased at first and then decreased with increasing stand age. The variation tendency of ecological dominance index was opposite to changing tendency of evenness index.(4) The individual biomass and biomass of each organ in the different age stand of Larix princicpis-rupprechtii Mayr. plantation increased with the increasing stand age, and the biomass growth rate of trunk were the fastest. The percentage of truck and root biomass accounting for whole plant biomass increased with increasing stand age. The percentage of bark, branches and leaves biomass accounting for whole plant biomass decreased with the increasing stand age.(5) The spatial distribution pattern of each organ biomass was different in the arbor layer in Larix princicpis-rupprechtii Mayr. plantation. In the 6-year-old plantation, distribution pattern was in the order of branches> trunk> bark> leaves> root. In the 12-year-old plantation, 22-year-old plantaion and 32-year-old plantaion, distribution patterns were in the order of trunk> branches> root> bark> leaves. In the arbor layer, the total biomass increased with increasing stand age, and the biomass was more accumulation in the trunk. In the different age stand of Larix princicpis-rupprechtii Mayr. plantation, the biomass in the shrub layer and herb layer were decreased at first and then increased with increasing stand age. In the 6-year-old plantaion, the percentage of above-ground biomass in the shrub layer and herb layer accouting for whole biomass were the highest, but the propotion were decreased in the 12-year-old plantaion, 22-year-old plantaion and 32-year-old plantaion. In the different age stand of Larix princicpis-rupprechtii Mayr. plantation, the total biomass changing tendency were same as the biomass of arbor layer. The percentage of the biomass of arbor layer increased with the increasing stand age.