Study On Biomass And Species Diversity Of Understory In Larix Olgensis Herry. Plantation

Based on the data of the field investigation, using the method of establishing biomass model, we studied the understory community structure, species diversity, understory biomass, and stand factots impacted on species diversty and biomass of Larix olgensis Herry. Plantation in Dongzhelenghe tree farm. The main results are asfollows:(1) There are 136 species of vascular plants at the flora of understory shrub layer and herb layer, belonging to 48 families and 107 genuses. Among them, the species of herb layer belonging to 38 families and 85 genuses and 105 species,77.21% of the total number, and there is no large family. The flora of richness of understory showed a decreasing trend with the increasing of forest stand age.(2) Margarlef richness index in the herb layer of Larix olgensis Herry. Plantation was much larger than the shrub layer, with the increasing stand age of forest, Margarlef richness index in the shrub layer of Larix olgensis Herry. Plantation decreased slowly, but Margarlef richness index in the herb layer appeared fluctuation variation, and trended to smooth and steady. Meanwhiles, Margarlef richness index of herb layer was much larger than the shrub layer. With the increasing stand age, Shannon-Wiener index of shrub layer appeared to steadily decline, and finally maintain at a certain level, but the index of herb layer a\varied at a little range. With the increasing stand age. Pielou evenness index in the shrub layer decreased, and the index of herb layer stayed at a low level. Pielou evenness index of herb layer and shrub layer remained at a low lever in the stage of mature forest and overmature forest. The variation tendency of ecological dominance index increased at first then decreased, and finally rised smoothly with the increasing stand age. Summing up the above, with the increasing stand age, the diversity of species of shrub layer and herb layer appeared fluctuation variation, and stayed at a steadily level in the stage of mature forest and overmature forest. (3) Quadratic polynomial and power function were the best biomass estimating models of shrub species, and the composite factors, such as steam aera, trunk volume, canopy projection aera, crown projection volume, were the best model parameters, they were had highly correlation. The biomass model of the shrub layer was WT=9.00E-06VD2+0.389VD+57.598(VD said trunk volume), it had high R2 value (0.933). The best biomass estimating models of herb layer is Quadratic polynomial, and seen the average height as the composite factors. The biomass model of the herb layer was WT=0.0001H2.3435 (H said average height); it had high R2 value (0.7158).(4) At different density, the species diversity of undergrowth of Larix olgensis Herry. Plantation were significant difference, and the species diversity of shrub layer was significantly positively correlated. The understory biomass accounted for a large proportion of stand biomass. The understory biomass increased with the increasing stand age.At different stand ages, the organ biomass of herb layer were greatly different, overground biomass of herbs played a dominant part at the stage of middle-age, and underground biomass of herb were the main part when at the stage of overmature forest. The species diversity of shrub layer significantly correlatied with its biomass, but the herb layer showed no significant corelationship with the biomass, that may be affected by the impact of the upper canopy layer, specific reasons needed further study.