The Effects On Biomass, Species Diversity And Soil Fertility Of Cunninghamia Lanceolata Plantation By Intermediate Cuttings And Interplanted With Broad-Leaved Tree

This essay carried out some experiments on Cunninghamia Lanceolata plantation by different intermediate cutting intensities and interplanted with broad-leaved trees in Experimental Center of Tropical Forestry of CAF to learn the relations between the growing development and stand structure of the plantation, and study the biomass in arborous layer, species diversity, physical and chemical characteristics of soil. In this paper, the regular patterns of growing development and stand structure of the plantation are unfolded, the relations between the biomass in arborous layer and thinning intensity are stated, the impact of species diversity by different intermediate cutting intensities is revealed, and the physical and chemical characteristics of soil in different intermediate cutting intensities are analyzed. The results are as following:①Intermediate cutting has played a noticeable role in raising DBH and average biomass of the plantation. Results showed that DBH constantly increased along with the thinning intensity. The bigger thinning intensity was, the greater DBH grew. Biomass in organs of the tree has significantly risen. Briefly, the sequence of growth rate in biomass of organs described as needle> bole> branch> bark> root.②Intermediate cutting can not improve the biomass of arborous layer on unit area in a short period. Tests have showed that Cunninghamia Lanceolata plantation, aged at 18a and reserved density of 650trees/hm2,1100trees/hm2,1250trees/hm2,1650trees/hm2, had a biomass in the arborous layer of 70.76 t/hm2,84.58 t/hm2,106.43 t/hm2,117.68 t/hm2 respectively. From ANOVA results, there was significant difference(P<0.05) in biomass of the arborous layer between highly thinning standing forest (cutting rate at 74%) and little thinning standing forest (cutting rate at 34%), while there was no significant difference(P> 0.05) among other standing forests.③There are 140 species in Cunninghamia Lanceolata plantation and they belongs to 63 families and 108 categories. These species are composed of 25 ferns,1 gymnosperm and 114 angiosperms. The dominant species under the forests were almost the same in different intermediate cutting stands. In shrub layer,7 species such as Oreocnide obovata, Vernonia esculenta, Mussaenda esquirolii, Saurauia tristyla, Ardisia japonica, Ficus hirta, Evodia lepta are mutual dominant species, with the importance value above 10. In herb layer,6 species such as Allantodia virescens, Cibotium barometz, Angiopteris fokiensis, Pteris setuloso-costulata, Blechnum orientale, Microlepia speluncae are mutual dominant species, with the importance value above 10. For liana, there were 5 species with the importance value above 20, and Ficus sarmentosa, Mussaenda pubescens, Dioscorea bulbifera, Piper mutabile were mutual dominant species. It might have some connection with the similar environmental conditions.④Intermediate cutting has different effects on species richness, diversity index and evenness index of Cunninghamia Lanceolata plantation. The test indicated that intermediate cutting can increase species richness. In various layers, as the thinning intensity increased, species richness grew slowly, and the number of helophytes grew while the number of sciophiles reduced. Both in shrub and herb layer, as the thinning intensity increased, Shannon-Wiener index and Simpson index descended like waves, and the evenness index (Jsw) gradually reduced while the ecological dominance(λ) raised.⑤The physical characteristics of soil have been improved by intermediate cutting. As the thinning intensity increased, the volume weight of soil reduced, the soil moisture content varied like 'U' parabolic shape and the soil total porosity percent varied like an open side down parabolic. Non-capillary pore percent dropped and soil permeability became worse along with the reserve density grows.⑥Intermediate cutting has different effects on soil nutrient. As the thinning intensity increased, hydrolyzable nitrogen and available P content varied like waves, soil organic matter, total N content and total K content varied like an open side down parabolic, total P content and available K content gradually reduced. There was an obvious reduce on available K content from high dense stand to low dense stands in 0～20cm soil layer.⑦The soil acidity of Cunninghamia Lanceolata plantation was relatively strong, its pH value varied from 4.1 to 4.5. The soil acidity of shallow soil was stronger than the deep soil. There was no regularities on exchangeable calcium and magnesium in 0～20cm soil layer, but they increased along with the thinning intensity in 20～40cm soil layer.