Study On The Effect Of Forest Cover On Biomass And Nutrient Content Of Fine Root Of Phyllostachys Violascens 'Prevernalis'

The study uses phyllostachys violascens 'Prevernalis'which cultivated for bamboo shoot in a large area of south of the Yangtze as research object. The experiments set one-year-mulching, two-year-mulching and no-mulching(as control) three treatment conditions in spring (April),summer(July),autumn(October) and winter(January) four seasons, according to the different diameter divided the fine roots into levelⅠroot (0 to 0.5mm), levelⅡroot (0.5-2mm) and levelⅢroot (2-5mm).Research the biomass and nutrient content (C, N, P and C/N, C/P, N/P) of the dynamic changes in different diameter classes.(1) Mulching treatments make the average annual total biomass of fine root decrease, levelⅠroot of one-year-mulching and two-year-mulching decreased 15.5% and 18.4%. LevelⅡdecreased 9.0% and 11.9%, levelⅢhad no significant change.(2) The seasonal change of biomass are significantly, spring is the minimum, autumn is the maximum, which generally presents a single speak curve. mulching treatment reduced the fine root biomass in spring, autumn and winter, which changes significantly the spring. After one year mulching, the biomass of levelⅠSignificantly decreased in the spring and sumer. levelⅡSignificantly decreased in spring.After two year mulching, the biomass of levelⅠSignificantly decreased in all year. levelⅡSignificantly decreased in spring, autumn and winter.(3) The biomass of Fine root is mainly distributed in the soil surface. Accounted 64% to 73% of total biomass.The mulching reduced the fine root biomass of soil surface and subsurface which decreased 6.6% and 11.3% Respectively after two years mulching.Mulching treatment Increased the ratio of surface fine root biomass in spring and summer,decreased in autumn and winter.(4) The diameter of fine roots N, P contents were higher than subsurface soil surface, The content of N, P was the highest (5.63-7.31mg·g-1,0.655-1.035 mg·g-1) in level I, lowest in levelⅢ(2.70-5.10mg·g-1,0.408-0.603mg·g-1), with the fine root diameter increased significantly decreased; fine root N, P content in seasons dynamics are more consistent, both in the spring minimum, Highest in autumn, the performance difference between summer and fall in the higher N content, P content are higher in autumn and winter.(5) Different mulching duration effect N, P content of fine roots, two-year-mulching had more significant impact than one-year-mulching. LevelⅠ,Ⅱroot N content increased significantly in the spring after one-year-mulching, P content increased significantly in summer and autumn,LevelⅢroots did not change significantly. LevelⅡ,Ⅲroot N content in the soil surface in spring and autumn increased significantly after two-year-mulching, LevelⅠ,Ⅱroots of the P content of the soil surface in summer and autumn increased significantly.(6) The N/P between the various diameter classes presents that levelⅠroot is the maximum (7.91:1), levelⅡroot is the minimum (6.77:1), the change of seasons shows level root is the maximum in April and is the maximum in next January. LevelⅡ,Ⅲroot is the maximum in July,lower in January and April.After two years mulching, N/P rootsⅢin the spring and summer of higher than the diameter of smaller unthinned fine roots N/P in summer than controls processing.(7) The total C content in the surface of fine root is slightly more than in the subsurface, and the difference in the different level and different seasons is not significant to fine root, mulching has no significant influence on it. Among each level of fine root, C/N and C/P inⅠlevel root is minimum,Ⅲlevel root was the highest,and with the increasing of fine root diameter rises; C/N and C/P in soil surface are below in soil subsurface; During different quarters, C/N and C/P are the highest in April, while in October is the lowest. Due to relative stability of C content, the influence of mulching to C/N and C/P is exactly opposite with the change rule of N and P.Comprehensive analysis shows as follows:The decline in biomass of fine root is the main reasons lead to woodland degradation. The mulching measure changed the fine root biomass by alter the environmental factors such as soil temperature, soil microbial, soil moisture and aeration degree. The purpose of mulching cultivated is to make temperature of soil increase in winter,and let Phyllostachys violascens 'Prevernalis'advance to sprout,which is the core and purpose of cultivation techniques. While mulching condition changed the environmental factors of woodland at the same time which lead the degradation of woodland is unnecessary. In mulching period and after mulching process, reduce the role of other environmental factors may alleviate the degree of degradation of the woodland.