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In this study, the cultivation of a large area south of the Yangtze River fine shoot bamboo praecox (Phyllostachys violascens' Prevernalis) for the study, after a year of coverage, coverage for two consecutive years and not covered by woodland (control) are three ways to deal with points four seasons of spring (April), summer (July) and fall (October) and winter (January), in accordance with the diameter to the praecox fine root divided into level I root (0 ~~ 0.5mm), the root level II ( 0.5 ~ 2mm) and grade Ⅲ root (2 ~ 5mm) three diameter classes praecox diameter distribution of fine root biomass, nutrient content (C, N, P, and the C / N, C / P, N / P) dynamic change related research. The main results are as follows: (1) coverage measures Lei Zhulin fine root biomass decreased in average annual total grade Ⅰ root coverage in one year and two years respectively, decreased by 15.5% and 18.4%, II class roots decreased 9.0% and 11.9%, grade III root biomass was no significant change. (2) under Phyllostachys praecox stands fine root biomass seasonal changes, lowest in spring and autumn the highest overall unimodal curve. Covering measures to reduce under Phyllostachys praecox stands fine root biomass in spring, autumn, winter, and spring was changed significantly. Year covering Ⅰ-class roots in the spring and summer, significantly reduce the II class roots significantly lower in the spring. After two years of coverage Ⅰ level root season were lower II class roots significantly lower in spring, autumn and winter. (3) fine root biomass is mainly distributed in the soil surface, the total biomass of 64% to 73% coverage while reducing the soil surface and subsurface fine root biomass, fine root biomass of two consecutive years of covering the soil surface and subsurface The amount decreased by 6.6% and 11.3%, respectively. Coverage processing so that the proportion of the surface fine root biomass in the spring and increased in summer, autumn, winter slightly lower. (4) The diameter fine root N and P content of the soil surface were higher than the subsurface; grade I root N in all plots, the the P highest concentrations (5.63 ~ 7.31 mg g-1; 0.655 to 1.035 mg g-1 Ⅲ grade) root lowest (2.70 ~ 5.10 mg · g-1; 0.408 ~ 0.603 mg · g-1), with the fine root diameter increased decreased significantly; fine root N, P content seasons dynamic changes more consistent, both in lowest in spring and autumn, the highest, the difference between the performance of the N content is higher in summer and autumn, P content is higher in autumn and winter. (5) the different coverage time on fine root N, P content affect, which two years covering the processing greater coverage than a year to cope with the effects. Year covering the soil surface I, class II root N content significantly increased in the spring, P content increased significantly in the summer and autumn, and III-class roots did not change significantly. Two years covering major so Ⅱ, III level root N content significantly increased in the spring and autumn the soil surface; I, class II root P content of the soil surface in the summer and fall significantly increase. (6) the fine roots N / P between the diameter class performance for the the grade Ⅰ root highest (7.91:1) the lowest grade II root (6.77:1), seasonal changes showed grade I root highest in spring and lowest in winter; Ⅱ III-class roots the highest summer, winter and spring low. After two years of coverage, the larger diameter fine roots N / P in the spring, summer, higher than that of still smaller diameter, fine roots N / P lower than that of the control in the summer and autumn. (7) C content of fine roots in different diameter classes, different soil, different seasonal differences were not significant, covering not significantly affect the fine root C content. Each size class between the fine roots, C / N and C / P grade I root lowest, the highest root level III, with the fine root diameter increases and higher; soil surface C / N and C / P below the soil subsurface ; different quarters, C / N and C / P is the highest in the spring and autumn minimum. Since the C content is relatively stable, impact and N of the coverage of the C / N and C / P, P variation opposite. Comprehensive analysis: the praecox fine root biomass decline Lei Zhulin degradation. The woodland cover measures mainly by changing the environmental factors of soil temperature, soil microorganisms, soil moisture and ventilation degrees, to change the fine root biomass. Mulching cultivation winter soil temperature increase praecox early shoots, which is the core purpose of cultivation techniques; the coverage simultaneously changing environmental factors Lei Zhulin ground, causing forest degradation, is unnecessary and non-cultivated purposes. Coverage as well as covering the end of the process, reducing the effect of other environmental factors, the level of degradation can alleviate coverage lead Leizhu Lin.
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