| Bamboo (Phyllostachy pubescens) is an important forest resource in southern China. It has been widely planted. And what's more, the area is getting to be greater and greater by substitution for broadleaved forest, Masson Pine and Chinese fir since farmer can get good economic benefits from bamboo. However, the information about the assessment of soil microorganism Phyllostachy pubescens under stand is less available. The objective of this essay was to find out the effects of long-term growing of bamboo and intensive management on soil Biological characteristics.1)Soil microbial biomass and diversity of soil under Phyllostachy pubescens stands with different level of management, which are tyPe1 under conventional Practice (CM), type 2 under 5-8 years'intensive management (IM) and type 3 under 8~10 years'IM respectively, was investigated to understand the effect of management on soil quality. It was found that intensive management practice significantly decreased (P<0.05 ) soil microbial biomass C (MBC) (in the order of CM > 5~8-years'IM > 8~10-years'IM ) but increased soil microbial respiration C (MRC) (in the order of type 2≈type 3 >type 1). Soil (0～20 cm) MBC under type 2 and type 3 decreased by relative 67.8%, 61.64% compared with type 1, while MRC increased by respective 23.5% and 25.8% compared with type 1. The average well color development (DAWC) value characteristic as soil microbial diversity declined with the intensive management time, DAWC value of type 2 and 3 at the time of 168 hours incubation decreased by 33.22% and 34.38% respectively compared with type 1. The results from the principle components analysis (PCA) implied that type 1 was separated from types 2 by PC1, type 2 and type 3 divided by PC2. The information from all above suggested that intensive Practice of Phyllostachy pubescens has a generally negative influence on soil microbial activity and community structure.2)Different grow histories of Mao bamboo forest land have different soil microbe development patterns. 6 soil samples on different grow history were collected representatively, these forests were built separately in 2002, 1996, 1990, 1980, 1960. At the same time, one Masson Pine forest land chosen from the same site type as control. In every plot, three soil samples were collected, 0～20 cm layer and 20～40 cm layer respectively. Then, we analyzed its basic features and microbe functional diversity. The results are as follows:0～20 cm layer: The DAWC of 1990's Phyllostachy pubescens forest land is significantly greater than 1960's. While others have no marked difference between each other, it is means that there's no rule in them, and it can not make soil organism fall off, if you keep a Mao bamboo forest for several years just with weed-cutting measure. The main factors are soil nutrients and soil moisture.Though principal component analysis (using the data of 120 h DAWC), we can find that, the carbon source utilization model of 1990's Mao bamboo forest soil microbe has great differences in these treating, it's PC1 (6.268) is significantly greater than others. Different layers ( 0～20 cm &20～40 cm ) have different carbon source utilization model. And what's more, as to Shannon index,Shannon evenness (J') , there is no difference between either different cultivation history or different soil layers.3)A microcosm's batch of soil from broad-leaved forest mixed with different percent of bamboo litter powder (CK, 0; treatment 1, 1%; treatment 2, 2%; treatment 3, 4%)was conducted in order to find out the influence of Phyllostachy pubescens litter on functional diversity and to reveal the formation mechanism of microbial community of soil under Phyllostachy pubescens. The changes in microbial functional diversity characterized as average well color development (DAWC) with the incubation time were determined by Biolog GN2 microbial plate. It was shown that the litter of Phyllostachy pubescens had improved the soil microbial activity in short period. However, a rapid decline was observed at the time of week 20, and by the time of week 30, the decline value of treatment 1, 2, 3 have reached 64.8%, 55.7% and 60.4% compared to ck. It was interesting to find that the larger DAWC value (P<0.05) was observed for control compared with the other treatments during week 20 to 30, but no significant difference among the treatments 1, 2 and 3 was measured.The Shannon index (H) and evenness index(J')of all treatments were found significantly smaller (P<0.05) in 30-week than 20-week except control with no significant difference. McIntosh index (U) for treatments 1, 2 and 3 descended from the 10th to the 30th week, while a rapidly decline for control was measured from the 20th to the 30th week. It can be concluded that the rate amount of leaf powder had led no significant difference in soil microbial diversity indices,yet the diversity indices of control are significantly greater (P<0.05) than the 3 treatments with bamboo litter at the 30th week, and implied that single litter input of bamboo leaf will lead the reduction of functional diversity of soil microbial community in a long time. |
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