衡阳紫色土丘陵坡地恢复过程中土壤微生物生物量与土壤养分演变

Dynamic Changes of Soil Microbial Biomass and Soil Nutrients along Re-Vegetation on Sloping-Land with Purple Soils in Hengyang of Hunan Province,South-Central China

土壤微生物直接参与养分循环、有机质分解等诸多生态过程,尤其在陆地生态系统C循环中发挥着重要作用（Pascual et al.,2000;Harris,2003;Schipper et al.,2001）。由于微生物对外界胁迫的反应要比植物和动物敏感,因此,微生物群落的大小、组成和活性在不同的管理措施之间差异明显（Bossio et al.,1995;Panikov,1999）。

Soil microbial biomass and soil nutrients at different vegetation restoration stages of sloping-land with purple soils in Hengyang were studied with method of space series instead of time series. Five typical sample plots with re- vegetation chronosequence grassplot （GTX） （6 a） , meadow thichet （MT） （ 13 a） , frutex（FX） （20 a） , arbor and frutex （AF） （30 a） , and arbor（AR） （50 a） were selected, and sloping farmland （CK） and top-level vegetation （TV） were chosen as the reference. The aim of this study is to investigate the dynamics of soil microbial biomass and nutrients. The correlation between soil microbial properties and soil nutrients were also examined. The results showed that： 1） Soil physico-chemical properties were obviously improved in the process of re-vegetation, and two peak values appeared at the year of 20 and 50. At 50 a, the content of SOC （ Soil organic carbon） , TN （ Total nitrogen） , C/N （ C/N ratio） , AN （ Alkali-hydrolyzed nitrogen）, TP（Total phosphorus） and AP（Available phosphorus） increased by 299%, 181%, 42%, 278%, 7% and 108% compared with CK, respectively, and the content of SOC, TN, AN and AP was 54%, 55%, 72% and 94% of the TV, respectively, BD （Bulk density） decreased by 14% compared with CK, and 132% of the TV; 2） Soil microbial biomass varied with increasing years of re-vegetation, and two peak values appeared at 20 a and 50 a. The MBC（Microbial biomass carbon）, MBN（Microbial biomass nitrogen） and MBP（Microbial biomass phosphorus） increased by 220% , 216% and 92% compared with CK, respectively, but they were only 51.41% , 55.55% and 65.78% of climax stage, respectively. MBC/SOC, MBN/TN and MBP/TP varied in the range of 3.71%- 4. 81% , 5.49% - 6. 67% and 1.29% - 2. 20% respectively. MBC/MBN increased significantly within 13 years, and kept stability between 13 a and 50 a. The RI （Respiration intensity） first increased and then decreased with the increasing years of re-vegetation, and was not synchronized with the change of SOC and MBC. The qCO2 （ Metabolic quotient） increased significantly within 20 years, then decreased rapidly, and reached the minimum at the year of 50 which was close to top-level vegetation ; 3 ） Correlation analysis showed that there were significant （P 〈0. 05 ） or highly significant （P 〈 0. 01 ） correlations between MBC, MBN, MBP, qCO2 and soil nutrients, restoration duration. The results indicate that it is possible to improve the eco-environment and soil properties naturally on sloping-land with purple soils in Hengyang of Hunan Province, South-central China, but more than 100 years would be required to reach the level of TV stage. Hence, it is necessary to improve ecology management to interfere and accelerate the pace of ecology re-vegetation for a sustainable and healthy ecosystem in this area.