Response Of Soil Quality To Vegetation Succession In Karst Region

The problems of poverty and environment degradation are the most serious both insouthwest Karst Region and the Loess Plateau of China. The South West of China, alsoknown as the Karst region is Characterized by water shortage, poor soil and reducedvegetation, the drought and waterlog is frequent, the contradiction between populationand land is very serious, and the local environment is extremely fragile, soilproductivity is reduced, as a result, soil quality becomes the key factor for maintainingthe structure and function of the degraded ecosystem, vegetation degradation is one ofthe reasons for economic problems in this area, vegetation renewal is one of the mostefficient ways to restore the eco-environment and alleviate the negative impact ofhuman activities on the environment. It is therefore important to study the relationshipbetween vegetation succession and soil fertility, to discuss the rule of vegetationresponse to soil quality and to clarify the ecological process and environmental benefitin estimating the eco-reconstructuring in the environment. Based on Guzhou village theenvironmental emigration area, which lies in northwest of Guangxi Province, based onstatistics and estimate index system of soil quality, the influence and response of soilquality to vegetation succession were evaluated. The results obtained are as follows:(1) Progressive succession can improve the physical condition of soil, increase soilfertility and reserve soil nutrients. Soil water content increased, while soil organicmatter was 2.27%, 3.23%, 6.35%, 9.00% at the grass stage,, grass-shrub stage, shrubstage and forest Stage respectively. The content of total phosphorus was higher at theearly stage than at any of the later stages, this indicate that phosphorus isn'taccumulated much in the later succession,changes in total phosphorus was0.063% (grassstage),0.115%(grass-shrub),0.097%(shrub stage)and0.040%(forest stage) respectively.In every succession, total kalium and soluble kalium increased at the beginning ofsuccession but decreased at the forest stage(2) With on-going succession, soil respiration (SR) decreased as follows forest stage＞grass-shrub stage＞shrub stage＞glass stage. There are the same tendency beweenO.M and Soil microbial biomass carbon(MBC), microbial biomass nitrogen(MBN).total amount of soil microbes increased with succession, were 2.83×10⁷number·g^-1soil (grass stage),3.28×10⁷ number·g^-1 soil(grass-shrub),6.57×10⁷ number·g^-1soil(shrub stage),7.15×10⁷ number·g^-1 soil (forest stage)respectively. Soil bacteriabeing the highest in number, followed by actinomycetes and lastly fungi. The rank orderis the same for both bacteria and actinomyces, the same tendency was observed betweenO.M and bacteria but there was no significant rule of fungi amount. Urease andphosphatase enhanced evidently with succession and correlated with O.M, the variety ofinvertase was not regulated but is correlative with SR.(3) Soil fertility accumulated with progressive succession. Integrated soil qualityindex (QI) increased with succession, respectively glass stage (0.09), grass-shrub stage(0.16), shrub stage (0.61), forest stage (0.89), progressive succession is a efficient wayto increase soil quality.