| Problems on resource, circumstance and population are always great for human beings. Those problems are more grave in karst region. Karst medium space has a two-layer frame in surface and below ground. So these karst series problems are lowness ability of making soils, distributing odds of surface water and groundwater, leakiness of fountain, alkalescence of circumstance, lowness of bio-diversity, rapidness converse succession of vegetation and fragility of soil character and entironment. And karst region produces many problems, e.g. rock desert, soil erosion and degeneration because of artificial influence and destruction. Degeneration problems of karst soil fertility are mostly soil leanness, vegetation reduction, and natural environment erosion and rock desert. When the karst entironment is unreasonable utilized (e.g. wasteland using, woods damage, cultivation of steep and slope and excess graze etc.) and produces obsolescence once, the problem is more grave and it is difficult to manage and renew because of its fragility particularity.Carbonate area gets to 41.05X 104 km2 in southwest China. It is the maximal continuum of karst mountain in the world. The dimensionality area is about 82.4 thousands km2 in Chongqing region. The carbonate area is to 32 thousands km2 and it occupies to 38.83% of Chongqing dimensionality area. And it mostly distributes in the northeast and southeast. The districts andVIcounties, which carbonate distribution area is beyond 50% of dimensionality area, include Nantong, Nanchuan, Wulong, Pengshui, Qianjiang, Youyang, Xiushan, Wuxi and Chengkou. The counties, which carbonate is beyond 30% include Fengdu, Fengjie and Wushan. And the counties that the carbonate is beyond 28% are Shizhu and Puling. As a kind of fragility ecosystem, it is necessary and important that the soil fertility, degeneration and reestablishment in karst circumstance are realized entirely.Three representative karst counties in Chongqing region are selected as sample sites in this research. They are Jinfo Mountain in Nanchuan county (natural protection section), Wuling Mountain in Qianjiang county (national emphases forest demonstration county which forest cover rate is beyond 50%) and Zhongliang Mountain in Beibei county (artificial destruction is very grave). Some main land use patterns i.e. woodland, garden, infield, abandon infield, shrub and grassplot are selected in those three sample sites. Four aspects on soil fertility index of karst environment under different land use patterns in these three sample sites, are revealed in this paper, by using the field test, indoor measure and analysis, outdoor experiment and field investigation, and the knowledge and technique of soil, ecology, physics and chemistry etc. They are physical characteristic (effective soil thickness, organic layer thickness, soil texture, water-stable aggregate and soil water etc.), chemical fertility (organism, omni-N, omni-P, omni-K, alkali-nitrogen, available P, available K and rapid available K etc.), soil animalcule (bacteria, fungi, actinomyces and their grosses) and soil-seed-pool (plant community diversity index) in karst ecosystem. The results are summarized below:1) Study on soil science indicates that soil granular structure is the focus adjuster for soil fertility and it affects the space, water-grasp, aeration and anti-erosion of soil. And the percentage of aggregate is one of the key index that decides the speed and extent of soil erosion, hardening and degeneration because the soil degeneration will first lead to the disappearance of crumb-structure. So it is very important that the physical course and character of soil in different land use pattern are realized. Study on granular structure in lateritevnsoil has already been reported in different land use pattern but it is little about soil fertility in karst environment.The better the soil structure, the higher the content of water-stable soil aggregate so there is an osculation correlation between aggregate and structure of soil. Percentage of...
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