Water yield is of great importance to the balance between supply and demand of water resources. The provision of freshwater for Dali is estimated and mapped in 1988, 1995, 2000, 2005 and 2008, using the Integrated Valuation of Environmental Services and Tradeoffs (InVEST) modeling toolset. The stability of water yield’s spatial variation is analyzed by a sorting method. The factors are explored which lead to the change in the relative water yield capacity. The yields at five points in time are compared, and the result of which shows a sharp fluctuation. The water yield curve is of a similar waveform as precipitation. An obvious and relatively stable spatial variation appears for water yield. The highest water yield areas are mainly located in the area where the elevation is high and both the elevation and the slope changes are large, and the main land uses are Shrub Land and High Coverage Grassland. The lowest areas are mainly in the eastern part of Erhai or the surrounding area. Precipitation, construction land expansion and the implementation of policy on land use are the three main factors which contribute to the change of the relative water yield capacity during 1988–2008 in Dali. In the study area, the water yield appears highly sensitive to the change in precipitation. The elasticity coefficient is calculated to illustrate the sensitivity of the water yield to the precipitation. When the elasticity index is larger, the risk of natural disaster will be higher.

This paper aimed at using the niche-fitness analysis method to assess soil fertility of cultivated land in Jianghan Plain in China. By introducing the niche-fitness theory into comprehensive analysis of soil fertility, an evaluation method was developed using geographic information systems (GIS) and the soil basic niche-fitness model (SBNFM). To begin with, 10 indicators were selected and used to assess the spatial differences of soil fertility for cultivated land, and its weight was decided using analytic hierarchy process (AHP). Soil samples were collected from topsoil (0–25 cm) in 58 units and examined for pH, organic matter (OM), total nitrogen (TN), etc. After standardizing soil attribute data of each unit, the optimum niche of every indicator was obtained and the soil basic niche-fitness value of each plot was calculated by using SBNFM. Finally, the soil fertility of the cultivated land was divided into four grades based on the shortest distance cluster analysis method in this area. Results indicate that the soil fertility of the cultivated land in this area was on the medium and high side, the percentages of area in grades 1, 2, 3 and 4 accounted for 33.43%, 35.99%, 22.70% and 7.88%, respectively; thus, approximately 70% of the cultivated land was classified in the top two grades. The linear-correlated relationship between niche-fitness value and rice yield has shown that SBNFM is an important and effective tool to analyze soil fertility and evaluate the quality of cultivated land. The above results might be helpful and support fertilizer management or agricultural activity in the study area.