The application of Gray GM (1,1) model and Verhulst model in the forecast of farmland in the karst area — A case in Bijie ecological experimental area

As a typical karst area with a dense population and fragile ecological environment as well as serious soil erosion in Bijie ecological experimental area, the farmland protection is particularly important. Based on the statistic data of farmland from 1998 to 2006 in Bijie Region, this paper forecasts the changes of farmland in karst region with GM (1,1) model and the Verhulst model respectively. The forecast results show that both GM (1,1) model and the Verhulst model reveal the cultivated land in Bijie Region decreases gradually in the next years. However, by the NC verification of the model, the change of the original data of the cultivated land in the study area shows an S curve. To the imitation of the original data, the prediction results of the grey GM (1,1) are more accuracy than the Verhulst model, while the Verhulst is more suitable for the forecast of the changes in the coming years of the cultivated land in the study area. It can provide the basis for the rational use of land resources, the preparation of land-use planning and the protection of farmland.