Assessment of China's food producing capacities using a web-based land evaluation engine and a grid-based GIS

In this paper, we present a computer-aided assessment of the producing capacities of major food crops in China, using the Web-based Land Evaluation System “WLES” as the evaluation engine, a grid-based GIS as the scale regulator and a relational database as the data manipulator. The WLES accepts client’s requests and provides LE services through its Web interfaces. The LE engine implements a three-step, hierarchical, deterministic land evaluation (LE) model, based on a quantification of the radiation-thermal production potential (FAO methodology), the water-limited production potential and the land production potential of the crops considered. Functional components such as the biomass calculator (BMC), the water balance simulator (WBS) and the land limitations evaluator (LLE) compute these potentials, respectively. Homogeneous 5 km by 5 km grid datasets were created to store the spatial distribution of the climatic, crop and soil parameters. Using the cell number as the key, all data were stored in the relational database for fast and easy access. A client-side script simulated the food production in 2005 considering, among others, the land use type and distribution, province-specific cropping system patterns, and the intensity of factor inputs, represented by the effective irrigation rate, the fertilizer application rate and the management level. The simulation process was looped to iterate all the 778,104 grid cells, and output stored in the database on a per cell basis. The evaluation results were cross-analyzed against the historic and current yield records of the crop variety and input level combinations for each province. This validation procedure reflected the reliability of the modelling approach and revealed the goodness of the production scenario design. Food producing capacities towards 2030 and 2050 were projected. Province-specific potential productivity index were calculated, and spatial patterns of the high-intermediate-low yielding croplands in food production were identified. The WLES, together with its full documentation, is available at http://weble.ugent.be/