Measuring urbanization-occupation and internal conversion of peri-urban cultivated land to determine changes in the peri-urban agriculture of the black soil region

Structural change in peri-urban cultivated land is an effective indicator of variations in the human-land relationship and can be used to evaluate the development of peri-urban agriculture (PUA) under the pressure of rapid urbanization. However, urbanization-occupation and internal conversion, two of the primary changes in peri-urban cultivated land, have rarely been comparatively studied, especially not in an area characterized by uniform and persistent agricultural structure. Therefore, the present paper selected Changchun City in the black soil region of northeast China as a representative case, and performed land use change and spatial cluster analyses to measure changes in rainfed land, paddy land, irrigated land and orchards in the peri-urban area throughout a period of rapid urbanization (1996-2015). The results indicate that irrigated land and orchards were mainly distributed within urban-adjacent areas, and paradoxically showed an evident decrease in quantity across time. The urbanization-occupied cultivated lands revealed an imbalance in the loss and gain of peri-urban cultivated land following rapid urbanization that favors grain production. Meanwhile, the results concerning internal conversion indicate a relatively strong conversion from non-staple food production to grain production. The cultivated lands converted for grain production in the peri-urban area were mostly located at the urban fringe and positively associated with the urbanization-occupied cultivated lands. However, the cultivated lands that were converted for the production of non-staple food were relatively small-scale, sparsely distributed and located far from the central urban area. Nevertheless, both types of internal conversion were gradually overshadowed by the ever-increasing urbanization. Our study revealed an impaired local supply of non-staple food and an overall reduction in the diversified use of peri-urban cultivated lands in the black soil region. These findings suggest that the current structure of peri-urban cultivated land in the black soil region of northeast China may well be insufficient for supporting sustainable PUA development.