Abstract: Based on a multilevel model, the expansion mechanism of farmland in Horqin steppe of northern China was studied at field, household, and village levels. The results showed that there was no significant difference among households in reclaiming the steppe. The households with extra labor force and relatively higher basic education tended to reclaim steppe if they lived mainly on cultivation and animal breeding, while those with large livestock number were not favorable for farmland expansion. Corn cultivation was more sensitive to economic situations, while rice planting was more constrained by natural conditions. Therefore, relatively good basic education might favor the conversion of grassland to farmland, while transferring residual labor forces might detain the trend.

Key words: heat stress, spatiotemporal distribution, double-early rice, dynamic indicator