Abstract: By the methods of classic statistics and geostatistics, this paper analyzed the spatial heterogeneity of soil moisture at 0-50 cm depth in different sampling grain sizes (1 m×1 m and 2 m×2 m) at the cropland-grassland boundary in agro-pastoral transitional zone of North China. In study area, the soil moisture at 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, and 40-50 cm depths of cropland, grassland, and cropland-grassland boundary presented moderate variance, and the  coefficient of variation (CV) of grassland was highrr than that of cropland. The CV increased with soil depth, and a significant linear regression relation(P＜0.05) was observed between them in sampling grain size 1 m×1 m. In sampling grain size 1 m×1 m, the spatial heterogeneity of soil moisture at different depths was obviously higher at croplandgrassland boundary than in cropland and grassland, which had a moderate to strong spatial dependency, and the range (A₀) was 7.65-30.99 m; whereas in sampling grain size 2 m×2 m, the spatial distribution of soil moisture at cropland-grassland boundary had both the moderate to strong spatial dependency and the pure nugget effect, and the A₀ was 4.16-18.86 m, suggesting that there existed ecological edge effect of soil moisture at croplandgrassland boundary.

Key words: cropland-grassland boundary, soil moisture, spatial heterogeneity, edge effect, peanut, calcium fertilizer, drought stress, physiological characteristics, yield and quality.