Slope grade difference of cropland spatial pattern in China

China’s requisition-compensation balance strategy has dramatically reshaped cropland spatial patterns, drawing multidisciplinary research attention. However, existing studies predominantly emphasize horizontal distribution, overlooking the significant influence of slope gradient on cropland spatial patterns. This paper proposes a slope location quotient (SLQ) index that reflects the relative advantage of cropland distribution and explores the slope grade difference of cropland spatial patterns in China at the county scale. The analysis adopts 30-m resolution digital elevation model with land cover data, taking 2672 counties with cropland ratio >1% as study units. The temporal scope covers 1990 and 2020, with slope gradients categorized into five grades: 0°~2°, 2°~6°, 6°~15°, 15°~25°, and 25°~90°. Results show that: 1) The inverse correlation between cropland area and slope gradient remained stable throughout the study period, with the variation in cropland area frequency across slope grades being less than 1%. 2) The spatial patterns of SLQ in 1990 and 2020 both transited stepwise with slope gradient, while ≤2° and >6° slopes exhibited opposing patterns. 3) The mean absolute variation of SLQ during 1990-2020 increased with slope gradient (R²=0.926, p<0.01). Particularly for slope grades > 15°, the mean absolute variation reached 0.26 (for 15°~25°) and 0.43 (for 25°~90°), respectively, and displayed a distinct southward-increasing and northward-decreasing pattern. This study offers novel slope-gradient perspectives for analyzing cropland spatial patterns. To enhance cropland protection benefits, reversing the steep cropland SLQ surge in southern China is recommended.