Lowering cropland use intensity through crop-fallow rotation optimization fosters a resilient water future in the central farming-pastoral ecotone of northern China

The central farming-pastoral ecotone of northern China (CFPENC), a key food-producing region, faces significant water resource challenges due to intensified agricultural activities. To address this, China initiated a pilot crop-fallow rotation system, yet its practical application remains largely unexplored. In this context, we developed a sensitive and high-resolution evaluation indicator for cropland use intensity (cLUI), using Ulanqab as a case study to investigate its spatiotemporal dynamics and ecological impacts over the past decade. Our analysis revealed an overall increase in Ulanqab's cLUI, with 59.09% of townships showing upward trends while 40.91% demonstrated downward shifts. Notably, the proportion of cropland exhibiting decreased cLUI was marginally higher. From 2010–2014, cLUI levels in Houshan and Qianshan were comparable, but Houshan significantly exceeded Qianshan from 2015 to 2019. Irrigated fields had the highest cLUI, followed by center pivot irrigation (CPI) fields and rainfed fields, with the fields implementing the green depressing cropping system (GDCS) showing the lowest. Approximately one-fifth of croplands exhibit moderate cLUI. Rising cLUI levels may exacerbate surface water shrinkage and groundwater depletion. Finally, we proposed a crop-fallow rotation regulation strategy to promote sustainable water management.