The response of agroecosystem water use efficiency to cropland change in northwest China’s Hexi Corridor
Linshan Yang, Qi Feng, Tiaoxue Lu, Jan Adamowski, Zhenliang Yin, Shadi Hatami, Meng Zhu, Xiaohu Wen
Abstract
China’s rapid population growth has inevitably led to a need for cropland expansion to meet food security challenges. In arid regions such an expansion is restricted by limited water resources, and an increase in productivity per cropland area must be achieved while still limiting water use. However, the response of agroecosystem Water Use Efficiency (WUEa.e.) to alterations in cropland use in Northwest China’s Hexi Corridor has not been documented in any great detail. This has limited our understanding of the region’s water-carbon interactions and, in particular, how effective cropland management and efficient water utilization protocols might be applied there. The response of the region’s WUEa.e. to different potential shifts in cropland was evaluated by drawing on growing season (2003–2020), Gross Primary Productivity (GPP) and actual evapotranspiration (ETcact) data. Over this period net cropland area increased, with 12.3 % of total cropland transferred in, but only 2.5 % of cropland transferred out. The trend in growing season WUEa.e. was greatest in cropland regions transferred in (p < 0.05), and lowest in the cropland transferred out, indicating irrigation and field management in cropland could ensure that WUEa.e. could be maintained at a higher level. Among the different cropland transformation types, the impact of cropland change on WUEa.e. was essentially determined by shifting correlations between GPP and ETcact. This correlation was weakened when the water supply increased, heightening the negative impact of ETcact on WUEa.e., while weakening the positive impact of GPP on WUEa.e.. There was a tradeoff point for the level of irrigation between improving WUEa.e. and crop yield. Suitable water-saving irrigation is crucial to maintaining a relatively high level of WUEa.e., yet not decreasing crop yield. Water-saving irrigation in the Shiyang River basin was deemed to have limited potential, whereas in the Shule River and Heihe River basins there remains some potential for such irrigation. The present study’s results can potentially inform agricultural water and land management in the region, and provide the basis for efficient water resources utilization.