The emergy of metabolism in different ecosystems under the same environmental conditions in the agro-pastoral ecotone of northern China

•The emergy inputs and outputs of ten ecosystems show obvious differences in the agro-pastoral ecotone of northern China.•Rain input constituted the highest renewable natural resource emergy.•Purchased emergy input is the direct cause of the development of the ecosystems under the same environmental conditions.•Groundwater was the most important non-renewable purchased energy for the production of economic crops.•Because of low environmental load and high sustainability, rain-fed artificial grassland has a high development potential.