Indirect vegetation enhancement and its temperature sensitivity along urban-rural gradient: Correcting cropland bias

Urbanization environments provide a harbinger for vegetation productivity response to future global change. However, the urban-rural ecosystem is complex, featuring a variety of vegetation types, particularly crops and their accompanying intensive human management activities, which may introduce bias in the quantitative assessment of the vegetation net primary productivity (NPP) responses to urbanization. Using a 30-m resolution NPP dataset for Xi'an, China, this study indicated that NPP indirect enhancement in urbanization environments would decrease after removing crop-dominated pixels. Also, the sensitivity of vegetation productivity to temperature along the urban-rural gradient increased markedly after cropland removal, with the response nearly doubling in magnitude. A threshold phenomenon was observed that, as the temperature increased to 14.66 ± 0.04 °C (corresponding to urban intensity >94 %), the indirect enhancement would reach its limit. We advocate that future urban planning should control construction intensity and maintain a certain proportion of green spaces to mitigate potential heat-related stress.