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The warming or cooling effects on regional climate in response to early land use change may be strengthened, weakened, or eliminated by the same or opposite effect in the subsequent land use/management period. Taking the Sanjiang Plain in China as our study area, this paper analyzed the surface temperature change due to land use/land management changes from the mid-1950s to 2015, based on the land surface temperature response model and the observation minus reanalysis (OMR) method using remote sensing data, meteorological observation data, and reanalysis data. Results revealed a magnitude of monthly mean land surface warming up to 1.31 degrees C due to the land use change from wetland to rain-fed farmland and a cooling effect of -1.32 degrees C caused by the land management change from rain-fed farmland to paddy fields during the growing season. The trends were confirmed using OMR method. Land surface temperature change based on remote sensing data was divided into radiative and nonradiative forcing. The nonradiative processes play a dominant role in regulating the local surface temperature. The monthly mean temperature differences in response to land use changes differ greatly during the growing season. The temperature difference was greater in May and June (spring) than in July and August (summer). Our study shows that the land use impact on regional climate could be switched dramatically, and it would be basically consistent with the impact of natural wetlands before reclamation in our study area right now, which provides important information for mitigating and adapting to global climate change at regional scale.

Plain Language Summary The Sanjiang Plain was once part of the Great Northern Wilderness in China, which has experienced extensive wetland drainage and farmland development since the mid-1950s. Then, large areas of rain-fed farmland have been rapidly transformed into paddy fields since the 1990s due to land management policies change and the pursuit of economic interests. The impacts of these successive land use changes on surface temperature were analyzed synthetically. We found that the warming effect of wetland reclamation over 40years has been eliminated due to the cooling effect of paddy field expansion since the 1990s. For both the change of wetland reclamation and paddy field expansion, the temperature difference was greater in May and June (spring) than in July and August (summer).