Magnitude and impacts of non-rainfall water inputs and nocturnal evapotranspiration on temperate grassland ecosystems

• Nocturnal water gains or losses varied across spatial and elevational gradients. • Nocturnal water gains were mainly driven by air temperature changes. • Nocturnal water losses were mainly driven by dew point depression. • Early-morning net ecosystem CO 2 fluxes did not benefit from nocturnal water gain. Non-rainfall water (NRW, mainly dew and fog) and night-time evapotranspiration (ET night ) are opposite phenomena which induce water gain and water loss of ecosystems, respectively. However, how NRW inputs and ET night vary across spatial scales, and what drives their flux magnitude is less clear. In this study, we combined highly-accurate micro-lysimeters with environmental measurements to investigate the spatial variability of NRW inputs and ET night at nine grasslands as well as the most important drivers of their flux magnitude. Further, we explored the influence of NRW inputs and ET night on net ecosystem CO 2 exchange in the morning hours. Our results showed that changes in NRW inputs and ET night were independent of elevation, but strongly affected by terrain. Moreover, NRW inputs and ET night were controlled by different environmental drivers, with NRW inputs mainly driven by air temperature changes and event duration, while ET night was mainly driven by dew point depression, soil moisture, and wind speed. Net ecosystem exchange in the early morning hours did not benefit from NRW inputs during the previous night. Our study revealed that the relevance of NRW inputs for temperate grasslands was low, but increasing ET night losses due to climate change will pose additional challenges to grasslands in the future.