Spatiotemporal differentiation of the terrestrial gross primary production response to climate constraints in a dryland mountain ecosystem of northwestern China

Monitoring seasonal and interannual variability in gross primary production (GPP) and attributing these changes to climate change across various ecosystems helps to predict the future climate-carbon cycle feedback. However, such studies are scarce in dryland mountain ecosystems, possibly because of high spatial heterogeneity in landscapes and terrain. To better understand how carbon fluxes of the dryland mountain ecosystem respond to meteorology, we identified the trend and driving mechanism related to GPP in the Qilian Mountains (QLMs) of northwestern China from 2000 to 2016 by adopting the vegetation photosynthesis model that incorporates satellite and meteorological data. Our results revealed contrasting GPP trends in the growing season (May-September) between 2000-2010 and 2010-2016. In the later period, widespread GPP reductions were found across almost the whole area, especially at the middle and end of the growing season. In the central part of the QLMs, GPP reductions were induced by warming hiatus in contrast to drought in the western and eastern parts. Responses of GPP to temperature, precipitation and solar radiation differed in seasons and biomes. The positive effect of rising temperature that increased GPP was dominant during the growing season. The interannual variability in GPP was positively related to precipitation in June and July, but was negatively related to precipitation in other months. A positive correlation between forest GPP and solar radiation occurred in all months but July. Desert GPP responded negatively to solar radiation in all months but September. Temperature and solar radiation accounted for most of the interannual variability in forest GPP. Temperature was the major climate constraints on the interannual variability in grassland GPP. Precipitation and solar radiation primarily controlled the interannual variability in desert GPP from July to September, while temperature became more limited than precipitation and solar radiation for desert GPP in May and June.