Spatio-temporal variations of vegetation carbon use efficiency and potential driving meteorological factors in the Yangtze River Basin

Understanding of the vegetation dynamics is essential for addressing the potential threats of terrestrial ecosystem. In recent years, the vegetation coverage of the Yangtze River Basin (YRB) has increased significantly, yet the spatio-temporal variations and potential driving meteorological factors of carbon use efficiency (CUE) under the context of global warming are still not clear. In this study, MODIS-based public-domain data during 2000–2015 was used to analyze these aspects in the YRB, a large river basin with powerful ecological functions in China. Spatio-temporal variations of CUE in different sub-basins and land cover types were investigated and the correlations with potential driving meteorological factors were examined. Results revealed that CUE in the YRB had strong spatiotemporal variability and varied remarkably in different land cover types. For the whole YRB, the average CUE of vegetated land was 0.519, while the long-term change trend of CUE was obscure. Along the rising altitude, CUE generally showed an increasing trend until the altitude of 3900 m and then followed by a decreasing trend. CUE of grasslands was generally higher than that of croplands, and then forest lands. The inter-annual variation of CUE in the YRB is likely to be driven by precipitation as a strong positive partial correlation between the inter-annual variability of CUE and precipitation was observed in most of sub-basins and land cover types in the YRB. The influence of temperature and relative humidity is also outstanding in certain regions and land cover types. Our findings are useful from the view point of carbon cycle and reasonable land cover management under the context of global warming.