Vegetation production is an important variable in terrestrial ecosystems, playing crucial roles in sustaining carbon balance, reducing atmospheric CO2 concentration, and mitigating global climate change. Satellite-based models, which benefit from spatially and temporally continuous remote sensing observations of vegetation growth conditions, are widely used for quantifying regional and global vegetation production. Satellite-based vegetation production models were initially simple statistical models, but later, process-based light use efficiency models were developed. The latest models are based on the relationship between solar-induced chlorophyll fluorescence and vegetation production. An increasing number of satellite-based studies are being conducted by Chinese scientists, who are developing and implementing plant production models, particularly by self-developing a number of light consumption efficiency models and establishing a long-term worldwide dataset of vegetation production. Furthermore, Chinese scientists have investigated the spatial and temporal patterns of vegetation using diverse models, significantly improving our understanding of terrestrial functions and structures. However, current models and estimation techniques need further improvement, and Chinese scientists had the opportunity to improve model capability and our understanding of vegetation production patterns and their regulating elements.
Global soil erosion redistributes a large amount of soil organic carbon (SOC) and is potential to significantly change the terrestrial carbon budget. However, there are large uncertainties in the redistribution of SOC within the terrestrial and aquatic ecosystems. Based on two national survey data sets on soil erosion and sediment measurements from hydrological stations, this study estimated the redistribution of sediment and SOC in the nine river basins of China during 1995China during -1996China during and 2010China during -2012. Over these two periods, 3.55-4.50 Pg of soil and 68.42-77.32 Tg C of SOC were eroded each year. For the SOC budget, on average 57% and 47% of the eroded SOC was deposited over land, 25% and 44% was deposited in the channel, and 18% and 8% was delivered into the sea during 1995-1996 and 2010-2012, respectively. Compared with the corresponding magnitudes during 1995-1996, the eroded SOC, the SOC deposited over land, and the SOC discharged into the sea decreased during 2010-2012, and only the SOC deposited into the river channel increased (from 19.5 to 30.1 Tg C yr −1 ). The changes in SOC deposition in the channel of the Yangtze River and the Yellow River basins demonstrate that the influence of human activities is extensive. Our results show that the erosion-induced redistribution of SOC alters the carbon budget of China.
Dry spell length (DSL), consecutive non‐rainy days between two precipitation events, play an important role in regulating soil moisture dynamics, terrestrial energy exchange as well as vegetation growth. According to the Clausius‐Clapeyron (C‐C) relationship, global warming can result in prolonged DSL. However, usually the amount of precipitation and its characteristics coincidentally varied with the changes of DSL under global warming, it remains unclear how the inter‐annual variation of precipitation interacts with the evolution of dry spells. In this study, the global long‐term in‐situ observation data set of daily precipitation during 1976–2019 was used to examine the spatiotemporal trends of growing season DSL and precipitation. Our results showed that the global mean growing season DSL significantly increased by 0.3 days decade−1 during 1976–1998 while no significant trend of that was observed during 1999–2019. In contrast, the growing season precipitation (Prec_GS) showed no significant trend in 1976–1998 whereas significant increase trend of that was observed in 1999–2019. To explore the impacts of precipitation on the evolution of dry spells, we examined the relationship between the growing season DSL and Prec_GS. We found that prevalent negative relationship was observed between growing season DSL and Prec_GS in 88% and 86% stations during the period of 1976–1998 and 1999–2019, respectively. Spatially, the mean annual Prec_GS and DSL showed significantly negative relationship, that is, the stations with more precipitation showed shorter DSL in growing season, and vice versa. The changes of mean annual Prec_GS explained 81% spatial variation of growing season DSL. Moreover, during the period of 1999–2019 significant increase of precipitation frequency and decrease of dry day frequency were also observed in addition to the increase of Prec_GS in this period. The decreased dry day frequency further resulted in the decrease of growing season DSL. By excluded the impacts of precipitation, the DSL/Prec_GS ratio showed significant decreasing trend during 1999–2019. Our study suggested that the spatiotemporal variations of DSL were modulated by the variation of precipitation. The impacts of precipitation changes on ecosystem by altering the dry spell evolution should be considered in modeling the terrestrial carbon and hydrological cycling in response to climate changes.
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