Nitrogen deposition differentially regulates the sensitivity of gross primary productivity to extreme drought versus wetness.

Global hydroclimatic variability is increasing with more frequent extreme dry and wet years, severely destabilizing terrestrial ecosystem productivity. However, what regulates the consequence of precipitation extremes on productivity remains unclear. Based on a 9-year field manipulation experiment on the Qinghai-Tibetan Plateau, we found that the responses of gross primary productivity (GPP) to extreme drought and wetness were differentially regulated by nitrogen (N) deposition. Over increasing N deposition, extreme dry events reduced GPP more. Among the 12 biotic and abiotic factors examined, this was mostly explained by the increased plant canopy height and proportion of drought-sensitive species under N deposition, making photosynthesis more sensitive to hydraulic stress. While extreme wet events increased GPP, their effect did not shift over N deposition. These site observations were complemented by a global synthesis derived from the GOSIF GPP dataset, which showed that GPP sensitivity to extreme drought was larger in ecosystems with higher N deposition, but GPP sensitivity to extreme wetness did not change with N deposition. Our findings indicate that intensified hydroclimatic variability would lead to a greater loss of land carbon sinks in the context of increasing N deposition, due to that GPP losses during extreme dry years are more pronounced, yet without a synchronous increase in GPP gains during extreme wet years. The study implies that the conservation and management against climate extremes merit particular attention in ecosystems subject to N deposition.

Decreasing Greenhouse Gas Emissions from the Municipal Solid Waste Sector in Chinese Cites.

Municipal solid waste (MSW) management systems play a crucial role in greenhouse gas (GHG) emissions in China. Although the government has implemented many policies to improve the MSW management system, the impact of these improvements on city-level GHG emission reduction remains largely unexplored. This study conducted a comprehensive analysis of both direct and downstream GHG emissions from the MSW sector, encompassing sanitary landfill, dump, incineration, and biological treatment, across 352 Chinese cities from 2001 to 2021 by adopting inventory methods recommended by the Intergovernmental Panel on Climate Change (IPCC). The results reveal that (1) GHG emissions from the MSW sector in China peaked at 70.6 Tg of CO2 equiv in 2018, followed by a significant decline to 47.6 Tg of CO2 equiv in 2021, (2) cities with the highest GHG emission reduction benefits in the MSW sector were historical emission hotspots over the past 2 decades, and (3) with the potential achievement of zero-landfilling policy by 2030, an additional reduction of 203.7 Tg of CO2 equiv is projected, with the emission reduction focus toward cities in South China (21.9%), Northeast China (17.8%), and Southwest China (17.3%). This study highlights that, even without explicit emission reduction targets for the MSW sector, the improvements of this sector have significantly reduced GHG emissions in China.

The feedback of greening on local hydrothermal conditions in Northern China.

Northern China has experienced a significant increase in vegetation cover over the past few decades. It lacks a comprehensive understanding of how greening impacts local hydrothermal conditions. To address this issue, in our study, the RegCM-CLM45 model was used to conduct a thorough assessment of the impacts of greening on temperature, vapor pressure deficit (VPD), precipitation, and soil moisture. The findings revealed that the local climatic effects of greening varied across different drought gradients based on the aridity index (AI). In drier regions with AI<0.3, the increased energy induced by greening tended to dissipate as sensible heat, exacerbating both warming and drought conditions. Conversely, in wetter regions with AI>0.3, a greater proportion of energy was lost through evapotranspiration, attenuating warming. Additionally, greening enhanced precipitation and soil moisture in drier regions and moderated their decline in wetter regions. Significantly, our research emphasized the effectiveness of grassland expansion and conservation as prime strategies for ecological restoration, particularly in drylands, where they could effectively alleviate soil drought. Given the diverse responses of different land cover transformations to local hydrothermal conditions in drylands, there is an urgent need to address potential adverse effects arising from inappropriate ecological restoration strategies and to develop an optimal restoration framework for the future.

Imbalance in lake variability but not embodying driving factors on the Qinghai-Tibetan Plateau calls on heterogeneous lake management.

Comprehensive regional remote analysis tends to neglect lakes in exorheic basins on the Qinghai-Tibetan Plateau (QTP), and a concurrent lack of discussions on whether there exist imbalanced explanations for the driving forces of both internal and external lakes is also present. We integrate multisourced lake datasets, high-resolution information, and available altimetry datasets to establish multiple mathematical models to meta-simulate lake volume changes, extend current lake variation datasets, and quantify the imbalance of variations and factors driving the water mass budget. The results showed that the primary cause of lake variations in QTP is net precipitation (57.75 ± 31.46%), followed by glacier runoff (33.53 ± 31.42%), and permafrost (8.34 ± 7.87%). Even though glacier runoff is currently considered as a weak factor of lake variation, heterogeneous results call for remaining attention in glacier-induced lake basins. Imbalance embodying in lake variability but not in contributions of driving factors, which calls for special lake management ways in different watersheds.