Climatic change controls productivity variation in global grasslands.

Detection and identification of the impacts of climate change on ecosystems have been core issues in climate change research in recent years. In this study, we compared average annual values of the normalized difference vegetation index (NDVI) with theoretical net primary productivity (NPP) values based on temperature and precipitation to determine the effect of historic climate change on global grassland productivity from 1982 to 2011. Comparison of trends in actual productivity (NDVI) with climate-induced potential productivity showed that the trends in average productivity in nearly 40% of global grassland areas have been significantly affected by climate change. The contribution of climate change to variability in grassland productivity was 15.2-71.2% during 1982-2011. Climate change contributed significantly to long-term trends in grassland productivity mainly in North America, central Eurasia, central Africa, and Oceania; these regions will be more sensitive to future climate change impacts. The impacts of climate change on variability in grassland productivity were greater in the Western Hemisphere than the Eastern Hemisphere. Confirmation of the observed trends requires long-term controlled experiments and multi-model ensembles to reduce uncertainties and explain mechanisms

On the use of an explicit chemical mechanism to dissect peroxy acetyl nitrate formation.

Peroxy acetyl nitrate (PAN) is a key component of photochemical smog and plays an important role in atmospheric chemistry. Though it has been known that PAN is produced via reactions of nitrogen oxides (NOx) with some volatile organic compounds (VOCs), it is difficult to quantify the contributions of individual precursor species. Here we use an explicit photochemical model--Master Chemical Mechanism (MCM) model--to dissect PAN formation and identify principal precursors, by analyzing measurements made in Beijing in summer 2008. PAN production was sensitive to both NOx and VOCs. Isoprene was the predominant VOC precursor at suburb with biogenic impact, whilst anthropogenic hydrocarbons dominated at downtown. PAN production was attributable to a relatively small class of compounds including NOx, xylenes, trimethylbenzenes, trans/cis-2-butenes, toluene, and propene. MCM can advance understanding of PAN photochemistry to a species level, and provide more relevant recommendations for mitigating photochemical pollution in large cities

Complex responses of spring vegetation growth to climate in a moisture-limited alpine meadow.

Since 2000, the phenology has advanced in some years and at some locations on the Qinghai-Tibetan Plateau, whereas it has been delayed in others. To understand the variations in spring vegetation growth in response to climate, we conducted both regional and experimental studies on the central Qinghai-Tibetan Plateau. We used the normalized difference vegetation index to identify correlations between climate and phenological greening, and found that greening correlated negatively with winter-spring time precipitation, but not with temperature. We used open top chambers to induce warming in an alpine meadow ecosystem from 2012 to 2014. Our results showed that in the early growing season, plant growth (represented by the net ecosystem CO2 exchange, NEE) was lower in the warmed plots than in the control plots. Late-season plant growth increased with warming relative to that under control conditions. These data suggest that the response of plant growth to warming is complex and non-intuitive in this system. Our results are consistent with the hypothesis that moisture limitation increases in early spring as temperature increases. The effects of moisture limitation on plant growth with increasing temperatures will have important ramifications for grazers in this system

The influence of nutrient management on soil organic carbon storage, crop production, and yield stability varies under different climates

Acknowledgements Present study was conducted with the support of German-Chinese cooperation on agriculture and climate change (CHN-19-02) and Coordination of International Research Cooperation on Soil Carbon Sequestration in Agriculture (CIRCASA 774378).Peer reviewedPostprin

Rural livelihoods and vulnerability to climate hazards in Ningxia, Northwest China

This study addresses how climate affects the livelihoods of people living in agricultural communities in Ningxia, one of the five autonomous regions in China. The analysis formed part of a vulnerability assessment to contribute to the development of an adaptation strategy for the region. Data were collected through questionnaires and focus group discussions in nine villages, three located in each of three different agro-ecosystems in the region. The survey results showed that drought has been a major hazard impacting rural livelihoods. Farmers in all three agro-ecosystems showed differing levels of vulnerability; susceptibility was higher, for instance, in the middle arid and southern rainfed mountainous areas, due to farmers’ greater exposure to climatic hazards and because a greater proportion of income originates from farming activities. Recent climate variability had affected many aspects of farmers’ livelihoods but it was not the only challenge they had faced. The perennially dry climate is a significant limiting factor for agricultural production in the region, greatly exacerbated by periodic reductions in moisture due to drought. Unsurprisingly, farmers have developed and continue to use a wide range of measures to retain and enhance soil moisture and to maintain agricultural production in this harsh environment: adaptation is an inherent feature of their behaviour, but their capacity to act is determined by a range of factors. When questioned on the constraints they faced respondents cited most often lack of money, water shortage and agricultural inputs. Because of the close alignment at the community and household level between adaptation and more generic individual and institutional aims for development there exists good potential to incorporate adaptation objectives and measures into mainstream development plans and poverty alleviation programmes