Climate change vigorously threats human livelihoods,places and biodiversity.To lock atmospheric CO_(2)up through biological,chemical and physical processes is one of the pathways to mitigate climate change.Agricultura...Climate change vigorously threats human livelihoods,places and biodiversity.To lock atmospheric CO_(2)up through biological,chemical and physical processes is one of the pathways to mitigate climate change.Agricultural soils have a significant carbon sink capacity.Soil carbon sequestration(SCS)can be accelerated through appropriate changes in land use and agricultural practices.There have been various meta-analyses performed by combining data sets to interpret the influences of some methods on SCS rates or stocks.The objectives of this study were:(1)to update SCS capacity with different landbased techniques based on the latest publications,and(2)to discuss complexity to assess the impacts of the techniques on soil carbon accumulation.This review shows that afforestation and reforestation are slow processes but have great potential for improving SCS.Among agricultural practices,adding organic matter is an efficient way to sequester carbon in soils.Any practice that helps plant increase C fixation can increase soil carbon stock by increasing residues,dead root material and root exudates.Among the improved livestock grazing management practices,reseeding grasses seems to have the highest SCS rate.展开更多
Two virtual joint centers for nitrogen agronomy were established between the UK and China to facilitate collaborative research aimed at improving nitrogen use efficiency(NUE)in agricultural production systems and redu...Two virtual joint centers for nitrogen agronomy were established between the UK and China to facilitate collaborative research aimed at improving nitrogen use efficiency(NUE)in agricultural production systems and reducing losses of reactive N to the environment.Major focus areas were improving fertilizer NUE,use of livestock manures,soil health,and policy development and knowledge exchange.Improvements to fertilizer NUE included attention to application rate in the context of yield potential and economic considerations and the potential of improved practices including enhanced efficiency fertilizers,plastic film mulching and cropping design.Improved utilization of livestock manures requires knowledge of the available nutrient content,appropriate manure processing technologies and integrated nutrient management practices.Soil carbon,acidification and biodiversity were considered as important aspects of soil health.Both centers identified a range of potential actions that could be taken to improve N management,and the research conducted has highlighted the importance of developing a systemslevel approach to assessing improvement in the overall efficiency of N management and avoiding unintended secondary effects from individual interventions.Within this context,the management of fertilizer emissions and livestock manure at the farm and regional scales appear to be particularly important targets for mitigation.展开更多
Closed-form bounds for the end-to-end performance of multihop communications with non-regenerative relays over Nakagami-m fading channels are investigated.Upper and lower bounds of the end-to-end signal-to-noise ratio...Closed-form bounds for the end-to-end performance of multihop communications with non-regenerative relays over Nakagami-m fading channels are investigated.Upper and lower bounds of the end-to-end signal-to-noise ratio(SNR)are first developed by using the monotonicity.Then,the probability density functions(PDFs),the cumulative distribution functions,and the momentgenerating functions(MGFs)of the bounds are derived.Using these results,the bounds for the outage and average bit error probability(ABEP)are obtained.Numerical and simulation results are executed to validate the tightness of the proposed bounds.展开更多
基金supported by the Biotechnology and Biological Sciences Research Council(BBS/E/C/000I0320 and BBS/E/C/000I0330)。
文摘Climate change vigorously threats human livelihoods,places and biodiversity.To lock atmospheric CO_(2)up through biological,chemical and physical processes is one of the pathways to mitigate climate change.Agricultural soils have a significant carbon sink capacity.Soil carbon sequestration(SCS)can be accelerated through appropriate changes in land use and agricultural practices.There have been various meta-analyses performed by combining data sets to interpret the influences of some methods on SCS rates or stocks.The objectives of this study were:(1)to update SCS capacity with different landbased techniques based on the latest publications,and(2)to discuss complexity to assess the impacts of the techniques on soil carbon accumulation.This review shows that afforestation and reforestation are slow processes but have great potential for improving SCS.Among agricultural practices,adding organic matter is an efficient way to sequester carbon in soils.Any practice that helps plant increase C fixation can increase soil carbon stock by increasing residues,dead root material and root exudates.Among the improved livestock grazing management practices,reseeding grasses seems to have the highest SCS rate.
基金supported through Newton Fund via UK BBSRC/NERC(BB/N013484/1 and BB/N013468/1)。
文摘Two virtual joint centers for nitrogen agronomy were established between the UK and China to facilitate collaborative research aimed at improving nitrogen use efficiency(NUE)in agricultural production systems and reducing losses of reactive N to the environment.Major focus areas were improving fertilizer NUE,use of livestock manures,soil health,and policy development and knowledge exchange.Improvements to fertilizer NUE included attention to application rate in the context of yield potential and economic considerations and the potential of improved practices including enhanced efficiency fertilizers,plastic film mulching and cropping design.Improved utilization of livestock manures requires knowledge of the available nutrient content,appropriate manure processing technologies and integrated nutrient management practices.Soil carbon,acidification and biodiversity were considered as important aspects of soil health.Both centers identified a range of potential actions that could be taken to improve N management,and the research conducted has highlighted the importance of developing a systemslevel approach to assessing improvement in the overall efficiency of N management and avoiding unintended secondary effects from individual interventions.Within this context,the management of fertilizer emissions and livestock manure at the farm and regional scales appear to be particularly important targets for mitigation.
基金This work was supported by the National Basic Research Program of China(Nos.2007CB310604 and 2009CB320401)the National Natural Science Foundation of China(Grant No.60772108).
文摘Closed-form bounds for the end-to-end performance of multihop communications with non-regenerative relays over Nakagami-m fading channels are investigated.Upper and lower bounds of the end-to-end signal-to-noise ratio(SNR)are first developed by using the monotonicity.Then,the probability density functions(PDFs),the cumulative distribution functions,and the momentgenerating functions(MGFs)of the bounds are derived.Using these results,the bounds for the outage and average bit error probability(ABEP)are obtained.Numerical and simulation results are executed to validate the tightness of the proposed bounds.
