Globally a large number of process-based models have been assessed for quantification of agricultural greenhouse gas (GHG) emissions. Modelling approaches minimize the presence of spatial variability of biogeochemical...Globally a large number of process-based models have been assessed for quantification of agricultural greenhouse gas (GHG) emissions. Modelling approaches minimize the presence of spatial variability of biogeochemical processes, leading to improved estimates of GHGs as well as identifying mitigation and policy options. The comparative performance of the three dynamic models (e.g., DNDC v9.4, DailyDayCent and ECOSSE v5+) with minimum numbers of common input parameters was evaluated against measured variables. Simulations were performed on conventionally-tilled spring barley crops receiving N fertilizer at 135 - 159 kg·N·ha<sup>-</sup><sup>1</sup>·yr<sup>-</sup><sup>1</sup> and crop residues at 3 t·ha<sup>-</sup><sup>1</sup>·yr<sup>-</sup><sup>1</sup>. For surface soil nitrate (0 - 10 cm), the ECOSSE and DNDC simulated values showed significant correlations with measured values (R<sup>2</sup> = 0.31 - 0.55, p 0.05). Only the ECOSSE-simulated N<sub>2</sub>O fluxes showed a significant relationship (R<sup>2</sup> = 0.33, p 0.05) with values measured from fertilized fields, but not with unfertilized ones. The DNDC and DailyDayCent models significantly underestimated seasonal/annual N<sub>2</sub>O fluxes compared to ECOSSE, with emission factors (EFs), based on an 8-year average, were 0.09%, 0.31% and 0.52%, respectively. Predictions of ecosystem respiration by both DailyDayCent and DNDC showed reasonable agreement with Eddy Covariance data (R<sup>2</sup> = 0.34 - 0.41, p 0.05). Compared to the measured value (3624 kg·C·ha<sup>-</sup><sup>1</sup>·yr<sup>-</sup><sup>1</sup>), the ECOSSE underestimated annual heterotrophic respiration by 7% but this was smaller than the DNDC (50%) and DailyDayCent (24%) estimates. All models simulated CH<sub>4</sub> uptake we展开更多
Aims In recent years,there has been an increasing interest in the impact of invasive alien plant species on the soil seed bank.Soil seed banks play an important role in determining the composition and dynamics of the ...Aims In recent years,there has been an increasing interest in the impact of invasive alien plant species on the soil seed bank.Soil seed banks play an important role in determining the composition and dynamics of the vegetation through time.Therefore,an ability to form a persistent seed bank and/or a capacity to alter the structure of the seed bank of invaded communities could be important factors in determining the success of many alien plant species.In this study,we report on a detailed assessment of the characteristics of the seed bank community associated with the herbaceous plant invader,Gunnera tinctoria,a newly emerging and potentially globally significant invasive plant species.This species,native to South America,is invasive in a range of wet habitats in Europe,Australasia and the USA.Methods A comprehensive assessment of the seed bank of invaded and comparable uninvaded areas was made at two points in time(May and October),at three sites in western Ireland.The seedling emergence approach was used to assess the structure(diversity,dominance and abundance)of the soil seed bank.Differences between invaded and uninvaded seed bank communities were investigated at the spatial scales of site,plot and depth.Important Findings Gunnera tinctoria formed a large persistent seed bank at the study sites.Approximately 30000 seedlings per square metre emerged from soils collected from invaded areas,of which 30%were found in deep soil layers.Seedlings of this invader represented 53–86%of the total number of seedlings associated with invaded areas.Both the transient and the more persistent component of the seed bank of invaded communities were significantly less diverse and abundant than those of uninvaded areas,and were characterized by higher dominance,even when seedlings of the invader were not included in the analysis.The seed bank of invaded areas was largely composed of seeds of agricultural weeds in addition to those of the invader.These results suggest that G.tinctoria has the capacity to profoundly alter the seed bank of invaded communities.These results have direct relevance for the development of control and management strategies,for this and other comparable invasive species,which should account for both quantitative and qualitative alterations in the seed bank community.Our study also suggests that control measures that result in disturbance of areas colonized by G.tinctoria could promote the germination of undesirable weeds.展开更多
Almost everyone now seems to have a view about alien plant introductions and their significance and there is an ever increasing body of information,both in the scien-tific and popular press,about the dangers of allowi...Almost everyone now seems to have a view about alien plant introductions and their significance and there is an ever increasing body of information,both in the scien-tific and popular press,about the dangers of allowing the uncontrolled spread of alien species.Virtually all possible impacts of plant invasions have been reported,including alterations in biogeochemical cycling,disruption of food webs,alterations in plant-plant,plant-insect and plant-microbe interactions and reductions in biodiversity,leading to the proposal that this is resulting in the creation of novel or emerging ecosystems that have no historical analogue(Hobbs et al.2009).展开更多
Carbon(C)and nitrogen(N)coupling processes in terrestrial ecosystems have the potential to modify the sensitivity of the global C cycle to climate change.But the degree to which C–N interactions contribute to the seq...Carbon(C)and nitrogen(N)coupling processes in terrestrial ecosystems have the potential to modify the sensitivity of the global C cycle to climate change.But the degree to which C–N interactions contribute to the sequestration of terrestrial ecosystem C(C_(seq)),both now and in the future,remains uncertain.In this study,we used a meta-analysis to quantitatively synthesize C and N responses from feld experiments on grasslands subjected to simulated warming and assessed the relative importance of three properties(changes in ecosystem N amount,redistribution of N among soil,litter and vegetation,and modifcations in the C:N ratio)associated with grassland C_(seq) in response to warming.Warming increased soil,litter and vegetation C:N ratios and approximately 2%of N shifted from the soil to vegetation and litter.Warming-induced grassland C_(seq) was the result of the net balance between increases in vegetation and litter C(111.2 g·m^(−2))and decreases in soil C(30.0 g·m^(−2)).Warming-induced accumulation of C stocks in grassland ecosystems indicated that the three processes examined were the main contributors to C_(seq),with the changes in C:N ratios in soil,litter and vegetation as the major contributors,followed by N redistribution,whilst a decrease in total N had a negative effect on C_(seq).These results indicate that elevated temperatures have a signifcant infuence on grassland C and N stocks and their coupling processes,suggesting that ecological models need to include C–N interactions for more accurate predictions of future terrestrial C storage.展开更多
文摘Globally a large number of process-based models have been assessed for quantification of agricultural greenhouse gas (GHG) emissions. Modelling approaches minimize the presence of spatial variability of biogeochemical processes, leading to improved estimates of GHGs as well as identifying mitigation and policy options. The comparative performance of the three dynamic models (e.g., DNDC v9.4, DailyDayCent and ECOSSE v5+) with minimum numbers of common input parameters was evaluated against measured variables. Simulations were performed on conventionally-tilled spring barley crops receiving N fertilizer at 135 - 159 kg·N·ha<sup>-</sup><sup>1</sup>·yr<sup>-</sup><sup>1</sup> and crop residues at 3 t·ha<sup>-</sup><sup>1</sup>·yr<sup>-</sup><sup>1</sup>. For surface soil nitrate (0 - 10 cm), the ECOSSE and DNDC simulated values showed significant correlations with measured values (R<sup>2</sup> = 0.31 - 0.55, p 0.05). Only the ECOSSE-simulated N<sub>2</sub>O fluxes showed a significant relationship (R<sup>2</sup> = 0.33, p 0.05) with values measured from fertilized fields, but not with unfertilized ones. The DNDC and DailyDayCent models significantly underestimated seasonal/annual N<sub>2</sub>O fluxes compared to ECOSSE, with emission factors (EFs), based on an 8-year average, were 0.09%, 0.31% and 0.52%, respectively. Predictions of ecosystem respiration by both DailyDayCent and DNDC showed reasonable agreement with Eddy Covariance data (R<sup>2</sup> = 0.34 - 0.41, p 0.05). Compared to the measured value (3624 kg·C·ha<sup>-</sup><sup>1</sup>·yr<sup>-</sup><sup>1</sup>), the ECOSSE underestimated annual heterotrophic respiration by 7% but this was smaller than the DNDC (50%) and DailyDayCent (24%) estimates. All models simulated CH<sub>4</sub> uptake we
基金Environmental Protection Agency Ireland,under the National Development Plan 2000–2006.
文摘Aims In recent years,there has been an increasing interest in the impact of invasive alien plant species on the soil seed bank.Soil seed banks play an important role in determining the composition and dynamics of the vegetation through time.Therefore,an ability to form a persistent seed bank and/or a capacity to alter the structure of the seed bank of invaded communities could be important factors in determining the success of many alien plant species.In this study,we report on a detailed assessment of the characteristics of the seed bank community associated with the herbaceous plant invader,Gunnera tinctoria,a newly emerging and potentially globally significant invasive plant species.This species,native to South America,is invasive in a range of wet habitats in Europe,Australasia and the USA.Methods A comprehensive assessment of the seed bank of invaded and comparable uninvaded areas was made at two points in time(May and October),at three sites in western Ireland.The seedling emergence approach was used to assess the structure(diversity,dominance and abundance)of the soil seed bank.Differences between invaded and uninvaded seed bank communities were investigated at the spatial scales of site,plot and depth.Important Findings Gunnera tinctoria formed a large persistent seed bank at the study sites.Approximately 30000 seedlings per square metre emerged from soils collected from invaded areas,of which 30%were found in deep soil layers.Seedlings of this invader represented 53–86%of the total number of seedlings associated with invaded areas.Both the transient and the more persistent component of the seed bank of invaded communities were significantly less diverse and abundant than those of uninvaded areas,and were characterized by higher dominance,even when seedlings of the invader were not included in the analysis.The seed bank of invaded areas was largely composed of seeds of agricultural weeds in addition to those of the invader.These results suggest that G.tinctoria has the capacity to profoundly alter the seed bank of invaded communities.These results have direct relevance for the development of control and management strategies,for this and other comparable invasive species,which should account for both quantitative and qualitative alterations in the seed bank community.Our study also suggests that control measures that result in disturbance of areas colonized by G.tinctoria could promote the germination of undesirable weeds.
文摘Almost everyone now seems to have a view about alien plant introductions and their significance and there is an ever increasing body of information,both in the scien-tific and popular press,about the dangers of allowing the uncontrolled spread of alien species.Virtually all possible impacts of plant invasions have been reported,including alterations in biogeochemical cycling,disruption of food webs,alterations in plant-plant,plant-insect and plant-microbe interactions and reductions in biodiversity,leading to the proposal that this is resulting in the creation of novel or emerging ecosystems that have no historical analogue(Hobbs et al.2009).
基金supported by the Excellent Youth Scholars Program and the Special Project on Hi-Tech Innovation Capacity(KJCX20210416)from Beijing Academy of Agriculture and Forestry Sciences(BAAFS)the National Key Research and Development Program of China(2017YFA0604604).
文摘Carbon(C)and nitrogen(N)coupling processes in terrestrial ecosystems have the potential to modify the sensitivity of the global C cycle to climate change.But the degree to which C–N interactions contribute to the sequestration of terrestrial ecosystem C(C_(seq)),both now and in the future,remains uncertain.In this study,we used a meta-analysis to quantitatively synthesize C and N responses from feld experiments on grasslands subjected to simulated warming and assessed the relative importance of three properties(changes in ecosystem N amount,redistribution of N among soil,litter and vegetation,and modifcations in the C:N ratio)associated with grassland C_(seq) in response to warming.Warming increased soil,litter and vegetation C:N ratios and approximately 2%of N shifted from the soil to vegetation and litter.Warming-induced grassland C_(seq) was the result of the net balance between increases in vegetation and litter C(111.2 g·m^(−2))and decreases in soil C(30.0 g·m^(−2)).Warming-induced accumulation of C stocks in grassland ecosystems indicated that the three processes examined were the main contributors to C_(seq),with the changes in C:N ratios in soil,litter and vegetation as the major contributors,followed by N redistribution,whilst a decrease in total N had a negative effect on C_(seq).These results indicate that elevated temperatures have a signifcant infuence on grassland C and N stocks and their coupling processes,suggesting that ecological models need to include C–N interactions for more accurate predictions of future terrestrial C storage.
