Background:More frequent and severe drought events due to climate change pose a major challenge for sustainable forage production in managed grasslands.This study investigated whether multispecies grassland communitie...Background:More frequent and severe drought events due to climate change pose a major challenge for sustainable forage production in managed grasslands.This study investigated whether multispecies grassland communities can provide greater resistance to and/or recovery from drought compared to monoculture communities.Methods:Mesocosms of Lolium perenne L.,Cichorium intybus L.,Trifolium repens L.and Trifolium pratense L.were established as monocultures,and a four-species mixture.A drought gradient with five levels of water supply ranging from a mild to a severe treatment was applied for 10 weeks,in each of 2 years.Shoot biomass was harvested to assess drought resistance,drought recovery and annual yields.Root mass density and specific root length were measured in Year 2.Results:Across the drought gradient,four-species communities had significantly larger annual yields than each of the four monocultures,indicating transgressive overyielding.This was despite relatively low drought resistance for four-species communities compared with L.perenne and C.intybus monocultures.Recovery of yields following drought was high for all communities.Conclusions:Multispecies swards with complementary traits can provide a viable adaptation option across a wide range of drought severities.Application of a stress gradient methodology allowed a more detailed understanding of stress responses.展开更多
Our understanding of the effects of elevated atmospheric CO2, singly and in combination with other environmental changes, on plant-soil interactions is incomplete. Elevated CO2 effects on C4 plants, though smaller tha...Our understanding of the effects of elevated atmospheric CO2, singly and in combination with other environmental changes, on plant-soil interactions is incomplete. Elevated CO2 effects on C4 plants, though smaller than on C3 species, are mediated mostly via decreased stomatal conductance and thus water loss. Therefore, we characterized the interactive effect of elevated CO2 and drought on soil microbial communities associated with a dominant C4 prairie grass, Andropogon gerardii Vitman. Elevated CO2 and drought both affected resources available to the soil microbial community. For example, elevated CO2 increased the soil C：N ratio and water content during drought, whereas drought alone decreased both. Drought significantly decreased soil microbial biomass. In contrast, elevated CO2 increased biomass while ameliorating biomass decreases that were induced under drought. Total and active direct bacterial counts and carbon substrate use （overall use and number of used sources） increased significantly under elevated CO2. Denaturing gradient gel electrophoresis analysis revealed that drought and elevated CO2, singly and combined, did not affect the soil bacteria community structure. We conclude that elevated CO2 alone increased bacterial abundance and microbial activity and carbon use, probably in response to increased root exudation. Elevated CO2 also limited drought-related impacts on microbial activity and biomass, which likely resulted from decreased plant water use under elevated CO2. These are among the first results showing that elevated CO2 and drought work in opposition to modulate plant-associated soil-bacteria responses, which should then influence soil resources and plant and ecosystem function.展开更多
基金FP7 Food,Agriculture and Fisheries,Biotechnology,Grant/Award Number:266018。
文摘Background:More frequent and severe drought events due to climate change pose a major challenge for sustainable forage production in managed grasslands.This study investigated whether multispecies grassland communities can provide greater resistance to and/or recovery from drought compared to monoculture communities.Methods:Mesocosms of Lolium perenne L.,Cichorium intybus L.,Trifolium repens L.and Trifolium pratense L.were established as monocultures,and a four-species mixture.A drought gradient with five levels of water supply ranging from a mild to a severe treatment was applied for 10 weeks,in each of 2 years.Shoot biomass was harvested to assess drought resistance,drought recovery and annual yields.Root mass density and specific root length were measured in Year 2.Results:Across the drought gradient,four-species communities had significantly larger annual yields than each of the four monocultures,indicating transgressive overyielding.This was despite relatively low drought resistance for four-species communities compared with L.perenne and C.intybus monocultures.Recovery of yields following drought was high for all communities.Conclusions:Multispecies swards with complementary traits can provide a viable adaptation option across a wide range of drought severities.Application of a stress gradient methodology allowed a more detailed understanding of stress responses.
基金Supported by the University of Toledo Department of Environmental Sciencesgrants from the National Science Foundation to S. Heckathorn and E.W.Hamilton.
文摘Our understanding of the effects of elevated atmospheric CO2, singly and in combination with other environmental changes, on plant-soil interactions is incomplete. Elevated CO2 effects on C4 plants, though smaller than on C3 species, are mediated mostly via decreased stomatal conductance and thus water loss. Therefore, we characterized the interactive effect of elevated CO2 and drought on soil microbial communities associated with a dominant C4 prairie grass, Andropogon gerardii Vitman. Elevated CO2 and drought both affected resources available to the soil microbial community. For example, elevated CO2 increased the soil C：N ratio and water content during drought, whereas drought alone decreased both. Drought significantly decreased soil microbial biomass. In contrast, elevated CO2 increased biomass while ameliorating biomass decreases that were induced under drought. Total and active direct bacterial counts and carbon substrate use （overall use and number of used sources） increased significantly under elevated CO2. Denaturing gradient gel electrophoresis analysis revealed that drought and elevated CO2, singly and combined, did not affect the soil bacteria community structure. We conclude that elevated CO2 alone increased bacterial abundance and microbial activity and carbon use, probably in response to increased root exudation. Elevated CO2 also limited drought-related impacts on microbial activity and biomass, which likely resulted from decreased plant water use under elevated CO2. These are among the first results showing that elevated CO2 and drought work in opposition to modulate plant-associated soil-bacteria responses, which should then influence soil resources and plant and ecosystem function.
