Fluctuations in soil greenhouse gas(GHG)are an important part of the terrestrial ecosystem carbon-nitrogen cycle,but uncertainties remain about the dynamic change and budget assessment of soil GHG flux.Using high freq...Fluctuations in soil greenhouse gas(GHG)are an important part of the terrestrial ecosystem carbon-nitrogen cycle,but uncertainties remain about the dynamic change and budget assessment of soil GHG flux.Using high frequency and consecutive soil GHG fluxes measured with an automatic dynamic chamber system,we tested the applicability of the current Forest-DNDC model in simulating soil CH4,CO2 and N2O fluxes in a temperate broad-leaved Korean pine forest at Changbai Mountain.The results showed that the Forest-DNDC model reproduced general patterns of environmental variables,however,simulated seasonal variation in soil temperature,snow melt processes and soil moisture partly deviated from measured variables,especially during the non-growing season.The modeled CH4 flux was close to the field measurement and co-varied mainly with soil temperature and snowpack.The modeled soil CO2 flux had the same seasonal trend to that of the observation along with variation in temperature,however,simulated CO2 flux in the growing season was underestimated.The modeled N2O flux attained a peak in summer due to the influence of temperature,which was apparently different from the observed peak of N2O flux in the freeze-thaw period.Meanwhile,both modeled CO2 flux and N2O flux were dampened by rainfall events.Apart from consistent estimation of annual soil CH4 flux,the annual accumulation of CO2 and N2O was underestimated.It is still necessary to further optimize model parameters and processes using long-term high-frequency observation data,especially transference of heat and water in soil and GHG producing mechanism.Continues work will improve modeling,ecosystem carbon-nitrogen budget assessment and estimation of soil GHGs flux from the site to the region.展开更多
In non-flooded lowland rain forests with low soil phosphorus(P)in parts of Amazonia,P cycling largely occurs via leaf litter recycling by arbuscular mycorrhizal(AM)fungal symbionts.Occasional high input of P into thes...In non-flooded lowland rain forests with low soil phosphorus(P)in parts of Amazonia,P cycling largely occurs via leaf litter recycling by arbuscular mycorrhizal(AM)fungal symbionts.Occasional high input of P into these ecosystems occurs during drought years with increased litterfall.As the length and frequency of drought events are projected to increase in the region,a single-dose nutrient addition experiment was carried out to test how this would impact P cycling.An application rate of 4 kg P ha^(-1) was used,which corresponds to twice the amount of litter-derived P in an average year.It was hypothesized that i)the added mineral P would be immobilized by soil microorganisms,leading to measurable increase in soil microbial biomass carbon(C)and P and ii)AM colonization rate would be reduced by the pulse in mineral P available for plant uptake.The results did not support either of our hypotheses.The addition of P did not have an effect on AM root colonization,nor was P immobilized by soil microbiota during the experimental period.The lack of a difference between the control and treatment at our study site could be attributed to the relatively low one-off dose of P applied that did not change either the colonization rate of roots by AM fungi or the amount of soil available labile P.To obtain a mechanistic understanding of the availability,capture,and use of P by plant-symbiont associations in tropical rain forest ecosystems,further integrated studies of the soil-plant system combining long-term nutrient manipulations,modeling,and experimental approaches are required.展开更多
基金National Key Research and Development Program of China(2017YFC0503801)National Natural Science Foundation of China(31570446)
文摘Fluctuations in soil greenhouse gas(GHG)are an important part of the terrestrial ecosystem carbon-nitrogen cycle,but uncertainties remain about the dynamic change and budget assessment of soil GHG flux.Using high frequency and consecutive soil GHG fluxes measured with an automatic dynamic chamber system,we tested the applicability of the current Forest-DNDC model in simulating soil CH4,CO2 and N2O fluxes in a temperate broad-leaved Korean pine forest at Changbai Mountain.The results showed that the Forest-DNDC model reproduced general patterns of environmental variables,however,simulated seasonal variation in soil temperature,snow melt processes and soil moisture partly deviated from measured variables,especially during the non-growing season.The modeled CH4 flux was close to the field measurement and co-varied mainly with soil temperature and snowpack.The modeled soil CO2 flux had the same seasonal trend to that of the observation along with variation in temperature,however,simulated CO2 flux in the growing season was underestimated.The modeled N2O flux attained a peak in summer due to the influence of temperature,which was apparently different from the observed peak of N2O flux in the freeze-thaw period.Meanwhile,both modeled CO2 flux and N2O flux were dampened by rainfall events.Apart from consistent estimation of annual soil CH4 flux,the annual accumulation of CO2 and N2O was underestimated.It is still necessary to further optimize model parameters and processes using long-term high-frequency observation data,especially transference of heat and water in soil and GHG producing mechanism.Continues work will improve modeling,ecosystem carbon-nitrogen budget assessment and estimation of soil GHGs flux from the site to the region.
基金a M.Sc.grant from the Brazilian Coordination for the Improvement of Higher Education Personnel(CAPES)a post-doctoral grant from the Portuguese Foundation for Science and Technology(No.SFRH/BPD/77795/2011)。
文摘In non-flooded lowland rain forests with low soil phosphorus(P)in parts of Amazonia,P cycling largely occurs via leaf litter recycling by arbuscular mycorrhizal(AM)fungal symbionts.Occasional high input of P into these ecosystems occurs during drought years with increased litterfall.As the length and frequency of drought events are projected to increase in the region,a single-dose nutrient addition experiment was carried out to test how this would impact P cycling.An application rate of 4 kg P ha^(-1) was used,which corresponds to twice the amount of litter-derived P in an average year.It was hypothesized that i)the added mineral P would be immobilized by soil microorganisms,leading to measurable increase in soil microbial biomass carbon(C)and P and ii)AM colonization rate would be reduced by the pulse in mineral P available for plant uptake.The results did not support either of our hypotheses.The addition of P did not have an effect on AM root colonization,nor was P immobilized by soil microbiota during the experimental period.The lack of a difference between the control and treatment at our study site could be attributed to the relatively low one-off dose of P applied that did not change either the colonization rate of roots by AM fungi or the amount of soil available labile P.To obtain a mechanistic understanding of the availability,capture,and use of P by plant-symbiont associations in tropical rain forest ecosystems,further integrated studies of the soil-plant system combining long-term nutrient manipulations,modeling,and experimental approaches are required.
