Aims Soil respiration(Rs)is a major process controlling soil carbon loss in forest ecosystems.However,the underlying mechanisms leading to variation in Rs along forest successional gradients are not well understood.In...Aims Soil respiration(Rs)is a major process controlling soil carbon loss in forest ecosystems.However,the underlying mechanisms leading to variation in Rs along forest successional gradients are not well understood.In this study,we investigated the effects of biotic and abiotic factors on Rs along a forest successional gradient in southeast China.Methods We selected 16 plots stratified by forest age,ranging from 20 to 120 years.In each plot,six shallow collars and six deep collars were permanently inserted into the soil.Shallow and deep collars were used to measure Rs and heterotrophic respiration(Rh),respectively.Autotrophic soil respiration(Ra)was estimated as the difference between Rs and Rh.Litter layer respiration(R_(L))was calculated by subtracting soil respiration measured in collars without leaf litter layer(R_(NL))from Rs.Rs was measured every 2 months,and soil temperature(ST)and soil volumetric water content(SVWC)were recorded every hour for 19 months.We calculated daily Rs using an exponential model dependent on ST.Daily Rs was summed to obtain cumulative annual Rs estimates.Structural equation modelling(SEM)was applied to identify the drivers of Rs during forest succession.Important Findings Rs showed significant differences among three successive stages,and it was the highest in the young stage.Ra was higher in the young stage than in the medium stage.Cumulative annual Rs and Ra peaked in the young and old stages,respectively.Cumulative annual Rh and respiration measured from soil organic matter(R_(SOM))decreased,whereas R_(L)increased with forest age.The SEM revealed that cumulative annual Rs was influenced by fine root biomass and SVWC.Our results indicated that the dominant force regulating Rs on a seasonal scale is ST;however,on a successional scale,belowground carbon emerges as the dominant influential factor.展开更多
Aims We investigated shifts in community-weighted mean traits(CWm)of 14 leaf functional traits along a secondary successional series in an evergreen broadleaf forest in subtropical southeast China.most of the investig...Aims We investigated shifts in community-weighted mean traits(CWm)of 14 leaf functional traits along a secondary successional series in an evergreen broadleaf forest in subtropical southeast China.most of the investigated traits have been reported to affect litter decomposition in previous studies.We asked whether changes in CWms along secondary succession followed similar patterns for all investigated traits and whether the shifts in CWm indicated a change in resource use strategy along the successional gradient.using community decomposition rates(k-rates)estimated from annual lit-ter production and standing litter biomass,we asked whether the dynamics of litter decomposition were related to changes in leaf functional traits along the successional series.Methods twenty-seven plots were examined for shifts in leaf CWm traits as well as in k-rates along a series of secondary forest succession cov-ered in the framework of the bEF-China project.We investigated whether the changes in CWms followed similar patterns for all traits with ongoing succession.three alternative linear models were used to reveal the general patterns of shifts in CWm trait values.moreover,multiple regression analysis was applied to investigate whether there were causal relationships between the changes in leaf functional traits and the dynamics of litter decomposition along secondary succession.We furthermore assessed which traits had the highest impact on community litter decomposition.Important Findingsshifts in CWm values generally followed logarithmic patterns for all investigated traits,whereas community k-rates remained stable along the successional gradient.In summary,the shifts in CWm values indicate a change in community resource use strategy from high nutrient acquisition to nutrient retention with ongoing succession.stands with higher CWm values of traits related to nutrient acquisition had also higher CWm values of traits related to chemical resistance,whereas stands with higher CWm values of traits related to nutrient retention exhibited higher CWm values in leaf physical defense.moreover,high values in CWm values related to nutritional quality(such as high leaf phosphorus concentrations)were found to promote com-munity k-rates,whereas high values in physical or chemical defense traits(such as high contents in polyphenols or high leaf toughness)decreased litter decomposition rates.In consequence,litter decom-position,which was simultaneously affected by these characteristics,did not change significantly along succession.our findings show that leaf decomposition within the investigated communities is dependent on the interplay of several traits and is a result from interactions of traits that affect decomposition in opposing directions.展开更多
基金EU 7th FP Project BACCARA(226299)and the National Basic Research Program of China(2014CB954004).
文摘Aims Soil respiration(Rs)is a major process controlling soil carbon loss in forest ecosystems.However,the underlying mechanisms leading to variation in Rs along forest successional gradients are not well understood.In this study,we investigated the effects of biotic and abiotic factors on Rs along a forest successional gradient in southeast China.Methods We selected 16 plots stratified by forest age,ranging from 20 to 120 years.In each plot,six shallow collars and six deep collars were permanently inserted into the soil.Shallow and deep collars were used to measure Rs and heterotrophic respiration(Rh),respectively.Autotrophic soil respiration(Ra)was estimated as the difference between Rs and Rh.Litter layer respiration(R_(L))was calculated by subtracting soil respiration measured in collars without leaf litter layer(R_(NL))from Rs.Rs was measured every 2 months,and soil temperature(ST)and soil volumetric water content(SVWC)were recorded every hour for 19 months.We calculated daily Rs using an exponential model dependent on ST.Daily Rs was summed to obtain cumulative annual Rs estimates.Structural equation modelling(SEM)was applied to identify the drivers of Rs during forest succession.Important Findings Rs showed significant differences among three successive stages,and it was the highest in the young stage.Ra was higher in the young stage than in the medium stage.Cumulative annual Rs and Ra peaked in the young and old stages,respectively.Cumulative annual Rh and respiration measured from soil organic matter(R_(SOM))decreased,whereas R_(L)increased with forest age.The SEM revealed that cumulative annual Rs was influenced by fine root biomass and SVWC.Our results indicated that the dominant force regulating Rs on a seasonal scale is ST;however,on a successional scale,belowground carbon emerges as the dominant influential factor.
文摘Aims We investigated shifts in community-weighted mean traits(CWm)of 14 leaf functional traits along a secondary successional series in an evergreen broadleaf forest in subtropical southeast China.most of the investigated traits have been reported to affect litter decomposition in previous studies.We asked whether changes in CWms along secondary succession followed similar patterns for all investigated traits and whether the shifts in CWm indicated a change in resource use strategy along the successional gradient.using community decomposition rates(k-rates)estimated from annual lit-ter production and standing litter biomass,we asked whether the dynamics of litter decomposition were related to changes in leaf functional traits along the successional series.Methods twenty-seven plots were examined for shifts in leaf CWm traits as well as in k-rates along a series of secondary forest succession cov-ered in the framework of the bEF-China project.We investigated whether the changes in CWms followed similar patterns for all traits with ongoing succession.three alternative linear models were used to reveal the general patterns of shifts in CWm trait values.moreover,multiple regression analysis was applied to investigate whether there were causal relationships between the changes in leaf functional traits and the dynamics of litter decomposition along secondary succession.We furthermore assessed which traits had the highest impact on community litter decomposition.Important Findingsshifts in CWm values generally followed logarithmic patterns for all investigated traits,whereas community k-rates remained stable along the successional gradient.In summary,the shifts in CWm values indicate a change in community resource use strategy from high nutrient acquisition to nutrient retention with ongoing succession.stands with higher CWm values of traits related to nutrient acquisition had also higher CWm values of traits related to chemical resistance,whereas stands with higher CWm values of traits related to nutrient retention exhibited higher CWm values in leaf physical defense.moreover,high values in CWm values related to nutritional quality(such as high leaf phosphorus concentrations)were found to promote com-munity k-rates,whereas high values in physical or chemical defense traits(such as high contents in polyphenols or high leaf toughness)decreased litter decomposition rates.In consequence,litter decom-position,which was simultaneously affected by these characteristics,did not change significantly along succession.our findings show that leaf decomposition within the investigated communities is dependent on the interplay of several traits and is a result from interactions of traits that affect decomposition in opposing directions.
