Aims Nitrogen(N)addition could affect the rate of forest litter and soil organic matter decomposition by regulating extracellular enzyme activity(EEa).The impact of N addition on EEa may differ across different age st...Aims Nitrogen(N)addition could affect the rate of forest litter and soil organic matter decomposition by regulating extracellular enzyme activity(EEa).The impact of N addition on EEa may differ across different age stands with different organic matter quality.We were interested in whether the impact of N addition on EEa in litter and mineral soil during the growing season was dependent on stand age of a larch plantation in North China.Methods We added three levels of N(0,20 and 50 kg N ha^(−1) year^(−1))in three age stands(11,20 and 45 years old)of Larix principis-rupprech-tii plantation in North China.We measured potential activities of β-1,4-glucosidase(b),cellobiohydrolase(Cb),β-1,4-N-acetyl-glucosaminidase(Nag)and phenol oxidase(Po)in litter(organic horizon)and mineral soil(0-10 cm)during the second growing sea-son after N amendment.We also measured C and N concentrations,microbial biomass C and N,and KCl-extractable ammonium and nitrate in both litter and mineral soil.Important Findings We observed unimodal patterns of EEa during the growing season in all three stands,consistent with the seasonal variations of soil temperature.stand age had a strong effect on EEa in both litter and mineral soil,and this effect differed between litter and mineral soil as well as between different enzymes.N addition did not significantly affect the activities of b or Cb but significantly suppressed the activity of Nag in litter.We also found stand age-specific responses of Po activity to N addition in both litter and mineral soil.N addition suppressed Po activity of the high C:N ratio litters in 20-and 45-year-old stands but had no significant effect on Po activity of the low C:N ratio litter in 11-year-old stand.moreover,N addition inhibited Po activity of the high C:N ratio soil in 20-year-old stand but had no significant impact on Po activity of the low C:N ratio soils in 11-and 45-year-old stands.overall,stand age had a greater effect on EEa in litter and mineral soil compared to 2 years of N addition.moreover,the effect of N addition on Po activity is stand age dependent,which may affect the long-term soil carbon storage in this forest.展开更多
Anthropogenic nitrogen(N)emissions to atmosphere have increased dramatically in China since 1980s,and this increase has aroused great concerns on its ecological impacts on terrestrial ecosystems.Previous studies have ...Anthropogenic nitrogen(N)emissions to atmosphere have increased dramatically in China since 1980s,and this increase has aroused great concerns on its ecological impacts on terrestrial ecosystems.Previous studies have showed that terrestrial ecosystems in China are acting as a large carbon(C)sink,but its potential in the future remains largely uncertain.So far little work on the impacts of the N deposition on C sequestration in China’s terrestrial ecosystems has been assessed at a national scale.Aiming to assess and predict how ecological processes especially the C cycling respond to the increasing N deposition in China’s forests,recently researchers from Peking University and their partners have established a manipulation experimental network on the ecological effects of the N deposition:Nutrient Enrichment Experiments in China’s Forests Project(NEECF).The NEECF comprises 10 experiments at 7 sites located from north to south China,covering major zonal forest vegetation in eastern China from boreal forest in Greater Khingan Mountains to tropical forests in Hainan Island.This paper introduces the framework of the NEECF project and its potential policy implications.展开更多
基金National Natural Science Foundation of China(#41171202,41125004).
文摘Aims Nitrogen(N)addition could affect the rate of forest litter and soil organic matter decomposition by regulating extracellular enzyme activity(EEa).The impact of N addition on EEa may differ across different age stands with different organic matter quality.We were interested in whether the impact of N addition on EEa in litter and mineral soil during the growing season was dependent on stand age of a larch plantation in North China.Methods We added three levels of N(0,20 and 50 kg N ha^(−1) year^(−1))in three age stands(11,20 and 45 years old)of Larix principis-rupprech-tii plantation in North China.We measured potential activities of β-1,4-glucosidase(b),cellobiohydrolase(Cb),β-1,4-N-acetyl-glucosaminidase(Nag)and phenol oxidase(Po)in litter(organic horizon)and mineral soil(0-10 cm)during the second growing sea-son after N amendment.We also measured C and N concentrations,microbial biomass C and N,and KCl-extractable ammonium and nitrate in both litter and mineral soil.Important Findings We observed unimodal patterns of EEa during the growing season in all three stands,consistent with the seasonal variations of soil temperature.stand age had a strong effect on EEa in both litter and mineral soil,and this effect differed between litter and mineral soil as well as between different enzymes.N addition did not significantly affect the activities of b or Cb but significantly suppressed the activity of Nag in litter.We also found stand age-specific responses of Po activity to N addition in both litter and mineral soil.N addition suppressed Po activity of the high C:N ratio litters in 20-and 45-year-old stands but had no significant effect on Po activity of the low C:N ratio litter in 11-year-old stand.moreover,N addition inhibited Po activity of the high C:N ratio soil in 20-year-old stand but had no significant impact on Po activity of the low C:N ratio soils in 11-and 45-year-old stands.overall,stand age had a greater effect on EEa in litter and mineral soil compared to 2 years of N addition.moreover,the effect of N addition on Po activity is stand age dependent,which may affect the long-term soil carbon storage in this forest.
基金National Basic Research Program of China on Global Change(2010CB950600)National Natural Science Foundation of China(#31021001)Ministry of Science and Technology(2010DFA31290).
文摘Anthropogenic nitrogen(N)emissions to atmosphere have increased dramatically in China since 1980s,and this increase has aroused great concerns on its ecological impacts on terrestrial ecosystems.Previous studies have showed that terrestrial ecosystems in China are acting as a large carbon(C)sink,but its potential in the future remains largely uncertain.So far little work on the impacts of the N deposition on C sequestration in China’s terrestrial ecosystems has been assessed at a national scale.Aiming to assess and predict how ecological processes especially the C cycling respond to the increasing N deposition in China’s forests,recently researchers from Peking University and their partners have established a manipulation experimental network on the ecological effects of the N deposition:Nutrient Enrichment Experiments in China’s Forests Project(NEECF).The NEECF comprises 10 experiments at 7 sites located from north to south China,covering major zonal forest vegetation in eastern China from boreal forest in Greater Khingan Mountains to tropical forests in Hainan Island.This paper introduces the framework of the NEECF project and its potential policy implications.