[Objective] The study aimed at investigating the effects of different geographic sites,soil chemical characteristics and nitrogen application levels on nitrogen accumulation and distribution in different organs and ut...[Objective] The study aimed at investigating the effects of different geographic sites,soil chemical characteristics and nitrogen application levels on nitrogen accumulation and distribution in different organs and utilization efficiency for mid-season hybrid rice.[Method] By using mid-season rice varieties II-you 7 and Yuxiangyou203 as the experimental materials,field experiment was conducted at seven ecological sites in four provinces or cities in Southwestern China in 2009.A total of four nitrogen application levels were set as follows:by using 75 kg/hm2 of P2O5 and 75 kg/hm2 of K2O as the base fertilizer,extra 0,90,150 and 210 kg/hm2 of nitrogen fertilizer(in which,base fertilizer,base-tillering fertilizer and base-earing fertilizer respectively accounted for 60%,20% and 20%.) was applied,respectively.In the split-plot design,fertilizer was considered as the main factor while rice variety was taken as the secondary factor.A total of eight treatments were set with three replications.[Result] Highly significant differences of grain yield were found among seven locations,two varieties,four nitrogen application levels,interactions of site × variety and site × nitrogen application level,but the interaction of variety ×nitrogen application level had no significant influence on rice yield.There were highly significant effects of site,varieties and nitrogen application level on dry matter production,nitrogen content,nitrogen utilization efficiency.Highly significant negative correlations between uptake efficiency and utilization efficiency for nitrogen were found;and multiple stepwise regression analysis showed that nitrogen uptake-utilization efficiency were significantly influenced by different ecological sites,chemical quality of soil and the levels of nitrogen application.[Conclusion] The research will provide theoretical and practical basis for the highly efficient application of nitrogen in mid-season hybrid rice cultivation.展开更多
Field plot experiment was conducted to study the effects of two slow-re- lease fertilizers and balanced fertilization on dry matter accumulation, yield, fertilizer use efficiency, nitrogen, phosphorus and potassium up...Field plot experiment was conducted to study the effects of two slow-re- lease fertilizers and balanced fertilization on dry matter accumulation, yield, fertilizer use efficiency, nitrogen, phosphorus and potassium uptake of peppers at Jiangna Town, Yanshan County, Yunnan Province in 2011. The results showed that the dry matter accumulation in dried pepper plant, pepper yield, nitrogen, phosphorus, potassium uptake in peppers were significantly increased in all the fertilizer treat- ments, compared with those in control (no fertilizer). Compared with conventional fertilization, balanced fertilization, slow-release compound fertilizer and slow-release urea fertilizer significantly increased dried pepper economic output by 20.94%, 17.5% and 14.54%, nitrogen uptake in dried peppers by 21.53%,18.46% and 13.19%, phosphorus uptake in dried peppers by 14.08%, 15.76% and 10.44%, potassium uptake in dried peppers by 22.66%, 15.73% and 16.28%; they also in- creased nitrogen and potassium use efficiency, but reduced potassium use efficiency due to the increased potassium addition. In treatments with balanced fertilization, slow-release compound fertilizer and slow-release urea fertilizer, the nitrogen utiliza- tion was 5.84%, 7.14% and 8.33% higher and the phosphorus utilization was 3.32%, 3.27% and 2.47% higher than those in treatment with conventional fertiliza- tion. In addition, the nitrogen application could be reduced by 20%-50% by bal- anced fertilization and the two slow-release fertilizers, thereby reducing environmen- tal pollution. Slow-release fertilizers could also reduce the frequency of fertilization and labor costs.展开更多
The effects of varying nitrogen (N): phosphorus (P) ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat...The effects of varying nitrogen (N): phosphorus (P) ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat culture experiments. Algal cultures were supplied with media containing PO4^3- in various concentrations to obtain a wide range of N:P ratios. Experiments to determine rates of N uptake and assimilation of different N sources (NO^3-, NH4^+, urea and glycine by P. minimum and NO3^-, NH4^+ by P. donghaiense) were conducted using ^15-N tracer techniques at each N:P ratio. The growth rates suggested nutrient limitation at both high and low N:P ratios relative to the Redfield ratio. On a diel basis, the growth of both species was regulated by the light-dark cycle, which may be a result of regulation of both lightdependent growth and light-independent nutrient uptake. Maximum growth rates of both species always occurred at the beginning of light phase. In P-rich medium (low N:P ratio), both species had higher N assimilation rates, suggesting N limitation. Low assimilation coefficients at high N:P ratios suggested P limitation of N uptake and assimilation. NO3 ^-and NH4^+ contributed more than 90% of the total N uptake of P. minimum. Reduced N sources were more quickly assimilated than NO3^-. Highest average daily growth rates were recorded near an N:P ratio of 12 for both species. The N uptake rates of cultures at N:P ratios near Redfield ratio were more balanced with growth rates. The linkage between growth rates and N uptake/assimilation rates were conceptually described by the variation of cell N quota. The N:P ratios affect the N uptake and growth of Prorocentrum spp., and may regulate their bloom progression in eutrophic ecosystems.展开更多
Gracilaria asiatica, being highly efficient in nutrient absorption, is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate. It was cultured in a laboratory simulating field conditions, ...Gracilaria asiatica, being highly efficient in nutrient absorption, is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate. It was cultured in a laboratory simulating field conditions, and its nutrient absorption was measured to evaluate effects of environmental conditions. Ammonia nitrogen (AN), nitrate nitrogen (NN), total inorganic nitrogen (TIN), and soluble reactive phosphorus (SRP) uptake rate and removal efficiency were determined in a 4~2 factorial design experiment in water temperatures (T) at 15~C and 25~C, algae biomass (AB) at 0.5 g/L and 1.0 g/L, total inorganic nitrogen (TIN) at 30 ~tmol/L and 60 ~tmol/L, and soluble reactive phosphorus (SRP) at 3 and 6 ~tmol/L. AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN, NN, TIN, and SRP (P〈0.001). G. asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L. Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations; nutrient removal efficiency decreased at higher environmental nutrient concentrations. The algae preferred to absorb AN to NN. Uptake rates of AN, NN, and SRP were significantly affected by temperature (P〈0.001); uptake rate was higher for the 25~C group than for the 15~C group at the initial experiment stage. Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups (P〈0.01). The four factors had significant interactive effects on absorption of N and P, implying that G. asiatica has great bioremedial potential in sea cucumber culture ponds.展开更多
Ammonia in wastewater is a major pollutant produced in industrial and agricultural wastewaters. Ammonia is often removed by conventional technologies such as pack tower aeration, biological treatment or adsorption as ...Ammonia in wastewater is a major pollutant produced in industrial and agricultural wastewaters. Ammonia is often removed by conventional technologies such as pack tower aeration, biological treatment or adsorption as ammonium ion onto zeolites. In many cases, conventional methods are very costly and inefficient, and therefore there is a need for an alternative separation technique for more efficient removal of ammonia from wastewaters. The aim of this study is to investigate the performance of combination of ozonation and absorption through membrane processes to remove ammonia from wastewater using NHSW (natural hot spring water) as absorbent. Experimental results show that hollow fiber membrane contactor has potential application for ammonia removal from wastewater. Operating variables such as time and pH of absorbent solution are found to remarkably influence the removal process efficiency.. Based on experimental results ozonation can improve ammonia removal efficiency through hollow fiber membrane contactor. Ammonia removal efficiencies and overall mass transfer coefficients increase with decreasing pH of absorbent solution.展开更多
Ammonium(NH+4) is the main nitrogen(N) form for rice crops, while NH+4near the root surface can be oxidized to nitrate(NO-3)by NH+4-oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N ...Ammonium(NH+4) is the main nitrogen(N) form for rice crops, while NH+4near the root surface can be oxidized to nitrate(NO-3)by NH+4-oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N supply is insufficient. We compared the remobilization of NO-3stored in the tissue and vacuolar between two rice(Oryza sativa L.) cultivars, Yangdao 6(YD6, indica)with a high N use efficiency(NUE) and Wuyujing 3(WYJ3, japonica) with a low NUE and measured the uptake of NO-3, expression of nitrate reductase(NR), NO-3transporter genes(NRTs), and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L-1NO-3. The results showed that both tissue NO-3concentration and vacuolar NO-3activity were higher in YD6 than WYJ3 under N starvation. YD6 showed a 2- to 3-fold higher expression of OsNRT2.1 in roots on the 1st and 4th day of N starvation and had significantly higher values of NO-3uptake(maximum uptake velocity, Vmax) than the cultivar WYJ3.Furthermore, YD6 had significantly higher leaf and root maximum NR activity(NRAmax) and actual NR activity(NRAact) as well as stronger root expression of the two NR genes after the 1st day of N starvation. There were no significant differences in NRAmax and NRAact between the two rice cultivars on the 4th day of N starvation. The results suggested that YD6 had stronger NRA under N starvation, which might result in better NO-3re-utilization from the vacuole, and higher capacity for NO-3uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3.展开更多
Aims The functions of global forests are threatened by the increasing frequency of severe drought.Due to drought inducing reductions in soil nutrient availability,efficiencies of nutrient use and resorption of trees b...Aims The functions of global forests are threatened by the increasing frequency of severe drought.Due to drought inducing reductions in soil nutrient availability,efficiencies of nutrient use and resorption of trees become crucial for forest functions and biogeochemical cycles.However,understanding the dynamics of responses of foliar nutrient use and resorption efficiencies to drought,especially in tropical or subtropical forests,is still limited.Our goal was to detect whether and how the importance of leaf nutrient use and resorption changes across different species in the hot and wet forests when suffering drought stress in different months.Methods Based on a 70%throughfall exclusion experiment in a subtropical forest,we collected green and senesced leaves of Schima superba and Lithocarpus glaber in different months from October 2016 to May 2019,to estimate the effects of drought on leaf nitrogen(N)and phosphorus(P)use and resorption efficiencies(i.e.NUE and PUE,NRE and PRE).Important Findings The effects of drought on nutrient use and resorption efficiencies varied between species and months.Based on a 2-year observation,drought had no effect on S.superba,but significantly decreased NUE,NRE and PRE of L.glaber by 3.4%,20.2%and 7.1%,respectively.Furthermore,the negative drought effects were aggravated by the natural summer drying in 2017.As a result,NUE and PUE of L.glaber were significantly depressed by 17.2%and 58.1%,while NRE and PRE were significantly reduced by 56.5%and 53.8%in August 2017.Moreover,the responses of NRE,PRE and NUE to drought were related with soil moisture(SM)for L.glaber,and when SM decreased to a threshold near 9 v/v%,drought effects were shifted from unresponsive to negative.Our results highlight a species-specific threshold response of nutrient use under drought in a subtropical forest.展开更多
Forest productivity and carbon(C) sequestration largely depend on soil N and P availability.To date,however,the temporal variation of nutrient limitation along forest succession is still under debate.Leaf stoichiometr...Forest productivity and carbon(C) sequestration largely depend on soil N and P availability.To date,however,the temporal variation of nutrient limitation along forest succession is still under debate.Leaf stoichiometry and nutrient resorption are important indicators for predicting nutrient limitation of plant growth.Here,we measured nitrogen(N)and phosphorus(P)concentrations in green leaves and leaf liter for all woody species at four stages of temperate forest succession,and analyzed how abiotic and biotic factors affect leaf stoichiometry and nutrient resorption along forest succession.At the individual scale,leaf N and P concentrations had a significant increase at the end of the succession,while no change in leaf N:P ratio was detected.Nitrogen resorption efficiency(NRE)increased significantly with succession,but P resorption efficiency(PRE)first increased and then decreased.Significant increases in NRE:PRE ratios only occurred at the end of the succession.Moreover,plant N cycling was less responsive to soil nutrient than P cycling.At the community scale,we found that leaf N and P concentrations first decreased and then increased along forest succession,which were mainly affected by Shannon-Wiener index and species richness.Leaf N:P ratio significantly varied with succession and was mainly determined by community-weighted mean diameter at breast height(DBH).NRE increased and was significantly influenced by species richness and DBH,while PRE was relatively stable along forest succession.Thus,the NRE:PRE ratios significantly increased,indicating that N limitation is exacerbated with the temperate forest succession.These results might reflect the intense interspecific competition for limiting resource in a higher biodiversity community.In conclusion,our findings highlight the importance of biotic factors in driving forest ecosystem nutrient cycling and provide valuable information for sustainable fertilizer management practices in China's temperate and boreal forests.展开更多
基金Supported by Construction of Southwestern Rice Innovation System,Science and Technology Project on Food Production (2006BAD02-A05)Agriculture Science Technology Achievement TransformationFund (2006GB2F000256)+2 种基金Sichuan Provincial Foundation for Lead-ers of Disciplines in ScienceProject of Rice Breeding Technology ofSichuanProgram Promoted by Sichuan Financial Administration~~
文摘[Objective] The study aimed at investigating the effects of different geographic sites,soil chemical characteristics and nitrogen application levels on nitrogen accumulation and distribution in different organs and utilization efficiency for mid-season hybrid rice.[Method] By using mid-season rice varieties II-you 7 and Yuxiangyou203 as the experimental materials,field experiment was conducted at seven ecological sites in four provinces or cities in Southwestern China in 2009.A total of four nitrogen application levels were set as follows:by using 75 kg/hm2 of P2O5 and 75 kg/hm2 of K2O as the base fertilizer,extra 0,90,150 and 210 kg/hm2 of nitrogen fertilizer(in which,base fertilizer,base-tillering fertilizer and base-earing fertilizer respectively accounted for 60%,20% and 20%.) was applied,respectively.In the split-plot design,fertilizer was considered as the main factor while rice variety was taken as the secondary factor.A total of eight treatments were set with three replications.[Result] Highly significant differences of grain yield were found among seven locations,two varieties,four nitrogen application levels,interactions of site × variety and site × nitrogen application level,but the interaction of variety ×nitrogen application level had no significant influence on rice yield.There were highly significant effects of site,varieties and nitrogen application level on dry matter production,nitrogen content,nitrogen utilization efficiency.Highly significant negative correlations between uptake efficiency and utilization efficiency for nitrogen were found;and multiple stepwise regression analysis showed that nitrogen uptake-utilization efficiency were significantly influenced by different ecological sites,chemical quality of soil and the levels of nitrogen application.[Conclusion] The research will provide theoretical and practical basis for the highly efficient application of nitrogen in mid-season hybrid rice cultivation.
基金Supported by Special Fund from Ministry of Agriculture for Scientific Research(200903025-05)~~
文摘Field plot experiment was conducted to study the effects of two slow-re- lease fertilizers and balanced fertilization on dry matter accumulation, yield, fertilizer use efficiency, nitrogen, phosphorus and potassium uptake of peppers at Jiangna Town, Yanshan County, Yunnan Province in 2011. The results showed that the dry matter accumulation in dried pepper plant, pepper yield, nitrogen, phosphorus, potassium uptake in peppers were significantly increased in all the fertilizer treat- ments, compared with those in control (no fertilizer). Compared with conventional fertilization, balanced fertilization, slow-release compound fertilizer and slow-release urea fertilizer significantly increased dried pepper economic output by 20.94%, 17.5% and 14.54%, nitrogen uptake in dried peppers by 21.53%,18.46% and 13.19%, phosphorus uptake in dried peppers by 14.08%, 15.76% and 10.44%, potassium uptake in dried peppers by 22.66%, 15.73% and 16.28%; they also in- creased nitrogen and potassium use efficiency, but reduced potassium use efficiency due to the increased potassium addition. In treatments with balanced fertilization, slow-release compound fertilizer and slow-release urea fertilizer, the nitrogen utiliza- tion was 5.84%, 7.14% and 8.33% higher and the phosphorus utilization was 3.32%, 3.27% and 2.47% higher than those in treatment with conventional fertiliza- tion. In addition, the nitrogen application could be reduced by 20%-50% by bal- anced fertilization and the two slow-release fertilizers, thereby reducing environmen- tal pollution. Slow-release fertilizers could also reduce the frequency of fertilization and labor costs.
基金supported by the University of Maryland Center for Environmental Science (UMCES), Horn Point Laboratory. This is UMCES contribution number 4503
文摘The effects of varying nitrogen (N): phosphorus (P) ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat culture experiments. Algal cultures were supplied with media containing PO4^3- in various concentrations to obtain a wide range of N:P ratios. Experiments to determine rates of N uptake and assimilation of different N sources (NO^3-, NH4^+, urea and glycine by P. minimum and NO3^-, NH4^+ by P. donghaiense) were conducted using ^15-N tracer techniques at each N:P ratio. The growth rates suggested nutrient limitation at both high and low N:P ratios relative to the Redfield ratio. On a diel basis, the growth of both species was regulated by the light-dark cycle, which may be a result of regulation of both lightdependent growth and light-independent nutrient uptake. Maximum growth rates of both species always occurred at the beginning of light phase. In P-rich medium (low N:P ratio), both species had higher N assimilation rates, suggesting N limitation. Low assimilation coefficients at high N:P ratios suggested P limitation of N uptake and assimilation. NO3 ^-and NH4^+ contributed more than 90% of the total N uptake of P. minimum. Reduced N sources were more quickly assimilated than NO3^-. Highest average daily growth rates were recorded near an N:P ratio of 12 for both species. The N uptake rates of cultures at N:P ratios near Redfield ratio were more balanced with growth rates. The linkage between growth rates and N uptake/assimilation rates were conceptually described by the variation of cell N quota. The N:P ratios affect the N uptake and growth of Prorocentrum spp., and may regulate their bloom progression in eutrophic ecosystems.
基金Supported by the Science and Technology Project of Tackling Key Problems in Shandong Province(No.2010GHY10505)the National Natural Science Foundation of China(No.31172426)
文摘Gracilaria asiatica, being highly efficient in nutrient absorption, is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate. It was cultured in a laboratory simulating field conditions, and its nutrient absorption was measured to evaluate effects of environmental conditions. Ammonia nitrogen (AN), nitrate nitrogen (NN), total inorganic nitrogen (TIN), and soluble reactive phosphorus (SRP) uptake rate and removal efficiency were determined in a 4~2 factorial design experiment in water temperatures (T) at 15~C and 25~C, algae biomass (AB) at 0.5 g/L and 1.0 g/L, total inorganic nitrogen (TIN) at 30 ~tmol/L and 60 ~tmol/L, and soluble reactive phosphorus (SRP) at 3 and 6 ~tmol/L. AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN, NN, TIN, and SRP (P〈0.001). G. asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L. Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations; nutrient removal efficiency decreased at higher environmental nutrient concentrations. The algae preferred to absorb AN to NN. Uptake rates of AN, NN, and SRP were significantly affected by temperature (P〈0.001); uptake rate was higher for the 25~C group than for the 15~C group at the initial experiment stage. Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups (P〈0.01). The four factors had significant interactive effects on absorption of N and P, implying that G. asiatica has great bioremedial potential in sea cucumber culture ponds.
文摘Ammonia in wastewater is a major pollutant produced in industrial and agricultural wastewaters. Ammonia is often removed by conventional technologies such as pack tower aeration, biological treatment or adsorption as ammonium ion onto zeolites. In many cases, conventional methods are very costly and inefficient, and therefore there is a need for an alternative separation technique for more efficient removal of ammonia from wastewaters. The aim of this study is to investigate the performance of combination of ozonation and absorption through membrane processes to remove ammonia from wastewater using NHSW (natural hot spring water) as absorbent. Experimental results show that hollow fiber membrane contactor has potential application for ammonia removal from wastewater. Operating variables such as time and pH of absorbent solution are found to remarkably influence the removal process efficiency.. Based on experimental results ozonation can improve ammonia removal efficiency through hollow fiber membrane contactor. Ammonia removal efficiencies and overall mass transfer coefficients increase with decreasing pH of absorbent solution.
基金Supported by the Special Fund for Agro-scientific Research in the Public Interest(No.200903001-5)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)of China+1 种基金the Natural Science Foundation of Jiangsu Province,China(No.BK2010440)China Postdoctoral Science Foundation(No.20110491439)
文摘Ammonium(NH+4) is the main nitrogen(N) form for rice crops, while NH+4near the root surface can be oxidized to nitrate(NO-3)by NH+4-oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N supply is insufficient. We compared the remobilization of NO-3stored in the tissue and vacuolar between two rice(Oryza sativa L.) cultivars, Yangdao 6(YD6, indica)with a high N use efficiency(NUE) and Wuyujing 3(WYJ3, japonica) with a low NUE and measured the uptake of NO-3, expression of nitrate reductase(NR), NO-3transporter genes(NRTs), and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L-1NO-3. The results showed that both tissue NO-3concentration and vacuolar NO-3activity were higher in YD6 than WYJ3 under N starvation. YD6 showed a 2- to 3-fold higher expression of OsNRT2.1 in roots on the 1st and 4th day of N starvation and had significantly higher values of NO-3uptake(maximum uptake velocity, Vmax) than the cultivar WYJ3.Furthermore, YD6 had significantly higher leaf and root maximum NR activity(NRAmax) and actual NR activity(NRAact) as well as stronger root expression of the two NR genes after the 1st day of N starvation. There were no significant differences in NRAmax and NRAact between the two rice cultivars on the 4th day of N starvation. The results suggested that YD6 had stronger NRA under N starvation, which might result in better NO-3re-utilization from the vacuole, and higher capacity for NO-3uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3.
基金supported by the National Natural Science Foundation of China(31800400 and 31722009)and the Natural Science Foundation of Shanghai(18ZR1412100).
文摘Aims The functions of global forests are threatened by the increasing frequency of severe drought.Due to drought inducing reductions in soil nutrient availability,efficiencies of nutrient use and resorption of trees become crucial for forest functions and biogeochemical cycles.However,understanding the dynamics of responses of foliar nutrient use and resorption efficiencies to drought,especially in tropical or subtropical forests,is still limited.Our goal was to detect whether and how the importance of leaf nutrient use and resorption changes across different species in the hot and wet forests when suffering drought stress in different months.Methods Based on a 70%throughfall exclusion experiment in a subtropical forest,we collected green and senesced leaves of Schima superba and Lithocarpus glaber in different months from October 2016 to May 2019,to estimate the effects of drought on leaf nitrogen(N)and phosphorus(P)use and resorption efficiencies(i.e.NUE and PUE,NRE and PRE).Important Findings The effects of drought on nutrient use and resorption efficiencies varied between species and months.Based on a 2-year observation,drought had no effect on S.superba,but significantly decreased NUE,NRE and PRE of L.glaber by 3.4%,20.2%and 7.1%,respectively.Furthermore,the negative drought effects were aggravated by the natural summer drying in 2017.As a result,NUE and PUE of L.glaber were significantly depressed by 17.2%and 58.1%,while NRE and PRE were significantly reduced by 56.5%and 53.8%in August 2017.Moreover,the responses of NRE,PRE and NUE to drought were related with soil moisture(SM)for L.glaber,and when SM decreased to a threshold near 9 v/v%,drought effects were shifted from unresponsive to negative.Our results highlight a species-specific threshold response of nutrient use under drought in a subtropical forest.
基金the National Natural Science Foundation of China(31870399,32071533)the Strategic Priority Research Program ofthe(Chinese Academy of Sciences(XDB31030000).
文摘Forest productivity and carbon(C) sequestration largely depend on soil N and P availability.To date,however,the temporal variation of nutrient limitation along forest succession is still under debate.Leaf stoichiometry and nutrient resorption are important indicators for predicting nutrient limitation of plant growth.Here,we measured nitrogen(N)and phosphorus(P)concentrations in green leaves and leaf liter for all woody species at four stages of temperate forest succession,and analyzed how abiotic and biotic factors affect leaf stoichiometry and nutrient resorption along forest succession.At the individual scale,leaf N and P concentrations had a significant increase at the end of the succession,while no change in leaf N:P ratio was detected.Nitrogen resorption efficiency(NRE)increased significantly with succession,but P resorption efficiency(PRE)first increased and then decreased.Significant increases in NRE:PRE ratios only occurred at the end of the succession.Moreover,plant N cycling was less responsive to soil nutrient than P cycling.At the community scale,we found that leaf N and P concentrations first decreased and then increased along forest succession,which were mainly affected by Shannon-Wiener index and species richness.Leaf N:P ratio significantly varied with succession and was mainly determined by community-weighted mean diameter at breast height(DBH).NRE increased and was significantly influenced by species richness and DBH,while PRE was relatively stable along forest succession.Thus,the NRE:PRE ratios significantly increased,indicating that N limitation is exacerbated with the temperate forest succession.These results might reflect the intense interspecific competition for limiting resource in a higher biodiversity community.In conclusion,our findings highlight the importance of biotic factors in driving forest ecosystem nutrient cycling and provide valuable information for sustainable fertilizer management practices in China's temperate and boreal forests.