During January to February in 2008,severe ice-snows occurred on 2.09×10^6 km^2 of south China and caused tremendous damage to the forests.Stem damage and crown debris input from the ice-snow in a Cunninghamia lan...During January to February in 2008,severe ice-snows occurred on 2.09×10^6 km^2 of south China and caused tremendous damage to the forests.Stem damage and crown debris input from the ice-snow in a Cunninghamia lanceolata stand in northern Guangdong Province,China,were investigated to determine the extent of ice-snow damage to trees and the nutrient distribution characteristics on woodland.Icicles were produced on branches and leaves of the C.lanceolata trees by sleets,resulting in all live trees were damaged by stem breakage.A strong positive correlation was found between the broken position of trees and diameter at breast height（DBH）.Nutrient concentrations varied according to components of crown debris.Total nutrient concentration graded in the following order：leaves 〉stembark 〉branches 〉stemwood.Crown debris input from ice-snows was 19.11 t·ha^-2,and branches,stemwood,leaves and stembark accounted for 37%,28%,27% and 8%,respectively.Nutrient distributions between components of crown debris differed drastically in 2008.The contribution of leaves to total nutrient accumulation of crown debris was 70%,whereas branches,stemwood and stembark contributed 13%,7% and 10%,respectively.Accumulations of N,P and K by the woodland were 105 067.9 t·ha^-2 in 2008,and the nutrients of crown debris,litter and the stand soil accounted for 0.18%,0.03% and 99.79%,respectively.The order of nutrient accumulation in leaves,branches,stembark,stemwood of crown debris and litter was N〉K〉P,but the nutrients stored in the soil were in the order of K 〉N 〉P.The N and P concentrations of litter in 2009 were greater than those in 2008,whereas its K concentration was smaller than that of the latter.N and P concentrations of stemwood and stembark in 2009 were slightly greater than those in 2009,whereas their K concentration was smaller than the latter.The N and P accumulations of stemwood and stembark of crown debris in 2009 were close to those in 2008,whereas their K accumulation was slightly smaller than the latter.The N,P and K accumulations of litter in 2009 was greater than those in 2008.展开更多
Microbial adaptation to salinity can be achieved through synthesis of organic osmolytes,which requires high amounts of energy;however,a single addition of plant residues can only temporarily improve energy supply to s...Microbial adaptation to salinity can be achieved through synthesis of organic osmolytes,which requires high amounts of energy;however,a single addition of plant residues can only temporarily improve energy supply to soil microbes.Therefore,a laboratory incubation experiment was conducted to evaluate the responses of soil microbes to increasing salinity with repeated additions of plant residues using a loamy sand soil with an electrical conductivity in saturated paste extract(EC_e) of 0.6 dS m^(-1).The soil was kept non-saline or salinized by adding different amounts of NaCl to achieve EC_e of 12.5,25.0 and 50.0 dS m^(-1).The non-saline soil and the saline soils were amended with finely ground pea residues at two rates equivalent to 3.9 and 7.8 g C kg^(-1) soil on days 0,15 and29.The soils receiving no residues were included as a control.Cumulative respiration per g C added over 2 weeks after each residue addition was always greater at 3.9 than 7.8 g C kg^(-1) soil and higher in the non-saline soil than in the saline soils.In the saline soils,the cumulative respiration per g C added was higher after the second and third additions than after the first addition except with3.9 g C kg^(-1) at EC_e of 50 dS m^(_1).Though with the same amount of C added(7.8 g C kg^(-1)),salinity reduced soil respiration to a lesser extent when 3.9 g C kg^(-1) was added twice compared to a single addition of 7.8 g C kg^(-1).After the third residue addition,the microbial biomass C concentration was significantly lower in the soils with EC_e of 25 and 50 dS m^(_1) than in the non-saline soil at3.9 g C kg^(-1),but only in the soil with EC_e of 50 dS m^(-1) at 7.8 g C kg^(-1).We concluded that repeated residue additions increased the adaptation of soil microbial community to salinity,which was likely due to high C availability providing microbes with the energy needed for synthesis of organic osmolytes.展开更多
文摘During January to February in 2008,severe ice-snows occurred on 2.09×10^6 km^2 of south China and caused tremendous damage to the forests.Stem damage and crown debris input from the ice-snow in a Cunninghamia lanceolata stand in northern Guangdong Province,China,were investigated to determine the extent of ice-snow damage to trees and the nutrient distribution characteristics on woodland.Icicles were produced on branches and leaves of the C.lanceolata trees by sleets,resulting in all live trees were damaged by stem breakage.A strong positive correlation was found between the broken position of trees and diameter at breast height（DBH）.Nutrient concentrations varied according to components of crown debris.Total nutrient concentration graded in the following order：leaves 〉stembark 〉branches 〉stemwood.Crown debris input from ice-snows was 19.11 t·ha^-2,and branches,stemwood,leaves and stembark accounted for 37%,28%,27% and 8%,respectively.Nutrient distributions between components of crown debris differed drastically in 2008.The contribution of leaves to total nutrient accumulation of crown debris was 70%,whereas branches,stemwood and stembark contributed 13%,7% and 10%,respectively.Accumulations of N,P and K by the woodland were 105 067.9 t·ha^-2 in 2008,and the nutrients of crown debris,litter and the stand soil accounted for 0.18%,0.03% and 99.79%,respectively.The order of nutrient accumulation in leaves,branches,stembark,stemwood of crown debris and litter was N〉K〉P,but the nutrients stored in the soil were in the order of K 〉N 〉P.The N and P concentrations of litter in 2009 were greater than those in 2008,whereas its K concentration was smaller than that of the latter.N and P concentrations of stemwood and stembark in 2009 were slightly greater than those in 2009,whereas their K concentration was smaller than the latter.The N and P accumulations of stemwood and stembark of crown debris in 2009 were close to those in 2008,whereas their K accumulation was slightly smaller than the latter.The N,P and K accumulations of litter in 2009 was greater than those in 2008.
文摘Microbial adaptation to salinity can be achieved through synthesis of organic osmolytes,which requires high amounts of energy;however,a single addition of plant residues can only temporarily improve energy supply to soil microbes.Therefore,a laboratory incubation experiment was conducted to evaluate the responses of soil microbes to increasing salinity with repeated additions of plant residues using a loamy sand soil with an electrical conductivity in saturated paste extract(EC_e) of 0.6 dS m^(-1).The soil was kept non-saline or salinized by adding different amounts of NaCl to achieve EC_e of 12.5,25.0 and 50.0 dS m^(-1).The non-saline soil and the saline soils were amended with finely ground pea residues at two rates equivalent to 3.9 and 7.8 g C kg^(-1) soil on days 0,15 and29.The soils receiving no residues were included as a control.Cumulative respiration per g C added over 2 weeks after each residue addition was always greater at 3.9 than 7.8 g C kg^(-1) soil and higher in the non-saline soil than in the saline soils.In the saline soils,the cumulative respiration per g C added was higher after the second and third additions than after the first addition except with3.9 g C kg^(-1) at EC_e of 50 dS m^(_1).Though with the same amount of C added(7.8 g C kg^(-1)),salinity reduced soil respiration to a lesser extent when 3.9 g C kg^(-1) was added twice compared to a single addition of 7.8 g C kg^(-1).After the third residue addition,the microbial biomass C concentration was significantly lower in the soils with EC_e of 25 and 50 dS m^(_1) than in the non-saline soil at3.9 g C kg^(-1),but only in the soil with EC_e of 50 dS m^(-1) at 7.8 g C kg^(-1).We concluded that repeated residue additions increased the adaptation of soil microbial community to salinity,which was likely due to high C availability providing microbes with the energy needed for synthesis of organic osmolytes.
