Nutrient retranslocation in trees is important in nutrient budgets and energy flows in forest ecosystems. We investigated nutrient retranslocation in the fine roots of a Manchurian Ash （Fraxinus mandshurica） and a L...Nutrient retranslocation in trees is important in nutrient budgets and energy flows in forest ecosystems. We investigated nutrient retranslocation in the fine roots of a Manchurian Ash （Fraxinus mandshurica） and a Larch （Larix olgensis） plantation in northeastern China. Nutrient retranslocation in the fine roots was investigated using three methods, specifically, nutrient concentration, the ratio of Ca to other elements （Ca/other elements ratio） and nutrient content. The method based on nutrient content proved most suitable when investigating nutrient retranslocation from fine roots of the two species. The nutrient-content-based method showed that there were retranslocations of N, P, K and Mg from the fine roots of Manchurian Ash, with retranslocation efficiencies of 13, 25, 65, and 38 %, respectively, whereas there were no Ca retranslocations. There were retranslocations of N, P, K, Ca and Mg from the fine roots of Larch, with retranslocation efficiencies of 31, 40, 52, 23 and 25 %, respectively.展开更多
In the semiarid sandy region of Northeast China,Mongolian pine(Pinus sylvestris var.mongolica)suffers dieback after the age of 35,while Japanese red pine(Pinus densiflora)and Chinese pine(Pinus tabuliformis)stay healt...In the semiarid sandy region of Northeast China,Mongolian pine(Pinus sylvestris var.mongolica)suffers dieback after the age of 35,while Japanese red pine(Pinus densiflora)and Chinese pine(Pinus tabuliformis)stay healthy.Foliar nutrient retranslocation reflects the nutrient conservation and utilization mechanism of plants in response to their habitats.However,the nutrient retranslocation strategies employed by three Pinus tree species to cope with nutrient limitations remain largely unknown.For this study,we investigated the seasonal variations in nitrogen(N)and phosphorus(P)concentrations of Mongolian pine,Japanese red pine,and Chinese pine plantations in terms of the green needles of all ages,senesced needles,and soil.Further,the N retranslocation efficiency(NRE),and P retranslocation efficiency(PRE),and correlations between the N:P ratios of needles and soil were analyzed.The results showed that,except for the spring NRE in 1-year-old needles of Mongolian pine,the spring NRE and PRE in 1-and 2-year-old needles of the three tree species were greater than zero.The autumn PRE was higher than zero for Mongolian pine,but lower than zero for Japanese red pine and Chinese pine.Among the three Pinus species,Mongolian pine showed greater spring PRE in 2-year-old needles,and PRE from 1-to 2-yearold needles,and from 2-year-old needles to litter.However,Japanese red pine had higher P concentrations and lower N:P ratios in senesced needles,while greater PRE was found in Chinese pine litter.Significant relationships between the N:P ratios were found in the current year and 1-year-old needles and soil in the Mongolian pine plantation,while there was an insignificant relationship between the N:P ratios of the needles and soil in the Chinese pine plantation.Thus,for Mongolian pine,the removal of P from needles in autumn,and higher P translocation from older needles under P-deficient soil may have contributed to the tree dieback.In contrast,Japanese red pine and Chinese pine stored P in their needles during autumn.Japanese red pine returned more P to the soil via litter,while Chinese pine maintained N:P homeostasis and increased P withdrawal prior to needle abscission.展开更多
We quantified biomass accumulation and nitrogen （N） re- translocation, allocation, and utilization of Changbai larch （Larix olgen- sis） seedlings subjected to four fertilization treatments （24, 59, 81, 117 kg.ha-...We quantified biomass accumulation and nitrogen （N） re- translocation, allocation, and utilization of Changbai larch （Larix olgen- sis） seedlings subjected to four fertilization treatments （24, 59, 81, 117 kg.ha-1 N） with an unfertilized control during summer and autumn 2009. Ammonium phosphate （18-46-0） was the fertilizer used in all treatments. On both sampling dates, the needles had greater biomass and N content than new （2009） stems and old （2008） stems, and coarse, medium and fine roots （diameters of 〉5, 2-5 mm, and 0-2 mm, respectively）. Higher N concentration was observed in old stems and coarse roots than that in new stems and medium roots. In mid-summer, fine roots had higher N concentration than coarse roots. The treatment with 24 kg.ha1 N had the greatest biomass and N content in needles and old stems, and highest net N retranslocation （NRA） and amount of N derived from soil. On Sep- tember 21, no N translocation was observed, while the treatment with 24 kg.ha^-1 N had the highest N utilization efficiency and fertilizer efficiency. Vector analysis revealed that all four fertilization treatments induced Nexcess relative to the control. The treatments with 59, 81, 117 kg.ha^-1 N induce N excess compared with treatments at 24 kg.ha-1 N. We conclude that the traditional local fertilizer application rates exceeded N require- ments and N uptake ability for Changbai larch seedlings. The application rate of 24 kg.ha^-1 N is recommended.展开更多
Using tracer techniques with the radioisotope 45Ca, the effects of boron supply from soil and nutrient solution on the retranslocation of 45Ca from leaves to other parts of rape plants were studied. Results indicated ...Using tracer techniques with the radioisotope 45Ca, the effects of boron supply from soil and nutrient solution on the retranslocation of 45Ca from leaves to other parts of rape plants were studied. Results indicated that only a small portion of foliar-applied 45Ca could be retranslocated to other parts of the rape plant. There was no pronounced effect of boron level in the soil on 45 Ca retranslocation. Increasing boron concentrations in the nutrient solution significantly reduced 45 Ca radioactivity in root and stem, but increased 45Ca uptake and 45 Ca translocation to the upper leaves of rape plants. It was suggested that45 Ca absorbed by newly developed roots was easily distributed to upper leaves of rape plants. Boron may alter distribution of calcium via its effect on root development or growth of newly developed roots.展开更多
The accurate assessment of actual tree stem respiration and its relation with temperature plays a considerable role in investigating the forest carbon cycle.An increasing number of research reports have indicated that...The accurate assessment of actual tree stem respiration and its relation with temperature plays a considerable role in investigating the forest carbon cycle.An increasing number of research reports have indicated that tree stem respiration determined with the commonlyapplied chamber gas exchange measuring system does not follow expectations regarding temperature relationships.This method is based on the nowadays widely-accepted theory that the respired CO_(2) in a tree stem would all diffuse outward into the atmosphere.However,it neglects partial CO_(2) that is dissolved in the xylem sap and is carried away by the transpirational stream.Scientists have started to realize that the respired CO_(2) measured with the chamber gas exchange method is only a portion of the total stem respiration(CO_(2) efflux),while the other portion,which is sometimes very substantial in quantity(thought to occupy maybe 15%-75%of the total stem respiration),is transported to the upper part of the stem and to the canopy by sap flow.This suggests that the CO_(2) produced by respiration is re-allocated within the stem.Accordingly,the change in CO_(2) efflux could be reflected in the rates of sap flow in addition to its dependence on temperature.Proper methods and instruments are required to quantify the internal and external CO_(2) fluxes in the trunk and their interaction with related environmental factors.展开更多
基金supported by the National Key Technology Research and Development Program(2012BAD21B0202-02)the Natural Science Foundation of Heilongjiang Province of China(C201340)the assisted project by Heilong Jiang Postdoctoral Funds for Scientific Research Initiation(LBH-Q13006)
文摘Nutrient retranslocation in trees is important in nutrient budgets and energy flows in forest ecosystems. We investigated nutrient retranslocation in the fine roots of a Manchurian Ash （Fraxinus mandshurica） and a Larch （Larix olgensis） plantation in northeastern China. Nutrient retranslocation in the fine roots was investigated using three methods, specifically, nutrient concentration, the ratio of Ca to other elements （Ca/other elements ratio） and nutrient content. The method based on nutrient content proved most suitable when investigating nutrient retranslocation from fine roots of the two species. The nutrient-content-based method showed that there were retranslocations of N, P, K and Mg from the fine roots of Manchurian Ash, with retranslocation efficiencies of 13, 25, 65, and 38 %, respectively, whereas there were no Ca retranslocations. There were retranslocations of N, P, K, Ca and Mg from the fine roots of Larch, with retranslocation efficiencies of 31, 40, 52, 23 and 25 %, respectively.
基金supported by the National Natural Science Foundation of China(Nos.32271846,31400613)the Key Program of Education Department of Liaoning Province(No.LJKZZ20220050).
文摘In the semiarid sandy region of Northeast China,Mongolian pine(Pinus sylvestris var.mongolica)suffers dieback after the age of 35,while Japanese red pine(Pinus densiflora)and Chinese pine(Pinus tabuliformis)stay healthy.Foliar nutrient retranslocation reflects the nutrient conservation and utilization mechanism of plants in response to their habitats.However,the nutrient retranslocation strategies employed by three Pinus tree species to cope with nutrient limitations remain largely unknown.For this study,we investigated the seasonal variations in nitrogen(N)and phosphorus(P)concentrations of Mongolian pine,Japanese red pine,and Chinese pine plantations in terms of the green needles of all ages,senesced needles,and soil.Further,the N retranslocation efficiency(NRE),and P retranslocation efficiency(PRE),and correlations between the N:P ratios of needles and soil were analyzed.The results showed that,except for the spring NRE in 1-year-old needles of Mongolian pine,the spring NRE and PRE in 1-and 2-year-old needles of the three tree species were greater than zero.The autumn PRE was higher than zero for Mongolian pine,but lower than zero for Japanese red pine and Chinese pine.Among the three Pinus species,Mongolian pine showed greater spring PRE in 2-year-old needles,and PRE from 1-to 2-yearold needles,and from 2-year-old needles to litter.However,Japanese red pine had higher P concentrations and lower N:P ratios in senesced needles,while greater PRE was found in Chinese pine litter.Significant relationships between the N:P ratios were found in the current year and 1-year-old needles and soil in the Mongolian pine plantation,while there was an insignificant relationship between the N:P ratios of the needles and soil in the Chinese pine plantation.Thus,for Mongolian pine,the removal of P from needles in autumn,and higher P translocation from older needles under P-deficient soil may have contributed to the tree dieback.In contrast,Japanese red pine and Chinese pine stored P in their needles during autumn.Japanese red pine returned more P to the soil via litter,while Chinese pine maintained N:P homeostasis and increased P withdrawal prior to needle abscission.
基金financially supported by the Special Industry Project of Ministry of Finance (Grant No. 201104051)"11th Five-Year Plant" National Key Technology and R&D Program from Chinese State Forestry Administration (Grant No. 2006BAD24B01)
文摘We quantified biomass accumulation and nitrogen （N） re- translocation, allocation, and utilization of Changbai larch （Larix olgen- sis） seedlings subjected to four fertilization treatments （24, 59, 81, 117 kg.ha-1 N） with an unfertilized control during summer and autumn 2009. Ammonium phosphate （18-46-0） was the fertilizer used in all treatments. On both sampling dates, the needles had greater biomass and N content than new （2009） stems and old （2008） stems, and coarse, medium and fine roots （diameters of 〉5, 2-5 mm, and 0-2 mm, respectively）. Higher N concentration was observed in old stems and coarse roots than that in new stems and medium roots. In mid-summer, fine roots had higher N concentration than coarse roots. The treatment with 24 kg.ha1 N had the greatest biomass and N content in needles and old stems, and highest net N retranslocation （NRA） and amount of N derived from soil. On Sep- tember 21, no N translocation was observed, while the treatment with 24 kg.ha^-1 N had the highest N utilization efficiency and fertilizer efficiency. Vector analysis revealed that all four fertilization treatments induced Nexcess relative to the control. The treatments with 59, 81, 117 kg.ha^-1 N induce N excess compared with treatments at 24 kg.ha-1 N. We conclude that the traditional local fertilizer application rates exceeded N require- ments and N uptake ability for Changbai larch seedlings. The application rate of 24 kg.ha^-1 N is recommended.
基金supported by the Nationa1 Natura1 Science Foundation of China(39770439).
文摘Using tracer techniques with the radioisotope 45Ca, the effects of boron supply from soil and nutrient solution on the retranslocation of 45Ca from leaves to other parts of rape plants were studied. Results indicated that only a small portion of foliar-applied 45Ca could be retranslocated to other parts of the rape plant. There was no pronounced effect of boron level in the soil on 45 Ca retranslocation. Increasing boron concentrations in the nutrient solution significantly reduced 45 Ca radioactivity in root and stem, but increased 45Ca uptake and 45 Ca translocation to the upper leaves of rape plants. It was suggested that45 Ca absorbed by newly developed roots was easily distributed to upper leaves of rape plants. Boron may alter distribution of calcium via its effect on root development or growth of newly developed roots.
基金National Natural Science Foundation of China (Grant No.30770328)the Natural Science Foundation of Guangdong Province (No.07006917)for support.
文摘The accurate assessment of actual tree stem respiration and its relation with temperature plays a considerable role in investigating the forest carbon cycle.An increasing number of research reports have indicated that tree stem respiration determined with the commonlyapplied chamber gas exchange measuring system does not follow expectations regarding temperature relationships.This method is based on the nowadays widely-accepted theory that the respired CO_(2) in a tree stem would all diffuse outward into the atmosphere.However,it neglects partial CO_(2) that is dissolved in the xylem sap and is carried away by the transpirational stream.Scientists have started to realize that the respired CO_(2) measured with the chamber gas exchange method is only a portion of the total stem respiration(CO_(2) efflux),while the other portion,which is sometimes very substantial in quantity(thought to occupy maybe 15%-75%of the total stem respiration),is transported to the upper part of the stem and to the canopy by sap flow.This suggests that the CO_(2) produced by respiration is re-allocated within the stem.Accordingly,the change in CO_(2) efflux could be reflected in the rates of sap flow in addition to its dependence on temperature.Proper methods and instruments are required to quantify the internal and external CO_(2) fluxes in the trunk and their interaction with related environmental factors.
