Young leaves are conventionally used in the analysis to study the nutrient status of evergreen plants and their responses to environmental changes, but the role of old leaves remains poorly understood. We selected two...Young leaves are conventionally used in the analysis to study the nutrient status of evergreen plants and their responses to environmental changes, but the role of old leaves remains poorly understood. We selected two stand types in 31-year-old Chinese fir（Cunninghamia lanceolata） plantations with similar soil conditions but different stand densities, to test the hypothesis that nitrogen（N） concentration of old leaves and twigs is more sensitive to stand density than that of young ones. Leaves and twigs were sampled and sorted into young（one-year-old） and old（two-and three-year-old） groups. Significant differences in N concentration and carbon： nitrogen ratio between the low-density stand and high-density stand were only found in the old leaves and twigs but not in the young ones.Although the N resorption efficiency did not vary significantly with stand density, the annual N resorption rates were increased in old leaves and relatively young twigs at high stand density. These results show the potential use of old tissues in the nutrient analysis in Chinese fir plantations. Testing the generality of these results could improve the use of foliar analysis as an indicator of nutrient status and environmental changes in evergreen tree species.展开更多
Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The ob...Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The objective of this research was to assess litterfall production,the potential deposition of macro and micronutrients through leaf and twig fall as well as macronutrient—use efficiency in three forest ecosystems at different altitudes： a pine forest mixed with deciduous species（S1）; a Quercus spp.forest（S2）; and,a Tamaulipan thornscrub forest（S3）.Total annual litterfall deposition was 594,742 and 533 g m^（-2） for S1,S2 and S3.Leaf litter was higher （68%） than twigs（18%）,reproductive structures（8%） or miscellaneous material（6%）.Micronutrient leaf deposition was higher for Fe followed by Mn,Zn and Cu.Macronutrient leaf deposition was higher for Ca followed by K,Mg and P.Even though P deposition in leaves and twigs was lower than other macronutrients,its nutrient use efficiency was higher than Ca,Mg or K.Altitude and species composition determine litter and nutrient deposition,with higher values at mid-altitudes（550 m）.Altitude is an important factor to consider when analyzing litter production as well as nutrient deposition as shown in this study.Litter production and nutrient deposition are expected to change in a scenario of global warming.展开更多
Background:Nitrogen(N)and phosphorus(P)are important elements for plant metabolism and growth.Therefore,the quantification of the scaling relationship of N to P in plant organs can help us understand many fundamental ...Background:Nitrogen(N)and phosphorus(P)are important elements for plant metabolism and growth.Therefore,the quantification of the scaling relationship of N to P in plant organs can help us understand many fundamental ecological processes.The general scaling relationships between N and P in leaves and in fine roots have been reported.As compared to leaves and fine roots,however,little information is available on the N versus P scaling relationship in the stems of woody plants,especially for twigs.In this study,a comprehensive dataset comprising 2,038 N=P paired observations for a total of 536 woody species was compiled and analyzed to determine whether a general scaling relationship exists.Results:The global mean values of twig N and P concentrations and N:P ratios were 9.33 mg⋅g^(-1),1.12 mg⋅g^(-1) and 10.16,respectively.Twig N and P concentrations and N:P ratios differed significantly within and across functional groups and biomes.Across all of the species,a uniform 0.67 scaling exponent of twig N to P was observed across different functional groups and biomes,i.e.,a 2/3-power scaling relationship was observed.However,this numerical value differed across different sites,albeit converging onto 0.67 with increasing sample sizes.Soil total phosphorus was the largest contributor to the variation in the numerical value of the scaling exponent.Conclusion:These results provide useful parameters for stoichiometric growth models,and advance our understanding of the mechanisms underlying plant nutrient dynamics.This study has potential implications in predicting responses of nutrient cycling in terrestrial ecosystem responses to changes in the environment.展开更多
桑枝是桑科植物桑(Mrous alba L.)的干燥嫩枝,具有祛风湿、利关节等功效,在传统中医中常用于治疗风湿痹病、关节酸痛麻木等病症。现代研究发现桑枝具有多种药理作用,包括调节糖脂代谢异常、抗氧化、抗菌、抗病毒等。生物碱是桑枝中重要...桑枝是桑科植物桑(Mrous alba L.)的干燥嫩枝,具有祛风湿、利关节等功效,在传统中医中常用于治疗风湿痹病、关节酸痛麻木等病症。现代研究发现桑枝具有多种药理作用,包括调节糖脂代谢异常、抗氧化、抗菌、抗病毒等。生物碱是桑枝中重要的活性成分,具有良好的降血糖作用,还具有调节糖脂代谢和肠道菌群、保护胰岛β细胞、改善葡萄糖刺激的胰岛素分泌功能、刺激GLP-1分泌等作用。文章通过对桑枝生物碱种类、体内合成通路、提取检测方法以及药理作用进行综述,为桑枝生物碱的深入研究及高效利用提供参考依据。展开更多
基金supported by the NSFC Projects of International Cooperation and Exchanges(31210103920)the National Key Research and Development Program(2016YFD0600202)+1 种基金the Gan-Po Distinguished Researcher Programthe Project of Jiangxi Provincial Department of Science and Technology(20144BBB70005)
文摘Young leaves are conventionally used in the analysis to study the nutrient status of evergreen plants and their responses to environmental changes, but the role of old leaves remains poorly understood. We selected two stand types in 31-year-old Chinese fir（Cunninghamia lanceolata） plantations with similar soil conditions but different stand densities, to test the hypothesis that nitrogen（N） concentration of old leaves and twigs is more sensitive to stand density than that of young ones. Leaves and twigs were sampled and sorted into young（one-year-old） and old（two-and three-year-old） groups. Significant differences in N concentration and carbon： nitrogen ratio between the low-density stand and high-density stand were only found in the old leaves and twigs but not in the young ones.Although the N resorption efficiency did not vary significantly with stand density, the annual N resorption rates were increased in old leaves and relatively young twigs at high stand density. These results show the potential use of old tissues in the nutrient analysis in Chinese fir plantations. Testing the generality of these results could improve the use of foliar analysis as an indicator of nutrient status and environmental changes in evergreen tree species.
基金supported by the PAICYT Grant CT259-15National Science and Technological Council(Grant250732)
文摘Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The objective of this research was to assess litterfall production,the potential deposition of macro and micronutrients through leaf and twig fall as well as macronutrient—use efficiency in three forest ecosystems at different altitudes： a pine forest mixed with deciduous species（S1）; a Quercus spp.forest（S2）; and,a Tamaulipan thornscrub forest（S3）.Total annual litterfall deposition was 594,742 and 533 g m^（-2） for S1,S2 and S3.Leaf litter was higher （68%） than twigs（18%）,reproductive structures（8%） or miscellaneous material（6%）.Micronutrient leaf deposition was higher for Fe followed by Mn,Zn and Cu.Macronutrient leaf deposition was higher for Ca followed by K,Mg and P.Even though P deposition in leaves and twigs was lower than other macronutrients,its nutrient use efficiency was higher than Ca,Mg or K.Altitude and species composition determine litter and nutrient deposition,with higher values at mid-altitudes（550 m）.Altitude is an important factor to consider when analyzing litter production as well as nutrient deposition as shown in this study.Litter production and nutrient deposition are expected to change in a scenario of global warming.
基金financially supported by the National Science Fund for Excellent Young Scholars (No. 31822010)the National Key Research and Development Program of China (No. 2020YFA0608102)+3 种基金the Biodiversity Survey and Assessment Project of the Ministry of Ecology and Environment,China (No. 2019HJ2096001006)National Scientific and Technological Program on Basic Resources Investigation (No.2019FY102002)the Innovation Base Project of Gansu Province (No.20190323)the Sichuan Science and Technology Program (No.2020YFH0005)
文摘Background:Nitrogen(N)and phosphorus(P)are important elements for plant metabolism and growth.Therefore,the quantification of the scaling relationship of N to P in plant organs can help us understand many fundamental ecological processes.The general scaling relationships between N and P in leaves and in fine roots have been reported.As compared to leaves and fine roots,however,little information is available on the N versus P scaling relationship in the stems of woody plants,especially for twigs.In this study,a comprehensive dataset comprising 2,038 N=P paired observations for a total of 536 woody species was compiled and analyzed to determine whether a general scaling relationship exists.Results:The global mean values of twig N and P concentrations and N:P ratios were 9.33 mg⋅g^(-1),1.12 mg⋅g^(-1) and 10.16,respectively.Twig N and P concentrations and N:P ratios differed significantly within and across functional groups and biomes.Across all of the species,a uniform 0.67 scaling exponent of twig N to P was observed across different functional groups and biomes,i.e.,a 2/3-power scaling relationship was observed.However,this numerical value differed across different sites,albeit converging onto 0.67 with increasing sample sizes.Soil total phosphorus was the largest contributor to the variation in the numerical value of the scaling exponent.Conclusion:These results provide useful parameters for stoichiometric growth models,and advance our understanding of the mechanisms underlying plant nutrient dynamics.This study has potential implications in predicting responses of nutrient cycling in terrestrial ecosystem responses to changes in the environment.
文摘桑枝是桑科植物桑(Mrous alba L.)的干燥嫩枝,具有祛风湿、利关节等功效,在传统中医中常用于治疗风湿痹病、关节酸痛麻木等病症。现代研究发现桑枝具有多种药理作用,包括调节糖脂代谢异常、抗氧化、抗菌、抗病毒等。生物碱是桑枝中重要的活性成分,具有良好的降血糖作用,还具有调节糖脂代谢和肠道菌群、保护胰岛β细胞、改善葡萄糖刺激的胰岛素分泌功能、刺激GLP-1分泌等作用。文章通过对桑枝生物碱种类、体内合成通路、提取检测方法以及药理作用进行综述,为桑枝生物碱的深入研究及高效利用提供参考依据。
