为研究极端干旱对牧草生长的影响,选择多年生黑麦草(Lolium perenne,Lp)和雀麦(Bromus valdivianus,Bv)给予80%~85%植物有效水(Plant available water,PAW)和20%~25%PAW 2种水分处理,分析两种牧草生长及体内水分状况对干旱胁迫的响应。...为研究极端干旱对牧草生长的影响,选择多年生黑麦草(Lolium perenne,Lp)和雀麦(Bromus valdivianus,Bv)给予80%~85%植物有效水(Plant available water,PAW)和20%~25%PAW 2种水分处理,分析两种牧草生长及体内水分状况对干旱胁迫的响应。研究表明:80%~85%PAW充足水分下,两种牧草生物量积累、水势(Water potential,WP)、相对含水量(Relative water content,RWC)和净光合速率(Net photosynthetic rate,Pn)无明显种间差异。Bv叶片宽而重,蒸腾速率(Transpiration rate,Tr)、CO_(2)总导度(Total conductance to CO_(2),CndCO_(2))和气孔导度(Conductance to H 2O,Gs)显著高于Lp。而Lp分蘗多、叶多汁,瞬时水分利用效率是Bv的1.63倍。20%~25%PAW对两种牧草生长影响不完全一致,叶饱和重、干重和叶面积有相反变化趋势,但与充足水分相比差异不显著;Pn,Tr,CndCO_(2),Gs和RWC则极显著降低,WP极显著降低了1.60 MPa,致使枯叶占比和叶温差显著升高。总之,雀麦和多年生黑麦草生长相近,水分利用模式不同;遭受极端干旱,不同种的两种牧草耐旱机制具有一定的共性,通过增强叶片持水力、降低水分循环、减少蒸腾失水以提高牧草抗旱性。展开更多
Warming and increased CO_(2)levels are generally believed to enhance photosynthetic rates(A)and tree growth,especially in alpine treelines.However,this positive effect may be limited by moisture availability.Here we c...Warming and increased CO_(2)levels are generally believed to enhance photosynthetic rates(A)and tree growth,especially in alpine treelines.However,this positive effect may be limited by moisture availability.Here we compare the radial growth and intrinsic water use efficiency(iWUE)of two widely-distributed evergreen needleleaf species,Tibetan juniper(Juniperus tibetica)and Balfour spruce(Picea balfouriana),at the same site near the treeline on the southeastern Tibetan Plateau using tree-ring width and dual isotopes(δ^(13)C andδ^(18)O).We observed that with a 70-ppm increase in atmospheric CO_(2)from 1954 to 2007,juniper radial growth was significantly stimulated,whereas spruce growth remained constant.Correlation analysis between tree-ring width and climate factors revealed that spruce was more moisture-sensitive than juniper.Although the increases in iWUE for juniper(22%)and spruce(26%)were similar,iWUE changes in spruce were more influenced by stomatal conductance(gs)rather than A,supporting that moisture availability inhibits spruce growth.Our study implies that predicting growth dynamics in alpine forests based on the growth-temperature relationship may be inadequate,as they are likely moisture-limited.It also suggests that increases in A may not be as widespread as previously thought,which helps improve forest productivity modeling.展开更多
Nitrogen(N)deposition alters the soil environment for forest trees,particularly in tropical regions,leading to variations in leaf traits.However,the adaptive responses of plantation tree species to chronic N depositio...Nitrogen(N)deposition alters the soil environment for forest trees,particularly in tropical regions,leading to variations in leaf traits.However,the adaptive responses of plantation tree species to chronic N deposition,via leaf trait modifications,remain poorly understood.We conducted a decade-long experiment involving N additions in two typical plantations dominated by Eucalyptus urophylla(EU)and Acacia auriculiformis(AA)in South China,to investigate species-specific leaf trait plasticity under N deposition.Our results showed that long-term N addition did not affect N and phosphorus(P)concentrations,sugar and starch levels,intrinsic water use efficiency(iWUE),and leaf mass per area(LMA),but lowered leaf total Carbon(C)content in both EU and AA.Moreover,it resulted in divergent traits between them,showing an increase in tannin and phenolics but a decrease in leaf water content(LWC)in AA but no such variations in EU.These differential responses were attributed to their unique leaf traits that EU contains high chemical defensive compounds and AA,as an N-fixing tree species,exhibits higher resource levels.The reduced leaf total C was redirected towards defense,without compromising iWUE through unchanged sugar and starch levels,particularly in AA.Our findings demonstrate that long-term N addition intensifies the coupling between C and water,resulting in a shift in C allocation in trees.Consequently,long-term N addition triggers different defensive strategies:a conservative defense in EU and an active defense in AA.This finding offers new insights into the adaptive mechanisms of forest plants under global change scenarios.展开更多
In the northwestern part of China,rational and efficient management of irrigation and nitrogen significantly affects the intensive production of greenhouse cucumbers(Cucumis sativus L).To evaluate the effects of diffe...In the northwestern part of China,rational and efficient management of irrigation and nitrogen significantly affects the intensive production of greenhouse cucumbers(Cucumis sativus L).To evaluate the effects of different combinations of water use and nitrogen(N)on yield,quality,and profitability of the greenhouse cucumbers that planted in 2018 Spring,nine combined treatments were applied.Results indicated the optimal irrigation and nitrogen demands for yield,quality and other indicators were different.The irrigation amount significantly affected the yield,and the yield gradually increased with increasing in irrigation.Single fruit weight(SFW)was significantly affected by the amount of irrigation,nitrogen and their interactions,and the higher amounts of N and irrigation were beneficial to the increase of SFW.The partial factor productivity of the applied N(PFPN)gradually increased with the nitrogen amount decline.Irrigation water use efficiency(IWUE)was closely related to the amount of irrigation.The higher irrigation amount would lead to the lower IWUE.When the amounts of irrigation and nitrogen were at an intermediate level,the content of vitamin C(VC)reached the maximum.As the amount of nitrogen was increased or irrigation was decreased,the Nitrate content(NC)would increase.Free amino acid(FAA)and NC followed a similar variation.When the amounts of irrigation and nitrogen both were at medium levels,the total soluble sugar concentration(TSSC)reached the highest.The multi-level fuzzy evaluation method was used to evaluate different indicators of cucumber.The weights of indicators in the first and second layer were determined by analytic hierarchy process(AHP)and entropy weight method,respectively.Then the fuzzy algorithm was used to comprehensively evaluate all the treatments.The evaluation results show that T4(irrigation,1957.6 m3/hm2;N,210 kg/hm2)is the best strategy for greenhouse cucumber irrigation and nitrogen management in the northwestern part of China.展开更多
文摘为研究极端干旱对牧草生长的影响,选择多年生黑麦草(Lolium perenne,Lp)和雀麦(Bromus valdivianus,Bv)给予80%~85%植物有效水(Plant available water,PAW)和20%~25%PAW 2种水分处理,分析两种牧草生长及体内水分状况对干旱胁迫的响应。研究表明:80%~85%PAW充足水分下,两种牧草生物量积累、水势(Water potential,WP)、相对含水量(Relative water content,RWC)和净光合速率(Net photosynthetic rate,Pn)无明显种间差异。Bv叶片宽而重,蒸腾速率(Transpiration rate,Tr)、CO_(2)总导度(Total conductance to CO_(2),CndCO_(2))和气孔导度(Conductance to H 2O,Gs)显著高于Lp。而Lp分蘗多、叶多汁,瞬时水分利用效率是Bv的1.63倍。20%~25%PAW对两种牧草生长影响不完全一致,叶饱和重、干重和叶面积有相反变化趋势,但与充足水分相比差异不显著;Pn,Tr,CndCO_(2),Gs和RWC则极显著降低,WP极显著降低了1.60 MPa,致使枯叶占比和叶温差显著升高。总之,雀麦和多年生黑麦草生长相近,水分利用模式不同;遭受极端干旱,不同种的两种牧草耐旱机制具有一定的共性,通过增强叶片持水力、降低水分循环、减少蒸腾失水以提高牧草抗旱性。
基金funded by the National Natural Science Foundation of China(No.42161144008).
文摘Warming and increased CO_(2)levels are generally believed to enhance photosynthetic rates(A)and tree growth,especially in alpine treelines.However,this positive effect may be limited by moisture availability.Here we compare the radial growth and intrinsic water use efficiency(iWUE)of two widely-distributed evergreen needleleaf species,Tibetan juniper(Juniperus tibetica)and Balfour spruce(Picea balfouriana),at the same site near the treeline on the southeastern Tibetan Plateau using tree-ring width and dual isotopes(δ^(13)C andδ^(18)O).We observed that with a 70-ppm increase in atmospheric CO_(2)from 1954 to 2007,juniper radial growth was significantly stimulated,whereas spruce growth remained constant.Correlation analysis between tree-ring width and climate factors revealed that spruce was more moisture-sensitive than juniper.Although the increases in iWUE for juniper(22%)and spruce(26%)were similar,iWUE changes in spruce were more influenced by stomatal conductance(gs)rather than A,supporting that moisture availability inhibits spruce growth.Our study implies that predicting growth dynamics in alpine forests based on the growth-temperature relationship may be inadequate,as they are likely moisture-limited.It also suggests that increases in A may not be as widespread as previously thought,which helps improve forest productivity modeling.
基金supported by National Natural Science Foundation of China(Grant No.31971459,42173077,31961143023).
文摘Nitrogen(N)deposition alters the soil environment for forest trees,particularly in tropical regions,leading to variations in leaf traits.However,the adaptive responses of plantation tree species to chronic N deposition,via leaf trait modifications,remain poorly understood.We conducted a decade-long experiment involving N additions in two typical plantations dominated by Eucalyptus urophylla(EU)and Acacia auriculiformis(AA)in South China,to investigate species-specific leaf trait plasticity under N deposition.Our results showed that long-term N addition did not affect N and phosphorus(P)concentrations,sugar and starch levels,intrinsic water use efficiency(iWUE),and leaf mass per area(LMA),but lowered leaf total Carbon(C)content in both EU and AA.Moreover,it resulted in divergent traits between them,showing an increase in tannin and phenolics but a decrease in leaf water content(LWC)in AA but no such variations in EU.These differential responses were attributed to their unique leaf traits that EU contains high chemical defensive compounds and AA,as an N-fixing tree species,exhibits higher resource levels.The reduced leaf total C was redirected towards defense,without compromising iWUE through unchanged sugar and starch levels,particularly in AA.Our findings demonstrate that long-term N addition intensifies the coupling between C and water,resulting in a shift in C allocation in trees.Consequently,long-term N addition triggers different defensive strategies:a conservative defense in EU and an active defense in AA.This finding offers new insights into the adaptive mechanisms of forest plants under global change scenarios.
基金This work was partially supported by the Key Research and Development Program of Shaanxi Province in China(Grant No.2018TSCXL-NY-05-03)the Xi'an Science and Technology Program in China(Grant No.2017050NC/NY011(2))the Key project for Innovation in Production,Education and Research of Yangling in China(Grant No.2017CXY-07).
文摘In the northwestern part of China,rational and efficient management of irrigation and nitrogen significantly affects the intensive production of greenhouse cucumbers(Cucumis sativus L).To evaluate the effects of different combinations of water use and nitrogen(N)on yield,quality,and profitability of the greenhouse cucumbers that planted in 2018 Spring,nine combined treatments were applied.Results indicated the optimal irrigation and nitrogen demands for yield,quality and other indicators were different.The irrigation amount significantly affected the yield,and the yield gradually increased with increasing in irrigation.Single fruit weight(SFW)was significantly affected by the amount of irrigation,nitrogen and their interactions,and the higher amounts of N and irrigation were beneficial to the increase of SFW.The partial factor productivity of the applied N(PFPN)gradually increased with the nitrogen amount decline.Irrigation water use efficiency(IWUE)was closely related to the amount of irrigation.The higher irrigation amount would lead to the lower IWUE.When the amounts of irrigation and nitrogen were at an intermediate level,the content of vitamin C(VC)reached the maximum.As the amount of nitrogen was increased or irrigation was decreased,the Nitrate content(NC)would increase.Free amino acid(FAA)and NC followed a similar variation.When the amounts of irrigation and nitrogen both were at medium levels,the total soluble sugar concentration(TSSC)reached the highest.The multi-level fuzzy evaluation method was used to evaluate different indicators of cucumber.The weights of indicators in the first and second layer were determined by analytic hierarchy process(AHP)and entropy weight method,respectively.Then the fuzzy algorithm was used to comprehensively evaluate all the treatments.The evaluation results show that T4(irrigation,1957.6 m3/hm2;N,210 kg/hm2)is the best strategy for greenhouse cucumber irrigation and nitrogen management in the northwestern part of China.
