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
Water resources are subjected to ever-increasing supply constraints due to extensive agricultural water demand for irrigated lands.Therefore,water-saving irrigation strategies need to be explored.The present study was...Water resources are subjected to ever-increasing supply constraints due to extensive agricultural water demand for irrigated lands.Therefore,water-saving irrigation strategies need to be explored.The present study was conducted to explore the possibilities of using regulated deficit irrigation(RDI)and partial root zone drying irrigation(PRD)methods as water-saving irrigation techniques for subsurface irrigation.The objective of this study are to assess the effects of RDI and PRD irrigation on the water productivity of vegetable crops(tomato)under SSD systems in arid climatic conditions,and to compare the responses of tomato crops to PRD,RDI,and FI under an SSD system in terms of productivity,crop quality,and the amount of water saved.The field experiment was conducted during the fall 2014-2015 and 2015-2016 seasons in an experimental field located on an educational farm owned by the Faculty of Food and Agriculture Sciences Department,King Saud University,Riyadh,Kingdom of Saudi Arabia.An area of 102.7 m^(2)(13 m×7.9 m)was allocated for the experiment to manage three treatments:RDI,PRD,and full irrigation(FI).The RDI and PRD treatments received 70%of the irrigation water volume of FI.Each was replicated three times.The most important results indicated that the soil water content(SWC)for the RDI and PRD treatments was lower than that of the FI treatments.FI had the highest stomatal conductance values(gs),while PRD had the lowest stomatal conductance values.The photosynthetic rate(A_(n))was lower under RDI and PRD compared to FI.However,there was no significant change in A_(n) between treatments for most readings taken during both time periods,which means that the water saving treatments(PRD and RDI)did not affect the net photosynthesis rate,thereby enhancing irrigation water use efficiency(IWUE)under DI treatments.The water-saving irrigation techniques decreased transpiration rate(T)compared to the FI treatment.The values of the abscisic acid(ABA)contents were higher under PRD and RDI than FI.The marketable yield under the FI treatment yielded the highest values.The fruit quality parameter results showed that the RDI and PRD treatments increased the total soluble solids,vitamin C,and titratable acidity of tomato compared to the FI treatment.Most of the minimum IWUE values were associated with FI.These results indicate the effects of deficit levels on IWUE.展开更多
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.
基金This Project was funded by the National Plan for Science,Technology and Innovation(MAARIFAH),King Abdulaziz City for Science and Technology,Kingdom of Saudi Arabia,Award Number(11-WAT1978-02).
文摘Water resources are subjected to ever-increasing supply constraints due to extensive agricultural water demand for irrigated lands.Therefore,water-saving irrigation strategies need to be explored.The present study was conducted to explore the possibilities of using regulated deficit irrigation(RDI)and partial root zone drying irrigation(PRD)methods as water-saving irrigation techniques for subsurface irrigation.The objective of this study are to assess the effects of RDI and PRD irrigation on the water productivity of vegetable crops(tomato)under SSD systems in arid climatic conditions,and to compare the responses of tomato crops to PRD,RDI,and FI under an SSD system in terms of productivity,crop quality,and the amount of water saved.The field experiment was conducted during the fall 2014-2015 and 2015-2016 seasons in an experimental field located on an educational farm owned by the Faculty of Food and Agriculture Sciences Department,King Saud University,Riyadh,Kingdom of Saudi Arabia.An area of 102.7 m^(2)(13 m×7.9 m)was allocated for the experiment to manage three treatments:RDI,PRD,and full irrigation(FI).The RDI and PRD treatments received 70%of the irrigation water volume of FI.Each was replicated three times.The most important results indicated that the soil water content(SWC)for the RDI and PRD treatments was lower than that of the FI treatments.FI had the highest stomatal conductance values(gs),while PRD had the lowest stomatal conductance values.The photosynthetic rate(A_(n))was lower under RDI and PRD compared to FI.However,there was no significant change in A_(n) between treatments for most readings taken during both time periods,which means that the water saving treatments(PRD and RDI)did not affect the net photosynthesis rate,thereby enhancing irrigation water use efficiency(IWUE)under DI treatments.The water-saving irrigation techniques decreased transpiration rate(T)compared to the FI treatment.The values of the abscisic acid(ABA)contents were higher under PRD and RDI than FI.The marketable yield under the FI treatment yielded the highest values.The fruit quality parameter results showed that the RDI and PRD treatments increased the total soluble solids,vitamin C,and titratable acidity of tomato compared to the FI treatment.Most of the minimum IWUE values were associated with FI.These results indicate the effects of deficit levels on IWUE.
