A study was conducted to detect the effect of water extracts from different parts such as root, bark, branch and leaf, of adult larch, Larix gmelini, trees on growth of Manchurian walnut, Juglans mandshudca, seedlings...A study was conducted to detect the effect of water extracts from different parts such as root, bark, branch and leaf, of adult larch, Larix gmelini, trees on growth of Manchurian walnut, Juglans mandshudca, seedlings and the allelopathy between the two tree species. Four concentrations （100 g. kg i, 50 g. kg^-1, 25 g. kg^-1 and 12.5 g. kg^-1） were prepared for each kind of extracts. Result showed that the water extracts with low and moderate concentrations accelerated the growth of collar diameter and increased biomass and root/shoot ratio of walnut seedlings. The water extracts from branches and barks with low and moderate concentrations accelerated the height growth of the seedlings, while those from leaves and roots slightly decreased the height growth of seedlings. The fact that application of water extracts of larch improved the growth of Manchurian walnut attributes possibly to the allelopathy between the two tree species.展开更多
The chemical element contents in tree rings are correlated with those in the soils near the tree roots. Theresults in the present study showed that the correlation between them could be described using the followinglo...The chemical element contents in tree rings are correlated with those in the soils near the tree roots. Theresults in the present study showed that the correlation between them could be described using the followinglogarithmic linear correlation model:lgC'(Z) = α(Z) + b(Z)lgC(Z).Therefore, by determining the chrono-sequence C(Z, t), where Z is the atomic number and t the year ofelemental contents in the annual growth rings of trees, we could get the chrono-sequence C'(Z, t) of elementalcontents in the soil, thus inferring the dynamic variations of relevant elemental contents in the soil.展开更多
The annual growth rings of ten trees and the soils near the tree roots were sampled from the mining area of lead-and zinc-dominant metals in the Xixia Mountain, Nanjing, for the determination of chemical element conte...The annual growth rings of ten trees and the soils near the tree roots were sampled from the mining area of lead-and zinc-dominant metals in the Xixia Mountain, Nanjing, for the determination of chemical element contents. The study results showed that the elemental contents in the tree rings were correlated with those in the soils, i. e., the elemental contents in the tree rings increased with those in the soils, even in the cases of different environments and different tree species. Therefore, a time-concentration sequence could be set up on the basis of determining the elemental contents in the successive annual growth rings of trees to qualitatively reflect the annual variations of relevant elements in the soils, and a time-concentration sequence of elemental contents in soils could also be established in terms of related model to reproduce the dynamic changes of the surroundings.展开更多
Aims In contrast to temperate regions,the reasons for growth reductions of individual tree species along elevational gradients in tropical mountain ranges are poorly known,especially for tropical conifers.We aimed at ...Aims In contrast to temperate regions,the reasons for growth reductions of individual tree species along elevational gradients in tropical mountain ranges are poorly known,especially for tropical conifers.We aimed at testing whether climatic or edaphic conditions are responsible for the reduced growth of Pinus kesiya,a widely distributed pine species of southern and south-eastern Asia,at higher elevations.Methods We analysed the stem diameter increment and the isotope discrimination against ^(13)C(△^(13)C)in tree rings of P.kesiya along an elevational gradient of~900 to~2000 m a.s.l.in the mountain ranges of South-Central Vietnam,and related growth to△^(13)C and to climatic and edaphic variables.Important findings We found no consistent correlation patterns between the basal area increment(BAI)of the trees and temperature or precipitation.In contrast,across the elevational gradient,we obtained significantly negative correlations of BAI with△^(13)C and with the C/N ratios and theδ^(15)N signature of the upper mineral soil.BAI was positively correlated with the concentrations of plant-available phosphorus(P_(a))and of“base”cations(calcium,magnesium,potassium)in the soil.We conclude that lower temperatures at higher elevations exert an indirect effect on tree growth by inducing higher C/N ratios and by reducing the rate of nitrogen(N)and P mineralization,which may be further hampered by lower concentrations of“base”cations(upon enhanced leaching by precipitation)and a negative feedback from low availability of mineralized N and P at higher elevations.Our results may be transferable to the uppermost growth limit of P.kesiya and to other montane regions of the species’occurrence.展开更多
Physiological and ecological mechanisms that define treelines are still debated. It has been suggested that the absence of trees above the treeline is caused by low temperatures that limit growth. Thus, we hypothesize...Physiological and ecological mechanisms that define treelines are still debated. It has been suggested that the absence of trees above the treeline is caused by low temperatures that limit growth. Thus, we hypothesized that there is a critical minimum temperature （CTmin） preventing xylogenesis at treeline. We tested this hypothesis by examining weekly xylogenesis across three and four growing seasons in two natural Smith fir （Abies georgei var. srnithii） treeline sites on the southeastern Tibetan Plateau. Despite differences in the timing of cell differentiation among years, minimum air temperature was the dominant climatic variable associated with xylem growth; the critical minimum temperature （CTmin） for the onset and end of xylogenesis occurred at 0.7 ±0.4 ℃. A process-based modelling chronology of tree-ring formation using this CTmin was consistent with actual tree-ring data. This extremely low CTmin permits Smith fir growing at treeline to complete annual xylem production and maturation and provides both support and a mechanism for treeline formation.展开更多
Aims Mechanisms of plant drought resistance include both tolerance and avoidance.Xylem vulnerability to embolism and turgor loss point are considered traits that confer tolerance,while leaf abscission and deciduousnes...Aims Mechanisms of plant drought resistance include both tolerance and avoidance.Xylem vulnerability to embolism and turgor loss point are considered traits that confer tolerance,while leaf abscission and deciduousness characterizes the avoidance strategy.While these mechanisms are thought to trade-off expressing a continuum among species,little is known on how variation in the timing and duration of leaf shedding in response to drought affect the relationship between xylem and leaf tolerance.In the present study,we explored the extent to which drought tolerance differs between two oak(Quercus)species that exhibit different leaf shedding behaviours.Particularly,we predicted that Q.deserticola Trel.,which loses leaves at the end of the dry season(late-deciduous)and is thus exposed to a greater risk of cavitation,would be more drought tolerant and more conservative in its water use than Q.laeta Liebm.,which loses its leaves for only a short period of time in the middle of the dry season(brevideciduous).Methods The study was conducted in central Mexico in a single population of each of the two oak species,separated from each other by a distance of 1.58 km,and by an altitudinal difference of 191 m.Quercus deserticola(late deciduous)is more frequent down slope,while Q.laeta(brevideciduous)tends to occur at higher elevations along the gradient.We assessed seasonal differences(rainy versus dry season)in native stem hydraulic conductivity,and tested for variation in xylem vulnerability to cavitation,leaf water use and leaf turgor loss point between the two species.Important Findings The two oak species did not differ in traits conferring drought tolerance,including xylem vulnerability to embolism,leaf turgor loss point,or stomatal conductance.However,both species had different performance during the dry season;the brevideciduous species had lower negative impact in the xylem function than the late-deciduous species.Overall,seasonal changes in plant physiological performance between the two oak species were determined by a reduction in the canopy leaf area.展开更多
基金This paper was supported by National Natural Science Foundation of China （No. 30400341） and Heilongjiang Provincial Science Foundation （No. C0320）Acknowledgement I thank Dr. YAN Xiu-feng for his help and guidance.
文摘A study was conducted to detect the effect of water extracts from different parts such as root, bark, branch and leaf, of adult larch, Larix gmelini, trees on growth of Manchurian walnut, Juglans mandshudca, seedlings and the allelopathy between the two tree species. Four concentrations （100 g. kg i, 50 g. kg^-1, 25 g. kg^-1 and 12.5 g. kg^-1） were prepared for each kind of extracts. Result showed that the water extracts with low and moderate concentrations accelerated the growth of collar diameter and increased biomass and root/shoot ratio of walnut seedlings. The water extracts from branches and barks with low and moderate concentrations accelerated the height growth of the seedlings, while those from leaves and roots slightly decreased the height growth of seedlings. The fact that application of water extracts of larch improved the growth of Manchurian walnut attributes possibly to the allelopathy between the two tree species.
文摘The chemical element contents in tree rings are correlated with those in the soils near the tree roots. Theresults in the present study showed that the correlation between them could be described using the followinglogarithmic linear correlation model:lgC'(Z) = α(Z) + b(Z)lgC(Z).Therefore, by determining the chrono-sequence C(Z, t), where Z is the atomic number and t the year ofelemental contents in the annual growth rings of trees, we could get the chrono-sequence C'(Z, t) of elementalcontents in the soil, thus inferring the dynamic variations of relevant elemental contents in the soil.
基金Project supported by the National Natural Science Foundation of China.
文摘The annual growth rings of ten trees and the soils near the tree roots were sampled from the mining area of lead-and zinc-dominant metals in the Xixia Mountain, Nanjing, for the determination of chemical element contents. The study results showed that the elemental contents in the tree rings were correlated with those in the soils, i. e., the elemental contents in the tree rings increased with those in the soils, even in the cases of different environments and different tree species. Therefore, a time-concentration sequence could be set up on the basis of determining the elemental contents in the successive annual growth rings of trees to qualitatively reflect the annual variations of relevant elements in the soils, and a time-concentration sequence of elemental contents in soils could also be established in terms of related model to reproduce the dynamic changes of the surroundings.
基金supported by the State of Vietnam through a PhD grant to L.T.H.(Grant No.4358/QĐ-BGDĐT)by the Deutscher Akadamischer Austauschdienst(DAADProject No.57163751)through covering travel costs of R.S.and F.M.T.
文摘Aims In contrast to temperate regions,the reasons for growth reductions of individual tree species along elevational gradients in tropical mountain ranges are poorly known,especially for tropical conifers.We aimed at testing whether climatic or edaphic conditions are responsible for the reduced growth of Pinus kesiya,a widely distributed pine species of southern and south-eastern Asia,at higher elevations.Methods We analysed the stem diameter increment and the isotope discrimination against ^(13)C(△^(13)C)in tree rings of P.kesiya along an elevational gradient of~900 to~2000 m a.s.l.in the mountain ranges of South-Central Vietnam,and related growth to△^(13)C and to climatic and edaphic variables.Important findings We found no consistent correlation patterns between the basal area increment(BAI)of the trees and temperature or precipitation.In contrast,across the elevational gradient,we obtained significantly negative correlations of BAI with△^(13)C and with the C/N ratios and theδ^(15)N signature of the upper mineral soil.BAI was positively correlated with the concentrations of plant-available phosphorus(P_(a))and of“base”cations(calcium,magnesium,potassium)in the soil.We conclude that lower temperatures at higher elevations exert an indirect effect on tree growth by inducing higher C/N ratios and by reducing the rate of nitrogen(N)and P mineralization,which may be further hampered by lower concentrations of“base”cations(upon enhanced leaching by precipitation)and a negative feedback from low availability of mineralized N and P at higher elevations.Our results may be transferable to the uppermost growth limit of P.kesiya and to other montane regions of the species’occurrence.
基金supported by the National Natural Science Foundations of China(41525001,41661144040,41601204)supported by the Bilateral Project between China and Slovenia(BI-CN/09–11-012)+1 种基金COST Action(FP1106,STRe ESS)supported by the Chinese Academy of Sciences President International Fellowship Initiative for Visiting Scientists(2016VBA074)
文摘Physiological and ecological mechanisms that define treelines are still debated. It has been suggested that the absence of trees above the treeline is caused by low temperatures that limit growth. Thus, we hypothesized that there is a critical minimum temperature （CTmin） preventing xylogenesis at treeline. We tested this hypothesis by examining weekly xylogenesis across three and four growing seasons in two natural Smith fir （Abies georgei var. srnithii） treeline sites on the southeastern Tibetan Plateau. Despite differences in the timing of cell differentiation among years, minimum air temperature was the dominant climatic variable associated with xylem growth; the critical minimum temperature （CTmin） for the onset and end of xylogenesis occurred at 0.7 ±0.4 ℃. A process-based modelling chronology of tree-ring formation using this CTmin was consistent with actual tree-ring data. This extremely low CTmin permits Smith fir growing at treeline to complete annual xylem production and maturation and provides both support and a mechanism for treeline formation.
基金supported by Dirección General de Asuntos de Personal Académico(DGAPA)from Universidad Nacional Autónoma de México(UNAM)[Grant no.IA203418 and IA204916 to F.P.G.,and IN207417 to A.G.R.].
文摘Aims Mechanisms of plant drought resistance include both tolerance and avoidance.Xylem vulnerability to embolism and turgor loss point are considered traits that confer tolerance,while leaf abscission and deciduousness characterizes the avoidance strategy.While these mechanisms are thought to trade-off expressing a continuum among species,little is known on how variation in the timing and duration of leaf shedding in response to drought affect the relationship between xylem and leaf tolerance.In the present study,we explored the extent to which drought tolerance differs between two oak(Quercus)species that exhibit different leaf shedding behaviours.Particularly,we predicted that Q.deserticola Trel.,which loses leaves at the end of the dry season(late-deciduous)and is thus exposed to a greater risk of cavitation,would be more drought tolerant and more conservative in its water use than Q.laeta Liebm.,which loses its leaves for only a short period of time in the middle of the dry season(brevideciduous).Methods The study was conducted in central Mexico in a single population of each of the two oak species,separated from each other by a distance of 1.58 km,and by an altitudinal difference of 191 m.Quercus deserticola(late deciduous)is more frequent down slope,while Q.laeta(brevideciduous)tends to occur at higher elevations along the gradient.We assessed seasonal differences(rainy versus dry season)in native stem hydraulic conductivity,and tested for variation in xylem vulnerability to cavitation,leaf water use and leaf turgor loss point between the two species.Important Findings The two oak species did not differ in traits conferring drought tolerance,including xylem vulnerability to embolism,leaf turgor loss point,or stomatal conductance.However,both species had different performance during the dry season;the brevideciduous species had lower negative impact in the xylem function than the late-deciduous species.Overall,seasonal changes in plant physiological performance between the two oak species were determined by a reduction in the canopy leaf area.
