Landscape boundaries are always indicated by the vegetation boundaries. As an ecotone between closed forest and treeline, alpine timberline may respond to global climate changes sensitively. The stability of timberlin...Landscape boundaries are always indicated by the vegetation boundaries. As an ecotone between closed forest and treeline, alpine timberline may respond to global climate changes sensitively. The stability of timberline and treeline depend not only on climate change, but also on the interaction of both sides of the ecosystems. Three natural boundaries existing in the timberline transitional zone are recognized: (1) timberline (upper limit of closed forest zone); (2) treeline (upper limit of tree islands zone); (3) tree species line (upper limit of individual tree growth). Paleobotanical and sedimentary evidences suggest that there were several times of climate fluctuation during the Holocene period in this area. The timberline of Taibai Mountain must have moved for four times on the millennium scale. Being a stochastic oscillation boundary, treeline appears in a semi stable condition on the century scale. The tree species line is even more unstable, which appears in an unstable status on the decades scale. The comparison of the stability within several landscape boundaries, shed light on the sensibility of these communities to various perturbation and environmental heterogeneity, i.e., herb community is the most sensitive one, which is followed by shrubs, and forest is the most stable one. Trees and shrubs can adapt to rocky and poor soils. On the contrary, alpine herbs are able to adapt to wetter and cooler soils. Finally, under a scenario of a temperature of 1.5 4.5℃ increase, the present timberline will be relatively stable but treeline and tree species line will move upward.展开更多
Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to expl...Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to explore the relationship between timberline elevation and latitude or temperature. However, these models are usually on regional scale and could not be applied to other regions; on the other hand, hemispherical-scale and continental-scale models are usually based on about 100 timberline data and are necessarily low in precision. The present article collects 516 data sites of timberline, and takes latitude, continentality and mass elevation effect （MEE） as independent variables and timberline elevation as dependent variable to develop a ternary linear regression meteorological data released by WorldClim and model. Continentality is calculated using the mountain base elevation （as a proxy of mass elevation effect） is extracted on the basis of SRTM 90-meter resolution elevation data. The results show that the coefficient of determination （R2） of the linear model is as high as 0.904, and that the contribution rate of latitude, continentality and MEE to timberline elevation is 45.02% （p=0.000）, 6.04% （p=0.000） and 48.94% （p=0.000）, respectively. This means that MEE is simply the primary factor contributing to the elevation distribution of timberline on the continental and hemispherical scales. The contribution rate of MEE to timberline altitude dif- fers in different regions, e.g., 50.49% （p=0.000） in North America, 48.73% （p=0.000） in the eastern Eurasia, and 43.6% （p=0.000） in the western Eurasia, but it is usually very high.展开更多
Different types of vegetation patches are alternately and randomly distributed in a timberline ecotone where the upper limit is the treeline and the lower limit is the timberline.However,most studies on timberline/tre...Different types of vegetation patches are alternately and randomly distributed in a timberline ecotone where the upper limit is the treeline and the lower limit is the timberline.However,most studies on timberline/treeline altitudinal distributions have simplified timberline or treeline as continuous curves and disregarded the fuzziness of timberline/treeline and the randomness of different vegetation patch distributions in a timberline ecotone.To study the altitudinal distribution characteristics of timberline and treeline from the perspective of uncertainty theory,we constructed the timberline and treeline elevation cloud models in Mt.Namjagbarwa in east Himalayas.Subsequently,we established multiple linear regression models by using nine influencing factors,namely,aspect,slope,topographic relief,dryness index,average temperature in January and July,latitude,summit syndrome(represented by the vertical distance from the peak),and snow effect(represented by the nearest distance from the snow)as independent variables,and the elevations of timberline/treeline as dependent variables.Then we compared the contributions of the nine factors in timberline,treeline,and the core and peripheral areas of timberline and treeline.The results show that 1)the timberline/treeline elevation cloud model can represent the overall characteristics(especially the uncertainty)of the altitudinal distributions of the timberline/treeline well.The uncertainty of treeline’s altitudinal distribution is higher than that of timberline(entropy and hyper entropy:207.59 m and 70.36 m for treeline elevation cloud;entropy and hyper entropy:191.17 m and 50.13 m for timberline elevation cloud).2)The influence of climate and topography on timberline and treeline are similar.The average temperature in July has a significant negative correlation with the timberline/treeline elevation in Mt.Namjagbarwa,which is the most critical factor that affects timberline and treeline elevation,explaining the altitudinal distribution of 44.01%timberline and 46.74%treeline.However,the contributions of the nine factors in core and peripheral areas of timberline and treeline area are evidently different.展开更多
As an important ecotone,the alpine timberline is the boundary between closed-canopy montane forest and alpine vegetation,and is highly sensitive to global and regional climate changes.We provided a way to identify and...As an important ecotone,the alpine timberline is the boundary between closed-canopy montane forest and alpine vegetation,and is highly sensitive to global and regional climate changes.We provided a way to identify and extract the alpine timberline in Yarlung Zangpo Grand Canyon Nature Reserve by using remote sensing data and spatial analysis based on land use/land cover classification and NDVI distribution characteristics.Combining DEM data,the influence of slope and aspect on the distribution of alpine timberline was explored.The results showed that the alpine timberline in Yarlung Zangpo Grand Canyon is transitional timberline,with the upper boundary approximately distributed at the elevation of 3422-4373 m,the lower boundary at approximately 3270-4164 m,with a width of about 110-280 m.Alpine timberline was mainly distributed on steep and very steep slopes ranging from 25°to 45°.The maximum elevation of both the upper and lower boundaries occurred on steep slopes.The distribution of alpine timberline varies with aspects,with sunny slopes having a higher boundary than shady slopes.展开更多
The growth,survival,and mortality of conifer species in response to the hydrothermal regime have received considerable attention.It is expected that the highest sensitivity of trees to the warming-drying climate will ...The growth,survival,and mortality of conifer species in response to the hydrothermal regime have received considerable attention.It is expected that the highest sensitivity of trees to the warming-drying climate will occur mainly at the edges of the species ranges.We focused on the responses to climate change of the drought-resistant larch(Larix sibirica)and the moisture-sensitive Siberian pine(Pinus sibirica)along the elevation gradient in the Tannu-Ola Ridge,the southern margin where those two species coexist in Siberia by using satellite data(MODIS,Landsat,and microwave),the indexes of gross(GPP)and net(NPP)primary productivity,and tree radial growth index(GI).We found that since the warming restart in the 2000s,the area of larch-dominated forests increased by~150%while the area of pine-dominated forests decreased by~10%.The Siberian pine has retreated at low elevations(<1800 m)and increased its area at higher ones.In contrast,the area of larch stands increased in both the uphill and downhill directions.Birch(Betula spp.)also increased its area at low elevations(about+120%).Since 2001,the forested area increased by~5%.A shrubification,i.e.,an increase in the area of shrubs,was observed at high elevations.The uphill rate of timberline and shrubline migration was about 0.3 m/a.Since the 2000s,vegetation NPP has increased by 13%.A notable correlation between NPP and the GI of larch and pine was found(r=0.5-0.7).At lower elevations,NPP positively correlated with precipitation and soil moisture,while air temperature and VPD(vapor pressure deficit)increase inhibited productivity.At high elevations,the effects of these variables on productivity reversed.The continuous decline of the Siberian pine forest indicates an inevitable retreat of this species at low elevations and its replacement by larch and birch.展开更多
文摘Landscape boundaries are always indicated by the vegetation boundaries. As an ecotone between closed forest and treeline, alpine timberline may respond to global climate changes sensitively. The stability of timberline and treeline depend not only on climate change, but also on the interaction of both sides of the ecosystems. Three natural boundaries existing in the timberline transitional zone are recognized: (1) timberline (upper limit of closed forest zone); (2) treeline (upper limit of tree islands zone); (3) tree species line (upper limit of individual tree growth). Paleobotanical and sedimentary evidences suggest that there were several times of climate fluctuation during the Holocene period in this area. The timberline of Taibai Mountain must have moved for four times on the millennium scale. Being a stochastic oscillation boundary, treeline appears in a semi stable condition on the century scale. The tree species line is even more unstable, which appears in an unstable status on the decades scale. The comparison of the stability within several landscape boundaries, shed light on the sensibility of these communities to various perturbation and environmental heterogeneity, i.e., herb community is the most sensitive one, which is followed by shrubs, and forest is the most stable one. Trees and shrubs can adapt to rocky and poor soils. On the contrary, alpine herbs are able to adapt to wetter and cooler soils. Finally, under a scenario of a temperature of 1.5 4.5℃ increase, the present timberline will be relatively stable but treeline and tree species line will move upward.
基金National Natural Science Foundation of China,No.41030528No.40971064
文摘Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to explore the relationship between timberline elevation and latitude or temperature. However, these models are usually on regional scale and could not be applied to other regions; on the other hand, hemispherical-scale and continental-scale models are usually based on about 100 timberline data and are necessarily low in precision. The present article collects 516 data sites of timberline, and takes latitude, continentality and mass elevation effect （MEE） as independent variables and timberline elevation as dependent variable to develop a ternary linear regression meteorological data released by WorldClim and model. Continentality is calculated using the mountain base elevation （as a proxy of mass elevation effect） is extracted on the basis of SRTM 90-meter resolution elevation data. The results show that the coefficient of determination （R2） of the linear model is as high as 0.904, and that the contribution rate of latitude, continentality and MEE to timberline elevation is 45.02% （p=0.000）, 6.04% （p=0.000） and 48.94% （p=0.000）, respectively. This means that MEE is simply the primary factor contributing to the elevation distribution of timberline on the continental and hemispherical scales. The contribution rate of MEE to timberline altitude dif- fers in different regions, e.g., 50.49% （p=0.000） in North America, 48.73% （p=0.000） in the eastern Eurasia, and 43.6% （p=0.000） in the western Eurasia, but it is usually very high.
基金supported by the National Natural Science Foundation of China(Grant No.41401111)the Natural Science Foundation of Shandong Province(Grant No.ZR2021MD080 and Grant No.ZR2014DQ017)the Shandong Agricultural Science and Technology Fund Project(Grant No.2019LY006)。
文摘Different types of vegetation patches are alternately and randomly distributed in a timberline ecotone where the upper limit is the treeline and the lower limit is the timberline.However,most studies on timberline/treeline altitudinal distributions have simplified timberline or treeline as continuous curves and disregarded the fuzziness of timberline/treeline and the randomness of different vegetation patch distributions in a timberline ecotone.To study the altitudinal distribution characteristics of timberline and treeline from the perspective of uncertainty theory,we constructed the timberline and treeline elevation cloud models in Mt.Namjagbarwa in east Himalayas.Subsequently,we established multiple linear regression models by using nine influencing factors,namely,aspect,slope,topographic relief,dryness index,average temperature in January and July,latitude,summit syndrome(represented by the vertical distance from the peak),and snow effect(represented by the nearest distance from the snow)as independent variables,and the elevations of timberline/treeline as dependent variables.Then we compared the contributions of the nine factors in timberline,treeline,and the core and peripheral areas of timberline and treeline.The results show that 1)the timberline/treeline elevation cloud model can represent the overall characteristics(especially the uncertainty)of the altitudinal distributions of the timberline/treeline well.The uncertainty of treeline’s altitudinal distribution is higher than that of timberline(entropy and hyper entropy:207.59 m and 70.36 m for treeline elevation cloud;entropy and hyper entropy:191.17 m and 50.13 m for timberline elevation cloud).2)The influence of climate and topography on timberline and treeline are similar.The average temperature in July has a significant negative correlation with the timberline/treeline elevation in Mt.Namjagbarwa,which is the most critical factor that affects timberline and treeline elevation,explaining the altitudinal distribution of 44.01%timberline and 46.74%treeline.However,the contributions of the nine factors in core and peripheral areas of timberline and treeline area are evidently different.
基金supported by the National Natural Science Foundation of China(Grant No.91647212)IWHR Research&Development Support Program(WE0163A052018)the Open Research Fund of Guangxi Key Laboratory of Water Engineering Materials and Structures,Guangxi Institute of Water Resources Research(Grant No.GXHRI-WEMS-2020-13)。
文摘As an important ecotone,the alpine timberline is the boundary between closed-canopy montane forest and alpine vegetation,and is highly sensitive to global and regional climate changes.We provided a way to identify and extract the alpine timberline in Yarlung Zangpo Grand Canyon Nature Reserve by using remote sensing data and spatial analysis based on land use/land cover classification and NDVI distribution characteristics.Combining DEM data,the influence of slope and aspect on the distribution of alpine timberline was explored.The results showed that the alpine timberline in Yarlung Zangpo Grand Canyon is transitional timberline,with the upper boundary approximately distributed at the elevation of 3422-4373 m,the lower boundary at approximately 3270-4164 m,with a width of about 110-280 m.Alpine timberline was mainly distributed on steep and very steep slopes ranging from 25°to 45°.The maximum elevation of both the upper and lower boundaries occurred on steep slopes.The distribution of alpine timberline varies with aspects,with sunny slopes having a higher boundary than shady slopes.
基金supported by the Tomsk State University Development Program(《Priority-2030》)the Basic Project of the Federal Research Center of the Scientific Center,no.FWES-2024-0023the Russian Science Foundation(project No.23-14-20015)。
文摘The growth,survival,and mortality of conifer species in response to the hydrothermal regime have received considerable attention.It is expected that the highest sensitivity of trees to the warming-drying climate will occur mainly at the edges of the species ranges.We focused on the responses to climate change of the drought-resistant larch(Larix sibirica)and the moisture-sensitive Siberian pine(Pinus sibirica)along the elevation gradient in the Tannu-Ola Ridge,the southern margin where those two species coexist in Siberia by using satellite data(MODIS,Landsat,and microwave),the indexes of gross(GPP)and net(NPP)primary productivity,and tree radial growth index(GI).We found that since the warming restart in the 2000s,the area of larch-dominated forests increased by~150%while the area of pine-dominated forests decreased by~10%.The Siberian pine has retreated at low elevations(<1800 m)and increased its area at higher ones.In contrast,the area of larch stands increased in both the uphill and downhill directions.Birch(Betula spp.)also increased its area at low elevations(about+120%).Since 2001,the forested area increased by~5%.A shrubification,i.e.,an increase in the area of shrubs,was observed at high elevations.The uphill rate of timberline and shrubline migration was about 0.3 m/a.Since the 2000s,vegetation NPP has increased by 13%.A notable correlation between NPP and the GI of larch and pine was found(r=0.5-0.7).At lower elevations,NPP positively correlated with precipitation and soil moisture,while air temperature and VPD(vapor pressure deficit)increase inhibited productivity.At high elevations,the effects of these variables on productivity reversed.The continuous decline of the Siberian pine forest indicates an inevitable retreat of this species at low elevations and its replacement by larch and birch.
