Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data,...Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data, the influence of precipitation, mean temperature and mean minimum temperature at yearly, seasonal and monthly scales on the tree-ring growth of Picea crossifolia was studied at treeline ecotones in the Qilian Mountains, northwestern China. The results show that growing season temperatures of previous and current years are important limiting factors on tree-ring growth, particularly June mean temperature and mean minimum temperature of current year. The precipitations in the previous winter and current spring have a positive correlation, and in the current fall has a negative correlation with tree-ring growth, but these correlations are not significant. Our results suggest that temperature controls tree-ring growth more strongly than precipitation at treeline ecotones in the Qilian Mountains.展开更多
Degradation of land/water ecotones in China is a serious problem and it is often neglected by people. The types of ecotone degradation are described and analyzed. The degradation of land/water ecotones enhanced the wa...Degradation of land/water ecotones in China is a serious problem and it is often neglected by people. The types of ecotone degradation are described and analyzed. The degradation of land/water ecotones enhanced the water quality reduction, bank erosion, desasters such as landslide, flood and drought, biodiversity reduction, lost of fertilized lands, decrease of the resource value of water scenic beauty and many others. The paper analyzes how these problems are related with each other.展开更多
Ecotones have received great attention due to its critical function in energy flux, species harbor, global carbon sequestration, and land-atmosphere interaction. This study investigated land use pattern and spatial he...Ecotones have received great attention due to its critical function in energy flux, species harbor, global carbon sequestration, and land-atmosphere interaction. This study investigated land use pattern and spatial heterogeneity of the ecotones among agricultural land, forest land, and grassland of the southeastern Da Hinggan Mountains in the northeastern China. The change of these delineated ecotones under different slopes and aridity conditions was analyzed by two landscape indices, edge density(ED) and core area percentage of landscape(CPL), to explore the inter-linkage between spatial structure of ecotones and socioeconomic development and land management. Specifically, the ecotones such as agriculture-forest(AF) ecotone, forest-grassland(FG) ecotone, and agriculture-forestgrassland(AFG) ecotone moved from the arid southeast to the humid northwest. The flat area with small slope is more edge-fragmented than the steep area since the ED decreases as the slope increases. The AF ecotone mostly found in the humid region is moving to more humid areas while the agriculture-grassland(AG) ecotone mostly found in the dry region is moving towards the drier region.展开更多
This paper studied the biomass distribution patterns of Lanix olgensis/swamp ecotones and Betula platyphlla/swamp ecotones in Changbai Mountain so as to provide theory foundation for the management of these natur...This paper studied the biomass distribution patterns of Lanix olgensis/swamp ecotones and Betula platyphlla/swamp ecotones in Changbai Mountain so as to provide theory foundation for the management of these nature resources, by setting up sample belts, investigating initial data along the environmental gradients change, and establishing regression models. By means of regression models, the biomass of communities, layers, tree species and organs was calculated. In this system, it was found that the community biomass inreased gradually along the environmental gradients change from swamp to forest in Changbai Mountain. Furthermore, the ecotoneal biomass distributed mainly over tree layer. The tree biomass distributed mainly in two or three dominate tree species.展开更多
Changes in vegetation structure in environments contact community characterize the ecotones and paragenese inside zonal vegetation site or altitude belt as of concrete environments while differences of cenotic structu...Changes in vegetation structure in environments contact community characterize the ecotones and paragenese inside zonal vegetation site or altitude belt as of concrete environments while differences of cenotic structures of communities between zones or between altitude belts as well. The aim of this work was research of structural-dynamic organization of phytocenoses forming under the conditions of environments contact and mountain tundra, forests (zonal taiga) and extrazonal steppes, zonal forest steppes of some areas at the Baikalian Siberia, Eastern Siberia of Russia.展开更多
During last decades, new trends appeared in the ecotones of the upper boundary of forests at the ridges surroundingLakeBaikal(Khamar-Daban and Baikal’sky Ridge): ones to advance of wood species (Pinus sibirica Du Tou...During last decades, new trends appeared in the ecotones of the upper boundary of forests at the ridges surroundingLakeBaikal(Khamar-Daban and Baikal’sky Ridge): ones to advance of wood species (Pinus sibirica Du Tour, Abies sibirica Ledeb., Larix sibirica Ledeb., Larix dahurica Lawson) out of timber stands into the area of subgoltsy with Pinus pumila (Pallas) Regel. up to mountain tundras. In average, this is from 100 to 200 - 300 meters (maximum up to500 m) in linear distance from the margin of dense timber stand. A burst of forests renewal occurred in 1989-1995, it resulted probably from a high productivity of the seeds of wood species due to warmer winters in 1980ies-1990ies which favoured the formation of favourable climate-edaphic conditions for the development of forest communities above the forests boundary on the ridges surrounding Lake Baikal.展开更多
Under conditions of a warmer climate,the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems.However,the above- and below-ground live biomass allocations among...Under conditions of a warmer climate,the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems.However,the above- and below-ground live biomass allocations among different vegetation types within the treeline ecotones are not well investigated.To determine the altitudinal patterns of above-/below-ground carbon allocation,we measured the root biomass and estimated the above-ground biomass(AGB) in a subalpine forest,treeline forest,alpine shrub,and alpine grassland along two elevational transects towards the alpine tundra in southeast Tibet.The AGB strongly declined with increasing elevation,which was associated with a decrease in the leaf area index and a consequent reduction in carbon gain.The fine root biomass(FRB) increased significantly more in the alpine shrub and grassland than in the treeline forest,whereas the coarse root biomass changed little with increasing altitudes,which led to a stable below-ground biomass(BGB) value across altitudes.Warm and infertile soil conditions might explain the large amount of FRB in alpine shrub and grassland.Consequently,the root toshoot biomass ratio increased sharply with altitude,which suggested a remarkable shift of biomass allocation to root systems near the alpine tundra.Our findings demonstrate contrasting changes in AGB and BGB allocations across treeline ecotones,which should be considered when estimating carbon dynamics with shifting treelines.展开更多
Conventional farming-pastoral ecotones methods of delineating were not quantitative and could not fully show their spatial distribution. The present paper attempts to develop quantitative methods for mapping farming-...Conventional farming-pastoral ecotones methods of delineating were not quantitative and could not fully show their spatial distribution. The present paper attempts to develop quantitative methods for mapping farming-pastoral ecotones in China. Nine indicators, related to temperature, precipitation and altitude aspects, were selected to quantify ecological susceptibility of vegetation （crops and forage）. Methods of analytic hierarchy process （AHP） and expert score ranking combined with fuzzy set theory were applied to assign the weight for each indicator and to define the membership functions. The geographic information system （GIS） was used to manage the spatial database and conduct the spatial analysis. According to the spatial calculation of evaluation model integrated with GIS, the ecological susceptibility of vegetation （crops and forage） was mapped. Three different zones, pastoral area, farming-pastoral ecotones and farming area, were classified by spatial cluster analysis and the maximum likelihood classification for the numeric map of vegetation ecological susceptibility by GIS. This map was validated by the economic statistical result based on the ratio of the output value from animal husbandry in total output value of agriculture by the National Bureau of Statistics in China, indicating that the mapping of the farming-pastoral ecotones may be accepted.展开更多
Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradi...Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.展开更多
An ecotone is a transition area between two biomes or two different ecosystems and are often fragile, sensitive and variable. Since the 1970s, the study of the ecotone has increasingly gained notoriety as an important...An ecotone is a transition area between two biomes or two different ecosystems and are often fragile, sensitive and variable. Since the 1970s, the study of the ecotone has increasingly gained notoriety as an important facet of ecological research. China, with a vast complex geology, climate and vegetation, is home to a variety of ecotones. This variety is witnessed in breeds, scales and sizes. This vast array has not only laid a solid foundation for scientific research but also enhanced China’s economic development, social development and cultural diversity conservation. According to the geographical distribution and ecological features of China’s large scale ecotone, ＂The trinity index system＂ has been established including land use types, natural climate characteristics and agricultural economic development to classify and define the spatial distribution of typical ecotones in China. Based on this classification, the natural environmental characteristics, environmental fragility and the existing problems of five kinds of typical ecotones have been studied. This study will lead to a comprehensive understanding of the evolutionary patterns of ecotones.展开更多
The agro-pastoral ecotone epitomizes the ecologically fragile semi-arid zone,where the soil microbiomes play a pivotal role in regulating its multifunctionality.However,whether and how changes in soil structure and or...The agro-pastoral ecotone epitomizes the ecologically fragile semi-arid zone,where the soil microbiomes play a pivotal role in regulating its multifunctionality.However,whether and how changes in soil structure and organic matter composition under different land uses affect microbial community structure remain unclear.Here,land-use types in the agro-pastoral ecotone,including shrubland(BF),artificial grassland(ArG),abandoned grassland(AbG),and maize farmland(MA),were chosen to explore the response relationships between soil microbial communities and the aggregates and dissolved organic matter(DOM)composition.The results showed that compared to MA,the macroaggregates in BF,AbG,and ArG were increased by 123.0,92.79,and 63.71%,respectively,while MA soil had the greatest abundance of<100μm particles.The higher aromatic carbon with high aromaticity and molecular weight in BF soil DOM contributed to its highest mineral-associated organic carbon level(12.61 g kg^(-1)),while MA soil organic carbon had highly efficient decomposition due to its high content of aliphatic and carboxy carbon,so it is prone to loss from the active carbon pools.The transition in land use from shrubland to grassland and farmland has facilitated the conversion of stable aromatic carbon to unstable carboxy carbon.The taxonomic analysis revealed that soil bacterial and fungal communities in the four land uses were dominated by Proteobacteria,Actinobacteriota,Chloroflexi,and Ascomycota.More taxonomic groups from phylum to family were enriched in BF soil.The DOM components and organic carbon are crucial variables shaping the composition of soil bacterial communities,jointly explaining 61.66% of the variance,while aggregates are important variables driving the composition of fungal communities,with an explanation rate of 20.49%.Our results suggest that DOM components and aggregates impact the soil microbial structure;and the transition in land use from agricultural land to grassland and shrubland in the agro-pastoral ecotone enhances aggregate stability,carbon sequestration potential,and microbial diversity.展开更多
The diversity and discontinuity of plant communities in the oasis–desert ecotone are largely shaped by variations in groundwater depth,yet the relationships between spatial distribution patterns and ecological niches...The diversity and discontinuity of plant communities in the oasis–desert ecotone are largely shaped by variations in groundwater depth,yet the relationships between spatial distribution patterns and ecological niches at a regional scale remain insufficiently understood.This study examined the oasis–desert ecotone in Qira County located in the Tarim Basin of China to investigate the spatial distribution of plant communities and groundwater depth as well as their relationships using an integrated approach that combined remote sensing techniques,field monitoring,and numerical modeling.The results showed that vegetation distribution exhibits marked spatial heterogeneity,with coverage ranked as follows:Tamarix ramosissima>Phragmites australis>Populus euphratica>Alhagi sparsifolia.Numerical simulations indicated that groundwater depths range from 2.00 to 65.00 m below the surface,with the system currently in equilibrium,sustaining an average annual recharge of 1.06×10^(8) m^(3) and an average annual discharge of 1.01×10^(8) m^(3).Groundwater depth strongly influences vegetation composition and structure:Phragmites australis dominates at average groundwater depth of 5.83 m,followed by Populus euphratica at average groundwater depth of 7.05 m.As groundwater depth increases,the community is initially predominated by Tamarix ramosissima(average groundwater depth of 8.35 m),then becomes a mixture of Tamarix ramosissima,Populus euphratica,and Karelinia caspia(average groundwater depth of 10.50 m),and finally transitions to Alhagi sparsifolia(average groundwater depth of 14.30 m).These findings highlight groundwater-dependent ecological thresholds that govern plant community composition and provide a scientific basis for biodiversity conservation,ecosystem stability,and vegetation restoration in the arid oasis–desert ecotone.展开更多
The agro-pastoral ecotone in northern China (APENC) is an ecologically fragile region with a variable climate and unbalanced socioeconomic development.Identifying the spatial range and transitional dynamics of the APE...The agro-pastoral ecotone in northern China (APENC) is an ecologically fragile region with a variable climate and unbalanced socioeconomic development.Identifying the spatial range and transitional dynamics of the APENC is crucial for understanding the delicate balance between regional ecology,the economy,and society.The human-Earth system provides a comprehensive research framework in which human activities and the natural environment are viewed as interdependent and dynamically interactive.Guided by the principles of human-Earth system science,in this study,the boundaries of the APENC are identified by integrating core parameters,including water,land,climate,ecology,and human factors.Raster-based spatial data analysis is employed to examine the spatial and temporal evolution of the APENC from 1990 to 2020.The APENC extends from northeast to southwest along the central axis of northern China,displaying trends of contraction and fragmentation over time,with its centre of gravity shifting closer to the Hu Huanyong Line.The peripheral areas exhibit heightened sensitivity to environmental and ecological changes,highlighting the region’s vulnerability to external pressures.In this study,management strategies grounded in sustainable development principles are proposed,a framework for integrating ecological changes with socioeconomic strategies is established,and actionable guidance for policymakers to promote sustainable development in this fragile and dynamic region is provided.展开更多
[Objectives] To analyze the dynamic changes of maximum vegetation coverage in Ili River Basin from 2006 to 2020,and to explore the vegetation change and its influencing factors in the forest-grassland ecotone of Ili r...[Objectives] To analyze the dynamic changes of maximum vegetation coverage in Ili River Basin from 2006 to 2020,and to explore the vegetation change and its influencing factors in the forest-grassland ecotone of Ili region.[Methods] The pixel dichotomy model was used to process the MODIS data and analyze the change of vegetation coverage in the Ili River Basin from 2006 to 2020.[Results] (i)The vegetation coverage in the Ili River Basin increases gradually from west to east,and fluctuates greatly between years.(ii)By monitoring the change rate of the maximum vegetation coverage,it is found that the vegetation coverage of the basin has experienced a process of first decline and then recovery in the past 15 years.(iii)In spatial distribution,vegetation coverage has improved in some regions,while it has deteriorated in others,which may be related to regional climate change and human activities.[Conclusions] The vegetation coverage in the Ili River Basin showed significant spatial and temporal differences during the study period,and its changes were affected by both natural and human factors.展开更多
Aims The diversity and structure of forest edges are a central issue in ecology.However,most studies have focused on anthropogenic for-est edges,being natural ones least understood.We studied the com-munities of shrub...Aims The diversity and structure of forest edges are a central issue in ecology.However,most studies have focused on anthropogenic for-est edges,being natural ones least understood.We studied the com-munities of shrubs and trees in natural edges of gallery forests with the main goal of learning what are the main factors that shape the structure and diversity of these natural sharp ecotones.Methods We evaluated 10 gallery forest sites,allocating in each of them three 15×20 m plots.The plots were laid out in relatively rectilinear stretches of forest edges,respecting a minimal distance of 10 m between each plot.As they are permanent plots and meant to study eventual fluctuations in the forest-grasslands limits,we allocated the plots with their longest side parallel to the forest edge and covering perpendicularly 5 m of the grassland and 10 m of forest.Inside the plots we identified,mapped and measured all shrub and tree individuals with diameter at breast height(DBH)≥1 cm.Important Findings Although many differences exist among the communities in terms of density and basal area,all of them were highly dense and had relatively low basal areas.In addition,both the number of individu-als and the basal area increased rapidly towards the forest interior.Our results also revealed that the edge communities are composed mainly by small individuals that demand a great amount of light.Both the vertical stratification and the proportion of the functional groups are similar among the sites yet change quickly in the first 10 m of the forest edge.However,the floristic similarities were low among the communities mainly due to the species turnover within each area.Therefore,although the overall structure is constant in the studied edges,the low floristic similarity among them possibly indicates that the species within the same functional groups are sub-stituting each other across the sites.Despite older and seemingly stable,our results showed the gallery forest edges are quite similar to the anthropogenic edges or recent clearings.This points out that,independent of the age,those characteristics are possibly permanent in edges.展开更多
Research on the multicomponent synergistic relationships between plants,litter,and soil from the perspective of ecological stoichiometry helps to understand nutrient cycling and distribution mechanisms within ecosyste...Research on the multicomponent synergistic relationships between plants,litter,and soil from the perspective of ecological stoichiometry helps to understand nutrient cycling and distribution mechanisms within ecosystems.This study focused on Juniperus saltuaria,the dominant tree species in the forestline ecotone of Sygera Mountains,southeastern Xizang,China.We systematically measured and analyzed the Carbon(C),nitrogen(N),and phosphorus(P)contents and their relationships in plants(leaves,branches,trunks,fine roots),litter(undecomposed layer,partially decomposed layer,fully decomposed layer),and soil(0-10 cm,10-20 cm,20-40 cm)at different slope positions.The results showed significant differences in the C,N,and P contents and stoichiometry of plants and soil at different slope positions,while no significant differences were observed among litter layers.At the same slope position,the C,N,and P contents in leaves and surface soil were the highest,with soil nutrients significantly decreasing with increasing depth.For litter,the C content in the undecomposed layer was significantly higher than that in the partially and fully decomposed layers while the P content showed the opposite trend.Surface soil(0-20 cm)exhibited a decoupled relationship with plants but a coupled relationship with litter while deep soil(20-40 cm)showed a coupled relationship with plants.J.saltuaria showed faster growth rates on uphill slope.In this study area,J.saltuaria exhibited consistent trends of N,P,and N:P ratios homeostasis across different slope positions and organs,with leaves and fine roots both limited by N.Significant interactive effects between plants,litter,and soil nutrients were observed across different slope positions.Positive correlations were found between leaf and litter,and between fine root and leaf while the relationships between litter and soil,and between soil and fine root,varied.This study helps improve our understanding of the nutrient interactions between plants,litter,and soil in dominant species of alpine forest ecosystems,as well as their ecological adaptation mechanisms.展开更多
Picea mongolica is an endemic and endangered species in China. Ecosystem made of Picea mongolica is a special sandy forest ecosystem in China. It is found at ecotone between forest and steppe, or agricultural district...Picea mongolica is an endemic and endangered species in China. Ecosystem made of Picea mongolica is a special sandy forest ecosystem in China. It is found at ecotone between forest and steppe, or agricultural district and pastoral area. Based on investigation, this paper discussed the formation and distribution of Picea mongolica and studied its nature according to ecotone theory. It is clarified that Picea mongolica belongs to Picea meyeri series. That is to say, it became a local race through long-term adaptation to the local climate, then formed allopatric semi-species, and finally turned into a taxonomical species. Picea mongolica forest is a super zonal climax community developing in ecotone between forest zone and steppe zone.展开更多
The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in thi...The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.展开更多
基金supported by the Major Research Plan of National Natural Science Foundation of China (No. 91025014),the National Natural Science Foundation of China (No. 30800147)
文摘Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data, the influence of precipitation, mean temperature and mean minimum temperature at yearly, seasonal and monthly scales on the tree-ring growth of Picea crossifolia was studied at treeline ecotones in the Qilian Mountains, northwestern China. The results show that growing season temperatures of previous and current years are important limiting factors on tree-ring growth, particularly June mean temperature and mean minimum temperature of current year. The precipitations in the previous winter and current spring have a positive correlation, and in the current fall has a negative correlation with tree-ring growth, but these correlations are not significant. Our results suggest that temperature controls tree-ring growth more strongly than precipitation at treeline ecotones in the Qilian Mountains.
文摘Degradation of land/water ecotones in China is a serious problem and it is often neglected by people. The types of ecotone degradation are described and analyzed. The degradation of land/water ecotones enhanced the water quality reduction, bank erosion, desasters such as landslide, flood and drought, biodiversity reduction, lost of fertilized lands, decrease of the resource value of water scenic beauty and many others. The paper analyzes how these problems are related with each other.
基金Under the auspices of'Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues'of Chinese Academy of Sciences(No.XDA05090310)
文摘Ecotones have received great attention due to its critical function in energy flux, species harbor, global carbon sequestration, and land-atmosphere interaction. This study investigated land use pattern and spatial heterogeneity of the ecotones among agricultural land, forest land, and grassland of the southeastern Da Hinggan Mountains in the northeastern China. The change of these delineated ecotones under different slopes and aridity conditions was analyzed by two landscape indices, edge density(ED) and core area percentage of landscape(CPL), to explore the inter-linkage between spatial structure of ecotones and socioeconomic development and land management. Specifically, the ecotones such as agriculture-forest(AF) ecotone, forest-grassland(FG) ecotone, and agriculture-forestgrassland(AFG) ecotone moved from the arid southeast to the humid northwest. The flat area with small slope is more edge-fragmented than the steep area since the ED decreases as the slope increases. The AF ecotone mostly found in the humid region is moving to more humid areas while the agriculture-grassland(AG) ecotone mostly found in the dry region is moving towards the drier region.
基金Chinese Academy of Sciences and National Education Committee
文摘This paper studied the biomass distribution patterns of Lanix olgensis/swamp ecotones and Betula platyphlla/swamp ecotones in Changbai Mountain so as to provide theory foundation for the management of these nature resources, by setting up sample belts, investigating initial data along the environmental gradients change, and establishing regression models. By means of regression models, the biomass of communities, layers, tree species and organs was calculated. In this system, it was found that the community biomass inreased gradually along the environmental gradients change from swamp to forest in Changbai Mountain. Furthermore, the ecotoneal biomass distributed mainly over tree layer. The tree biomass distributed mainly in two or three dominate tree species.
文摘Changes in vegetation structure in environments contact community characterize the ecotones and paragenese inside zonal vegetation site or altitude belt as of concrete environments while differences of cenotic structures of communities between zones or between altitude belts as well. The aim of this work was research of structural-dynamic organization of phytocenoses forming under the conditions of environments contact and mountain tundra, forests (zonal taiga) and extrazonal steppes, zonal forest steppes of some areas at the Baikalian Siberia, Eastern Siberia of Russia.
文摘During last decades, new trends appeared in the ecotones of the upper boundary of forests at the ridges surroundingLakeBaikal(Khamar-Daban and Baikal’sky Ridge): ones to advance of wood species (Pinus sibirica Du Tour, Abies sibirica Ledeb., Larix sibirica Ledeb., Larix dahurica Lawson) out of timber stands into the area of subgoltsy with Pinus pumila (Pallas) Regel. up to mountain tundras. In average, this is from 100 to 200 - 300 meters (maximum up to500 m) in linear distance from the margin of dense timber stand. A burst of forests renewal occurred in 1989-1995, it resulted probably from a high productivity of the seeds of wood species due to warmer winters in 1980ies-1990ies which favoured the formation of favourable climate-edaphic conditions for the development of forest communities above the forests boundary on the ridges surrounding Lake Baikal.
基金supported by the National Natural Science Foundation of China (41561011)the Natural Science Foundation of Jiangxi Province, China (20151BAB213029)
文摘Under conditions of a warmer climate,the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems.However,the above- and below-ground live biomass allocations among different vegetation types within the treeline ecotones are not well investigated.To determine the altitudinal patterns of above-/below-ground carbon allocation,we measured the root biomass and estimated the above-ground biomass(AGB) in a subalpine forest,treeline forest,alpine shrub,and alpine grassland along two elevational transects towards the alpine tundra in southeast Tibet.The AGB strongly declined with increasing elevation,which was associated with a decrease in the leaf area index and a consequent reduction in carbon gain.The fine root biomass(FRB) increased significantly more in the alpine shrub and grassland than in the treeline forest,whereas the coarse root biomass changed little with increasing altitudes,which led to a stable below-ground biomass(BGB) value across altitudes.Warm and infertile soil conditions might explain the large amount of FRB in alpine shrub and grassland.Consequently,the root toshoot biomass ratio increased sharply with altitude,which suggested a remarkable shift of biomass allocation to root systems near the alpine tundra.Our findings demonstrate contrasting changes in AGB and BGB allocations across treeline ecotones,which should be considered when estimating carbon dynamics with shifting treelines.
基金supported by the National Western Special Project (Project No. 2003BA901A20)
文摘Conventional farming-pastoral ecotones methods of delineating were not quantitative and could not fully show their spatial distribution. The present paper attempts to develop quantitative methods for mapping farming-pastoral ecotones in China. Nine indicators, related to temperature, precipitation and altitude aspects, were selected to quantify ecological susceptibility of vegetation （crops and forage）. Methods of analytic hierarchy process （AHP） and expert score ranking combined with fuzzy set theory were applied to assign the weight for each indicator and to define the membership functions. The geographic information system （GIS） was used to manage the spatial database and conduct the spatial analysis. According to the spatial calculation of evaluation model integrated with GIS, the ecological susceptibility of vegetation （crops and forage） was mapped. Three different zones, pastoral area, farming-pastoral ecotones and farming area, were classified by spatial cluster analysis and the maximum likelihood classification for the numeric map of vegetation ecological susceptibility by GIS. This map was validated by the economic statistical result based on the ratio of the output value from animal husbandry in total output value of agriculture by the National Bureau of Statistics in China, indicating that the mapping of the farming-pastoral ecotones may be accepted.
基金based upon work while an author served at the National Science Foundation(USA)
文摘Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.
基金Specific Research on Public Service of Environmental Protection in China (No. 201109025, No. 200909021)the National Special Commonweal Study on Environmental Protection of China (No. 201209027)
文摘An ecotone is a transition area between two biomes or two different ecosystems and are often fragile, sensitive and variable. Since the 1970s, the study of the ecotone has increasingly gained notoriety as an important facet of ecological research. China, with a vast complex geology, climate and vegetation, is home to a variety of ecotones. This variety is witnessed in breeds, scales and sizes. This vast array has not only laid a solid foundation for scientific research but also enhanced China’s economic development, social development and cultural diversity conservation. According to the geographical distribution and ecological features of China’s large scale ecotone, ＂The trinity index system＂ has been established including land use types, natural climate characteristics and agricultural economic development to classify and define the spatial distribution of typical ecotones in China. Based on this classification, the natural environmental characteristics, environmental fragility and the existing problems of five kinds of typical ecotones have been studied. This study will lead to a comprehensive understanding of the evolutionary patterns of ecotones.
基金funded by the Inner Mongolia Local Science and Technology Development Fund Projects,China(2021GG0393)。
文摘The agro-pastoral ecotone epitomizes the ecologically fragile semi-arid zone,where the soil microbiomes play a pivotal role in regulating its multifunctionality.However,whether and how changes in soil structure and organic matter composition under different land uses affect microbial community structure remain unclear.Here,land-use types in the agro-pastoral ecotone,including shrubland(BF),artificial grassland(ArG),abandoned grassland(AbG),and maize farmland(MA),were chosen to explore the response relationships between soil microbial communities and the aggregates and dissolved organic matter(DOM)composition.The results showed that compared to MA,the macroaggregates in BF,AbG,and ArG were increased by 123.0,92.79,and 63.71%,respectively,while MA soil had the greatest abundance of<100μm particles.The higher aromatic carbon with high aromaticity and molecular weight in BF soil DOM contributed to its highest mineral-associated organic carbon level(12.61 g kg^(-1)),while MA soil organic carbon had highly efficient decomposition due to its high content of aliphatic and carboxy carbon,so it is prone to loss from the active carbon pools.The transition in land use from shrubland to grassland and farmland has facilitated the conversion of stable aromatic carbon to unstable carboxy carbon.The taxonomic analysis revealed that soil bacterial and fungal communities in the four land uses were dominated by Proteobacteria,Actinobacteriota,Chloroflexi,and Ascomycota.More taxonomic groups from phylum to family were enriched in BF soil.The DOM components and organic carbon are crucial variables shaping the composition of soil bacterial communities,jointly explaining 61.66% of the variance,while aggregates are important variables driving the composition of fungal communities,with an explanation rate of 20.49%.Our results suggest that DOM components and aggregates impact the soil microbial structure;and the transition in land use from agricultural land to grassland and shrubland in the agro-pastoral ecotone enhances aggregate stability,carbon sequestration potential,and microbial diversity.
基金financially supported by the Tianchi Talents Program of Xinjiang Uygur Autonomous Region(E5358525,2025–2026)the Major Science and Technology Special Project of Xinjiang Uygur Autonomous Region(2024A03009-4)+4 种基金the Third Xinjiang Scientific Expedition Program(2022xjkk010402)the National Key Research and Development Program of China(2022FY202305-06)the Tianshan Talents Program of Xinjiang Uygur Autonomous Region(2022TSYCJU0002)the Outstanding Member of the Youth Innovation Promotion Association of the Chinese Academy of Sciences(20192024–2026).
文摘The diversity and discontinuity of plant communities in the oasis–desert ecotone are largely shaped by variations in groundwater depth,yet the relationships between spatial distribution patterns and ecological niches at a regional scale remain insufficiently understood.This study examined the oasis–desert ecotone in Qira County located in the Tarim Basin of China to investigate the spatial distribution of plant communities and groundwater depth as well as their relationships using an integrated approach that combined remote sensing techniques,field monitoring,and numerical modeling.The results showed that vegetation distribution exhibits marked spatial heterogeneity,with coverage ranked as follows:Tamarix ramosissima>Phragmites australis>Populus euphratica>Alhagi sparsifolia.Numerical simulations indicated that groundwater depths range from 2.00 to 65.00 m below the surface,with the system currently in equilibrium,sustaining an average annual recharge of 1.06×10^(8) m^(3) and an average annual discharge of 1.01×10^(8) m^(3).Groundwater depth strongly influences vegetation composition and structure:Phragmites australis dominates at average groundwater depth of 5.83 m,followed by Populus euphratica at average groundwater depth of 7.05 m.As groundwater depth increases,the community is initially predominated by Tamarix ramosissima(average groundwater depth of 8.35 m),then becomes a mixture of Tamarix ramosissima,Populus euphratica,and Karelinia caspia(average groundwater depth of 10.50 m),and finally transitions to Alhagi sparsifolia(average groundwater depth of 14.30 m).These findings highlight groundwater-dependent ecological thresholds that govern plant community composition and provide a scientific basis for biodiversity conservation,ecosystem stability,and vegetation restoration in the arid oasis–desert ecotone.
基金National Natural Science Foundation of China,No.42293271,No.42401321,No.42371210Fundamental Research Funds for the Central Universities,CHD,No.300102354101。
文摘The agro-pastoral ecotone in northern China (APENC) is an ecologically fragile region with a variable climate and unbalanced socioeconomic development.Identifying the spatial range and transitional dynamics of the APENC is crucial for understanding the delicate balance between regional ecology,the economy,and society.The human-Earth system provides a comprehensive research framework in which human activities and the natural environment are viewed as interdependent and dynamically interactive.Guided by the principles of human-Earth system science,in this study,the boundaries of the APENC are identified by integrating core parameters,including water,land,climate,ecology,and human factors.Raster-based spatial data analysis is employed to examine the spatial and temporal evolution of the APENC from 1990 to 2020.The APENC extends from northeast to southwest along the central axis of northern China,displaying trends of contraction and fragmentation over time,with its centre of gravity shifting closer to the Hu Huanyong Line.The peripheral areas exhibit heightened sensitivity to environmental and ecological changes,highlighting the region’s vulnerability to external pressures.In this study,management strategies grounded in sustainable development principles are proposed,a framework for integrating ecological changes with socioeconomic strategies is established,and actionable guidance for policymakers to promote sustainable development in this fragile and dynamic region is provided.
基金General Program of Natural Science Foundation of Xinjiang Uygur Autonomous Region(2022D01A275)Project of Inner Mongolia M-Grass Ecology and Environment(Group)Co.,Ltd.(2022-NFGA-004).
文摘[Objectives] To analyze the dynamic changes of maximum vegetation coverage in Ili River Basin from 2006 to 2020,and to explore the vegetation change and its influencing factors in the forest-grassland ecotone of Ili region.[Methods] The pixel dichotomy model was used to process the MODIS data and analyze the change of vegetation coverage in the Ili River Basin from 2006 to 2020.[Results] (i)The vegetation coverage in the Ili River Basin increases gradually from west to east,and fluctuates greatly between years.(ii)By monitoring the change rate of the maximum vegetation coverage,it is found that the vegetation coverage of the basin has experienced a process of first decline and then recovery in the past 15 years.(iii)In spatial distribution,vegetation coverage has improved in some regions,while it has deteriorated in others,which may be related to regional climate change and human activities.[Conclusions] The vegetation coverage in the Ili River Basin showed significant spatial and temporal differences during the study period,and its changes were affected by both natural and human factors.
基金This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)of Brazil(478086/2008-3).
文摘Aims The diversity and structure of forest edges are a central issue in ecology.However,most studies have focused on anthropogenic for-est edges,being natural ones least understood.We studied the com-munities of shrubs and trees in natural edges of gallery forests with the main goal of learning what are the main factors that shape the structure and diversity of these natural sharp ecotones.Methods We evaluated 10 gallery forest sites,allocating in each of them three 15×20 m plots.The plots were laid out in relatively rectilinear stretches of forest edges,respecting a minimal distance of 10 m between each plot.As they are permanent plots and meant to study eventual fluctuations in the forest-grasslands limits,we allocated the plots with their longest side parallel to the forest edge and covering perpendicularly 5 m of the grassland and 10 m of forest.Inside the plots we identified,mapped and measured all shrub and tree individuals with diameter at breast height(DBH)≥1 cm.Important Findings Although many differences exist among the communities in terms of density and basal area,all of them were highly dense and had relatively low basal areas.In addition,both the number of individu-als and the basal area increased rapidly towards the forest interior.Our results also revealed that the edge communities are composed mainly by small individuals that demand a great amount of light.Both the vertical stratification and the proportion of the functional groups are similar among the sites yet change quickly in the first 10 m of the forest edge.However,the floristic similarities were low among the communities mainly due to the species turnover within each area.Therefore,although the overall structure is constant in the studied edges,the low floristic similarity among them possibly indicates that the species within the same functional groups are sub-stituting each other across the sites.Despite older and seemingly stable,our results showed the gallery forest edges are quite similar to the anthropogenic edges or recent clearings.This points out that,independent of the age,those characteristics are possibly permanent in edges.
基金funded by the National Ministry of Science and Technology Ecological Station(LZF2020-2025)the Longterm Ecological Observation Study of Alpine Pine in Southeast Tibet(Science and Technology Innovation Base)(XZ202301JD0001G)+1 种基金the Graduate Student Innovation Project of Tibet Agriculture and Animal Husbandry College(YJS2023-01)the Tibet Agriculture and Animal Husbandry College Talent Team Development Fund Project(XZNMXYRCXM-2024-10).
文摘Research on the multicomponent synergistic relationships between plants,litter,and soil from the perspective of ecological stoichiometry helps to understand nutrient cycling and distribution mechanisms within ecosystems.This study focused on Juniperus saltuaria,the dominant tree species in the forestline ecotone of Sygera Mountains,southeastern Xizang,China.We systematically measured and analyzed the Carbon(C),nitrogen(N),and phosphorus(P)contents and their relationships in plants(leaves,branches,trunks,fine roots),litter(undecomposed layer,partially decomposed layer,fully decomposed layer),and soil(0-10 cm,10-20 cm,20-40 cm)at different slope positions.The results showed significant differences in the C,N,and P contents and stoichiometry of plants and soil at different slope positions,while no significant differences were observed among litter layers.At the same slope position,the C,N,and P contents in leaves and surface soil were the highest,with soil nutrients significantly decreasing with increasing depth.For litter,the C content in the undecomposed layer was significantly higher than that in the partially and fully decomposed layers while the P content showed the opposite trend.Surface soil(0-20 cm)exhibited a decoupled relationship with plants but a coupled relationship with litter while deep soil(20-40 cm)showed a coupled relationship with plants.J.saltuaria showed faster growth rates on uphill slope.In this study area,J.saltuaria exhibited consistent trends of N,P,and N:P ratios homeostasis across different slope positions and organs,with leaves and fine roots both limited by N.Significant interactive effects between plants,litter,and soil nutrients were observed across different slope positions.Positive correlations were found between leaf and litter,and between fine root and leaf while the relationships between litter and soil,and between soil and fine root,varied.This study helps improve our understanding of the nutrient interactions between plants,litter,and soil in dominant species of alpine forest ecosystems,as well as their ecological adaptation mechanisms.
基金National Natural Science Foundation of China (39670133 39900019 30070129).
文摘Picea mongolica is an endemic and endangered species in China. Ecosystem made of Picea mongolica is a special sandy forest ecosystem in China. It is found at ecotone between forest and steppe, or agricultural district and pastoral area. Based on investigation, this paper discussed the formation and distribution of Picea mongolica and studied its nature according to ecotone theory. It is clarified that Picea mongolica belongs to Picea meyeri series. That is to say, it became a local race through long-term adaptation to the local climate, then formed allopatric semi-species, and finally turned into a taxonomical species. Picea mongolica forest is a super zonal climax community developing in ecotone between forest zone and steppe zone.
文摘The woodland-steppe ecotone in the. southern Nei Mongol Plateau is located at the northern edge of the east Asian monsoon influences. A marked southeastern - northwestern (SE - NW) precipitation gradient exists in this region. Quantitative reconstruction of palaeo-precipitation of this region is helpful to reveal the development of monsoon climate and to predict die future desertification. Based on modern vegetation and surface pollen studies, a pollen-precipitation transfer function in the study region was established. Pollen data from three sediment sequences within the ecotone were used to reconstruct palaeo-precipitation during the Holocene. The processes of precipitation changes in the three sequences were quite different. There was a tendency of precipitation declined from the onset of the Holocene to 1 100 a BP in Haoluku. But, in Liuzhouwan and Xiaoniuchang, both located south of Haoluku, the annual precipitation reached highest values during 7 800 - 6 200 a BP and 7 200 - 5 000 a BP, respectively. The influences of southwestern (SW) monsoon and the variances of topographical conditions have possibly caused these temporal-spatial variances.
