Anthropogenic activities have become more and more important in characterizing the landscape, but their impacts are still restricted by natural environments. This paper discusses the interactions of anthropogenic acti...Anthropogenic activities have become more and more important in characterizing the landscape, but their impacts are still restricted by natural environments. This paper discusses the interactions of anthropogenic activity, vegetation activity and topography through describing the spatial distribution of land cover and vegetation activity (represented by Normalized Difference Vegetation Index, NDVI) along topographic gradient in a mountainous area of southwestern China. Our results indicate that the existing landscape pattern is controlled by anthropogenic activities as well as topographic factors. Intensive anthropogenic activities mainly occur in areas with relatively low elevation, gentle and concave slopes, as these areas are easy and convenient to attain for human. Because of the destruction by human, some land cover types (mainly grassland and shrub) are only found in relatively harsher environments. This study also finds that topographic wetness index (W) used in other places only reflects runoff generation capacity, but not indicate the real spatial pattern of soil water content in this area. The relationships between NDVI and W, and NDVI and length slope factor (LSF) show that runoff and erosion have complex effects on vegetation activity. Greater values of W and LSF will lead to stronger capacity to produce runoff and transport sediment, and thereby increase soil water content and soil deposition, whereas beyond a certain threshold runoff and erosion are so strong that they would destruct vegetation growth. This study provides information needed to successfully restore native vegetation, improve land management, and promote sustainable development in mountainous areas, especially for developing regions.展开更多
Aims Woody plants are widely distributed in various grassland types along the altitudinal/climatic gradients in Xinjiang,China.Considering previously reported change in carbon(C)storage following woody plant encroachm...Aims Woody plants are widely distributed in various grassland types along the altitudinal/climatic gradients in Xinjiang,China.Considering previously reported change in carbon(C)storage following woody plant encroachment in grasslands and the mediating effect of climate on this change,we predicted that a positive effect of woody plants on plant C storage in semiarid grasslands may revert to a negative effect in arid grasslands.We first investigated the spatial variation of aboveground C(AGC)and belowground C(BGC)storage among grassland types and then tested our prediction.Methods We measured the living AGC storage,litter C(LC)and BGC storage of plants in two physiognomic types,wooded grasslands(aboveground biomass of woody plants at least 50%)and pure grasslands without woody plants in six grassland types representing a gradient form semiarid to arid conditions across Xinjiang.Important Findings Living AGC,LC,BGC and total plant C storage increased from desert to mountain meadows.These increases could also be explained by increasing mean annual precipitation(MAP)or decreasing mean annual temperature(MAT),suggesting that grassland types indeed represented an aridity gradient.Woody plants had an effect on the plant C storage both in size and in distribution relative to pure grasslands.The direction and strength of the effect of woody plants varied with grassland types due to the mediating effect of the climate,with wetter conditions promoting a positive effect of woody plants.Woody plants increased vegetation-level AGC through their high AGC relative to herbaceous plants.However,more negative effects of woody plants on herbaceous plants with increasing aridity led to a weaker increase in the living AGC in arid desert,steppe desert and desert steppe than in the less arid other grassland types.Under greater aridity(lower MAP and higher MAT),woody plants allocated less biomass to roots and had lower BGC and had a more negative impact on herbaceous plant production,thereby reducing vegetation-level BGC in the desert,steppe desert and desert steppe.In sum,this resulted in a negative effect of woody plants on total plant C storage in the most arid grasslands in Xinjiang.As a consequence,we predict that woody plant encroachment may decrease rather than increase C storage in grasslands under future drier conditions.展开更多
The decomposition of plant litter is a major process of equivalent status to primary production in ecosystem functioning.The spatiotemporal changes in the composition and dynamics of litter fungal community along a cl...The decomposition of plant litter is a major process of equivalent status to primary production in ecosystem functioning.The spatiotemporal changes in the composition and dynamics of litter fungal community along a climate gradient ranging from arid desert to humid-Mediterranean regions in Israel was examined using wheat straw litter bags placed at four selected sites along the climate gradient,arid,semi-arid,Mediterranean,and humid-Mediterranean sites.Litter samples were collected over a two-year decomposition period to evaluate litter weight loss,moisture,C:N ratio,fungal composition,and isolate density.The litter decomposition rate was found to be the highest during the first year of the study at the Mediterranean and arid sites.Although the Shannon-Wiener index values of the fungal communities in the litter samples were the highest at the humid-Mediterranean site,the number of fungal species was not significantly different between the four study sites.Different fungal groups were found to be related to different study sites:Basidiomycota,Mucoromycotina,and teleomorphic Ascomycota were associated with the humid-Mediterranean site,while Coelomycetes were mostly affected by the arid site.Our results indicate that climate factors play an important role in determining the structure of saprotrophic fungal communities in the decomposing litter and in mediating plant litter decomposition processes.展开更多
基金the National Natural Science Foundation of China (40621061)the Project of Chinese Academy of Sciences (KZCX2-XB2-02-31) for their financial support
文摘Anthropogenic activities have become more and more important in characterizing the landscape, but their impacts are still restricted by natural environments. This paper discusses the interactions of anthropogenic activity, vegetation activity and topography through describing the spatial distribution of land cover and vegetation activity (represented by Normalized Difference Vegetation Index, NDVI) along topographic gradient in a mountainous area of southwestern China. Our results indicate that the existing landscape pattern is controlled by anthropogenic activities as well as topographic factors. Intensive anthropogenic activities mainly occur in areas with relatively low elevation, gentle and concave slopes, as these areas are easy and convenient to attain for human. Because of the destruction by human, some land cover types (mainly grassland and shrub) are only found in relatively harsher environments. This study also finds that topographic wetness index (W) used in other places only reflects runoff generation capacity, but not indicate the real spatial pattern of soil water content in this area. The relationships between NDVI and W, and NDVI and length slope factor (LSF) show that runoff and erosion have complex effects on vegetation activity. Greater values of W and LSF will lead to stronger capacity to produce runoff and transport sediment, and thereby increase soil water content and soil deposition, whereas beyond a certain threshold runoff and erosion are so strong that they would destruct vegetation growth. This study provides information needed to successfully restore native vegetation, improve land management, and promote sustainable development in mountainous areas, especially for developing regions.
基金supported by the National Natural Science Foundation of China(U1603235,31500450)the strategic priority research program of the Chinese Academy of Sciences(XDA05050405)Bernhard Schmid was supported by the University of Zürich Research Priority Program on Global Change and Biodiversity(URPP GCB).
文摘Aims Woody plants are widely distributed in various grassland types along the altitudinal/climatic gradients in Xinjiang,China.Considering previously reported change in carbon(C)storage following woody plant encroachment in grasslands and the mediating effect of climate on this change,we predicted that a positive effect of woody plants on plant C storage in semiarid grasslands may revert to a negative effect in arid grasslands.We first investigated the spatial variation of aboveground C(AGC)and belowground C(BGC)storage among grassland types and then tested our prediction.Methods We measured the living AGC storage,litter C(LC)and BGC storage of plants in two physiognomic types,wooded grasslands(aboveground biomass of woody plants at least 50%)and pure grasslands without woody plants in six grassland types representing a gradient form semiarid to arid conditions across Xinjiang.Important Findings Living AGC,LC,BGC and total plant C storage increased from desert to mountain meadows.These increases could also be explained by increasing mean annual precipitation(MAP)or decreasing mean annual temperature(MAT),suggesting that grassland types indeed represented an aridity gradient.Woody plants had an effect on the plant C storage both in size and in distribution relative to pure grasslands.The direction and strength of the effect of woody plants varied with grassland types due to the mediating effect of the climate,with wetter conditions promoting a positive effect of woody plants.Woody plants increased vegetation-level AGC through their high AGC relative to herbaceous plants.However,more negative effects of woody plants on herbaceous plants with increasing aridity led to a weaker increase in the living AGC in arid desert,steppe desert and desert steppe than in the less arid other grassland types.Under greater aridity(lower MAP and higher MAT),woody plants allocated less biomass to roots and had lower BGC and had a more negative impact on herbaceous plant production,thereby reducing vegetation-level BGC in the desert,steppe desert and desert steppe.In sum,this resulted in a negative effect of woody plants on total plant C storage in the most arid grasslands in Xinjiang.As a consequence,we predict that woody plant encroachment may decrease rather than increase C storage in grasslands under future drier conditions.
文摘The decomposition of plant litter is a major process of equivalent status to primary production in ecosystem functioning.The spatiotemporal changes in the composition and dynamics of litter fungal community along a climate gradient ranging from arid desert to humid-Mediterranean regions in Israel was examined using wheat straw litter bags placed at four selected sites along the climate gradient,arid,semi-arid,Mediterranean,and humid-Mediterranean sites.Litter samples were collected over a two-year decomposition period to evaluate litter weight loss,moisture,C:N ratio,fungal composition,and isolate density.The litter decomposition rate was found to be the highest during the first year of the study at the Mediterranean and arid sites.Although the Shannon-Wiener index values of the fungal communities in the litter samples were the highest at the humid-Mediterranean site,the number of fungal species was not significantly different between the four study sites.Different fungal groups were found to be related to different study sites:Basidiomycota,Mucoromycotina,and teleomorphic Ascomycota were associated with the humid-Mediterranean site,while Coelomycetes were mostly affected by the arid site.Our results indicate that climate factors play an important role in determining the structure of saprotrophic fungal communities in the decomposing litter and in mediating plant litter decomposition processes.
