Fire is a natural disturbance occurring every few years in many grasslands ecosystems.However,since European colonization,fire has been highly reduced or even suppressed in Argentinean grasslands,fostering ignitable m...Fire is a natural disturbance occurring every few years in many grasslands ecosystems.However,since European colonization,fire has been highly reduced or even suppressed in Argentinean grasslands,fostering ignitable material accumulation.This has led to occasional catastrophic controldemanding fire events,extended for larger areas.The aims of this work are to study vegetation recovery and change after a non-natural fire event in mountain grasslands.The study area is located in the Ventania mountain system,mid-eastern Argentina.We studied vegetation recovery after fire(January 2014)in two different communities:grass-steppes(grasslands)and shrub-steppes(open low shrublands).We measured vegetation cover,species richness and bare ground percentage in burned and unburned areas 1,4,8,11 and 23 months after fire.Vegetation surveys were also performed at the end of the growing season(December)11 and 23 months after fire.Data were analyzed using regression analysis,ANOVA and multivariate analysis(NMS,PERMANOVA).Both communities increased their vegetation cover at the same rate,without differences between burned and unburned areas after two years.Species richness was higher in shrublands and their recovery was alsofaster than in grasslands.Considering functional composition,besides transient changes during the first year after fire,there were no differences in abundance of different functional vegetation groups two years after fire.At the same time,shrublands showed no differences in species composition,while grasslands had a different species composition in burned and unburned plots.Also,burned grassland showed a higher species richness than unburned grassland.Data shown mountain vegetation in Pampas grassland is adapted to fire,recovering cover and richness rapidly after fire and thus reducing soil erosion risks.Vegetation in mountain Pampas seems to be well adapted to fire,but in grasslands species composition has changed due to fire.Nonetheless,these changes seem to be not permanent since prefire species are still present in the area.展开更多
Aims After abandonment of grasslands,secondary succession leads to the invasion by woody species.This process begins with the accumulation of tree litter in the forest–grassland ecotone.Our objectives were to determi...Aims After abandonment of grasslands,secondary succession leads to the invasion by woody species.This process begins with the accumulation of tree litter in the forest–grassland ecotone.Our objectives were to determine the relationships between litter amounts and vegetation composition and cover along natural forest–grassland ecotones and to experimentally study the initial effects of tree litter accumulation on grassland vegetation and on microsite conditions.Methods We established 11 transects varying from 12 to 15 m in length in different forest–grassland ecotones in the Lahn-Dill highlands,Germany,and measured the mass and cover of tree litter and the cover and composition of vegetation at five sequential positions along each transect by using 1 m2 plots with five replications.In a field experiment,we established plots subjected to different litter amounts(0,200 and 600g m^(−2))and evaluated changes in grassland vegetation,soil temperature and soil nutrient availability below the litter layer.Important Findings Tree litter amounts decrease from 650 to 65g m^(−2) across the forest–grassland ecotone.Vegetation changed from shrubs and annual species(adapted to more stressful conditions)in the forests edge to grasses,rosettes and hemirosette species(with higher competitive abilities)in the grassland.These anthropogenic forest–grassland ecotones showed abrupt edges,and the two adjacent ecosystems were characterized by different species pools and functional groups.In the field experiment,the presence of a litter layer reduced vegetation biomass and cover;the species richness was only reduced in the treatment with high litter(600g m^(−2)).Additionally,adding litter on top of vegetation also reduced thermal amplitude and the number of frost days,while increasing the availability of some nutrients,such as nitrogen and aluminium,the latter being an indicator of soil acidification.Adding a tree litter layer of 600g m^(−2) in grassland areas had strong effects on the composition and diversity of grassland vegetation by reducing the cover of several key grassland species.In,or near,forest edges,litter accumulation rapidly changes established vegetation,microsite conditions and soil nutrients.展开更多
基金supported by the ANPCyT under grant PICT 2014-0865CONICET and Universidad Nacional del Sur from Argentina
文摘Fire is a natural disturbance occurring every few years in many grasslands ecosystems.However,since European colonization,fire has been highly reduced or even suppressed in Argentinean grasslands,fostering ignitable material accumulation.This has led to occasional catastrophic controldemanding fire events,extended for larger areas.The aims of this work are to study vegetation recovery and change after a non-natural fire event in mountain grasslands.The study area is located in the Ventania mountain system,mid-eastern Argentina.We studied vegetation recovery after fire(January 2014)in two different communities:grass-steppes(grasslands)and shrub-steppes(open low shrublands).We measured vegetation cover,species richness and bare ground percentage in burned and unburned areas 1,4,8,11 and 23 months after fire.Vegetation surveys were also performed at the end of the growing season(December)11 and 23 months after fire.Data were analyzed using regression analysis,ANOVA and multivariate analysis(NMS,PERMANOVA).Both communities increased their vegetation cover at the same rate,without differences between burned and unburned areas after two years.Species richness was higher in shrublands and their recovery was alsofaster than in grasslands.Considering functional composition,besides transient changes during the first year after fire,there were no differences in abundance of different functional vegetation groups two years after fire.At the same time,shrublands showed no differences in species composition,while grasslands had a different species composition in burned and unburned plots.Also,burned grassland showed a higher species richness than unburned grassland.Data shown mountain vegetation in Pampas grassland is adapted to fire,recovering cover and richness rapidly after fire and thus reducing soil erosion risks.Vegetation in mountain Pampas seems to be well adapted to fire,but in grasslands species composition has changed due to fire.Nonetheless,these changes seem to be not permanent since prefire species are still present in the area.
基金This work was supported by Alexander von Humboldt Foundation by means of a postdoctoral fellowship(A.L.).
文摘Aims After abandonment of grasslands,secondary succession leads to the invasion by woody species.This process begins with the accumulation of tree litter in the forest–grassland ecotone.Our objectives were to determine the relationships between litter amounts and vegetation composition and cover along natural forest–grassland ecotones and to experimentally study the initial effects of tree litter accumulation on grassland vegetation and on microsite conditions.Methods We established 11 transects varying from 12 to 15 m in length in different forest–grassland ecotones in the Lahn-Dill highlands,Germany,and measured the mass and cover of tree litter and the cover and composition of vegetation at five sequential positions along each transect by using 1 m2 plots with five replications.In a field experiment,we established plots subjected to different litter amounts(0,200 and 600g m^(−2))and evaluated changes in grassland vegetation,soil temperature and soil nutrient availability below the litter layer.Important Findings Tree litter amounts decrease from 650 to 65g m^(−2) across the forest–grassland ecotone.Vegetation changed from shrubs and annual species(adapted to more stressful conditions)in the forests edge to grasses,rosettes and hemirosette species(with higher competitive abilities)in the grassland.These anthropogenic forest–grassland ecotones showed abrupt edges,and the two adjacent ecosystems were characterized by different species pools and functional groups.In the field experiment,the presence of a litter layer reduced vegetation biomass and cover;the species richness was only reduced in the treatment with high litter(600g m^(−2)).Additionally,adding litter on top of vegetation also reduced thermal amplitude and the number of frost days,while increasing the availability of some nutrients,such as nitrogen and aluminium,the latter being an indicator of soil acidification.Adding a tree litter layer of 600g m^(−2) in grassland areas had strong effects on the composition and diversity of grassland vegetation by reducing the cover of several key grassland species.In,or near,forest edges,litter accumulation rapidly changes established vegetation,microsite conditions and soil nutrients.
