Annual growth rings of roots in perennial forbs have been used in studies of climate change and the ecology of grasslands. However, little has been done in this aspect of research in China. In this study, we report th...Annual growth rings of roots in perennial forbs have been used in studies of climate change and the ecology of grasslands. However, little has been done in this aspect of research in China. In this study, we report the characteristics of growth rings in the main roots of 13 herb species sampled in Duolun of the Inner Mongolia grassland in northern China. The results show that around two thirds of the species possess clearly demarcated annual rings in the root xylem. Some species of the same genera show different patterns in anatomical structure of the root xylem. Standardized annual ring widths of three species, Potentilla anserine L., Cymbaria dahurica L. and Lespedeza daurica （Laxm.） Schindh, show a common linear trend, indicating a continued favorable growth condition in the sampling sites. Our results provide evidence that growth rings in roots of some perennial forbs in the Inner Mongolia grassland can serve as a new and useful indicator of past changes in the grassland environment.展开更多
Aims Mesic grasslands have a long evolutionary history of grazing by large herbivores and as a consequence,grassland species have numerous adaptations allowing them to respond favourably to grazing.Although empirical ...Aims Mesic grasslands have a long evolutionary history of grazing by large herbivores and as a consequence,grassland species have numerous adaptations allowing them to respond favourably to grazing.Although empirical evidence has been equivocal,theory predicts that such adaptations combined with alterations in resources can lead to grazing-induced overcompensation in aboveground net primary production(ANPP;grazed ANPP>ungrazed ANPP)under certain conditions.We tested two specific predictions from theory.First,overcompensation is more likely to occur in annually burned grasslands because limiting nutrients that would be lost with frequent fires are recycled through grazers and stimulate ANPP.Second,overcompensation of biomass lost to grazers is more likely to occur in unburned sites where grazing has the greatest effect on increasing light availability through alterations in canopy structure.Methods We tested these nutrient versus light-based predictions in grazed grasslands that had been annually burned or protected from fire for>20 years.We assessed responses in ANPP to grazing by large ungulates using both permanent and moveable grazing exclosures(252 exclosures from which biomass was harvested from 3192 quadrats)in a 2-year study.Study sites were located at the Konza Prairie Biological Station(KPBS)in North America and at Kruger National Park(KNP)in South Africa.At KPBS,sites were grazed by North American bison whereas in KNP sites were grazed either by a diverse suite of herbivores(e.g.blue wildebeest,Burchell’s zebra,African buffalo)or by a single large ungulate(African buffalo).Important Findings We found no evidence for overcompensation in either burned or unburned sites,regardless of grazer type.Thus,there was no support for either mechanism leading to overcompensation.Instead,complete compensation of total biomass lost to grazers was the most common response characterizing grazing–ANPP relationships with,in some cases,undercompensation of grass ANPP being offset by increased ANPP of forbs likely due t展开更多
The structure and function of plant communities in alpine meadow ecosystems are potentially susceptible to climate warming.Here,we utilized a unique field manipulation experiment in an alpine meadow on the Qinghai-Tib...The structure and function of plant communities in alpine meadow ecosystems are potentially susceptible to climate warming.Here,we utilized a unique field manipulation experiment in an alpine meadow on the Qinghai-Tibetan Plateau and investigated the responses of plant species diversity,composition,biomass,and net primary productivity(NPP)at both community and functional group levels to whole-soil-profile warming(3–4℃ across 0–100 cm)during 2018–2021.Plant species diversity,biomass and NPP(both above-and belowground)at the community level showed remarkable resistance to warming.However,plant community composition gradually shifted over time.Over the whole experimental warming period,aboveground biomass of legumes significantly decreased by 45%.Conversely,warming significantly stimulated aboveground biomass of forbs by 84%,likely because of better growth and competitive advantages from the warming-induced stimulation of soil water and other variables.However,warming showed minor effects on aboveground biomass of grasses and sedges.Overall,we emphasize that experimental warming may significantly affect plant community composition in a short term by triggering adjustments in plant interspecific competition or survival strategies,which may cause potential changes in plant productivity over a more extended period and lead to changes in carbon source-sink dynamics in the alpine meadow ecosystem.展开更多
The nutritive value of rangelands in Southern Darfur, Sudan could be improved by introduction and multiplication of nutritious forbs with the objective of increasing livestock production in the area. The present study...The nutritive value of rangelands in Southern Darfur, Sudan could be improved by introduction and multiplication of nutritious forbs with the objective of increasing livestock production in the area. The present study was conducted to evaluate the nutritive value and palatability of eleven range forbs collected at flowering stage from Gahzal Gawazat, Southern Darfur, Sudan using chemical analysis. The crude protein (CP) ranged from 6.8% in Oxygonum atriplicifolium with lowest digestible crude protein (DCP) 2.8% to 16.4% in Zornia diphylla with highest DCP 11.73%. The highest and the lowest crude fiber (CF) values were obtained in Commelina spp (56.4%) and Sesamum alatum (25.9%), respectively. NDF and DMI values were maximum and minimum for Zornia diphylla (44.9 and 2.67%) and Alysicarpus glumaceus (35.3 and 3.4%), respectively. The total digestible nutrients (TDN) ranged from 57.1% in Blepharis linariifolia to 69.3% in Tribulus terrestris with highest digestible energy (DE) in later while the lowest DE was obtained in Commelina spp (2.4%). The calculated in vitro organic matter digestibility (IVOMD) was highest for the Canavalia ensiformis (50.27%) and lowest value (43.17%) for Commelina spp. Zornia diphylla, Tribulus terrestris and Sesamum alatum showed highest nutritive value, while Alysicarpus glumaceus, Oldenlandia senegalensis and Chrozophora brocchiana showed highest palatability. It is concluded that these rangeland forbs are palatable and their CP and energy contents are sufficient to support different classes of livestock in South Darfur, Sudan.展开更多
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 ignitab...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 perman展开更多
Aims We aimed to improve the understanding of the carbon and nutri-ent physiological responses and adaptation of semi-arid grassland plants to environmental changes.Methods We investigated plant leaf non-structural ca...Aims We aimed to improve the understanding of the carbon and nutri-ent physiological responses and adaptation of semi-arid grassland plants to environmental changes.Methods We investigated plant leaf non-structural carbohydrate(NSC=solu-ble sugars+starch),nitrogen(N)and phosphorus(P)levels in an Inner Mongolian semi-arid grassland community treated with water,N and P additions for 8 years.Two dominant grasses(Agropyron cris-tatum(L.)Gaertn.,Stipa krylovii Roshev.)and two forbs(Artemisia frigida Willd.,Potentilla bifurca L.)were analyzed.Important Findings Water addition decreased plant leaf N and P concentrations,whereas N and P addition increased them,indicating that the semi-arid grassland studied suffers from a shortage of N and P sup-ply.Both N and P addition decreased the levels of soluble sugars,starch and thus also NSC in plant leaves,which may be attributed to(i)increased carbohydrate consumption associated with a higher growth rate,and(ii)a dilution effect of greater plant size under N and P addition.Water addition tended to increase the leaf NSC levels both in the grasses(+9.2%)and forbs(+0.6%only),which may be a result of increased photosynthesis of plants with increased water availability.Under conditions of ambient and increased water supply in the present study,N addition resulted in an N/P ratio of>16 in the grasses but a significantly lower N/P ratio of<11 in the forb species.This finding implies that growth of the two grass spe-cies will be limited mainly by P availability but the forbs will still be mainly limited by N supply if N deposition,alone or in combination with summer precipitation,continues to increase as predicted in Inner Mongolia.展开更多
文摘Annual growth rings of roots in perennial forbs have been used in studies of climate change and the ecology of grasslands. However, little has been done in this aspect of research in China. In this study, we report the characteristics of growth rings in the main roots of 13 herb species sampled in Duolun of the Inner Mongolia grassland in northern China. The results show that around two thirds of the species possess clearly demarcated annual rings in the root xylem. Some species of the same genera show different patterns in anatomical structure of the root xylem. Standardized annual ring widths of three species, Potentilla anserine L., Cymbaria dahurica L. and Lespedeza daurica （Laxm.） Schindh, show a common linear trend, indicating a continued favorable growth condition in the sampling sites. Our results provide evidence that growth rings in roots of some perennial forbs in the Inner Mongolia grassland can serve as a new and useful indicator of past changes in the grassland environment.
基金US National Science Foundation Ecosystem Studies,Long-term Ecological Research and Research Experiences for Undergraduates Programs.
文摘Aims Mesic grasslands have a long evolutionary history of grazing by large herbivores and as a consequence,grassland species have numerous adaptations allowing them to respond favourably to grazing.Although empirical evidence has been equivocal,theory predicts that such adaptations combined with alterations in resources can lead to grazing-induced overcompensation in aboveground net primary production(ANPP;grazed ANPP>ungrazed ANPP)under certain conditions.We tested two specific predictions from theory.First,overcompensation is more likely to occur in annually burned grasslands because limiting nutrients that would be lost with frequent fires are recycled through grazers and stimulate ANPP.Second,overcompensation of biomass lost to grazers is more likely to occur in unburned sites where grazing has the greatest effect on increasing light availability through alterations in canopy structure.Methods We tested these nutrient versus light-based predictions in grazed grasslands that had been annually burned or protected from fire for>20 years.We assessed responses in ANPP to grazing by large ungulates using both permanent and moveable grazing exclosures(252 exclosures from which biomass was harvested from 3192 quadrats)in a 2-year study.Study sites were located at the Konza Prairie Biological Station(KPBS)in North America and at Kruger National Park(KNP)in South Africa.At KPBS,sites were grazed by North American bison whereas in KNP sites were grazed either by a diverse suite of herbivores(e.g.blue wildebeest,Burchell’s zebra,African buffalo)or by a single large ungulate(African buffalo).Important Findings We found no evidence for overcompensation in either burned or unburned sites,regardless of grazer type.Thus,there was no support for either mechanism leading to overcompensation.Instead,complete compensation of total biomass lost to grazers was the most common response characterizing grazing–ANPP relationships with,in some cases,undercompensation of grass ANPP being offset by increased ANPP of forbs likely due t
基金supported by the National Natural Science Foundation of China (42141006,31971528 and 31988102).
文摘The structure and function of plant communities in alpine meadow ecosystems are potentially susceptible to climate warming.Here,we utilized a unique field manipulation experiment in an alpine meadow on the Qinghai-Tibetan Plateau and investigated the responses of plant species diversity,composition,biomass,and net primary productivity(NPP)at both community and functional group levels to whole-soil-profile warming(3–4℃ across 0–100 cm)during 2018–2021.Plant species diversity,biomass and NPP(both above-and belowground)at the community level showed remarkable resistance to warming.However,plant community composition gradually shifted over time.Over the whole experimental warming period,aboveground biomass of legumes significantly decreased by 45%.Conversely,warming significantly stimulated aboveground biomass of forbs by 84%,likely because of better growth and competitive advantages from the warming-induced stimulation of soil water and other variables.However,warming showed minor effects on aboveground biomass of grasses and sedges.Overall,we emphasize that experimental warming may significantly affect plant community composition in a short term by triggering adjustments in plant interspecific competition or survival strategies,which may cause potential changes in plant productivity over a more extended period and lead to changes in carbon source-sink dynamics in the alpine meadow ecosystem.
文摘The nutritive value of rangelands in Southern Darfur, Sudan could be improved by introduction and multiplication of nutritious forbs with the objective of increasing livestock production in the area. The present study was conducted to evaluate the nutritive value and palatability of eleven range forbs collected at flowering stage from Gahzal Gawazat, Southern Darfur, Sudan using chemical analysis. The crude protein (CP) ranged from 6.8% in Oxygonum atriplicifolium with lowest digestible crude protein (DCP) 2.8% to 16.4% in Zornia diphylla with highest DCP 11.73%. The highest and the lowest crude fiber (CF) values were obtained in Commelina spp (56.4%) and Sesamum alatum (25.9%), respectively. NDF and DMI values were maximum and minimum for Zornia diphylla (44.9 and 2.67%) and Alysicarpus glumaceus (35.3 and 3.4%), respectively. The total digestible nutrients (TDN) ranged from 57.1% in Blepharis linariifolia to 69.3% in Tribulus terrestris with highest digestible energy (DE) in later while the lowest DE was obtained in Commelina spp (2.4%). The calculated in vitro organic matter digestibility (IVOMD) was highest for the Canavalia ensiformis (50.27%) and lowest value (43.17%) for Commelina spp. Zornia diphylla, Tribulus terrestris and Sesamum alatum showed highest nutritive value, while Alysicarpus glumaceus, Oldenlandia senegalensis and Chrozophora brocchiana showed highest palatability. It is concluded that these rangeland forbs are palatable and their CP and energy contents are sufficient to support different classes of livestock in South Darfur, Sudan.
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 perman
基金The National Natural Science Foundation of China(41371076,31370009)the National Key Basic Research Program of China(2011CB403204)the State Key Laboratory of Forest and Soil Ecology(LFSE2013-01).
文摘Aims We aimed to improve the understanding of the carbon and nutri-ent physiological responses and adaptation of semi-arid grassland plants to environmental changes.Methods We investigated plant leaf non-structural carbohydrate(NSC=solu-ble sugars+starch),nitrogen(N)and phosphorus(P)levels in an Inner Mongolian semi-arid grassland community treated with water,N and P additions for 8 years.Two dominant grasses(Agropyron cris-tatum(L.)Gaertn.,Stipa krylovii Roshev.)and two forbs(Artemisia frigida Willd.,Potentilla bifurca L.)were analyzed.Important Findings Water addition decreased plant leaf N and P concentrations,whereas N and P addition increased them,indicating that the semi-arid grassland studied suffers from a shortage of N and P sup-ply.Both N and P addition decreased the levels of soluble sugars,starch and thus also NSC in plant leaves,which may be attributed to(i)increased carbohydrate consumption associated with a higher growth rate,and(ii)a dilution effect of greater plant size under N and P addition.Water addition tended to increase the leaf NSC levels both in the grasses(+9.2%)and forbs(+0.6%only),which may be a result of increased photosynthesis of plants with increased water availability.Under conditions of ambient and increased water supply in the present study,N addition resulted in an N/P ratio of>16 in the grasses but a significantly lower N/P ratio of<11 in the forb species.This finding implies that growth of the two grass spe-cies will be limited mainly by P availability but the forbs will still be mainly limited by N supply if N deposition,alone or in combination with summer precipitation,continues to increase as predicted in Inner Mongolia.
