Livestock grazing is the most extensive land use in global drylands and one of the most extensive stressors of biological soil crusts(biocrusts).Despite widespread concern about the importance of biocrusts for global ...Livestock grazing is the most extensive land use in global drylands and one of the most extensive stressors of biological soil crusts(biocrusts).Despite widespread concern about the importance of biocrusts for global carbon(C)cycling,little is known about whether and how long-term grazing alters soil organic carbon(SOC)stability and stock in the biocrust layer.To assess the responses of SOC stability and stock in the biocrust layer to grazing,from June to September 2020,we carried out a large scale field survey in the restored grasslands under long-term grazing with different grazing intensities(represented by the number of goat dung per square meter)and in the grasslands strictly excluded from grazing in four regions(Dingbian County,Shenmu City,Guyuan City and Ansai District)along precipitation gradient in the hilly Loess Plateau,China.In total,51 representative grassland sites were identified as the study sampling sites in this study,including 11 sites in Guyuan City,16 sites in Dingbian County,15 sites in Shenmu City and 9 sites in Ansai District.Combined with extensive laboratory analysis and statistical analysis,at each sampling site,we obtained data on biocrust attributes(cover,community structure,biomass and thickness),soil physical-chemical properties(soil porosity and soil carbon-to-nitrogen ratio(C/N ratio)),and environmental factors(mean annual precipitation,mean annual temperature,altitude,plant cover,litter cover,soil particle-size distribution(the ratio of soil clay and silt content to sand content)),SOC stability index(SI)and SOC stock(SOCS)in the biocrust layer,to conduct this study.Our results revealed that grazing did not change total biocrust cover but markedly altered biocrust community structure by reducing plant cover,with a considerable increase in the relative cover of cyanobacteria(23.1%)while a decrease in the relative cover of mosses(42.2%).Soil porosity and soil C/N ratio in the biocrust layer under grazing decreased significantly by 4.1%–7.2%and 7.2%–13.3%,respectively,compared with those under grazing exclusion.The shifted biocrust community structure ultimately resulted in an average reduction of 15.5%in SOCS in the biocrust layer under grazing.However,compared with higher grazing(intensity of more than 10.00 goat dung/m2),light grazing(intensity of 0.00–10.00 goat dung/m2 or approximately 1.20–2.60 goat/(hm2•a))had no adverse effect on SOCS.SOC stability in the biocrust layer remained unchanged under long-term grazing due to the offset between the positive effect of the decreased soil porosity and the negative effect of the decreased soil C/N ratio on the SOC resistance to decomposition.Mean annual precipitation and soil particle-size distribution also regulated SOC stability indirectly by influencing soil porosity through plant cover and biocrust community structure.These findings suggest that proper grazing might not increase the CO_(2) release potential or adversely affect SOCS in the biocrust layer.This research provides some guidance for proper grazing management in the sustainable utilization of grassland resources and C sequestration in biocrusts in the hilly regions of drylands.展开更多
Harboring polyextremotolerant microbial topsoil communities,biological soil crusts(biocrusts)occur across various climatic zones,and have been well studied in the terrestrial drylands.However,little is known about the...Harboring polyextremotolerant microbial topsoil communities,biological soil crusts(biocrusts)occur across various climatic zones,and have been well studied in the terrestrial drylands.However,little is known about the functional metabolic potential of microbial communities involved in the biogeochemical processes during the early succession of biocrusts on the tropical reef islands.We collected 26 biocrusts and bare soil samples from the Xisha Islands and Nansha Islands,and applied a functional gene array(GeoChip 5.0)to reveal nitrogen(N)cycling processes involved in these samples.Both physicochemical measurement and enzyme activity assay were utilized to characterize the soil properties.Results revealed the composition of N-cycling functional genes in biocrusts was distinct from that in bare soil.Additionally,microorganisms in biocrusts showed lower functional potential related to ammonification,denitrification,N assimilation,nitrification,N fixation,and dissimilatory nitrate reduction to ammonium compared to bare soils.Although the abundance of nifH gene was lower in biocrusts,nitrogenase activity was significantly higher compared to that in bare soils.Precipitation,soil physicochemical properties(i.e.,soil available copper,soil ammonia N and pH)and soil biological properties(i.e.,β-glucosidase,fluorescein diacetate hydrolase,alkaline protease,urease,alkaline phosphatase,catalase and chlorophyll a)correlated to the N-cycling functional genes structure.Nitrate N and ammonia N were more abundant in biocrusts than bare soil,while pH value was higher in bare soil.Our results suggested biocrusts play an important role in N-cycling in coral sand soil,and will be helpful in understanding the development and ecological functions of biocrusts on tropical reef islands.展开更多
Since natural restoration combined with artificial auxiliary measures may achieve a relatively rapid restoration effect at a lower cost,it has become an essential measure for the ecological restoration of rock slopes....Since natural restoration combined with artificial auxiliary measures may achieve a relatively rapid restoration effect at a lower cost,it has become an essential measure for the ecological restoration of rock slopes.Previous studies have focused heavily on the relationship between substrate nutrients and water conditions and the development of mosses on the rock surface,but quantitative characterization of substantial effect of rock surface texture(e.g.,microrelief)on moss growth is absent.The undulating microrelief on the rock surface can increase the heterogeneity of the microhabitat,which may be an important factor affecting the development of mossdominated biocrusts.In this study,the roughness of rock surfaces,moss coverage and biomass,weight and major nutrient contents of soils within the biocrusts were measured in the western mountainous area of Sichuan Province,Southwest China to further examine the role of rock surface microrelief in the biocrusts.The results showed that three main factors affecting the development of the biocrusts were bryophyte emergence,soil accumulation,and lithology.The presence of moss accelerates soil formation on rock surfaces and lead to the accumulation of nutrients so that all parts of the moss-dominated biocrusts system can develop synergistically.It was found that a microrelief structure with a roughness between 1.5 and 2.5 could gather soil and bryophyte propagules effectively,which may have a strong relationship with the angle of repose.When the roughness is 1.5,the corresponding undulation angle is very close to the theoretical minimum value of the undulation angle calculated according to the relationships between the undulation angle of the protrusion,slope and angle of repose.展开更多
Biocrusts(BSCs)are widely distributed in frozen ground regions on the Qinghai-Tibet Plateau,and they are considered an important component of cold ecosystems.However,the specific impacts of BSCs on frozen soil remains...Biocrusts(BSCs)are widely distributed in frozen ground regions on the Qinghai-Tibet Plateau,and they are considered an important component of cold ecosystems.However,the specific impacts of BSCs on frozen soil remains relatively unclear.The aim of our study was to clarify the influence of BSCs(light BSCs and dark BSCs in two different succession stages)on the physical properties and ecological stoichiometry characteristics of frozen soil.Our results showed that BSCs increased the silt particle content in 20–40 cm soil layer,leading to a decrease in soil bulk density.And the field water capacity increased about 10%–40%compared to bare land.Additionally,BSCs significantly increased the contents of soil organic carbon(SOC,22.6–30.8 g kg^(-1))and total nitrogen(TN,2.1–2.8 g kg^(-1))in the upper 40 cm soil layer,both of them were approximately 1.3–2.0 and 1.3–4.0 times higher than those observed in bare land.However,BSCs did not have significant influence on soil total phosphorus(TP).BSCs had a significant impact on the stoichiometric ratios within 40 cm.The C/N ratios of the two types of BSCs ranged from 8.8 to 13.5,the C/P ratios ranged from 6.6 to 13.8,and the N/P ratios ranged from 0.6 to 1.2,which were all higher than those of the bare land.There were no significant differences among the C/N,C/P,and N/P ratios between two types of BSCs.However,the increment of C/P and N/P ratios of dark BSCs were significantly higher than those of light BSCs within 0–30 cm,which indicated that a reduction in the availability of phosphorus during the later stages of BSCs succession.These findings provided a theoretical basis for further research on the ecological functions of BSCs in frozen ground regions.展开更多
Despite the promising outcomes observed in individual applications of biochar and polyvinyl alcohol(PVA)in soil,the impact of their combined usage remains inadequately understood.This study systematically explores the...Despite the promising outcomes observed in individual applications of biochar and polyvinyl alcohol(PVA)in soil,the impact of their combined usage remains inadequately understood.This study systematically explores the effects of concurrent biochar and PVA application on key soil parameters,including pH,water-holding capacity(WHC),and dynamic moisture content(MC),and the photosynthetic resilience and growth of the cyanobacterium Microcoleus vaginatus in a desert soil.Biochars,generated at different pyrolysis temperatures(300-600℃),were applied to the soil at varying rates(1%-6%),while PVA was introduced at a mass percentage of 0.05%.The photosynthetic resilience and biomass accumulation of M.vaginatus in different treatments were examined every 7 d during the 28-d exposure to dry conditions after 60-d water supply.The combined application of biochar and PVA resulted in a reduction of soil pH,coupled with significant improvements in WHC and dynamic MC.Moreover,this combined approach exhibited superior effects on the photosynthetic resilience and crust thickness(0.9-3.5 mm)of M.vaginatus compared to the application of biochar and PVA in isolation.Incremental increase in biochar application rate from 0% to 6% demonstrated a notable enhancement in the chlorophyll a content of M.vaginatus.Cyanobacterial crust thickness and exopolysaccharide content exhibited positive correlations with biochar application rate.Thus,combined application of biochar and PVA is cost-effective for enhancing soil properties and cyanobacterial biomass,which is of significance for combating desertification.展开更多
The loess plains cover approximately 2000.00 km2 of the northern Negev Desert,accounting for about 9%of Israel's total land area.As elsewhere,the loess in the Negev Desert is composed of wind-transported dust and ...The loess plains cover approximately 2000.00 km2 of the northern Negev Desert,accounting for about 9%of Israel's total land area.As elsewhere,the loess in the Negev Desert is composed of wind-transported dust and sand particles that have been deposited in sink sites.The loess deposits are characteristically covered by biocrusts,which constitute a substantial share of the region's primary productivity.The biocrusts regulate the vascular vegetation communities,including herbaceous and woody plants,many of which are endemic and/or endangered plant species.Throughout history,the region's main land-uses have been based on extensive livestock grazing and runoff-harvesting agriculture,which both still exist to some extent.These land-uses did not challenge the sustainability of the geo-ecosystems over centuries and millennia.At present,predominant land-uses include intensive rangelands(1016.81 km2,encompassing 51%of the loess plains'area),croplands(encompassing both rainfed and irrigated cropping systems:930.92 km2,47%of the loess plains'area),and afforestation lands(158.75 km2).These current land-uses impose substantial challenges to the functioning of the loess plains.Further,urban and rural settlements have expanded considerably in the last decades(158.45 km2),accompanied by mass construction of infrastructures.Altogether,these new land-uses have caused widespread soil erosion,soil structure deformation,depletion of soil organic carbon,environmental contamination,native vegetation removal,invasion of plant species,and habitat fragmentation.Recent climate change has intensified these stressors,exacerbating adverse impacts and forming feedback loops that intensify land degradation and desertification.The declining ecosystem functioning over recent decades emphasizes the urgent need for passive and active restoration schemes.While some of these efforts have proven to be successful,other have failed.Therefore,proactive policy making and environmental legislation are needed to plan and develop schemes aimed at halting land degradation,while simultaneously maximizing nature conservation and restoration of degraded lands across the loess plains.Such actions are expected to increase the regions'capacity for climate change mitigation and adaptation.展开更多
Soil erosion caused by unsustainable grazing is a major driver of grassland ecosystem degradation in many semi-arid hilly areas in China.Thus,grazing exclusion is considered as an effective method for solving this iss...Soil erosion caused by unsustainable grazing is a major driver of grassland ecosystem degradation in many semi-arid hilly areas in China.Thus,grazing exclusion is considered as an effective method for solving this issue in such areas.However,some ecological and economic problems,such as slow grassland rejuvenation and limited economic conditions,have become obstacles for the sustainable utilization of grassland ecosystem.Accordingly,we hypothesized that the conflict between grassland use and soil conservation may be balanced by a reasonable grazing intensity.In this study,a two-year grazing fence experiment with five grazing intensity gradients was conducted in a typical grassland of the Loess Plateau in China to evaluate the responses of vegetation characteristics and soil and water losses to grazing intensity.The five grazing intensity gradients were 2.2,3.0,4.2,6.7,and 16.7 goats/hm2,which were represented by G1-G5,respectively,and no grazing was used as control.The results showed that a reasonable grazing intensity was conducive to the sustainable utilization of grassland resources.Vegetation biomass under G1-G4 grazing intensity significantly increased by 51.9%,42.1%,36.9%,and 36.7%,respectively,compared with control.In addition,vegetation coverage increased by 19.6%under G1 grazing intensity.Species diversity showed a single peak trend with increasing grazing intensity.The Shannon-Wiener diversity index under G1-G4 grazing intensities significantly increased by 22.8%,22.5%,13.3%,and 8.3%,respectively,compared with control.Furthermore,grazing increased the risk of soil erosion.Compared with control,runoff yields under G1-G5 grazing intensities increased by 1.4,2.6,2.8,4.3,and 3.9 times,respectively,and sediment yields under G1-G5 grazing intensities were 3.0,13.0,20.8,34.3,and 37.7 times greater,respectively,than those under control.This result was mainly attributed to a visible decrease in litter biomass after grazing,which decreased by 50.5%,72.6%,79.0%,80.0%,and 76.9%,respectively,under G1-G5 grazing intensities.By weighing the grassland productivity and soil conservation function,we found that both two aims were achieved at a low grazing intensity of less than 3.5 goats/hm2.Therefore,it is recommended that grassland should be moderately utilized with grazing intensity below 3.5 goats/hm2 in semi-arid hilly areas to achieve the dual goals of ecological and economic benefits.The results provide a scientific basis for grassland utilization and health management in semi-arid hilly areas from the perspective of determining reasonable grazing intensity to maintain both grassland production and soil conservation functions.展开更多
基金supported by the National Natural Science Foundation of China (41830758)the "Light of the West" Cross Team-Key Laboratory Cooperative Research Project of the Chinese Academy of Sciences
文摘Livestock grazing is the most extensive land use in global drylands and one of the most extensive stressors of biological soil crusts(biocrusts).Despite widespread concern about the importance of biocrusts for global carbon(C)cycling,little is known about whether and how long-term grazing alters soil organic carbon(SOC)stability and stock in the biocrust layer.To assess the responses of SOC stability and stock in the biocrust layer to grazing,from June to September 2020,we carried out a large scale field survey in the restored grasslands under long-term grazing with different grazing intensities(represented by the number of goat dung per square meter)and in the grasslands strictly excluded from grazing in four regions(Dingbian County,Shenmu City,Guyuan City and Ansai District)along precipitation gradient in the hilly Loess Plateau,China.In total,51 representative grassland sites were identified as the study sampling sites in this study,including 11 sites in Guyuan City,16 sites in Dingbian County,15 sites in Shenmu City and 9 sites in Ansai District.Combined with extensive laboratory analysis and statistical analysis,at each sampling site,we obtained data on biocrust attributes(cover,community structure,biomass and thickness),soil physical-chemical properties(soil porosity and soil carbon-to-nitrogen ratio(C/N ratio)),and environmental factors(mean annual precipitation,mean annual temperature,altitude,plant cover,litter cover,soil particle-size distribution(the ratio of soil clay and silt content to sand content)),SOC stability index(SI)and SOC stock(SOCS)in the biocrust layer,to conduct this study.Our results revealed that grazing did not change total biocrust cover but markedly altered biocrust community structure by reducing plant cover,with a considerable increase in the relative cover of cyanobacteria(23.1%)while a decrease in the relative cover of mosses(42.2%).Soil porosity and soil C/N ratio in the biocrust layer under grazing decreased significantly by 4.1%–7.2%and 7.2%–13.3%,respectively,compared with those under grazing exclusion.The shifted biocrust community structure ultimately resulted in an average reduction of 15.5%in SOCS in the biocrust layer under grazing.However,compared with higher grazing(intensity of more than 10.00 goat dung/m2),light grazing(intensity of 0.00–10.00 goat dung/m2 or approximately 1.20–2.60 goat/(hm2•a))had no adverse effect on SOCS.SOC stability in the biocrust layer remained unchanged under long-term grazing due to the offset between the positive effect of the decreased soil porosity and the negative effect of the decreased soil C/N ratio on the SOC resistance to decomposition.Mean annual precipitation and soil particle-size distribution also regulated SOC stability indirectly by influencing soil porosity through plant cover and biocrust community structure.These findings suggest that proper grazing might not increase the CO_(2) release potential or adversely affect SOCS in the biocrust layer.This research provides some guidance for proper grazing management in the sustainable utilization of grassland resources and C sequestration in biocrusts in the hilly regions of drylands.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences under contract Nos XDA13020301 and XDA13010500the Fund of Innovation Academy of South China Sea Ecology and Environmental EngineeringChinese Academy of Sciences under contract No.ISEE2018PY01。
文摘Harboring polyextremotolerant microbial topsoil communities,biological soil crusts(biocrusts)occur across various climatic zones,and have been well studied in the terrestrial drylands.However,little is known about the functional metabolic potential of microbial communities involved in the biogeochemical processes during the early succession of biocrusts on the tropical reef islands.We collected 26 biocrusts and bare soil samples from the Xisha Islands and Nansha Islands,and applied a functional gene array(GeoChip 5.0)to reveal nitrogen(N)cycling processes involved in these samples.Both physicochemical measurement and enzyme activity assay were utilized to characterize the soil properties.Results revealed the composition of N-cycling functional genes in biocrusts was distinct from that in bare soil.Additionally,microorganisms in biocrusts showed lower functional potential related to ammonification,denitrification,N assimilation,nitrification,N fixation,and dissimilatory nitrate reduction to ammonium compared to bare soils.Although the abundance of nifH gene was lower in biocrusts,nitrogenase activity was significantly higher compared to that in bare soils.Precipitation,soil physicochemical properties(i.e.,soil available copper,soil ammonia N and pH)and soil biological properties(i.e.,β-glucosidase,fluorescein diacetate hydrolase,alkaline protease,urease,alkaline phosphatase,catalase and chlorophyll a)correlated to the N-cycling functional genes structure.Nitrate N and ammonia N were more abundant in biocrusts than bare soil,while pH value was higher in bare soil.Our results suggested biocrusts play an important role in N-cycling in coral sand soil,and will be helpful in understanding the development and ecological functions of biocrusts on tropical reef islands.
基金supported by the Project of Assessment on Post-quake Ecosystem and Environment Recovery in Jiuzhaigou under Grant 5132202020000046the National Key Research and Development Programme of China under Grant 2017YFC0504902。
文摘Since natural restoration combined with artificial auxiliary measures may achieve a relatively rapid restoration effect at a lower cost,it has become an essential measure for the ecological restoration of rock slopes.Previous studies have focused heavily on the relationship between substrate nutrients and water conditions and the development of mosses on the rock surface,but quantitative characterization of substantial effect of rock surface texture(e.g.,microrelief)on moss growth is absent.The undulating microrelief on the rock surface can increase the heterogeneity of the microhabitat,which may be an important factor affecting the development of mossdominated biocrusts.In this study,the roughness of rock surfaces,moss coverage and biomass,weight and major nutrient contents of soils within the biocrusts were measured in the western mountainous area of Sichuan Province,Southwest China to further examine the role of rock surface microrelief in the biocrusts.The results showed that three main factors affecting the development of the biocrusts were bryophyte emergence,soil accumulation,and lithology.The presence of moss accelerates soil formation on rock surfaces and lead to the accumulation of nutrients so that all parts of the moss-dominated biocrusts system can develop synergistically.It was found that a microrelief structure with a roughness between 1.5 and 2.5 could gather soil and bryophyte propagules effectively,which may have a strong relationship with the angle of repose.When the roughness is 1.5,the corresponding undulation angle is very close to the theoretical minimum value of the undulation angle calculated according to the relationships between the undulation angle of the protrusion,slope and angle of repose.
基金supported by the National Natural Science Foundation of China(Grant No.41601072)the Key Project of National Natural Science Foundation of China(Grant No.41830758)。
文摘Biocrusts(BSCs)are widely distributed in frozen ground regions on the Qinghai-Tibet Plateau,and they are considered an important component of cold ecosystems.However,the specific impacts of BSCs on frozen soil remains relatively unclear.The aim of our study was to clarify the influence of BSCs(light BSCs and dark BSCs in two different succession stages)on the physical properties and ecological stoichiometry characteristics of frozen soil.Our results showed that BSCs increased the silt particle content in 20–40 cm soil layer,leading to a decrease in soil bulk density.And the field water capacity increased about 10%–40%compared to bare land.Additionally,BSCs significantly increased the contents of soil organic carbon(SOC,22.6–30.8 g kg^(-1))and total nitrogen(TN,2.1–2.8 g kg^(-1))in the upper 40 cm soil layer,both of them were approximately 1.3–2.0 and 1.3–4.0 times higher than those observed in bare land.However,BSCs did not have significant influence on soil total phosphorus(TP).BSCs had a significant impact on the stoichiometric ratios within 40 cm.The C/N ratios of the two types of BSCs ranged from 8.8 to 13.5,the C/P ratios ranged from 6.6 to 13.8,and the N/P ratios ranged from 0.6 to 1.2,which were all higher than those of the bare land.There were no significant differences among the C/N,C/P,and N/P ratios between two types of BSCs.However,the increment of C/P and N/P ratios of dark BSCs were significantly higher than those of light BSCs within 0–30 cm,which indicated that a reduction in the availability of phosphorus during the later stages of BSCs succession.These findings provided a theoretical basis for further research on the ecological functions of BSCs in frozen ground regions.
基金the financial support from the National Natural Science Foundation of China(Nos.22378154 and 21975089)the Fundamental Research Funds for the Central Universities of China(No.2017KFKJFP002)。
文摘Despite the promising outcomes observed in individual applications of biochar and polyvinyl alcohol(PVA)in soil,the impact of their combined usage remains inadequately understood.This study systematically explores the effects of concurrent biochar and PVA application on key soil parameters,including pH,water-holding capacity(WHC),and dynamic moisture content(MC),and the photosynthetic resilience and growth of the cyanobacterium Microcoleus vaginatus in a desert soil.Biochars,generated at different pyrolysis temperatures(300-600℃),were applied to the soil at varying rates(1%-6%),while PVA was introduced at a mass percentage of 0.05%.The photosynthetic resilience and biomass accumulation of M.vaginatus in different treatments were examined every 7 d during the 28-d exposure to dry conditions after 60-d water supply.The combined application of biochar and PVA resulted in a reduction of soil pH,coupled with significant improvements in WHC and dynamic MC.Moreover,this combined approach exhibited superior effects on the photosynthetic resilience and crust thickness(0.9-3.5 mm)of M.vaginatus compared to the application of biochar and PVA in isolation.Incremental increase in biochar application rate from 0% to 6% demonstrated a notable enhancement in the chlorophyll a content of M.vaginatus.Cyanobacterial crust thickness and exopolysaccharide content exhibited positive correlations with biochar application rate.Thus,combined application of biochar and PVA is cost-effective for enhancing soil properties and cyanobacterial biomass,which is of significance for combating desertification.
基金supported by the Ministry of Science and Technologfunded by the Deshe Institute(Order Number 17-7480430).
文摘The loess plains cover approximately 2000.00 km2 of the northern Negev Desert,accounting for about 9%of Israel's total land area.As elsewhere,the loess in the Negev Desert is composed of wind-transported dust and sand particles that have been deposited in sink sites.The loess deposits are characteristically covered by biocrusts,which constitute a substantial share of the region's primary productivity.The biocrusts regulate the vascular vegetation communities,including herbaceous and woody plants,many of which are endemic and/or endangered plant species.Throughout history,the region's main land-uses have been based on extensive livestock grazing and runoff-harvesting agriculture,which both still exist to some extent.These land-uses did not challenge the sustainability of the geo-ecosystems over centuries and millennia.At present,predominant land-uses include intensive rangelands(1016.81 km2,encompassing 51%of the loess plains'area),croplands(encompassing both rainfed and irrigated cropping systems:930.92 km2,47%of the loess plains'area),and afforestation lands(158.75 km2).These current land-uses impose substantial challenges to the functioning of the loess plains.Further,urban and rural settlements have expanded considerably in the last decades(158.45 km2),accompanied by mass construction of infrastructures.Altogether,these new land-uses have caused widespread soil erosion,soil structure deformation,depletion of soil organic carbon,environmental contamination,native vegetation removal,invasion of plant species,and habitat fragmentation.Recent climate change has intensified these stressors,exacerbating adverse impacts and forming feedback loops that intensify land degradation and desertification.The declining ecosystem functioning over recent decades emphasizes the urgent need for passive and active restoration schemes.While some of these efforts have proven to be successful,other have failed.Therefore,proactive policy making and environmental legislation are needed to plan and develop schemes aimed at halting land degradation,while simultaneously maximizing nature conservation and restoration of degraded lands across the loess plains.Such actions are expected to increase the regions'capacity for climate change mitigation and adaptation.
基金National Key Research and Development Program of China(2022YFD1300803)National Natural Science Foundation of China(42377357).
文摘Soil erosion caused by unsustainable grazing is a major driver of grassland ecosystem degradation in many semi-arid hilly areas in China.Thus,grazing exclusion is considered as an effective method for solving this issue in such areas.However,some ecological and economic problems,such as slow grassland rejuvenation and limited economic conditions,have become obstacles for the sustainable utilization of grassland ecosystem.Accordingly,we hypothesized that the conflict between grassland use and soil conservation may be balanced by a reasonable grazing intensity.In this study,a two-year grazing fence experiment with five grazing intensity gradients was conducted in a typical grassland of the Loess Plateau in China to evaluate the responses of vegetation characteristics and soil and water losses to grazing intensity.The five grazing intensity gradients were 2.2,3.0,4.2,6.7,and 16.7 goats/hm2,which were represented by G1-G5,respectively,and no grazing was used as control.The results showed that a reasonable grazing intensity was conducive to the sustainable utilization of grassland resources.Vegetation biomass under G1-G4 grazing intensity significantly increased by 51.9%,42.1%,36.9%,and 36.7%,respectively,compared with control.In addition,vegetation coverage increased by 19.6%under G1 grazing intensity.Species diversity showed a single peak trend with increasing grazing intensity.The Shannon-Wiener diversity index under G1-G4 grazing intensities significantly increased by 22.8%,22.5%,13.3%,and 8.3%,respectively,compared with control.Furthermore,grazing increased the risk of soil erosion.Compared with control,runoff yields under G1-G5 grazing intensities increased by 1.4,2.6,2.8,4.3,and 3.9 times,respectively,and sediment yields under G1-G5 grazing intensities were 3.0,13.0,20.8,34.3,and 37.7 times greater,respectively,than those under control.This result was mainly attributed to a visible decrease in litter biomass after grazing,which decreased by 50.5%,72.6%,79.0%,80.0%,and 76.9%,respectively,under G1-G5 grazing intensities.By weighing the grassland productivity and soil conservation function,we found that both two aims were achieved at a low grazing intensity of less than 3.5 goats/hm2.Therefore,it is recommended that grassland should be moderately utilized with grazing intensity below 3.5 goats/hm2 in semi-arid hilly areas to achieve the dual goals of ecological and economic benefits.The results provide a scientific basis for grassland utilization and health management in semi-arid hilly areas from the perspective of determining reasonable grazing intensity to maintain both grassland production and soil conservation functions.
