On an agrosilvopastoral farm in central Italy where Maremmana cattle graze in Turkey oak forests,we evaluated the impact of different livestock densities on stand structure,tree diversity and natural regeneration in f...On an agrosilvopastoral farm in central Italy where Maremmana cattle graze in Turkey oak forests,we evaluated the impact of different livestock densities on stand structure,tree diversity and natural regeneration in four types of grazed areas based on the grazing regime adopted:calf-grazed,high-intensity-grazed,low-intensity-grazed,ungrazed control.For each area,we set up three permanent circular plots(radius of 15 m)to survey the structural and dasometric characteristics of the overstorey,understorey,and regeneration layer.The results showed that grazing negatively affected the complexity of the forest structure and its potential to regenerate and maintain a high level of biodiversity.The differences in stand structure observed between the grazing areas were closely related to livestock density.The most sensitive components of the system were the understorey and the regeneration layers.Contrarily,the current grazing management did not affect the dominant tree structure or its composition.Our findings identified medium-term monitoring and regeneration management as the two significant aspects to consider when assessing sustainable livestock.New forests can be established by excluding graz-ing for about 20–25 years.展开更多
Background Livestock production is an economically significant activity in grassland-based production systems with herbivory,a critical process in modifying plant structure and regulating biomass dynamics in these are...Background Livestock production is an economically significant activity in grassland-based production systems with herbivory,a critical process in modifying plant structure and regulating biomass dynamics in these areas.Methods A grazing simulation experiment was undertaken in a semi-arid environment in Kenya to determine the effects of clipping frequency and intensity on the morphology and productivity of Cenchrus ciliaris and Panicum maximum grass ecotypes.The ecotypes were clipped at different frequencies(every 2,4,and 12 weeks)and different intensities(5,10,and 15 cm clipping heights).The morphological responses of the grass ecotypes and biomass yields were determined.Results The grass ecotypes showed significantly(p<0.05)varied responses to cutting frequency and intensity.Morphological parameters,tillering,and biomass production were all affected by clipping frequency and intensity.The highest dry matter(DM)yields were recorded under low frequency(LF)clipping,followed by moderate frequency(MF)clipping and high frequency(HF)clipping.LF clipping in C.ciliaris ecotype Kilifi was 20%and 31%more compared to MF and HF clipping.No significant difference in yields was found by cutting the C.ciliaris ecotype Magadi at 4-and 12-week intervals,even though clipping at 2-week intervals cumulatively yielded less biomass.There was a biomass yield reduction in P.maximum ecotype Taveta of 23%and 25%for MF and HF clipping,respectively,while for ecotype Isinya,the reduction was 13%and 15%for MF and HF,respectively.Clipping intensity had a significant(p<0.05)effect on cumulative yields in C.ciliaris ecotypes,but not P.maximum.Ecotypic differences were apparent in both C.ciliaris and P.maximum ecotype DM yields.Conclusions The results in this study suggest that clipping range grass ecotypes less frequently(4-and 12-week intervals)and at 10 and 15 cm stubble heights results in higher biomass yields.Generally,LF and MF grazing and cutting strategies are advantageous for semi-arid lands.Combinations of frequent and high-intensity utilization grazing strategies should be discouraged as they are likely to lead to reduced biomass yields and negative effects both on grasses and on the environment.展开更多
Elucidating the distribution of the grazing pressure requires an understanding of the grazing activities.In this study,we analyzed the grazing behavior of yaks in Three-RiverSource Region(TRSR)and identified the main ...Elucidating the distribution of the grazing pressure requires an understanding of the grazing activities.In this study,we analyzed the grazing behavior of yaks in Three-RiverSource Region(TRSR)and identified the main factors influencing the distribution of grazing intensity(GI)using trajectory data and remote sensing datasets.Our results revealed that a semi-resident transhumance strategy is employed in this region.The average grazing time(GT)of four GPS collars over the year was 11.84 h/day(N6),11.01 h/day(N11),9.25 h/day(N18),and 11.61 h/day(N24).GT was generally higher in warm seasons(summer and autumn)than in cold seasons(spring and winter).The average daily moving speed was found to be closely related to the pasture size of different herders and the seasons.Geodetector analysis identified the distance to camp(DOC)as the most important single factor influencing the distribution of GI,explaining up to 52% of the GI variations.However,relying solely on this factor may not accurately depict the actual GI distribution.When pairwise factors interacted,the explanatory power of the model increased,ranging from 34.55% to 63.26%.Our study highlights the importance of considering multiple factors when predicting grazing intensity,as grazing activities tend to cluster near settlements,but other factors may also be influential.展开更多
Aims Grasslands are the world’s most extensive terrestrial ecosystem,and are a major feed source for livestock.Meeting increasing demand for meat and other dairy products in a sustainable manner is a big challenge.At...Aims Grasslands are the world’s most extensive terrestrial ecosystem,and are a major feed source for livestock.Meeting increasing demand for meat and other dairy products in a sustainable manner is a big challenge.At a field scale,Global Positioning System and ground-based sensor technologies provide promising tools for grassland and herd management with high precision.With the growth in availability of spaceborne remote sensing data,it is therefore important to revisit the relevant methods and applications that can exploit this imagery.In this article,we have reviewed the(i)current status of grassland monitoring/observation methods and applications based on satellite remote sensing data,(ii)the technological and methodological developments to retrieve different grassland biophysical parameters and management characteristics(i.e.degradation,grazing intensity)and(iii)identified the key remaining challenges and some new upcoming trends for future development.Important Findings The retrieval of grassland biophysical parameters have evolved in recent years from classical regression analysis to more complex,efficient and robust modeling approaches,driven by satellite data,and are likely to continue to be the most robust method for deriving grassland information,however these require more high quality calibration and validation data.We found that the hypertemporal satellite data are widely used for time series generation,and particularly to overcome cloud contamination issues,but the current low spatial resolution of these instruments precludes their use for field-scale application in many countries.This trend may change with the current rise in launch of satellite constellations,such as RapidEye,Sentinel-2 and even the microsatellites such as those operated by Skybox Imaging.Microwave imagery has not been widely used for grassland applications,and a better understanding of the backscatter behaviour from different phenological stages is needed for more reliable products in cloudy regions.The development of hyperspectral satellite instrumentation and analytical methods will help for more detailed discrimination of habitat types,and the development of tools for greater end-user operation.展开更多
Aims Natural 15N abundance provides integrated information about nitrogen(N)input,transformation and output,indirectly reflecting N cycling traits within terrestrial ecosystems.However,relationships between natural 15...Aims Natural 15N abundance provides integrated information about nitrogen(N)input,transformation and output,indirectly reflecting N cycling traits within terrestrial ecosystems.However,relationships between natural 15N abundance and N cycling processes are poorly understood in China.Here,our primary objectives were to(i)examine the effects of grazing at varying levels of intensity on d15N of soils and plants in a semi-arid grassland;(ii)detect the relationships between d15N of soils and four major N cycling processes(i.e.mineralization,nitrification,denitrification and ammonia volatilization);and(iii)determine whether d15N of soils can be used as an indicator of N cycling in this semi-arid grassland.Methods The field experiment was conducted within the long-term(17-year)grazing enclosures in a semi-arid grassland in Inner Mongolia.Five grazing intensities(0.00,1.33,2.67,4.00 and 5.33 sheep ha1)were designed.d15N values of topsoils(0–10 cm),surface soils(0–2 cm)and plants were measured in 2006.Differences in d15N of soils and plants between the five grazing intensities were examined.Rates of four soil N cycling processes were measured periodically during the 2005 and 2006 growing seasons.The d15N values of topsoils were linked to the four N cycling processes to investigate their relationships.Important Findings The d15N values of topsoils(5.20–5.96&)were substantially higher than the d15N values of plants(2.51–2.93&)and surface soils(1.44–2.92&)regardless of grazing intensities.The 15N-depleted N losses during microbial decomposition of organic matter in concert with the downward movement of residual substrate over time are the possible causes of higher d15N values in topsoils than in surface soils.In addition,the d15N values of topsoils were positively correlated with the d15N values of both plants and surface soils.Grazing,especially the high-intensity grazing(5.33 sheep ha1),resulted in a significant decrease in d15N of surface soils.However,no statistically significant variations in d15N of topsoils and plants were found in response to grazing.The d15N values of topsoils exhibited significant dependence on the cumulative rates of NH3 volatilization,net nitrification and denitrification in 2005 but not in 2006.展开更多
Aims Understanding how environmental factors and human activity drive plant community assembly remains a major challenge in community ecology.Two opposing processes,namely determinis-tic environmental filtering and no...Aims Understanding how environmental factors and human activity drive plant community assembly remains a major challenge in community ecology.Two opposing processes,namely determinis-tic environmental filtering and nondeterministic elements such as interspecies competition,can be quantified by analyzing trait distri-butions in the community-assembly process.Methods We examined the trait-mediated effects of environmental filtering and stochastic process and the distribution over time of nine traits related to vegetative growth,regenerative phase,dispersal capability,decom-position and interspecific competition in plant communities along a degradation gradient in the Xilin River Basin,Inner Mongolia,China.We analyzed the turnover of environmental trait filtering and the diver-gence/convergence of different traits along the degradation gradient.Important Findings Our results showed the following.(i)The patterns of trait distribu-tion and filtering were strongly dependent upon the degradation gradient and trait types.Most traits were filtered intensely in degraded grasslands.(ii)Plants with two different strategies showed contrasting trait-distribution patterns.The traits that were related to biological matter cycling showed divergent pat-terns in highly degraded grasslands,while convergent patterns along the overall gradient were demonstrated in traits associated with other plant strategies.This suggests that the coexistence of multiple‘biological matter cycling-related niches’might be a basic structuring pattern of plant communities in our study area.(iii)The simultaneous occurrence of strong filtering and diver-gence revealed that environmental filtering does not necessar-ily prevent competition,and that different traits show different signatures.展开更多
基金This research is related to the project GO NEWTON“Agroforestry Network in Tuscany”,financed by the Tuscany Region through the Measure 16.2 of Rural Development Plan 2014-2020 to promote agroforestry systems by spreading knowledge to farmers and promoting innovation in the Tuscan territory.
文摘On an agrosilvopastoral farm in central Italy where Maremmana cattle graze in Turkey oak forests,we evaluated the impact of different livestock densities on stand structure,tree diversity and natural regeneration in four types of grazed areas based on the grazing regime adopted:calf-grazed,high-intensity-grazed,low-intensity-grazed,ungrazed control.For each area,we set up three permanent circular plots(radius of 15 m)to survey the structural and dasometric characteristics of the overstorey,understorey,and regeneration layer.The results showed that grazing negatively affected the complexity of the forest structure and its potential to regenerate and maintain a high level of biodiversity.The differences in stand structure observed between the grazing areas were closely related to livestock density.The most sensitive components of the system were the understorey and the regeneration layers.Contrarily,the current grazing management did not affect the dominant tree structure or its composition.Our findings identified medium-term monitoring and regeneration management as the two significant aspects to consider when assessing sustainable livestock.New forests can be established by excluding graz-ing for about 20–25 years.
文摘Background Livestock production is an economically significant activity in grassland-based production systems with herbivory,a critical process in modifying plant structure and regulating biomass dynamics in these areas.Methods A grazing simulation experiment was undertaken in a semi-arid environment in Kenya to determine the effects of clipping frequency and intensity on the morphology and productivity of Cenchrus ciliaris and Panicum maximum grass ecotypes.The ecotypes were clipped at different frequencies(every 2,4,and 12 weeks)and different intensities(5,10,and 15 cm clipping heights).The morphological responses of the grass ecotypes and biomass yields were determined.Results The grass ecotypes showed significantly(p<0.05)varied responses to cutting frequency and intensity.Morphological parameters,tillering,and biomass production were all affected by clipping frequency and intensity.The highest dry matter(DM)yields were recorded under low frequency(LF)clipping,followed by moderate frequency(MF)clipping and high frequency(HF)clipping.LF clipping in C.ciliaris ecotype Kilifi was 20%and 31%more compared to MF and HF clipping.No significant difference in yields was found by cutting the C.ciliaris ecotype Magadi at 4-and 12-week intervals,even though clipping at 2-week intervals cumulatively yielded less biomass.There was a biomass yield reduction in P.maximum ecotype Taveta of 23%and 25%for MF and HF clipping,respectively,while for ecotype Isinya,the reduction was 13%and 15%for MF and HF,respectively.Clipping intensity had a significant(p<0.05)effect on cumulative yields in C.ciliaris ecotypes,but not P.maximum.Ecotypic differences were apparent in both C.ciliaris and P.maximum ecotype DM yields.Conclusions The results in this study suggest that clipping range grass ecotypes less frequently(4-and 12-week intervals)and at 10 and 15 cm stubble heights results in higher biomass yields.Generally,LF and MF grazing and cutting strategies are advantageous for semi-arid lands.Combinations of frequent and high-intensity utilization grazing strategies should be discouraged as they are likely to lead to reduced biomass yields and negative effects both on grasses and on the environment.
基金The Second Tibetan Plateau Scientific Expedition and Research,No.2019QZKK0603Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA20040201National Natural Science Foundation of China,No.41671104。
文摘Elucidating the distribution of the grazing pressure requires an understanding of the grazing activities.In this study,we analyzed the grazing behavior of yaks in Three-RiverSource Region(TRSR)and identified the main factors influencing the distribution of grazing intensity(GI)using trajectory data and remote sensing datasets.Our results revealed that a semi-resident transhumance strategy is employed in this region.The average grazing time(GT)of four GPS collars over the year was 11.84 h/day(N6),11.01 h/day(N11),9.25 h/day(N18),and 11.61 h/day(N24).GT was generally higher in warm seasons(summer and autumn)than in cold seasons(spring and winter).The average daily moving speed was found to be closely related to the pasture size of different herders and the seasons.Geodetector analysis identified the distance to camp(DOC)as the most important single factor influencing the distribution of GI,explaining up to 52% of the GI variations.However,relying solely on this factor may not accurately depict the actual GI distribution.When pairwise factors interacted,the explanatory power of the model increased,ranging from 34.55% to 63.26%.Our study highlights the importance of considering multiple factors when predicting grazing intensity,as grazing activities tend to cluster near settlements,but other factors may also be influential.
基金Teagasc Walsh Fellowship Program for funding this research.
文摘Aims Grasslands are the world’s most extensive terrestrial ecosystem,and are a major feed source for livestock.Meeting increasing demand for meat and other dairy products in a sustainable manner is a big challenge.At a field scale,Global Positioning System and ground-based sensor technologies provide promising tools for grassland and herd management with high precision.With the growth in availability of spaceborne remote sensing data,it is therefore important to revisit the relevant methods and applications that can exploit this imagery.In this article,we have reviewed the(i)current status of grassland monitoring/observation methods and applications based on satellite remote sensing data,(ii)the technological and methodological developments to retrieve different grassland biophysical parameters and management characteristics(i.e.degradation,grazing intensity)and(iii)identified the key remaining challenges and some new upcoming trends for future development.Important Findings The retrieval of grassland biophysical parameters have evolved in recent years from classical regression analysis to more complex,efficient and robust modeling approaches,driven by satellite data,and are likely to continue to be the most robust method for deriving grassland information,however these require more high quality calibration and validation data.We found that the hypertemporal satellite data are widely used for time series generation,and particularly to overcome cloud contamination issues,but the current low spatial resolution of these instruments precludes their use for field-scale application in many countries.This trend may change with the current rise in launch of satellite constellations,such as RapidEye,Sentinel-2 and even the microsatellites such as those operated by Skybox Imaging.Microwave imagery has not been widely used for grassland applications,and a better understanding of the backscatter behaviour from different phenological stages is needed for more reliable products in cloudy regions.The development of hyperspectral satellite instrumentation and analytical methods will help for more detailed discrimination of habitat types,and the development of tools for greater end-user operation.
基金State Key Basic Research and Development Program of China(2010CB833502)Chinese Academy of Sciences(KZCX2-XB2-01).
文摘Aims Natural 15N abundance provides integrated information about nitrogen(N)input,transformation and output,indirectly reflecting N cycling traits within terrestrial ecosystems.However,relationships between natural 15N abundance and N cycling processes are poorly understood in China.Here,our primary objectives were to(i)examine the effects of grazing at varying levels of intensity on d15N of soils and plants in a semi-arid grassland;(ii)detect the relationships between d15N of soils and four major N cycling processes(i.e.mineralization,nitrification,denitrification and ammonia volatilization);and(iii)determine whether d15N of soils can be used as an indicator of N cycling in this semi-arid grassland.Methods The field experiment was conducted within the long-term(17-year)grazing enclosures in a semi-arid grassland in Inner Mongolia.Five grazing intensities(0.00,1.33,2.67,4.00 and 5.33 sheep ha1)were designed.d15N values of topsoils(0–10 cm),surface soils(0–2 cm)and plants were measured in 2006.Differences in d15N of soils and plants between the five grazing intensities were examined.Rates of four soil N cycling processes were measured periodically during the 2005 and 2006 growing seasons.The d15N values of topsoils were linked to the four N cycling processes to investigate their relationships.Important Findings The d15N values of topsoils(5.20–5.96&)were substantially higher than the d15N values of plants(2.51–2.93&)and surface soils(1.44–2.92&)regardless of grazing intensities.The 15N-depleted N losses during microbial decomposition of organic matter in concert with the downward movement of residual substrate over time are the possible causes of higher d15N values in topsoils than in surface soils.In addition,the d15N values of topsoils were positively correlated with the d15N values of both plants and surface soils.Grazing,especially the high-intensity grazing(5.33 sheep ha1),resulted in a significant decrease in d15N of surface soils.However,no statistically significant variations in d15N of topsoils and plants were found in response to grazing.The d15N values of topsoils exhibited significant dependence on the cumulative rates of NH3 volatilization,net nitrification and denitrification in 2005 but not in 2006.
基金This work was supported by The State Key Basic Research Development Program of China[2012CB722201]The National Science Foundation of China[31460154]The Key Science and Technology Program of Inner Mongolia Autonomous Region.
文摘Aims Understanding how environmental factors and human activity drive plant community assembly remains a major challenge in community ecology.Two opposing processes,namely determinis-tic environmental filtering and nondeterministic elements such as interspecies competition,can be quantified by analyzing trait distri-butions in the community-assembly process.Methods We examined the trait-mediated effects of environmental filtering and stochastic process and the distribution over time of nine traits related to vegetative growth,regenerative phase,dispersal capability,decom-position and interspecific competition in plant communities along a degradation gradient in the Xilin River Basin,Inner Mongolia,China.We analyzed the turnover of environmental trait filtering and the diver-gence/convergence of different traits along the degradation gradient.Important Findings Our results showed the following.(i)The patterns of trait distribu-tion and filtering were strongly dependent upon the degradation gradient and trait types.Most traits were filtered intensely in degraded grasslands.(ii)Plants with two different strategies showed contrasting trait-distribution patterns.The traits that were related to biological matter cycling showed divergent pat-terns in highly degraded grasslands,while convergent patterns along the overall gradient were demonstrated in traits associated with other plant strategies.This suggests that the coexistence of multiple‘biological matter cycling-related niches’might be a basic structuring pattern of plant communities in our study area.(iii)The simultaneous occurrence of strong filtering and diver-gence revealed that environmental filtering does not necessar-ily prevent competition,and that different traits show different signatures.
