The Three-River Headwaters region in China is an ecological barrier providing en- vironmental protection and regional sustainable development for the mid-stream and down- stream areas, which also plays an important ro...The Three-River Headwaters region in China is an ecological barrier providing en- vironmental protection and regional sustainable development for the mid-stream and down- stream areas, which also plays an important role in animal husbandry in China. This study estimated the grassland yield in the Three-River Headwaters region based on MODIS NPP data, and calculated the proper livestock-carrying capacity of the grassland. We analyzed the overgrazing number and its spatial distribution characteristics through data comparison be- tween actual and proper livestock-carrying capacity. The results showed the following： （1） total grassland yield （hay） in the Three-River Headwaters region was 10.96 million tons in 2010 with an average grassland yield of 465.70 kg/hm2 （the spatial distribution presents a decreasing trend from the east and southeast to the west and northwest in turn）; （2） the proper livestock-carrying capacity in the Three-River Headwaters region is 12.19 million sheep units （hereafter described as ＂SU＂）, and the average stocking capacity is 51.27 SU [the proper carrying capacity is above 100 SU/km2 in the eastern counties, 60 SU/km2 in the cen- tral counties （except Madoi County）, and 30 SU/km2 in the western counties]; and （3） total overgrazing number was 6.52 million SU in the Three-River Headwaters region in 2010, with an average overgrazing ratio of 67.88% and an average overgrazing number of 27.43 SU/km2 A higher overgrazing ratio occurred in Tongde, Xinghai, Yushu, Henan and Z^kog. There was no overgrazing in Zhiduo, Tanggula Township and Darlag, Qumerleb and Madoi. The re- mainder of the counties had varying degrees of overgrazing.展开更多
The soil constituents and relations between the variation of soil resources and plant communities in three adjacent sites representing the overgrazing, reclamation and comparatively undisturbed communities respectivel...The soil constituents and relations between the variation of soil resources and plant communities in three adjacent sites representing the overgrazing, reclamation and comparatively undisturbed communities respectively were quantified and examined in study area in Huailai Basin, Hebei Province, China. There have been significantly greater constituent of C, N, P in the soils of shrubland site. Corg, Ntotal, Navail and Pavail were between 1.18 and 3.90 times more concentrated in the soils of shrubland site in comparison with the other two sites. Although the Ptotal concentration was lower in shrubland soils than in overgrazed rangeland soils, the Pavail concentration, however, was significantly greater in the soils of shrubland site, and increased by 59.1% and even 289.6% in the soils of shrubland site comparing to those in the soils of range-land and millet field sites. Among the three sites, CV exceeding 40% were found for SO4, Cl, and F ion. The CV of organic carbon also exceeded 40% but only in the soils of millet field site. The highest CV were found for F, SO4 ion in the soils of shrubland and overgrazed rangeland sites, while for Cl and SO4 ion in those of millet field site. The results also showed that the introductions of shrubs are of vital importance for the accumulation of soil nutrients and maintenance of soil fertilities, and also for the restoration and reconstruction of desertified ecosystems.展开更多
ALASHAN AND ORDOS,Inner Mongolia-Dust,five centimeters thick, and rat holes cover the landscape of the Shilekai village,about 300 kilometers from the city of Ordos, Inner Mongolia.
Background Overgrazing was assumed to increase the population density of small mammals that are the intermediate hosts of Echinococcus multilocularis, the pathogen of alveolar echinococcosis in the Qinghai Tibet Plate...Background Overgrazing was assumed to increase the population density of small mammals that are the intermediate hosts of Echinococcus multilocularis, the pathogen of alveolar echinococcosis in the Qinghai Tibet Plateau. This research tested the hypothesis that overgrazing might promote Echinococcus multilocularis transmission through increasing populations of small mammal, intermediate hosts in Tibetan pastoral communities. Methods Grazing practices, small mammal indices and dog Echinococcus multilocularis infection data were collected to analyze the relation between overgrazing and Echinococcus multilocularis transmission using nonparametric tests and multiple stepwise logistic regression. Results In the investigated area, raising livestock was a key industry. The communal pastures existed and the available forage was deficient for grazing. Open （common） pastures were overgrazed and had higher burrow density of small mammals compared with neighboring fenced （private） pastures; this high overgrazing pressure on the open pastures measured by neighboring fenced area led to higher burrow density of small mammals in open pastures. The median burrow density of small mammals in open pastures was independently associated with nearby canine Echinococcus multilocularis infection （P=-0.003, OR=1.048）. Conclusion Overgrazing may promote the transmission of Echinococcus multilocularis through increasing the population density of small mammals.展开更多
Semiarid Patagonia represents 25%of the rangeland area in Argentina,and sheep overgrazing has degraded about a third of it in the past.In this century,depleted domestic stocks have mostly stabilized,but Guanaco popula...Semiarid Patagonia represents 25%of the rangeland area in Argentina,and sheep overgrazing has degraded about a third of it in the past.In this century,depleted domestic stocks have mostly stabilized,but Guanaco populations have grown.These native camelids share habitat and diets with sheep,but their effect on vegetation is poorly understood and has long been debated.We set up an exclusion experiment in Monte León and Cañadón Vaca,a semiarid shrubland grassland in southern Patagonia,currently grazed only by guanacos.Vegetation baselines were studied in 2016 in twelve plots,and half of them were protected from guanaco grazing.Thirty-six plots were cleared to study revegetation.Vegetation was reassessed in 2021,and changes were evaluated using a paired t-test.Within protected plots,vegetation cover increased,bare soil diminished,and vegetated patches grew in size,but the density of the patch-interpatch arrangement did not change.Biodiversity,measured by richness and the Shan-non-Wiener(SW)index,grew significantly.Nutrient recycling increased,as did the Stability and Infiltration Land Function indexes,although these last differences were not significant.Vegetation cover under guanaco grazing also increased,mainly due to the growth of dwarf shrubs,a typical tendency in sheep grazing-induced transitions in the region.Vegetated patches under grazing fragmented,resulting in smaller patches and denser patch struc-tures,while diversity and land function indexes remained unchanged.Young plants established in cleared plots without guanacos showed higher cover density and individual size.These effects are similar to those observed in numerous experimental sheep exclosures.Guanaco grazing may thus prevent restoration and contribute to the generalized land degradation processes that overgrazing has been causing in Patagonia for over a century.展开更多
Remote sensing data from the Terra Moderate-Resolution Imaging Spectroradiometer (MODIS) and geospatial data were used to estimate grass yield and livestock carrying capacity in the Tibetan Autonomous Prefecture of Go...Remote sensing data from the Terra Moderate-Resolution Imaging Spectroradiometer (MODIS) and geospatial data were used to estimate grass yield and livestock carrying capacity in the Tibetan Autonomous Prefecture of Golog, Qing-hai, China. The MODIS-derived normalized difference vegetation index (MODIS-NDVI) data were correlated with the aboveground green biomass (AGGB) data from the aboveground harvest method. Regional regression model between the MODIS-NDVI and the common logarithm (LOG10) of the AGGB was significant (r2 = 0.51, P < 0.001), it was, there-fore, used to calculate the maximum carrying capacity in sheep-unit year per hectare. The maximum livestock carrying capacity was then adjusted to the theoretical livestock carrying capacity by the reduction factors (slope, distance to water, and soil erosion). Results indicated that the grassland conditions became worse, with lower aboveground palatable grass yield, plant height, and cover compared with the results obtained in 1981. At the same time, although the actual livestock numbers decreased, they still exceeded the proper theoretical livestock carrying capacity, and overgrazing rates ranged from 27.27% in Darlag County to 293.99% in Baima County. Integrating remote sensing and geographical information system technologies, the spatial and temporal conditions of the alpine grassland, trend, and projected stocking rates could be forecasted for decision making.展开更多
Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau （QTP） in China. However, it is lacking of studies on the effects of warming and...Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau （QTP） in China. However, it is lacking of studies on the effects of warming and grazing on plant and soil properties in these alpine ecosystems. In this study, we reported the related research from manipulative experiment in 2010-2012 in the QTP. The aim of this study was to investigate the individual and combined effects of warming and clipping on plant and soil properties in the alpine meadow ecosystem. Infrared radiators were used to simulate climate warming starting in July 2010, while clipping was performed once in Octo- ber 2011 to simulate the local livestock grazing. The experiment was designed as a randomized block consisting of five replications and four treatments： control （CK）, warming （W）, clipping （C） and warming＋clipping combination （WC）. The plant and soil properties were investigated in the growing season of the alpine meadow in 2012. The results showed that W and WC treatments significantly decreased relative humidity at 20-cm height above ground as well as significantly increases air temperature at the same height, surface temperature, and soil temperature at the depth of 0-30 cm. However, the C treatment did not significantly decrease soil moisture and soil temperature at the depth of 0-60 cm. Relative to CK, vegetation height and species number increased significantly in W and WC treatment, respectively, while vegetation aboveground biomass decreased significantly in C treatment in the early growing season. However, vegetation cover, species diversity, belowground biomass and soil properties at the depth of 0-30 cm did not differ significantly in W, C and WC treatments. Soil moisture increased at the depth of 40-100 cm in W and WC treatments, while belowground biomass, soil activated carbon, organic carbon and total nitrogen increased in the 30-50 cm soil layer in W, C and WC treatments. Although the initial responses of plant and soil properties to experimental warming and clipping were slow and weak, the drought induced by the down- ward shift of soil moisture in the upper soil layers may induce plant belowground biomass to transfer to the deeper soil layers. This movement would modify the distributions of soil activated carbon, organic carbon and total nitrogen However, long-term data collection is needed to further explain this interesting phenomenon.展开更多
St udying the changes in nutrient use strategies induced by grazing can provide insight into the process of grassland degradation and is important for improving grassland quality and enhancing ecosystem function. Domi...St udying the changes in nutrient use strategies induced by grazing can provide insight into the process of grassland degradation and is important for improving grassland quality and enhancing ecosystem function. Dominant species in meadow steppe can optimize their use of limiting resources; however, the regulation of nutrient use strategies across grazing gradients is not fully understood. Therefore, in this study, we report an in situ study in which the impact of grazing rates on nutrient use strategies of Leymus chinensis, the dominant plant species in eastern Eurasian temperate steppes, was investigated. We conducted a large randomized controlled experiment（conducted continuously for five years in grassland plots in a natural pasture in Ha ilar, eastern Mongolia Plateau, China） to assess the effects of grazing rate treatments（0.00, 0.23, 0.34, 0.46, 0.69, and 0.92 adult cattle unit（AU） ha-1） on L. chinensis along a grazing gradient and employed a random sampling approach to compare the accumulation, allocation, and stoichiometry of C, N, and P in leaves and stems. Ou r findings demonstrated the follows：（i） The height of L. chinensis decreased with an increase in the grazing gradient, and the concentrations of C, N, and P significantly increased;（ii） the accumulation of C, N, and P per individual was negatively correlated with the concentration of aboveground tissues, suggesting that there was a tradeoff in L. chinensis between nutrient accumulation and concentration at the individual scale;（iii） the leaf-to-stem ratio of C, N, and P accumulation increased with grazing intensity, indicating a tradeoff in nutrient allocation and plant size at the individual plant level; and（iv） grazing rates were negatively correlated with the ratios of C：N and C：P in the stem; however, these ratios in leaves significantly increased with grazing intensity. Our findings suggest that L. chinensis in meadow steppe adapts to grazing disturbance through tradeoffs between plant size and nutrient use strategies. Moreover, our results imply that grazing produces a compensatory effect on nutrient use efficiency between the stems and leaves of L. chinensis.展开更多
Rangelands of Central Asia (referring to Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan in this study), the largest contiguous area of grazed land in the world, serve as an important source of livelih...Rangelands of Central Asia (referring to Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan in this study), the largest contiguous area of grazed land in the world, serve as an important source of livelihood for pastoral and agro-pastoral communities in this region. They also play an important role in absorbing CO<sub>2</sub> as a global carbon sink. However, unsustainable management of rangelands has led to their degradation hugely by downgrading their potential agro-ecological, environmental and socio-economical roles. This paper reviewed the rangeland degradation in Central Asia, a topic which so far has received only scant coverage in the international scientific literature. It also provided examples of successful experiences and outlined possible options that land managers can adopt to enhance the sustainable management of these vast degraded rangelands. The experiences and lessons described in this paper may also be relevant for other degraded rangeland areas, especially in the developing countries. The causes of rangeland degradation within the Central Asian region are numerous, complex and inter-related. Therefore, while addressing the factors associated with improper rangeland management may shed some light on the causes of rangeland degradation, the scope of this paper would not be all-encompassing for the major causes of degradation. There is a need to develop and widely apply the viable and locally accepted and adapted packages of technical, institutional and policy options for sustainable rangeland management. Incentivizing the collective action of small-scale pastoralists who group together to facilitate access to remote pastures can reduce the degree of overgrazing within community pastures, such as those near the settlements. We also found that migratory grazing through pooling of resources among small-scale pastoralists can increase household income. After their independence, most Central Asian countries adopted various rangeland tenure arrangements. However, the building of enhanced capacities of pasture management and effective local rangeland governance structures can increase the likelihood, which will be sustainable and equitable. Finally, this paper presented several promising technical options, aiming at reversing the trend of rangeland degradation in Central Asia.展开更多
Horqin Sandy Land is a fragile, seriously desertified region located in Inner Mongolia of China. Over- grazing is one of the primary drivers of desertification in this region. We investigated whether the establishment...Horqin Sandy Land is a fragile, seriously desertified region located in Inner Mongolia of China. Over- grazing is one of the primary drivers of desertification in this region. We investigated whether the establishment of grazing exclosures in areas with active sand dunes enhances soil carbon （C） sequestration and benefits soil re- covery. The results showed that soil organic C storage was 1.4, 1.9, and 3.5 times, and light fraction C storage was 2.3, 3.2, and 4.4 times in the 100-cm topsoil after 7, 12, and 25 years of grazing exclusion, respectively, compared to the case in active sand dunes. The light fraction of soil played an important role in soil C sequestration, although it might not change rapidly to provide an early indication of how soil C is increasing in response to grazing exclusion. The results indicated that soils could potentially sequester up to 13.8 Mt C in 25 years if active sand dunes in the study area were to be protected by exclosures. This corresponds to 12.8% of the estimated carbon loss （107.53 Mt） that has been associated with desertification over the past century in the Horqin Sandy Land. Our results suggested that exclosures have the capacity to increase soil C sequestration; however, decades will be required for soil C to recover to historical grassland levels observed prior to desertification.展开更多
We undertook ethnobotanical study of forage/fodder plant species used by the Afar and Oromo （Kereyu and lttu） Nations in and around the semi=arid Awash National Park （ANP）, Ethiopia. The study aimed at investigati...We undertook ethnobotanical study of forage/fodder plant species used by the Afar and Oromo （Kereyu and lttu） Nations in and around the semi=arid Awash National Park （ANP）, Ethiopia. The study aimed at investigating and documenting indigenous knowledge （IK） on forage/fodder plant species and threats to their survival. Ninety-six in= formants between 20 and 80 years old were selected using prior informa- tion. Data were collected using semi-structured interview, guided field wail discussion and field observation. Preference ranking, Jaccard＇s coefficient of similarity and priority ranking were used for data analysis. One hundred twenty-six forage/fodder species of 90 genera and 43 fami- lies were collected in the study area. More than 88% of the species were reported with their vernacular names, where 68% were reported by the Afar Nation and 70% by the Oromo Nation. Family Poaceae was repre- sented by 25 species （20%）, followed by Fabaceae 18 （14%）. Preference ranking for the most preferred forage grasses as perceived by key informants revealed that Chrysopogon plumulosus was the most important forage/fodder species. Overgrazing was the major threat in the study area, scoring 22%.展开更多
In the study area located in Western Kenya near the Lake Victoria, severe soil erosion occurred and it thought to relate to vegetation degradation caused by overgrazing. The livestock density estimated by analyzing sa...In the study area located in Western Kenya near the Lake Victoria, severe soil erosion occurred and it thought to relate to vegetation degradation caused by overgrazing. The livestock density estimated by analyzing satellite image (1.39 TLU/ha for available grazing lands) was lower than that of measured for seven farmers’ grazing lands using GPSs (4.41 TLU/ha, 2011) with variation from 0.83 to 12.36 TLU/ha. Thus, it is clear that the grasslands used by farmers are limited compared with the area of estimated available land for grazing identified by analyzing the satellite image. According to growth-consumption rate model that was developed by the Nyangito et al. (2008) in southeastern Kenya, if livestock density reaches over 7 TLU/ha, pasture growth rate became lower than consumption rate. Grass biomasses of the grazing lands were kept low (less than 50 g/50 × 50 cm2) under high livestock density (three farmers out of seven were higher than 7 TLU/ha). In addition, rainfall pattern is very unstable and we observed stunted growth of grasses during dry spells. Therefore, we concluded that overgrazing. It means that inhibition of continuous re-growth of grasses due to high grazing pressure has been occurred even for small area and contributed to the soil erosion.展开更多
Sahel of Africa is one of the most seriously desertified regions in the world. It becomes notorious owing to severe drought anddesertification occurred during 1968-1973 in the region. This paperdiscusses the causes an...Sahel of Africa is one of the most seriously desertified regions in the world. It becomes notorious owing to severe drought anddesertification occurred during 1968-1973 in the region. This paperdiscusses the causes and essence of desertification in Sahel. Firstiy, thechanges of social and economic conditions in West Africa and theirinfluence on desertification are analysized. Then the pattem ofdesertification is described, and the causes and essence are interpreted.Finally, the author proposes some measures for prevation and control of desertification in the area.展开更多
One of the species candidates to rehabilitate arid rangelands of Morocco is Artemisia herba-alba Asso. （white Wormwood）. Unfortunately, overgrazing is by far the most important factor causing the reduction of cover ...One of the species candidates to rehabilitate arid rangelands of Morocco is Artemisia herba-alba Asso. （white Wormwood）. Unfortunately, overgrazing is by far the most important factor causing the reduction of cover and disappearance of this plant. In order to assess the effect of season and grazing on the recovery ofA. herba-alba Asso., plants of similar size were collected from Gourrama region and transplanted in the Experimental Station of Errachidia. These plants were submitted to different clipping heights （Cl = 8 cm, C2 = 15 cm, C3 = 25 cm） during two growing periods： autumn （stage of seed filling） and spring （before the starting of flowering）. Mean results show highly significant （P 〈 0.01） differences between the three treatments during the two periods. The increase of the plant volume clipped influences the performances of production and regrowth, the study has shown that the cutting level C 1 affect negatively the Artemisia performances, in fact 60% of plants cut at this height have died after the second clipping against 25% for C2 and 4.2% for C3. The parameters of growth and modular dynamic of branches are also affected by the cutting height C 1. The phytomass produced after the first cutting results in highly significant differences （P 〈 0.0 l） between the three cutting heights. Finally, the study demonstrated that for better regrowth, the taller height C3 is the most convenient for white Wormwood during the two periods, but the cutting height C2 can also be adopted for the autumn period.展开更多
Biodiversity is a multidimensional concept involving several scientific disciplines. The study of biodiversity allows to initiate a multidisciplinary analysis and ecological reading of an environmental problem. The ob...Biodiversity is a multidimensional concept involving several scientific disciplines. The study of biodiversity allows to initiate a multidisciplinary analysis and ecological reading of an environmental problem. The objective of this study is the knowledge of plant biodiversity and risk factors affecting the plant diversity in forest formations of Saida province （Algeria）. Plant biodiversity is estimated at 77 species with 37 best represented families （Asteraceae, Lamiaceae and Fabaceae）. The geophytes dominate with a rate of 44.15%. Among the degradation factors that threaten the biodiversity in the study area, the forest fires, overgrazing and trampling by domestic animals was mentioned.展开更多
As a result of overgrazing and deforestation in the mid-1950s, along with the advent of global warming, China is now affected by deforestation as it is impacting 400 million people. Researchers estimate that this scou...As a result of overgrazing and deforestation in the mid-1950s, along with the advent of global warming, China is now affected by deforestation as it is impacting 400 million people. Researchers estimate that this scourge costs the Chinese Government 213 billion yuan ($31 billion) a year. However, China is also the first nation to see the vast swathes of its desert lands decline by more than 2,400 square km a year.Achieving this impressive feat is in large part due to the Kubuqi model of desertification control. The Kubuqi Desert of "Yellow Peril," as it is colloquially called, is located in the Hanggin Banner of Ordos City, the Inner Mongolia Autonomous Region in north China, covering an area of 18,600 square km. This makes it the seventh largest desert in China. Yet despite the often negative connotations of arid lands, today's Kubuqi is a symbol of life, development and hope.展开更多
Background Alveolar echinococcosis is a major zoonosis of public health significance in western China. Overgrazing was recently assumed as a potential risk factor for transmission of alveolar echinococcosis. The resea...Background Alveolar echinococcosis is a major zoonosis of public health significance in western China. Overgrazing was recently assumed as a potential risk factor for transmission of alveolar echinococcosis. The research was designed to further test the overgrazing hypothesis by investigating how overgrazing influenced the burrow density of intermediate host small mammals and how the burrow density of small mammals was associated with dog Echinococcus multilocularis infection. Methods The study sites were chosen by previous studies which found areas where the alveolar echinococcosis was prevalent. The data, including grass height, burrow density of intermediate host small mammals, dog and fox fecal samples as well as Global Positioning System （GPS） position, were collected from field investigations in Shiqu County, Sichuan Province, China. The fecal samples were analyzed using copro-PCR. The worms, teeth, bones and hairs in the fecal samples were visually examined. Single factor and multifactor analyses tools including chi square and generalized linear models were applied to these data. Results By using grass height as a proxy of grazing grass in the pasture led to lower small mammals＇ pressure in the homogenous pasture, this study found that taller burrow density （X2=4.670, P=0.031, coefficient=-1.570）. The Echinococcus multilocularis worm burden in dogs was statistically significantly related to the maximum density of the intermediate host Ochotona spp. （X2=5.250, P=-0.022, coefficient=0.028）. The prevalence in owned dogs was positively correlated to the number of stray dogs seen within a 200 meter radius （Wald X2=8.375, P=-0.004, odds ratio=1.198）. Conclusions Our findings support the hypothesis that overgrazing promotes transmission of alveolar echinococcosis and confirm the role of stray dogs in the transmission of alveolar echinococcosis.展开更多
Changing environmental and socio-economic conditions make land degradation,a major concern in Central and East Asia.Globally satellite imagery,particularly Normalized Difference Vegetation Index(NDVI)data,has proved a...Changing environmental and socio-economic conditions make land degradation,a major concern in Central and East Asia.Globally satellite imagery,particularly Normalized Difference Vegetation Index(NDVI)data,has proved an effective tool for monitoring land cover change.This study examines 33 grassland water points using vegetation field studies and remote sensing techniques to track desertification on the Mongolian plateau.Findings established a significant correlation between same-year field observation(line transects)and NDVI data,enabling an historical land cover perspective to be developed from 1998 to 2006.Results show variable land cover patterns in Mongolia with a 16%decrease in plant density over the time period.Decline in cover identified by NDVI suggests degradation;however,continued annual fluctuation indicates desertificationirreversible land cover changehas not occurred.Further,in situ data documenting greater cover near water points implies livestock overgrazing is not causing degradation at water sources.In combination of the two research methodsremote sensing and field surveysstrengthen findings and provide an effective way to track desertification in dryland regions.展开更多
Degradation of meadow ecosystems in the largest alpine region of the world,i.e.,the Qinghai-Tibetan Plateau(QTP),is a crucial ecological issue that has ardently discussed in recent years.Many factors,such as livestock...Degradation of meadow ecosystems in the largest alpine region of the world,i.e.,the Qinghai-Tibetan Plateau(QTP),is a crucial ecological issue that has ardently discussed in recent years.Many factors,such as livestock overgrazing,climate change and overpopulation of small mammals are treated as important factors that cause the degradation of meadow ecosystems in the QTP.However,there are few hypotheses focus on the potential role of plant compensatory growth on meadow degradation.We proposed a compensatory growth-related hypothesis to understand the potential degradation process of meadow ecosystems in the QTP.We discussed that there are two stages of meadow degradation,i.e.the beginning stage of meadow degradation that is triggered by high-strength overcompensation;and the intensification stage of meadow degradation,which are driven by external factors such as climate warming,small mammals and thawing of permafrost.The mechanism of meadow degradation driven by plant compensatory growth is the asynchronism of plant consumption and the availability of soil nutrients.Our hypothesis that plant compensatory growth drives meadow degradation under the overgrazing condition requires re-examination and modification by testing the balance between soil nutrient cycling rates and the strength of plant compensatory growth in alpine regions.展开更多
The main grassland plain of Nech Sar National Park(NSNP)is a federally managed protected area in Ethiopia designated to protect endemic and endangered species.However,like other national parks in Ethiopia,the park has...The main grassland plain of Nech Sar National Park(NSNP)is a federally managed protected area in Ethiopia designated to protect endemic and endangered species.However,like other national parks in Ethiopia,the park has experienced significant land cover change over the past few decades.Indeed,the livelihoods of local populations in such developing countries are entirely dependent upon natural resources and,as a result,both direct and indirect anthropogenic pressures have been placed on natural parks.While previous research has looked at land cover change in the region,these studies have not been spatially explicit and,as a result,knowledge gaps in identifying systematic transitions continue to exist.This study seeks to quantify the spatial extent and land cover change trends in NSNP,identify the strong signal transitions,and identify and quantify the location of determinants of change.To this end,the author classifies panchromatic aerial photographs in 1986,multispectral SPOT imagery in 2005,and Sentinel imagery in 2019.The spatial extent and trends of land cover change analysis between these time periods were conducted.The strong signal transitions were systematically identified and quantified.Then,the basic driving forces of the change were identified.The locations of these transitions were also identified and quantified using the spatially explicit statistical model.The analysis revealed that over the past three decades(1986–2019),nearly 52%of the study area experienced clear landscape change,out of which the net change and swap change attributed to 39%and 13%,respectively.The conversion of woody vegetation to grassland(~5%),subsequently grassland-to-open-overgrazed land(28.26%),and restoration of woody vegetation(0.76%)and grassland(0.72%)from riverine forest and open-overgrazed land,respectively,were found to be the fully systematic transitions whereas the rest transitions were recorded either partly systematic or random transitions.The location of these most systematic land cover transitions identified through the spatially explicit statistical modeling showed drivers due to biophysical conditions,accessibility,and urban/market expansions,coupled with successive government policies for biodiversity management,geo-politics,demographic,and socioeconomic factors.These findings provide important insights into biodiversity loss,land degradation,and ecosystem disruption.Therefore,the model for predicted probability generally suggests a 0.75 km and 0.72 km buffers which are likely to protect forest and grassland from conversion to grassland and open-overgrazed land,respectively.展开更多
基金The Chinese National Non-profit Program for Environment Protection,No.201109030
文摘The Three-River Headwaters region in China is an ecological barrier providing en- vironmental protection and regional sustainable development for the mid-stream and down- stream areas, which also plays an important role in animal husbandry in China. This study estimated the grassland yield in the Three-River Headwaters region based on MODIS NPP data, and calculated the proper livestock-carrying capacity of the grassland. We analyzed the overgrazing number and its spatial distribution characteristics through data comparison be- tween actual and proper livestock-carrying capacity. The results showed the following： （1） total grassland yield （hay） in the Three-River Headwaters region was 10.96 million tons in 2010 with an average grassland yield of 465.70 kg/hm2 （the spatial distribution presents a decreasing trend from the east and southeast to the west and northwest in turn）; （2） the proper livestock-carrying capacity in the Three-River Headwaters region is 12.19 million sheep units （hereafter described as ＂SU＂）, and the average stocking capacity is 51.27 SU [the proper carrying capacity is above 100 SU/km2 in the eastern counties, 60 SU/km2 in the cen- tral counties （except Madoi County）, and 30 SU/km2 in the western counties]; and （3） total overgrazing number was 6.52 million SU in the Three-River Headwaters region in 2010, with an average overgrazing ratio of 67.88% and an average overgrazing number of 27.43 SU/km2 A higher overgrazing ratio occurred in Tongde, Xinghai, Yushu, Henan and Z^kog. There was no overgrazing in Zhiduo, Tanggula Township and Darlag, Qumerleb and Madoi. The re- mainder of the counties had varying degrees of overgrazing.
文摘The soil constituents and relations between the variation of soil resources and plant communities in three adjacent sites representing the overgrazing, reclamation and comparatively undisturbed communities respectively were quantified and examined in study area in Huailai Basin, Hebei Province, China. There have been significantly greater constituent of C, N, P in the soils of shrubland site. Corg, Ntotal, Navail and Pavail were between 1.18 and 3.90 times more concentrated in the soils of shrubland site in comparison with the other two sites. Although the Ptotal concentration was lower in shrubland soils than in overgrazed rangeland soils, the Pavail concentration, however, was significantly greater in the soils of shrubland site, and increased by 59.1% and even 289.6% in the soils of shrubland site comparing to those in the soils of range-land and millet field sites. Among the three sites, CV exceeding 40% were found for SO4, Cl, and F ion. The CV of organic carbon also exceeded 40% but only in the soils of millet field site. The highest CV were found for F, SO4 ion in the soils of shrubland and overgrazed rangeland sites, while for Cl and SO4 ion in those of millet field site. The results also showed that the introductions of shrubs are of vital importance for the accumulation of soil nutrients and maintenance of soil fertilities, and also for the restoration and reconstruction of desertified ecosystems.
文摘ALASHAN AND ORDOS,Inner Mongolia-Dust,five centimeters thick, and rat holes cover the landscape of the Shilekai village,about 300 kilometers from the city of Ordos, Inner Mongolia.
基金the Health Department of Sichuan Province the Ecology of Infectious Diseases Program from USA National Institutes of Health (No. 1565)the French Embassy in Beijing
文摘Background Overgrazing was assumed to increase the population density of small mammals that are the intermediate hosts of Echinococcus multilocularis, the pathogen of alveolar echinococcosis in the Qinghai Tibet Plateau. This research tested the hypothesis that overgrazing might promote Echinococcus multilocularis transmission through increasing populations of small mammal, intermediate hosts in Tibetan pastoral communities. Methods Grazing practices, small mammal indices and dog Echinococcus multilocularis infection data were collected to analyze the relation between overgrazing and Echinococcus multilocularis transmission using nonparametric tests and multiple stepwise logistic regression. Results In the investigated area, raising livestock was a key industry. The communal pastures existed and the available forage was deficient for grazing. Open （common） pastures were overgrazed and had higher burrow density of small mammals compared with neighboring fenced （private） pastures; this high overgrazing pressure on the open pastures measured by neighboring fenced area led to higher burrow density of small mammals in open pastures. The median burrow density of small mammals in open pastures was independently associated with nearby canine Echinococcus multilocularis infection （P=-0.003, OR=1.048）. Conclusion Overgrazing may promote the transmission of Echinococcus multilocularis through increasing the population density of small mammals.
基金Resources for this study were obtained from INTA Projects.
文摘Semiarid Patagonia represents 25%of the rangeland area in Argentina,and sheep overgrazing has degraded about a third of it in the past.In this century,depleted domestic stocks have mostly stabilized,but Guanaco populations have grown.These native camelids share habitat and diets with sheep,but their effect on vegetation is poorly understood and has long been debated.We set up an exclusion experiment in Monte León and Cañadón Vaca,a semiarid shrubland grassland in southern Patagonia,currently grazed only by guanacos.Vegetation baselines were studied in 2016 in twelve plots,and half of them were protected from guanaco grazing.Thirty-six plots were cleared to study revegetation.Vegetation was reassessed in 2021,and changes were evaluated using a paired t-test.Within protected plots,vegetation cover increased,bare soil diminished,and vegetated patches grew in size,but the density of the patch-interpatch arrangement did not change.Biodiversity,measured by richness and the Shan-non-Wiener(SW)index,grew significantly.Nutrient recycling increased,as did the Stability and Infiltration Land Function indexes,although these last differences were not significant.Vegetation cover under guanaco grazing also increased,mainly due to the growth of dwarf shrubs,a typical tendency in sheep grazing-induced transitions in the region.Vegetated patches under grazing fragmented,resulting in smaller patches and denser patch struc-tures,while diversity and land function indexes remained unchanged.Young plants established in cleared plots without guanacos showed higher cover density and individual size.These effects are similar to those observed in numerous experimental sheep exclosures.Guanaco grazing may thus prevent restoration and contribute to the generalized land degradation processes that overgrazing has been causing in Patagonia for over a century.
基金Supported by the National Basic Research Program (973 Program) of China (Nos.2009CB421102 and 2005CB422005-01)the Second Scheme of CAS Action Plan for the Development of Western China (No.KZCX2-XB2-06-02)the National Key Technology R&D Program of China (No.2006BAC01A02-01)
文摘Remote sensing data from the Terra Moderate-Resolution Imaging Spectroradiometer (MODIS) and geospatial data were used to estimate grass yield and livestock carrying capacity in the Tibetan Autonomous Prefecture of Golog, Qing-hai, China. The MODIS-derived normalized difference vegetation index (MODIS-NDVI) data were correlated with the aboveground green biomass (AGGB) data from the aboveground harvest method. Regional regression model between the MODIS-NDVI and the common logarithm (LOG10) of the AGGB was significant (r2 = 0.51, P < 0.001), it was, there-fore, used to calculate the maximum carrying capacity in sheep-unit year per hectare. The maximum livestock carrying capacity was then adjusted to the theoretical livestock carrying capacity by the reduction factors (slope, distance to water, and soil erosion). Results indicated that the grassland conditions became worse, with lower aboveground palatable grass yield, plant height, and cover compared with the results obtained in 1981. At the same time, although the actual livestock numbers decreased, they still exceeded the proper theoretical livestock carrying capacity, and overgrazing rates ranged from 27.27% in Darlag County to 293.99% in Baima County. Integrating remote sensing and geographical information system technologies, the spatial and temporal conditions of the alpine grassland, trend, and projected stocking rates could be forecasted for decision making.
基金financially supported by the Hundred Talent Program of Chinese Academy of Sciences and the National Natural Science Foundation of China (41301211, 41201195)
文摘Climate warming and livestock grazing are known to have great influences on alpine ecosystems like those of the Qinghai-Tibetan Plateau （QTP） in China. However, it is lacking of studies on the effects of warming and grazing on plant and soil properties in these alpine ecosystems. In this study, we reported the related research from manipulative experiment in 2010-2012 in the QTP. The aim of this study was to investigate the individual and combined effects of warming and clipping on plant and soil properties in the alpine meadow ecosystem. Infrared radiators were used to simulate climate warming starting in July 2010, while clipping was performed once in Octo- ber 2011 to simulate the local livestock grazing. The experiment was designed as a randomized block consisting of five replications and four treatments： control （CK）, warming （W）, clipping （C） and warming＋clipping combination （WC）. The plant and soil properties were investigated in the growing season of the alpine meadow in 2012. The results showed that W and WC treatments significantly decreased relative humidity at 20-cm height above ground as well as significantly increases air temperature at the same height, surface temperature, and soil temperature at the depth of 0-30 cm. However, the C treatment did not significantly decrease soil moisture and soil temperature at the depth of 0-60 cm. Relative to CK, vegetation height and species number increased significantly in W and WC treatment, respectively, while vegetation aboveground biomass decreased significantly in C treatment in the early growing season. However, vegetation cover, species diversity, belowground biomass and soil properties at the depth of 0-30 cm did not differ significantly in W, C and WC treatments. Soil moisture increased at the depth of 40-100 cm in W and WC treatments, while belowground biomass, soil activated carbon, organic carbon and total nitrogen increased in the 30-50 cm soil layer in W, C and WC treatments. Although the initial responses of plant and soil properties to experimental warming and clipping were slow and weak, the drought induced by the down- ward shift of soil moisture in the upper soil layers may induce plant belowground biomass to transfer to the deeper soil layers. This movement would modify the distributions of soil activated carbon, organic carbon and total nitrogen However, long-term data collection is needed to further explain this interesting phenomenon.
基金supported by the National Basic Research Program of China (2014CB138806)the International Science and Technology Cooperation Project of China (2013DFR30760)+1 种基金the Natural Science Foundation Committee of Inner Mongolia, China (ZD201502)the Basic Research Funding Project of Institute of Grassland Research, Chinese Academy of Agricultural Sciences (1610332015005)
文摘St udying the changes in nutrient use strategies induced by grazing can provide insight into the process of grassland degradation and is important for improving grassland quality and enhancing ecosystem function. Dominant species in meadow steppe can optimize their use of limiting resources; however, the regulation of nutrient use strategies across grazing gradients is not fully understood. Therefore, in this study, we report an in situ study in which the impact of grazing rates on nutrient use strategies of Leymus chinensis, the dominant plant species in eastern Eurasian temperate steppes, was investigated. We conducted a large randomized controlled experiment（conducted continuously for five years in grassland plots in a natural pasture in Ha ilar, eastern Mongolia Plateau, China） to assess the effects of grazing rate treatments（0.00, 0.23, 0.34, 0.46, 0.69, and 0.92 adult cattle unit（AU） ha-1） on L. chinensis along a grazing gradient and employed a random sampling approach to compare the accumulation, allocation, and stoichiometry of C, N, and P in leaves and stems. Ou r findings demonstrated the follows：（i） The height of L. chinensis decreased with an increase in the grazing gradient, and the concentrations of C, N, and P significantly increased;（ii） the accumulation of C, N, and P per individual was negatively correlated with the concentration of aboveground tissues, suggesting that there was a tradeoff in L. chinensis between nutrient accumulation and concentration at the individual scale;（iii） the leaf-to-stem ratio of C, N, and P accumulation increased with grazing intensity, indicating a tradeoff in nutrient allocation and plant size at the individual plant level; and（iv） grazing rates were negatively correlated with the ratios of C：N and C：P in the stem; however, these ratios in leaves significantly increased with grazing intensity. Our findings suggest that L. chinensis in meadow steppe adapts to grazing disturbance through tradeoffs between plant size and nutrient use strategies. Moreover, our results imply that grazing produces a compensatory effect on nutrient use efficiency between the stems and leaves of L. chinensis.
基金the Asian Development Bank,the International Center for Agricultural Research in the Dry Areas,Russian Scientific Fund(14-38-00023)the CGIAR Research Program on Dryland Systems for their support and funding
文摘Rangelands of Central Asia (referring to Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan in this study), the largest contiguous area of grazed land in the world, serve as an important source of livelihood for pastoral and agro-pastoral communities in this region. They also play an important role in absorbing CO<sub>2</sub> as a global carbon sink. However, unsustainable management of rangelands has led to their degradation hugely by downgrading their potential agro-ecological, environmental and socio-economical roles. This paper reviewed the rangeland degradation in Central Asia, a topic which so far has received only scant coverage in the international scientific literature. It also provided examples of successful experiences and outlined possible options that land managers can adopt to enhance the sustainable management of these vast degraded rangelands. The experiences and lessons described in this paper may also be relevant for other degraded rangeland areas, especially in the developing countries. The causes of rangeland degradation within the Central Asian region are numerous, complex and inter-related. Therefore, while addressing the factors associated with improper rangeland management may shed some light on the causes of rangeland degradation, the scope of this paper would not be all-encompassing for the major causes of degradation. There is a need to develop and widely apply the viable and locally accepted and adapted packages of technical, institutional and policy options for sustainable rangeland management. Incentivizing the collective action of small-scale pastoralists who group together to facilitate access to remote pastures can reduce the degree of overgrazing within community pastures, such as those near the settlements. We also found that migratory grazing through pooling of resources among small-scale pastoralists can increase household income. After their independence, most Central Asian countries adopted various rangeland tenure arrangements. However, the building of enhanced capacities of pasture management and effective local rangeland governance structures can increase the likelihood, which will be sustainable and equitable. Finally, this paper presented several promising technical options, aiming at reversing the trend of rangeland degradation in Central Asia.
基金supported by the National Natural Science Foundation of China(4090104931060060)+1 种基金the Major State Basic Research Development Program of China(2009CB 421303)the 'Qing Lan' Talent Engineering Funds of Lanzhou Jiaotong University(QL-08-14A)
文摘Horqin Sandy Land is a fragile, seriously desertified region located in Inner Mongolia of China. Over- grazing is one of the primary drivers of desertification in this region. We investigated whether the establishment of grazing exclosures in areas with active sand dunes enhances soil carbon （C） sequestration and benefits soil re- covery. The results showed that soil organic C storage was 1.4, 1.9, and 3.5 times, and light fraction C storage was 2.3, 3.2, and 4.4 times in the 100-cm topsoil after 7, 12, and 25 years of grazing exclusion, respectively, compared to the case in active sand dunes. The light fraction of soil played an important role in soil C sequestration, although it might not change rapidly to provide an early indication of how soil C is increasing in response to grazing exclusion. The results indicated that soils could potentially sequester up to 13.8 Mt C in 25 years if active sand dunes in the study area were to be protected by exclosures. This corresponds to 12.8% of the estimated carbon loss （107.53 Mt） that has been associated with desertification over the past century in the Horqin Sandy Land. Our results suggested that exclosures have the capacity to increase soil C sequestration; however, decades will be required for soil C to recover to historical grassland levels observed prior to desertification.
文摘We undertook ethnobotanical study of forage/fodder plant species used by the Afar and Oromo （Kereyu and lttu） Nations in and around the semi=arid Awash National Park （ANP）, Ethiopia. The study aimed at investigating and documenting indigenous knowledge （IK） on forage/fodder plant species and threats to their survival. Ninety-six in= formants between 20 and 80 years old were selected using prior informa- tion. Data were collected using semi-structured interview, guided field wail discussion and field observation. Preference ranking, Jaccard＇s coefficient of similarity and priority ranking were used for data analysis. One hundred twenty-six forage/fodder species of 90 genera and 43 fami- lies were collected in the study area. More than 88% of the species were reported with their vernacular names, where 68% were reported by the Afar Nation and 70% by the Oromo Nation. Family Poaceae was repre- sented by 25 species （20%）, followed by Fabaceae 18 （14%）. Preference ranking for the most preferred forage grasses as perceived by key informants revealed that Chrysopogon plumulosus was the most important forage/fodder species. Overgrazing was the major threat in the study area, scoring 22%.
文摘In the study area located in Western Kenya near the Lake Victoria, severe soil erosion occurred and it thought to relate to vegetation degradation caused by overgrazing. The livestock density estimated by analyzing satellite image (1.39 TLU/ha for available grazing lands) was lower than that of measured for seven farmers’ grazing lands using GPSs (4.41 TLU/ha, 2011) with variation from 0.83 to 12.36 TLU/ha. Thus, it is clear that the grasslands used by farmers are limited compared with the area of estimated available land for grazing identified by analyzing the satellite image. According to growth-consumption rate model that was developed by the Nyangito et al. (2008) in southeastern Kenya, if livestock density reaches over 7 TLU/ha, pasture growth rate became lower than consumption rate. Grass biomasses of the grazing lands were kept low (less than 50 g/50 × 50 cm2) under high livestock density (three farmers out of seven were higher than 7 TLU/ha). In addition, rainfall pattern is very unstable and we observed stunted growth of grasses during dry spells. Therefore, we concluded that overgrazing. It means that inhibition of continuous re-growth of grasses due to high grazing pressure has been occurred even for small area and contributed to the soil erosion.
文摘Sahel of Africa is one of the most seriously desertified regions in the world. It becomes notorious owing to severe drought anddesertification occurred during 1968-1973 in the region. This paperdiscusses the causes and essence of desertification in Sahel. Firstiy, thechanges of social and economic conditions in West Africa and theirinfluence on desertification are analysized. Then the pattem ofdesertification is described, and the causes and essence are interpreted.Finally, the author proposes some measures for prevation and control of desertification in the area.
文摘One of the species candidates to rehabilitate arid rangelands of Morocco is Artemisia herba-alba Asso. （white Wormwood）. Unfortunately, overgrazing is by far the most important factor causing the reduction of cover and disappearance of this plant. In order to assess the effect of season and grazing on the recovery ofA. herba-alba Asso., plants of similar size were collected from Gourrama region and transplanted in the Experimental Station of Errachidia. These plants were submitted to different clipping heights （Cl = 8 cm, C2 = 15 cm, C3 = 25 cm） during two growing periods： autumn （stage of seed filling） and spring （before the starting of flowering）. Mean results show highly significant （P 〈 0.01） differences between the three treatments during the two periods. The increase of the plant volume clipped influences the performances of production and regrowth, the study has shown that the cutting level C 1 affect negatively the Artemisia performances, in fact 60% of plants cut at this height have died after the second clipping against 25% for C2 and 4.2% for C3. The parameters of growth and modular dynamic of branches are also affected by the cutting height C 1. The phytomass produced after the first cutting results in highly significant differences （P 〈 0.0 l） between the three cutting heights. Finally, the study demonstrated that for better regrowth, the taller height C3 is the most convenient for white Wormwood during the two periods, but the cutting height C2 can also be adopted for the autumn period.
文摘Biodiversity is a multidimensional concept involving several scientific disciplines. The study of biodiversity allows to initiate a multidisciplinary analysis and ecological reading of an environmental problem. The objective of this study is the knowledge of plant biodiversity and risk factors affecting the plant diversity in forest formations of Saida province （Algeria）. Plant biodiversity is estimated at 77 species with 37 best represented families （Asteraceae, Lamiaceae and Fabaceae）. The geophytes dominate with a rate of 44.15%. Among the degradation factors that threaten the biodiversity in the study area, the forest fires, overgrazing and trampling by domestic animals was mentioned.
文摘As a result of overgrazing and deforestation in the mid-1950s, along with the advent of global warming, China is now affected by deforestation as it is impacting 400 million people. Researchers estimate that this scourge costs the Chinese Government 213 billion yuan ($31 billion) a year. However, China is also the first nation to see the vast swathes of its desert lands decline by more than 2,400 square km a year.Achieving this impressive feat is in large part due to the Kubuqi model of desertification control. The Kubuqi Desert of "Yellow Peril," as it is colloquially called, is located in the Hanggin Banner of Ordos City, the Inner Mongolia Autonomous Region in north China, covering an area of 18,600 square km. This makes it the seventh largest desert in China. Yet despite the often negative connotations of arid lands, today's Kubuqi is a symbol of life, development and hope.
文摘Background Alveolar echinococcosis is a major zoonosis of public health significance in western China. Overgrazing was recently assumed as a potential risk factor for transmission of alveolar echinococcosis. The research was designed to further test the overgrazing hypothesis by investigating how overgrazing influenced the burrow density of intermediate host small mammals and how the burrow density of small mammals was associated with dog Echinococcus multilocularis infection. Methods The study sites were chosen by previous studies which found areas where the alveolar echinococcosis was prevalent. The data, including grass height, burrow density of intermediate host small mammals, dog and fox fecal samples as well as Global Positioning System （GPS） position, were collected from field investigations in Shiqu County, Sichuan Province, China. The fecal samples were analyzed using copro-PCR. The worms, teeth, bones and hairs in the fecal samples were visually examined. Single factor and multifactor analyses tools including chi square and generalized linear models were applied to these data. Results By using grass height as a proxy of grazing grass in the pasture led to lower small mammals＇ pressure in the homogenous pasture, this study found that taller burrow density （X2=4.670, P=0.031, coefficient=-1.570）. The Echinococcus multilocularis worm burden in dogs was statistically significantly related to the maximum density of the intermediate host Ochotona spp. （X2=5.250, P=-0.022, coefficient=0.028）. The prevalence in owned dogs was positively correlated to the number of stray dogs seen within a 200 meter radius （Wald X2=8.375, P=-0.004, odds ratio=1.198）. Conclusions Our findings support the hypothesis that overgrazing promotes transmission of alveolar echinococcosis and confirm the role of stray dogs in the transmission of alveolar echinococcosis.
文摘Changing environmental and socio-economic conditions make land degradation,a major concern in Central and East Asia.Globally satellite imagery,particularly Normalized Difference Vegetation Index(NDVI)data,has proved an effective tool for monitoring land cover change.This study examines 33 grassland water points using vegetation field studies and remote sensing techniques to track desertification on the Mongolian plateau.Findings established a significant correlation between same-year field observation(line transects)and NDVI data,enabling an historical land cover perspective to be developed from 1998 to 2006.Results show variable land cover patterns in Mongolia with a 16%decrease in plant density over the time period.Decline in cover identified by NDVI suggests degradation;however,continued annual fluctuation indicates desertificationirreversible land cover changehas not occurred.Further,in situ data documenting greater cover near water points implies livestock overgrazing is not causing degradation at water sources.In combination of the two research methodsremote sensing and field surveysstrengthen findings and provide an effective way to track desertification in dryland regions.
基金This work was supported by the National Natural Science Foundation of China[31901394]the Second Tibetan Plateau Scientific Expedition and Research[2019QZKK0307]Young Elite Scientists Sponsorship Program by CAST[2019QNRC001].
文摘Degradation of meadow ecosystems in the largest alpine region of the world,i.e.,the Qinghai-Tibetan Plateau(QTP),is a crucial ecological issue that has ardently discussed in recent years.Many factors,such as livestock overgrazing,climate change and overpopulation of small mammals are treated as important factors that cause the degradation of meadow ecosystems in the QTP.However,there are few hypotheses focus on the potential role of plant compensatory growth on meadow degradation.We proposed a compensatory growth-related hypothesis to understand the potential degradation process of meadow ecosystems in the QTP.We discussed that there are two stages of meadow degradation,i.e.the beginning stage of meadow degradation that is triggered by high-strength overcompensation;and the intensification stage of meadow degradation,which are driven by external factors such as climate warming,small mammals and thawing of permafrost.The mechanism of meadow degradation driven by plant compensatory growth is the asynchronism of plant consumption and the availability of soil nutrients.Our hypothesis that plant compensatory growth drives meadow degradation under the overgrazing condition requires re-examination and modification by testing the balance between soil nutrient cycling rates and the strength of plant compensatory growth in alpine regions.
文摘The main grassland plain of Nech Sar National Park(NSNP)is a federally managed protected area in Ethiopia designated to protect endemic and endangered species.However,like other national parks in Ethiopia,the park has experienced significant land cover change over the past few decades.Indeed,the livelihoods of local populations in such developing countries are entirely dependent upon natural resources and,as a result,both direct and indirect anthropogenic pressures have been placed on natural parks.While previous research has looked at land cover change in the region,these studies have not been spatially explicit and,as a result,knowledge gaps in identifying systematic transitions continue to exist.This study seeks to quantify the spatial extent and land cover change trends in NSNP,identify the strong signal transitions,and identify and quantify the location of determinants of change.To this end,the author classifies panchromatic aerial photographs in 1986,multispectral SPOT imagery in 2005,and Sentinel imagery in 2019.The spatial extent and trends of land cover change analysis between these time periods were conducted.The strong signal transitions were systematically identified and quantified.Then,the basic driving forces of the change were identified.The locations of these transitions were also identified and quantified using the spatially explicit statistical model.The analysis revealed that over the past three decades(1986–2019),nearly 52%of the study area experienced clear landscape change,out of which the net change and swap change attributed to 39%and 13%,respectively.The conversion of woody vegetation to grassland(~5%),subsequently grassland-to-open-overgrazed land(28.26%),and restoration of woody vegetation(0.76%)and grassland(0.72%)from riverine forest and open-overgrazed land,respectively,were found to be the fully systematic transitions whereas the rest transitions were recorded either partly systematic or random transitions.The location of these most systematic land cover transitions identified through the spatially explicit statistical modeling showed drivers due to biophysical conditions,accessibility,and urban/market expansions,coupled with successive government policies for biodiversity management,geo-politics,demographic,and socioeconomic factors.These findings provide important insights into biodiversity loss,land degradation,and ecosystem disruption.Therefore,the model for predicted probability generally suggests a 0.75 km and 0.72 km buffers which are likely to protect forest and grassland from conversion to grassland and open-overgrazed land,respectively.
