Vegetation traits and soil properties in response to utilization patterns of grassland in Hulun Buir City,Inner Mongolia,China

Numerous studies have focused on vegetation traits and soil properties in grassland, few of which concerned about effects of human utilization patterns on grassland yet. Thus, this study hypothesized that human disturbance （e.g., grazing, mowing and fencing） triggered significant variation of biomass partitioning and carbon reallocation. Besides, there existed some differences of species diversity and soil fertility. To address these hypotheses of grassland with diverse utilization patterns in Hulun Buir City, Inner Mongolia, China, we sampled in situ about aboveground biomass （AGB） and belowground biomass （BGB） to evaluate their biomass allocation. Species diversity and soil properties were also investigated. Subsequently, we discussed the relationship of species diversity with environmental conditions, using data collected from 23 sites during the ecological project period of Returning Grazing Lands to Grasslands （RGLG） program. The results were as follows： 1） both AGB and BGB were lower on grazing regime than those on fencing and mowing, but the ratio of root-to-shoot （R/S） was higher on grazing regime than the other two utilization patterns; 2） neither of evenness and Simpson Index was different significantly among all grassland utilization patterns in desert, typical, and meadow grassland at 0.05. In meadow grassland, species richness of fencing pattern was significantly higher than that of grazing pattern （p 〈 0.05）; 3） both of soil organic carbon content and soil available phosphorous content were increased significantly on fencing pattern than grazing pattern （p 〈 0.05） in desert grassland, and mowing patterns increased the soil nutrients （soil organic carbon, soil total phosphorous, soil available phosphorous, and soil total nitrogen） significantly compared with grazing patterns （p 〈 0.05） in typical grassland. However, there were no significant differences among utilization patterns in meadow grassland. In conclusion, both of AGB and BGB were increased s     

Soil Erosion and Vegetation Succession in Alpine Kobresia Steppe Meadow Caused by Plateau Pika A Case Study of Nagqu County, Tibet

This paper evaluated the impacts of mounds created by the plateau pika (Ochotona curzoniae) on the vege- tation composition, structure, and species diversity of an alpine Kobresia steppe meadow in Nagqu County, Tibet Autonomous Region, China. Based on mound height or the depth of erosion pit, we defined five stages of erosion and compared the floristic features of communities at these stages with those in undisturbed sites. In the study area, the mounds and pits covered up to 7% of the total area. Lancea tibetica, Lamiophlomis rotata, and Potentilla bifurca were the dominant species in erosion pits, and Kobresia pygmaea, the dominant species in undisturbed sites, became a com- panion species in eroded areas. In the process of erosion, the original vegetation was covered by soil ejected by the pika, then the mounds were gradually eroded by wind and rain, and finally erosion pits formed. The vegetation coverage in- creased with increasing erosion stages but remained significantly lower than that in undisturbed sites. Improved coverage eventually reduced soil erosion, and pit depth eventually stabilized at around 20cm. Aboveground biomass increased with increasing erosion stage, but the proportion of low-quality forage reached more than 94%. The richness index and Shannon-Wiener index increased significantly with increasing erosion stage, but the richness index in mound and pit areas was significantly lower than that in undisturbed sites.     

Degradation significantly decreased the ecosystem multifunctionality of three alpine grasslands: evidences from a large-scale survey on the Qinghai-Tibetan Plateau

Owing to the joint effects of ecosystem fragility,anthropogenic disturbance and climate change,alpine grasslands(alpine meadow,alpine steppe and alpine desert)have experienced serious degradation during the past several decades.Grasslands degradation has severely affected the delivery of ecosystem multifunctionality(EMF)and services,and then threatens the livelihood of local herdsmen and ecological security of China.However,we still lack comprehensive insights about the effects of degradation and climatic factors on EMF of alpine grasslands,especially for alpine desert ecosystem.Therefore,we applied a large-scale field investigation to answer this question.Our results suggested grassland degradation significantly decreased the belowground ecosystem multifunctionality(BEMF)and EMF of alpine grasslands and aboveground ecosystem multifunctionality(AEMF)of alpine meadow,while did not reduce the AEMF of alpine steppe and desert.Except for the insignificant difference between degraded steppe and degraded desert in AEMF,the alpine meadow showed the highest AEMF,BEMF and EMF,alpine steppe ranked the second and alpine desert was the lowest.AEMF,BEMF and EMF of health alpine grasslands were strongly affected by mean annual precipitation(MAP)(19%-51%)and mean annual temperature(MAT)(9%-36%),while those of degraded meadow and degraded desert were not impacted by precipitation and temperature.AEMF and BEMF showed a synergistic relationship in healthy alpine grasslands(12%-28%),but not in degraded grasslands.Our findings emphasized the urgency of implementing the feasible ecological restoration project to mitigate the negative influences of grassland degradation on EMF of alpine ecosystems.     

Do mowing regimes affect plant and soil biological activity in the mountain meadows of Southern Poland?

The soil biological activity of mountain meadows is a significant factor that determines the health and utility of these regions. The climax stage of this area is forest, but to maintain semi-natural grassland, which is characterised by high biodiversity,low-intensity land use(mowing or grazing) is necessarily required. To understand the effect of various mowing regimes on the soil biological activity and plants, the soil microbial activity(microbial biomass carbon, dehydrogenase activity and number of the cultivable fraction of soil microbial community),annelids community(density and species composition earthworms and enchytraeids) and plant species composition were investigated. The study area was located in the Pieniny National Park in the Carpathian Mountains, in a meadow belonging to the association Dactylis glomerata-Poa trivialis. The investigated variants were divided according to mowing regime:traditional scything – hand mowing(HM), mechanical mowing(MM), or the abandonment of mowing – nonmowing(NM). The microbial activities(expressed by,e.g. microbial biomass carbon and the number of phosphorus bacteria) were affected by the mowing regime. The density of earthworms was higher in the HM and MM than in the NM variants. The largest changes in plant species composition were caused by the abandonment of mowing(NM). The mean number of plant species was positively correlated with soil moisture, earthworm density, and microbial activity(expressed indirectly by dehydrogenases activity). The soil microbial community, such as vegetative bacteria forms and ammonifying bacteria,were positively associated with pH value, and the microbial and total organic carbon content. The results presented here indicate that there is no single form of optimal management for all living organisms.Decisions about mowing regimes, or abandonment of use, should be preceded by multi-aspect studies,including plants and soil biota.     

Alterations to biological soil crusts with alpine meadow retrogressive succession affect seeds germination of three plant species

Biological soil crusts (BSCs) are the important components of alpine meadow ecosystems. The extent and morphology of BSCs vary greatly with alpine meadow retrogressive succession due to grazing pressure. There is significant interest in impacts of crust composition on plant seed germination, especially in (semi-) arid environments. However, little is known about the influences of BSCs, and their associations with alpine meadow succession, on germination of typical alpine meadow vascular plant species. In a full factorial common-garden experiment, we studied effects of: (1) crust type, (2) seed position, and (3) surface texture on seed germination. We chose three typical alpine meadow plant species (i.e. Poa pratensis, Tibetia himalaica and Potentillen nivea), which belonged to different functional groups (graminoids, legumes, and forbs) and play important roles in all alpine meadow succession stages. Crust type and seed position influenced seed germination, and the inhibitory effects of BSCs depended on the crust type and seed species tested. The major factors influencing seed germination were BSC type, seed position, soil texture, and the interactions between BSC type and seed position; species and seed position; species and surface texture; and species, crust type, and surface texture. Cyanobacteria crust significantly inhibited germination of all seeds. Seed position also had a significant effect on seed germination (p < 0.001). Fewer seedlings germinated on the surface than below the surface, this was especially true for P. nivea. seeds within cyanobacteria and lichen crusts. Only germination rates of T. himalaica on the soil surface were significantly correlated with plant occurrence frequency within the alpine meadow community. The poor correlation for the other two species is possibly that they are perennials. Our results clearly demonstrated that BSCs can be biological filters during seed germination, depending on the BSC succession stage. Through their influences on seed germination, BSCs can strongly influence community assemblages throughout alpine meadow retrogressive succession.     

Pollen-based reconstructions of Holocene vegetation and climatic change of Tibetan Plateau

A synthesis of Holocene pollen records from the Tibetan Plateau shows the history of vegetation and climatic changes during the Holocene. Palynological evidences from 24 cores/sections have been compiled and show that the vegetation shifted from subalpine/alpine conifer forest to subalpine/alpine evergreen sclerophyllous forest in the southeastern part of the plateau; from alpine steppe to alpine desert in the central, western and northern part; and from alpine meadow to alpine steppe in the eastern and southern plateau regions during the Holocene. These records show that increases in precipitation began about 9 ka from the southeast, and a wide ranging level of increased humidity developed over the entire of the plateau around 8-7 ka, followed by aridity from 6 ka and a continuous drying over the plateau after 4-3 ka. The changes in Holocene climates of the plateau can be interpreted qualitatively as a response to orbital forcing and its secondary effects on the Indian Monsoon which expanded northwards     

Mapping the vegetation distribution of the permafrost zone on the Qinghai-Tibet Plateau

In this paper,an updated vegetation map of the permafrost zone in the Qinghai-Tibet Plateau(QTP) was delineated.The vegetation map model was extracted from vegetation sampling with remote sensing(RS) datasets by decision tree method.The spatial resolution of the map is 1 km×1 km,and in it the alpine swamp meadow is firstly distinguished in the high-altitude areas.The results showed that the total vegetated area in the permafrost zone of the QTP is 1,201,751 km~2.In the vegetated region,50,260 km~2 is the areas of alpine swamp meadow,583,909 km~2 for alpine meadow,332,754 km~2 for alpine steppe,and 234,828 km~2 for alpine desert.This updated vegetation map in permafrost zone of QTP could provide more details about the distribution of alpine vegetation types for studying the vegetation mechanisms in the land surface processes of highaltitude areas.     

A Method for Alpine Wetland Delineation and Features of Border: Zoigê Plateau,China

Accurate wetland delineation is the basis of wetland definition and mapping, and is of great importance for wetland management and research. The Zoigê Plateau on the Qinghai-Tibet Plateau was used as a research site for research on alpine wetland delineation. Several studies have analyzed the spatiotemporal pattern and dynamics of these alpine wetlands, but none have addressed the issues of wetland boundaries. The objective of this work was to discriminate the upper boundaries of alpine wetlands by coupling ecological methods and satellite observations. The combination of Landsat 8 images and supervised classification was an effective method for rapid identification of alpine wetlands in the Zoigê Plateau. Wet meadow was relatively stable compared with hydric soils and wetland hydrology and could be used as a primary indicator for discriminating the upper boundaries of alpine wetlands. A slope of less than 4.5° could be used as the threshold value for wetland delineation. The normalized difference vegetation index(NDVI) in 434 field sites showed that a threshold value of 0.3 could distinguish grasslands from emergent marsh and wet meadow in September. The median normalized difference water index(NDWI) of emergent marsh remained more stable than that of wet meadow and grasslands during the period from September until July of the following year. The index of mean density in wet meadow zones was higher than the emergent and upland zones. Over twice the number of species occurred in the wet meadow zone compared with the emergent zone, and close to the value of upland zone. Alpine wetlands in the three reserves in 2014 covered 1175.19 km2 with a classification accuracy of 75.6%. The combination of ecological methods and remote sensing technology will play an important role in wetland delineation at medium and small scales. The correct differentiation between wet meadow and grasslands is the key to improving the accuracy of future wetland delineation.     

三江源区不同退化程度的高寒草甸光谱特征分析

 青海三江源区是长江、黄河、澜沧江3大河流的发源地。草地是该区域的主体生态系统,高寒草甸是其主要类型。近30年来,三江源地区草地发生了大面积的退化,不同退化程度的高寒草甸光谱特征是高寒草甸遥感分类和退化监测的重要依据。2009年8月作者在青海省三江源区对高山嵩草、矮嵩草和藏嵩草3种未退化高寒草甸,以及4种不同退化程度的高山嵩草草甸,进行了地面光谱测量和草地样方调查。同时对实测光谱曲线进行了比较,提取和分析了它们在557nm、675nm和760nm处反射率,以及"红边"斜率。结果表明,3种高寒草甸的光谱曲线,以及4种退化程度高寒草甸和未退化高寒草甸的光谱曲线在557nm处的反射率差异较小,在675nm和760nm处的反射率及"红边"斜率存在明显差异,能有效区分高寒草甸,可为高寒草甸遥感自动分类和退化监测提供依据。不同退化程度的高寒草甸地上生物量与其光谱曲线的"红边"斜率和归一化植被指数(NDVI)线性拟合的确定系数分别为0.93和0.87,其相关性较好,可用于高寒草甸地上生物量的估算。本文提取的光谱反射率的"红边"斜率不仅能有效区分3种典型高寒草甸和不同退化程度的高寒草甸,且与高寒草甸地上生物量的关系优于NDVI,对高寒草甸识别分类,退化监测和生物量估算有重要意义。     

Effects of patch size,disturbances on diversity and structural traits of tropical semi-evergreen forest in the lowland Indo Burma hotspot: implication on conservation of the threatened tree species

Information on geographic distribution, population and threat status of most globally red listed species in the Indo Burma zone are inadequate. Given the increase in the prevalence of isolated forest patches in the part of this hotspot, evaluation is necessary on how size of the remnant forest patches and on-going disturbances affects structure and diversity of remaining habitats including the population of some globally threatened tree species. Quantitative vegetation inventory by 500 m long and 10 m wide (0.5 ha) line transects were randomly set in nine fragmented tropical semi-evergreen forest patches in Tripura, Northeast India. The studied forests patches grouped into small, medium and large based on their respected sizes. Spatial variability was analysed in woody species diversity and structure along the patch size gradients and their response to both patch size and anthropogenic disturbances. Out of 167 species, 13 identified as red-listed species by IUCN under the present inventory. Most of the diversity and structural parameters showed statistically significant positive response with the forest patch size, except for stand dominance, disturbance, sapling density and number of aggregated distribution pattern decreased when patch size increased. In addition, most of the diversity and structural attributes showed negative response with disturbances. Present baseline data would serve as an effective tool for management and protection of this important forest type. Future habitat restoration programme and strategies for relocation of additional population and re-introduction of those globally threatened trees are recommended.     

Distribution of soil carbon in different grassland types of the Qinghai-Tibetan Plateau

Accurate estimate of soil carbon storage is essential to reveal the role of soil in global carbon cycle. However, there is large uncertainty on the estimation of soil organic carbon (SOC) storage in grassland among previous studies, and the study on soil inorganic carbon (SIC) is still lack. We surveyed 153 sites during plant peak growing season and estimated SOC and SIC for temperate desert, temperate steppe, alpine steppe, steppe meadow, alpine meadow and swamp, which covered main grassland in the Qinghai Plateau during 2011 to 2012. The results showed that the vertical and spatial distributions of SOC and SIC varied by grassland types. The SOC amount mainly decreased from southeast to northwest, whereas the SIC amount increased from southeast to northwest. The magnitude of SOC amount in the top 50 cm across grassland types ranked by: swamp > alpine meadow > steppe meadow > temperate steppe > alpine steppe > temperate desert, while the SIC amount showed an opposite order. There was a great deal of variation in proportion of SOC and SIC among different grassland types (from 55.17 to 94.59 for SOC and 5.14 to 44.83 for SIC). The total SOC and SIC storage was 5.78 Pg and 1.37 Pg, respectively, in the top 50 cm of soil in Qinghai Province. The mixed linear model revealed that grassland types was the predominant factor in spatial variations of SOC amount while grassland types and soil pH accounted for those of SIC amount. Our results suggested that the community shift of alpine meadow towards alpine grassland induced by climate warming would decrease carbon sequestration capacity by 6.0 kg C m².     

Clipping Alters the Response of Biomass Production to Experimental Warming: A Case Study in an Alpine Meadow on the Tibetan Plateau,China

Predicting how human activity will influence the response of alpine grasslands to future warming has many uncertainties.In this study, a field experiment with controlled warming and clipping was conducted in an alpine meadow at three elevations(4313 m, 4513 m and 4693 m) in Northern Tibet to test the hypothesis that clipping would alter warming effect on biomass production.Open top chambers(OTCs) were used to increase temperature since July,2008 and the OTCs increased air temperature by approximately 0.9o C ~ 1.8o C during the growing in2012.Clipping was conducted three times one year during growing season and the aboveground parts of all live plants were clipped to approximately 0.01 m in height using scissors since 2009.Gross primary production(GPP) was calculated from the Moderate-Resolution Imaging Spectroradiometer GPP algorithm and aboveground plant production was estimated using the surface-measured normalized difference vegetation index in 2012.Warming decreased the GPP, aboveground biomass(AGB) and aboveground net primary production(ANPP) at all three elevations when clipping was not applied.In contrast, warming increased AGB at all three elevations, GPP at the two lower elevations and ANPP at the two higher elevations when clipping was applied.These findings show that clipping reduced the negative effect of warming on GPP, AGB and ANPP, suggesting that clipping may reduce the effect of climate warming on GPP, AGB and ANPP in alpine meadows on the Tibetan Plateau, and therefore, may be a viable strategy for mitigating the effects of climate change on grazing and animal husbandry on the Tibetan Plateau.     

Response of biomass spatial pattern of alpine vegetation to climate change in permafrost region of the Qinghai-Tibet Plateau,China

Alpine ecosystems in permafrost region are extremely sensitive to climate changes.To determine spatial pattern variations in alpine meadow and alpine steppe biomass dynamics in the permafrost region of the Qinghai-Tibet Plateau,China,calibrated with historical datasets of above-ground biomass production within the permafrost region's two main ecosystems,an ecosystem-biomass model was developed by employing empirical spatialdistribution models of the study region's precipitation,air temperature and soil temperature.This model was then successfully used to simulate the spatio-temporal variations in annual alpine ecosystem biomass production under climate change.For a 0.44°C decade-1 rise in air temperature,the model predicted that the biomasses of alpine meadow and alpine steppe remained roughly the same if annual precipitation increased by 8 mm per decade-1,but the biomasses were decreased by 2.7% and 2.4%,respectively if precipitation was constant.For a 2.2°C decade-1 rise in air temperature coupled with a 12 mm decade-1 rise in precipitation,the model predicted that the biomass of alpine meadow was unchanged or slightly increased,while that of alpine steppe was increased by 5.2%.However,in the absence of any rise in precipitation,the model predicted 6.8% and 4.6% declines in alpine meadow and alpine steppe biomasses,respectively.The response of alpine steppe biomass to the rising air temperatures and precipitation was significantly lesser and greater,respectively than that of alpine meadow biomass.A better understanding of the difference in alpine ecosystem biomass production under climate change is greatly significant with respect to the influence of climate change on the carbon and water cycles in the permafrost regions of the Qinghai-Tibet Plateau.     

Progress in studies on geographical environments of the Qinghai-Xiang plateau

The Qinghai-Xizang (Tibet) Plateau area was subjected to twice uplift and planation in the Tertiary. Intense uplifting of the plateau area has given rise to drastic changes and differentiation of physical environment on the plateau and the surrounding area since 3.4 Ma B.P. Significant environmental changes with dry tendency in interior of the plateau had occurred during the last 150 ka B.P. By comparative study on several mountains of the plateau, two systems of the structure-type of the altitudinal belt are identified and nine groups are subdivided. A distribution model with close relevance to highland uplift effect has been generalized. A number of striking geo-ecological phenomen and their spatial pattern such as moisture corridor, dry valleys, high-cold meadow zone, and high-cold arid core area are investigated and discussed. Based on the thermal conditions, moisture regimes and variation in landforms of the plateau is sequentially demarcated. A tentative scheme of 2 temperature belts, 10 natural zones and 28 physical districts has been proposed not including southern slopes of the East Himalayas. The Qinghai-Xizang Plateau is sensitive to “green house effect”, showing close relation with global change. Characteristics of temperature and precipitation on the plateau during the last 2000 years, and response of glaciers, snow deposit and permafrost on the plateau to global change are dealt with in the present paper. Under the auspices of Chinese National Key Project for Basic Research (G1998040800) and CAS project on the Qinghai-Xizang Plateau (KZ951 - A1 - 204, KZ95T - 06)     

Effects of grazing exclusion on plant productivity and soil carbon,nitrogen storage in alpine meadows in northern Tibet,China

Grazing exclusion is widely adopted in restoring degraded alpine grasslands on the Qinghai-Tibetan Plateau. However, its effectiveness remains poorly understood. In this study, we investigated the effects of grazing exclusion on plant productivity, species diversity and soil organic carbon （SOC） and soil total nitrogen （STN） storage along a transect spanning from east to west of alpine meadows in northern Tibet, China. After six years of grazing exclusion, plant cover, aboveground biomass （AGB）, belowground biomass （BGB）, SOC and STN were increased, but species diversity indices declined. The enhancement of AGB and SOC caused by grazing exclusion was correlated positively with mean annual precipitation （MAP）. Grazing exclusion led to remarkable biomass increase of sedge species, especially Kobresia pygmaea, whereas decrease of biomass in forbs and no obvious change in grass, leguminous and noxious species. Root biomass was concentrated in the near surface layer （10 cm） after grazing exclusion. The effects of grazing exclusion on SOC storage were confined to shallow soil layer in sites with lower MAP. It is indicated that grazing exclusion is an effective measure to increase forage production and enhance soil carbon sequestration in the studied region. The effect is more efficient in sites with higher precipitation. However, the results revealed a tradeoff between vegetation restoration and ecological biodiversity. Therefore, carbon pools recover more quickly than plant biodiversity in the alpine meadows. We suggest that grazing exclusion should be combined with other measures to reconcile grassland restoration and biodiversitv conservation.     

Soil organic carbon contents,aggregate stability,and humic acid composition in different alpine grasslands in Qinghai-Tibet Plateau

Alpine grassland soils on Qinghai-Tibet Plateau store approximately 33.5 Pg of organic carbon(C) at 0–0.75 m depth and play an important role in the global carbon cycle.We investigated soil organic C(SOC),water-soluble organic C(WSOC),easily oxidizable organic C(EOC),humic C fractions,aggregate-associated C,aggregate stability,and humic acid(HA) composition along an east-west transect across Qinghai-Tibet Plateau,and explored their spatial patterns and controlling factors.The contents of SOC,WSOC,EOC,humic C fractions and aggregate-associated C,the proportions of macroaggregates(2-0.25) and micro-aggregates(0.25-0.053 mm),and the aggregate stability indices all increased in the order alpine desert alpine steppe alpine meadow.The alkyl C,O-alkyl C,and aliphatic C/aromatic C ratio of HA increased as alpine desert alpine meadow alpine steppe,and the trends were reverse for the aromatic C and HB/HI ratio.Mean annual precipitation and aboveground biomass weresignificantly correlated with the contents of SOC and its fractions,the proportions of macro- and microaggregates,and the aggregate stability indices along this transect.Among all these C fractions,SOC content and aggregate stability were more closely associated with humic C and silt and clay sized C in comparison with WSOC,EOC,and macro- and microaggregate C.The results suggested that alpine meadow soils containing higher SOC exhibited high soil aggregation and aggregate stability.Mean annual precipitation should be the main climate factor controlling the spatial patterns of SOC,soil aggregation,and aggregate stability in this region.The resistant and stable C fractions rather than labile C fractions are the major determinant of SOC stocks and aggregate stability.     

Degradation of wetlands on the Qinghai-Tibet Plateau: A comparison of the effectiveness of three indicators

The Qinghai-Tibet Plateau encompasses a large quantity of wetlands, some of which have been degraded to varying severity levels. In the literature, a number of degradation indicators have been proposed to evaluate ecological health of wetlands, but their effectiveness in the plateau environment remains unknown. In this study, we assessed the effectiveness of three degradation indicators, soil moisture content at 10 cm deep, vegetative cover, and density of pika burrows. The degradation severity of wetlands in Maduo County on the Qinghai-Tibet Plateau is enumerated at four levels, intact, slight, moderate and severe. Analysis of 106 samples collected in the field demonstrates that the density of pika burrows is the least reliable indicator. By comparison, vegetative cover and underlying soil moisture content are more reliable, even though neither is a perfect indicator as the difference among adjacent levels of severity as revealed by t-test is not always statistically significant. The imperfection of vegetative cover as an indicator is due to its variation among different types of wetlands. The limitation of moisture content is attributed to its non-linear relationship with wetland degradation. Above the threshold of about 50% in moisture content wetlands are unlikely to be degraded. It is recommended that moisture be measured at the point near the surface and vegetative cover be further differentiated by species in order to improve their effectiveness.     

Restoration prospects for Heitutan degraded grassland in the Sanjiangyuan

In many ecosystems ungulates have coexisted with grasslands over long periods of time. However, high densities of grazing animals may change the floristic and structural characteristics of vegetation, reduce biodiversity, and increase soil erosion, potentially triggering abrupt and rapid changes in ecosystem condition. Alternate stable state theory provides a framework for understanding this type of dynamic. In the Sanjiangyuan atop the Qinghai-Tibetan plateau (QTP), grassland degradation has been accompanied by irruptions of native burrowing animals, which has accentuated the loss of ground cover. Severely degraded areas of alpine meadows are referred to as ’Heitutan’. Here, using the framework of alternate stable state theory, we describe the proximate and ultimate drivers of the formation of Heitutan on the QTP, and we assess prospects for recovery, in relation to the degree of biophysical alteration, of these alpine meadows. Effective rehabilitation measures must address the underlying causes of degradation rather than their symptoms. Heitutan degradation is not uni-causal. Rather it reflects different mechanisms operating at different spatio-temporal scales across this vast region. Underlying causes include overly aggressive exploitation of the grasslands (e.g. overgrazing), amplification of grazing and erosion damage by small mammals when outbreaks occur, and/or climate change. Given marked variability in environmental conditions and stressors, restorative efforts must vary across the region. Restoration efforts are likely toyield greatest success if moderately and severely degraded areas are targeted as the first priority in management programmes, before these areas are transformed into extreme Heitutan.     

四川草原MODIS数据的产草量估算

四川草原是我国5大牧区之一,其可利用的天然草地占全省草原总面积的85%,准确掌握草原产草量信息对草原管理和当地经济发展具有重要意义。本研究利用2011年7月MODIS不同分辨率(250m、500m、1km)NDVI、EVI产品和同期地面调查数据(共181个采样点),对四川草原4种主要草地类型(即高寒草甸草地、高寒灌木草地、高寒沼泽草地和山地疏林草地)产草量鲜重分类型建立估产模型。研究发现,NDVI对该地区4种主要草地类型产草量的拟合效果普遍优于EVI;相对于500m和1km的遥感数据,250m的遥感数据拟合效果较好;分草地类型建立模型的效果优于对全体样本建立模型;该地区除高寒沼泽草地用幂函数模型拟合效果较好外,其余均用指数模型进行建模效果较好;对该地区各草地类型建立的最优估产模型,精度均在70%以上,回归判定系数R2在0.75以上;利用最优模型对2011年四川省草原进行估产,总体估产精度约为90%。     

Topographic controls on alpine treeline patterns on Changbai Mountain,China

The control mechanisms of topography on alpine treeline pattern are critical to understanding treeline dynamics and future changes. These mechanisms have not been understood quite well enough because of increasing human disturbance and low data resolution. In this study, the relationship between the treeline pattern and topography was analyzed based on high spatial resolution remote sensing data and a digital elevation model in an area in Changbai Mountain with little human disturbance. Future treeline patterns were also predicted. The results showed that(a) aspects with high solar radiation and low snow cover have a high coverage rate of trees,(b) the peak coverage rate of trees switches from low slopes(5°) to medium slopes(5°~25°) as the elevation rises because of the extreme environment,(c) the coverage rate of trees is a function that depends on environmental factors controlled by topography,(d) the future treeline pattern is controlled by new temperature mechanisms, new environmental factors and the reallocation effect of topography. Our research implies that topography controls the treeline pattern and changes in the treeline pattern associated with global warming, due to the effect of global warming on environmental factors. This study may well explain the causes of heterogeneous changes in the treeline pattern in the horizontal direction as well as differences in treeline response to climate warming.