Water points and their influence on grazing resources in central northern Namibia

Debate among scientists about ecological dynamics and appropriate management of semi‐arid rangelands has led to a challenge of received wisdoms of range management and pastoral development in dryland Africa. In our study, we investigated impacts of grazing on grass composition around permanent water points along a pipeline and around a traditional hand‐dug well in an important grazing area in central northern Namibia. Grass species abundance and selected environmental variables sampled along transects radiating out from these water points were analysed using Canonical Correspondence Analysis (CCA). Significant grazing‐induced changes, manifested by palatable perennial grasses being replaced by less palatable annual grasses, were identified around water points along the pipeline. There annual grasses Schmidtia kalihariensis and Aristida stipioides dominate the vegetation as far as 5 km from the water points. No significant grazing‐induced changes in grass composition were observed around the hand‐dug well. Private ownership leading to stronger control of access to traditional wells compared to the open access water points along the pipeline seems to be a key factor preventing overutilisation of grazing resources around the former. Copyright © 2007 John Wiley & Sons, Ltd.     

Short‐term degradation of semiarid grasslands—results from a controlled‐grazing experiment in Northern China

The assessment of grassland degradation due to overgrazing is a global challenge in semiarid environments. In particular, investigations of beginning steppe degradation after a change or intensification of the land use are needed in order to detect and adjust detrimental land‐use management rapidly and thus prevent severe damages in these sensitive ecosystems. A controlled‐grazing experiment was established in Inner Mongolia (China) in 2005 that included ungrazed (UG) and heavily grazed plots with grazing intensities of 4.5 (HG4.5) and 7.5 (HG7.5) sheep per hectare. Several soil and vegetation parameters were investigated at all sites before the start of the experiment. Topsoil samples were analyzed for soil organic C (SOC), total N (N_tot), total S (S_tot), and bulk density (BD). As vegetation parameters, aboveground net primary productivity (ANPP), tiller density (TD), and leaf‐area index (LAI) were determined. After 3 y of the grazing experiment, BD increased and SOC, N_tot, S_tot, ANPP, and LAI significantly decreased with increasing grazing intensity. These sensitive parameters can be regarded as early‐warning indicators for degradation of semiarid grasslands. Vegetation parameters were, however, more sensitive not only to grazing but also to temporal variation of precipitation between 2006 and 2008. Contrary, soil parameters were primarily affected by grazing and resistant against climatic variations. The assessment of starting conditions in the study area and the application of defined grazing intensities is essential for the investigation of short‐term degradation in semiarid environments.     

Impact of protection and free grazing on sand dune vegetation in the Rajasthan Desert,India

In the Thar (Rajasthan) Desert of India, sand dunes and sandy plains dominate the landscape. Livestock raising and marginal land cultivation are the main occupations. Owing to the high growth rates of human and livestock populations and a decrease in pasture area and its primary productivity, these lands bear acute grazing pressure. Average rainfall is low and vegetation growth is restricted to the short rainy season of two to four months duration. Often there are years of lower than normal rainfall. In these circumstances, fenced areas, established to stabilize formerly active sand dunes, are increasingly opened to grazing to prevent high stock mortality during droughts. This study was conducted in four fenced and one open site, representative of the region's different vegetation types and grazing pressures. The impact of 2 and 5 per cent free grazing pressure on protected sand dune vegetation density and cover was tested in the two fenced sites. The vegetation data for grazed sites are compared with those for the two ungrazed fenced (protected) and one unfenced (open) site subjected to unlimited grazing pressure throughout the year. The vegetation sampling was carried out by the qaudrat and line-transect method before and after grazing from November 1984 to October 1986. It shows a significant reduction in the density and cover of many palatable species and an increase of unpalatable plants. The effect of vegetation degradation is greater in the unfenced area. The low grazing pressure on the fenced sand dunes sites can still cause drastic changes in the vegetation density and cover. Protection resulted in reduced sand erosion and enhanced growth of palatable plants in the fenced sites under similar climatic and edaphic conditions to the unfenced sites. The grazing pressure in the unfenced areas remains high to extreme during the year, due to low land productivity and high feed demand. The regeneration rate is very slow under the constant (3rd to 5th degree) overgrazing. Low intensity grazing pressure on the fenced sites during droughts can cause heavy utilization and mortality of palatable vegetation.     

Tradeoffs in the Rehabilitation of a Succulent Karoo Rangeland

Rangeland rehabilitation has multiple, sometimes conflicting goals, such as the reestablishment of the predisturbance vegetation, soil protection, and forage production. The rehabilitation techniques should be also cost‐effective and practicable. Given the difficulties and high costs of restoring Succulent Karoo rangelands and the continuously high grazing pressure in the communal lands, tradeoffs should be accepted in the achievement of these goals. We tested the capability of paddock manure redistribution to reverse degradation trends in a heavily grazed Succulent Karoo rangeland in South Africa. Over 3 years, the effects of the manure application were compared with areas planted with mature shrubs as a benchmark for a predisturbance vegetation structure and with four popular rehabilitation techniques: (1) livestock exclusion; (2) brushpacking (coverage of dead shrubs); (3) mineral fertilizing; and (4) microcatchment construction. Manure was, besides planting, the only treatment that resulted in a significant increase in drought‐resistant vegetation cover, but it compromised the dominance of native vegetation. In the manure plots, a pasture‐like vegetation of non‐native forage plants (which germinated mainly from seeds in the dung), developed (foremost Atriplex semibaccata). Manure application counteracted erosion as effectively as the planted shrubs and brushpacks. Expected negative side effects such as a decrease in plant species richness or salinization of topsoil were not detected. We also checked the potential of topsoil salinization by the halophytic A. semibaccata and found it to be low. For sites where a decrease in grazing pressure is unrealistic under current land tenure, redistribution of manure should be further explored to mitigate acute symptoms of degradation. Copyright © 2013 John Wiley & Sons, Ltd.     

Spatial Assessment of Land Degradation Risk for the Okavango River Catchment,Southern Africa

The Okavango catchment in southern Africa is subject to environmental as well as socio‐economic transformation processes such as population growth and climate change. The degradation of soil and vegetation by deforestation and overgrazing is one of the downsides of this development, reducing the capacity of the land to provide ecosystem functions and services. In this study, climate simulations are brought together with secondary socioeconomic, pedologic and remote‐sensing data in a GIS‐based assessment of the factors commonly associated with land degradation risk. A high resolution overview is provided for decision‐makers and stakeholders in the region by identifying priority intervention areas where a long‐term decline in ecosystem function and land productivity is most likely to occur. The approach combines 19 risk factors into seven individual ratings for topography, landcover, soil, demography, infrastructure, livestock pressure and climate. These ratings are then weighted and combined into an integrated degradation risk index (DRI). The results show that the land degradation risk is quite heterogeneously distributed in the study area and caused by different factors. Three hot‐spots are identified and compared, one of which is in the far northwestern part of the catchment, one around the local center Rundu and one on the outskirts of the Okavango Delta. We conclude that the approach is suitable to give an overview on degradation risk in the study area, although the classification process is a crucial procedure that should be standardized for further research. Copyright © 2015 John Wiley & Sons, Ltd.     

Grazing‐induced alterations of soil hydraulic properties and functions in Inner Mongolia,PR China

Increasing grazing intensities of sheep and goats can lead to an increasing degradation of grasslands. We investigated four plots of different grazing intensities (heavily grazed, winter‐grazed, ungrazed since 1999, and ungrazed since 1979) in Inner Mongolia, PR China, in order to study the effects of trampling‐induced mechanical stresses on soil hydraulic properties. Soil water transport and effective evapotranspiration under “heavily grazed” and “ungrazed since 1979” were modeled using the HYDRUS‐1D model. Model calibration was conducted using data collected from field studies. The field data indicate that grazing decreases soil C content and hydrophobicity. Pore volume is reduced, and water‐retention characteristics are modified, the saturated hydraulic conductivity decreases, and its anisotropy (vertical vs. horizontal conductivity) is influenced. Modeling results revealed higher evapotranspiration on the ungrazed site (ungrazed since 1979) compared to the grazed site (heavily grazed) due to wetter soil conditions, more dense vegetation, litter cover, and decreased runoff and drainage, respectively. Grazing modified the partitioning of evapotranspiration with lower transpiration and higher evaporation at the grazed site owing to reduced root water uptake due to reduced evaporation and a patchy soil cover.     

The effects of land‐use change on plant–soil–erosion relations,Nyereg Hill,Hungary

Vegetation of the Tihany Peninsula in Hungary has undergone serious changes caused by heavy trampling and overgrazing during the last century. In Tihany, the vegetation started to change towards anthropogenic associations. After grazing ceased, vegetation started to rearrange. There were no significant changes in species composition on trampled areas (on the ridge of the hill) between the examinations in 1994 and 2002. As a result of ceased grazing, the proportion of natural species was high in the grasslands of the S Nyereg Hill in 1994, while during the 2002 investigations, forest and scrub expanded at a rate that did not leave space for grassland on shallow soils and slope steppe (closing dry grasslands on hilly areas). The coverage of Elymus repens decreased, while Festuca species increased. The possible effects of plant‐cover change on soil loss were examined with the USLE (Universal Soil Loss Equation) model on the sloping areas. Eliminating harmful effects can decrease soil degradation, but the original state of soils can be restored only after a long period (hundreds of years). Further degradation of soils assists the expansion of drought‐resistant species and weeds in the associations. In 2007, soil‐thickness measurements and on‐site examinations were carried out to check the results of the former surveys and modeling.     

Changing grazing systems in central north Namibia

Current and historical livestock movement patterns are explored in a semi‐arid communal environment in central–north Namibia, placed in context of increasing population, large‐scale enclosures, increased water supply and changing vegetation. Farmer's knowledge of movements, rangeland potential, vegetation condition and plant indicators was gathered and analysed with various methods such as Canonical Correspondence Analysis (CCA). Local rangeland units were mapped with Landsat TM imagery and analysed with a Geographical Information System (GIS). The data suggest that good grazing was previously maintained by low herbivore pressure and frequent fires in a management regime controlled by hunter‐gatherers and limited permanent water supply. Population increase in settled areas starts migration to more fertile land units in previous prime grazing areas causing a conflict between grazing and cropping and a decrease in grazing condition triggering further migration and need for new water supply. Recent large‐scale enclosures are targeting predominantly more fertile land units with the most palatable perennial grass species and water, causing further conflict for communal farmers. Having reached the frontier of the traditional land there is no space for further expansion, resulting in the need to adapt to uncertainty with annual grasses more dependent on rainfall. Livestock movement patterns have changed drastically for large herd owners from transhumance and migration to largely permanent cattle posts. Small herd owners face increasing longer movements between kraals , water points, depending on less suitable and decreased unfenced grazing lands. Copyright © 2006 John Wiley & Sons, Ltd.     

1982—2015年中国植被NDVI时空变化特征及其驱动分析

在全球气候变化背景下,多数研究关注植被年际变化趋势及其对降水和气温的响应而忽略了辐射因子的影响。探究持续性和波动变化过程的空间分异特征和定量揭示不同植被类型对季节性多气候要素（降水、气温和辐射）响应规律需进一步深入,并识别植被退化人类活动影响区对中国生态环境保护具有重要意义。该研究基于AVHRR NDVI3g遥感数据、CCI全球土地覆被数据和ERA5-Land数据,采用多元线性回归模型和残差分析等方法,从区域和全国尺度上分析1982-2015年中国植被NDVI（Normalized Difference Vegetation Index）时空变化特征,研究其对季节性气候变化和人类活动的响应。研究结果表明：1）中国的植被变化在空间上具有明显的区域特征,呈现出自东南向西北递减的趋势,变化率范围为-0.016～0.029/a。2）根据Hurst指数分析,80.62%的植被处于持续稳定变化状态。草地和林地的变化趋势趋于不稳定,易受气候变化和人类活动的影响。3）准噶尔盆地、青藏高原以及内蒙古锡林郭勒盟等区域的植被NDVI与气温和太阳辐射呈负相关性,而在云贵高原、黄土高原南部、四川盆地等地区表现为正相关性。4）残差分析结果表明,干旱导致新疆准噶尔盆地和内蒙古中部等干旱区植被退化,而温度和辐射增加是促进东部沿海平原、黄土高原南部、四川盆地和云贵高原西南部等地区植被改善的主要原因。21世纪以来人类活动逐渐加强,包括黄土高原水土保持和退耕还林工程、阿拉善荒漠治理、沿海城市群和东北工业基地的建设等。具体表现为内蒙古阿拉善高原、黄土高原中西部和北部以及华南大部分地区植被改善,东北大、小兴安岭、长白山东部和长江三角洲地区植被退化。该研究对植被变化及其驱动因素的研究,可识别植被退化区,为将来生态修复工程的实施和生态文明建设提供理论依据,助力区域绿色可持续发展。     

巴山南部山区乡村聚落时空变化特征及影响因素——以重庆市城口县为例

为探究山区乡村聚落的时空变化特征,以巴山南部城口县为例,基于2010年、2015年、2019年乡村聚落斑块数据,通过GIS空间分析和景观指数方法,从聚落分布、规模、形态和区位4个角度分析了城口县乡村聚落的时空变化特征,并运用空间误差回归模型揭示其影响因素。结果表明：(1)城口县乡村聚落空间集聚趋势增强;聚落分布呈现“西北密,东南疏”,高密度区范围向乡镇中心缩减;(2)与2010年比较,2019年城口县聚落数量减少而规模明显增加;乡村聚落规模以小型化为主,由小规模逐渐向大规模发展;聚落形状不规则并趋于复杂化,乡镇中心周边及主要道路河流两侧的形状不规则程度较大,且程度增大;(3)聚落主要分布在海拔<1 500 m,坡度<25°范围内,沿河流和道路呈带状分布;低地缓坡处和河流道路两侧为聚落扩张区,海拔和坡度较高的地区为聚落收缩区;(4)人口规模、坡度和距乡镇中心距离是城口县乡村聚落规模变化的首要因素。综上所述,自然因素塑造城口县乡村聚落的基本格局,而区位因素、社会经济因素及政策因素进一步推动乡村聚落演化。研究结果可为秦巴山区乡村聚落布局优化提供依据,对改善山地乡村人居环境、推动山...     

Palaeoecology of degraded blanket mire in South Wales: Data to inform conservation management

Many European blanket mires are degraded and contain few Sphagna. In Wales, more than half exhibit symptoms of degradation. We used palaeoecological techniques to chronicle recent vegetation history at two upland localities in South Wales to provide an understanding of the contribution of various factors in mire degradation and to aid wider conservation management strategies. The data suggest a major vegetation change post-dated the start of the industrial revolution. There was evidence for increased burning activity, but as this phenomenon was not present in all profiles it seems unlikely that fire was the principal or sole agent in vegetation change. Rather, increased atmospheric input, plus a change in grazing pressure, may have been responsible. The implications for conservation management are far-reaching. The present overwhelming dominance of Molinia at Hirwaun Common is unprecedented. So also is a local dominance of Calluna, shown in one area at Mynydd Llangatwg. Hence, the approbation often accorded to Callunetum needs to be tempered with the knowledge that its presence in the Mynydd Llangatwg landscape is not long-standing. Indeed, millennial-scale dominance of Sphagnum imbricatum characterizes the earlier record. Its demise and that of Drosera intermedia took place in historical times. Both localities show floristic impoverishment within the 20th Century, with relatively recent single-taxon supremacy. So, conservation management to reduce the current pre-eminence of Molinia would not run counter to long-established dominance; ways to achieve this are suggested. The methods used in this study have wide applicability in mire conservation.     

石油城市县域农村居民点空间格局分析

应用渐变尺度研究方法和GIS的空间分析功能,对大庆市肇源县的农村居民点空间格局进行分析。在油田用地周围建立的步长为1 km,范围为研究区边界的12个缓冲区,宏观上农村居民点用地的个数和面积随步长的增加呈现出先快后慢的递减趋势;在不同集中程度的油田用地集中区内,农村居民点的个数和面积占全部农村居民点的个数和面积的比例,与该集中程度下油田用地的面积占全部油田用地面积的比例呈现非常相似的规律性变化。在公路周围建立的步长为1 km,范围为研究区边界的15个缓冲区内,宏观上农村居民点的个数和面积随步长的增加也呈现出先快后慢的递减趋势。由此说明油田用地和公路在宏观上对农村居民点空间格局具有显著的影响,油田用地和公路的选址及位置的改动对石油城市县域农村居民点空间格局的影响必须予以足够重视。     

放牧强度对中国内蒙古草原土壤水分状况与通量的影响

In the past few decades,the increase in grazing intensity has led to soil degradation and desertification in Inner Mongolia grassland,China,due to population growth and shift in the socio-economic system.Two sites with different grazing intensities,continuous grazing site(CG) with 1.2 sheep ha 1 year 1 and heavy grazing site(HG) with 2.0 sheep ha 1 year 1,were investigated at the Inner Mongolia Grassland Ecosystem Research Station(43 37 50 N,116 42 18 E) situated in the northern China to i) characterize the temporal distribution of soil water content along soil profile;and ii) quantify the water fluxes as affected by grazing intensity.Soil water content was monitored by time domain reflectometry(TDR) probes.Soil water retention curves were determined by pressure membrane extractor,furthermore processed by RETC(RETention Curve) software.Soil matric potential,plant available water and water flux were calculated using these data.Both sites showed an identical seasonal soil water dynamics within four defined hydraulic periods:1) wetting transition coincided with a dramatic water increase due to snow and frozen soil thawing from March to April;2) wet summer,rainfall in accordance with plant growth from May to September;3) drying transition,a decrease of soil water from October to November due to rainfall limit;and 4) dry winter,freezing from December to next February.Heavy grazing largely reduced soil water content by 43%-48% and plant available water by 46%-61% as compared to the CG site.During growing season net water flux was nearly similar between HG(242 mm) and CG(223 mm) sites between 5 and 20 cm depths.However,between 20 and 40 cm depths,the upward flux was more pronounced at HG site than at CG site,indicating that water was depleted by root uptake at HG site but stored at CG site.In semi-arid grassland ecosystem,grazing intensity can affect soil water regime and flux,particularly in the growing season.     

Land Use and Cover Dynamics Since 1964 in the Afro‐Alpine Vegetation Belt: Lib Amba Mountain in North Ethiopia

Human‐induced land use and land cover (LUC) changes threaten the ecosystem services of the vulnerable tropical afro‐alpine vegetation. Several LUC change studies are available for the Ethiopian highlands, but relatively little is known about LUC change in the afro‐alpine zones. In this study, LUC changes between 1964 and 2012 were mapped for the afro‐alpine zone of Lib Amba Mountain, part of the Abune Yosef Mountains in North Ethiopia. Historical LUC was derived from georeferenced aerial photographs of 1964 and 1982, and the present LUC (2012) from Bing Map satellite imagery. Based on these successive LUC maps a time‐depth map, LUC proportions, LUC transition matrices and LUC change trajectories were calculated. Two main phases of LUC change could be distinguished linked to the neo‐Boserupian perspective. (i) Between 1964 and 1982, there were large‐scale deforestation and general degradation of the vegetation above 3500 m, in a period of low population pressure; (ii) Between 1982 and 2012, an intensification of land use prevailed accompanied with a slight regeneration of the vegetation and the Erica arborea L. forest, under increased population pressure. Depth interviews indicated that local and governmental land management measures are very important for the protection against vegetation depletion and soil degradation. Quick recovery of the forest on Lib Amba provides confidence that degraded afro‐alpine areas would benefit in a short time from complete protection, given the vicinity of remaining patches of afro‐alpine vegetation. Management interventions are thus vital to restore the important ecosystem services of the afro‐alpine vegetation belt. Copyright © 2015 John Wiley & Sons, Ltd.     

Influences of continuous grazing and livestock exclusion on soil properties in a degraded sandy grassland, Inner Mongolia, northern China

Overgrazing is one of the main causes of desertification in the semiarid Horqin sandy grassland of northern China. Excluding grazing livestock is considered as an alternative to restore vegetation in degraded sandy grassland in this region. However, few data are available concerning the impacts of continuous grazing and livestock exclusion on soil properties. In this paper, characteristics of vegetation and soil properties under continuous grazing and exclusion of livestock for 5 and 10 years were examined in representative degraded sandy grassland. Continuous grazing resulted in a considerable decrease in ground cover, which accelerates soil erosion by wind, leading to a further coarseness in surface soil, loss of soil organic C and N, and a decrease in soil biological properties. The grassland under continuous grazing is in the stage of very strong degradation. Excluding livestock grazing enhances vegetation recovery, litter accumulation, and development of annual and perennial grasses. Soil organic C and total N concentrations, soil biological properties including some enzyme activities and basal soil respiration improved following 10-year exclusion of livestock, suggesting that degradation of the grassland is being reversed. The results suggest that excluding grazing livestock on the desertified sandy grassland in the erosion-prone Horqin region has a great potential to restore soil fertility, sequester soil organic carbon and improve biological activity. Soil restoration is a slow process although the vegetation can recover rapidly after removal of livestock. A viable option for sandy grassland management should be to adopt proper exclosure in a rotation grazing system in the initial stage of grassland degradation.     

Historical Land‐use and Vegetation Change in Northern Kwazulu‐Natal,South Africa

The role of anthropogenic activity is increasingly recognized as an agent of environmental change. Photographs, taken more than 130 years ago in KwaZulu‐Natal, South Africa, show a very different landscape to that viewed today. In attempting to understand some of the dynamics behind the changes in the landscape, we explored the history of land‐use in communal rangelands in KwaZulu‐Natal from the arrival of Iron Age man through to modern practices. Communal farming is frequently cited as a major cause of environmental degradation. Traditional lifestyles have been eroded by social, political and economic changes since the arrival of European explorers and settlers in the early 1800s. This may have contributed to encroachment by woody plants into the open savannas and grasslands of KwaZulu‐Natal in recent times because of increased grazing pressure and, perhaps reduced fires. Furthermore, there is decreasing dependence on wood for everyday needs due to the increased availability of electricity. Interviews with a number of community members indicate that they have noted a change in climate and in vegetation structure. Their observations have been confirmed by climate data and historic photographs. Environmental planners need to view change in a holistic manner, taking cognisance not only of the physical changes but also of the history of land‐use and human needs and to give credence to community perceptions. Copyright © 2015 John Wiley & Sons, Ltd.     

山地丘陵区农村居民点空间分布特征及影响机制分析（英文稿）

山地丘陵区是受人类活动和自然因素干扰的特殊区域,也是人地关系矛盾突出的地区,是国土空间治理的重点与难点区域。分析山地丘陵区农村居民点的分布特征,对实现乡村重建与乡村振兴具有重要意义。 该研究试图构建研究框架,结合重庆石船镇的案例,从定量和定性两方面探讨山区农村居民点的空间分布特征。结果表明：1）山地丘陵区农村居民点空间分布存在显著差异;农村居民点大多位于低海拔、平缓地形、低灾害风险、离水中等距离、靠近城镇和道路的地区,人口规模、宜居环境等因素影响农村居民点的发展、选址和扩张。2）山地丘陵区高密度地区农村居民点空间分布呈现随机分布、分散分布或均匀分布的特征,而低密度地区农村居民点空间分布呈现聚集分布的特征。 农村居民点更有可能集中在人口密度高的地区,如海拔较低、坡度较缓、距水源中等、地质灾害风险低的地区。3）自然因素、区位因素和社会经济因素相互关联,在不同时期表现出不同的耦合模式,决定了山区农村居民点的数量和分布。随着区域经济社会的发展,自然因素对乡村聚落空间分布的影响逐渐减弱,而区位因素、城镇化、产业发展、交通条件、政府政策等规划因素是改变山区农村居民点空间形态的主导力量。 空间治理的差异性策略是实现山区乡村聚落可持续利用和优化布局的必要条件。     

Vegetation,Wildlife, and Livestock Responses to Planned Grazing Management in an African Pastoral Landscape

Rangelands are vital for wildlife conservation and socio‐economic well‐being, but many face widespread degradation because in part of poor grazing management practices. Planned grazing management, typically involving time‐controlled rotational livestock grazing, is widely touted as a tool for promoting sustainable rangelands. However, real‐world assessments of its efficacy have been lacking in communal pastoral landscapes globally, and especially in Africa. We performed landscape‐scale assessment of the effects of planned grazing on selected vegetation, wildlife, and cattle attributes across wide‐ranging communally managed pastoral rangelands in northern Kenya. We found that planned grazing enhanced vegetation condition through a 17% increase in normalized difference vegetation index, 45–234% increases in herbaceous vegetation foliar cover, species richness and diversity, and a 70% reduction in plant basal gap. In addition, planned grazing increased the presence (44%) and species richness (53%) of wild ungulates and improved cattle weight gain (>71%) during dry periods when cattle were in relatively poor condition. These changes occurred relatively rapidly (within 5 years) and despite grazing incursion incidents and higher livestock stocking rates in planned grazing areas. These results demonstrate, for the first time in Africa, the positive effects of planned grazing implementation in communal pastoral rangelands. These improvements can have broad implications for biodiversity conservation and pastoral livelihoods. Copyright © 2017 John Wiley & Sons, Ltd.     

干旱风沙区水库边缘植被-风力侵蚀的变化及成因

[目的] 对干旱风沙区水库边缘植被覆盖度和土壤风力侵蚀的动态变化及其成因进行分析,为该库区风沙危害的防治提供依据。[方法] 基于Landsat影像使用像元二分模型计算植被覆盖度,运用定性与定量相结合的方法,研究甘肃省瓜州县桥子水库边缘植被变化和风力侵蚀状况。[结果] 2006,2011,2018年植被覆盖度分别为0.15,0.13和0.35,水库边缘的植被呈先减后增的趋势,其生长有远离水库的趋势。2006-2011年桥子库群周边环境变化剧烈,2011-2018年植被退化速度减缓。研究区强烈以上侵蚀面积比例仍较大（50%以上）。[结论] 研究区植被和侵蚀变化的原因除了气候等自然因素外,地下水补给量减少,水位降低,超生态负荷扩大绿洲,不合理的种植业结构、耕作方式及牧业发展等人为因素加速了天然植被退化和局部侵蚀,而采取的草场封育、固沙造林等治理和修复措施在一定程度上延缓这一进程。建议采取生态引水、补给地下水、发展节水农业、禁垦禁牧、调整产业结构、恢复植被等抢救性措施和预防保护治理措施,以维护绿洲的持久稳定。     

沙棘植物"柔性坝"沟道土壤水分时空动态变化研究

沙棘植物柔性坝是一种防止沟道土壤侵蚀、拦沙保水的新型生物工程,特别适合于生态环境恶劣的砒砂岩地区。在内蒙古准格尔旗砒砂岩地区东一支沟开展了沙棘植物柔性坝野外拦沙保水实验,结果表明,沙棘植物柔性坝各部位的土壤剖面含水量年内、年际时空动态变化有着明显的差异,沙棘植物柔性坝对沟道土壤水分具有显著的调节作用,降雨、地表植被种类、植被生长状况、土壤理化性质、地形和当地水文气象条件等是影响土壤水分时空变异的重要因子,而其中降雨和地表植被是主要影响因素。