Physical impact of grazing by sheep on soil parameters in the Nama Karoo subshrub/grass rangeland of South Africa

The direct short-term impact of three rates of stocking (4, 8 and 16 small-stock units [SSU] ha^?1) was quantified in terms of soil characteristics of arid Nama Karoo vegetation (subshrub/grass). Mature Merino wethers grazed in the experimental plots throughout May in 1995 and 1996 (the plots were not subjected to grazing at any other time). Stocking rate proved inversely related to initial infiltration rate. Light trampling (4 SSU ha^?1) loosened the topsoil sufficiently to increase the initial infiltration rate: infiltration capacity of soil in fields stocked at 4 SSU ha^?1 and 16 SSU ha^?1 was 17% higher and 14% lower respectively than that of soil of ungrazed rangeland over the two grazing periods. Increased soil compaction and greater bulk density due to higher stocking rates significant decreased the infiltration rate. Compared to ungrazed rangeland stocking rates of 4, 8 and 16 SSU ha^?1 over the two grazing periods increased bulk density respectively by 2.73%, 6.67% and 8.945% and compaction by 10.90%, 16.78% and 20.90%. No grazing also increased bulk density and soil compaction and decreased infiltration rate. Light stocking (4 SSU ha^?1) influenced all soil parameters most favourably. From a hydrologic point of view, grazing levels and rotation schemes need to be tailored for sustainable utilization of arid subshrub/grass vegetation by livestock.     

The influence of flood frequency, geomorphic setting and grazing on plant communities and plant biomass on a large dryland floodplain

Plant communities on semi-arid floodplains are ecologically important and support a diverse local and regional fauna and often pastoral economies. Water resource development may affect these communities and economies by decreasing water supply; determining the nature of these relationships is not straightforward because of the complex nature of plant responses to wetting and possible interactions with other drivers. We investigate the effects of reduced wetting on vegetation by examining spatial patterns in plant communities and above-ground herbaceous plant biomass across a flood frequency gradient, geomorphic settings and grazing exclosures. Community and biomass changes were also examined over time in relation to wetting events. The results demonstrate the importance of wetting on plant communities across timescales. At longer timescales, flood frequency influences community composition; at shorter timescales, wetting increase plant biomass and has a secondary influence on community composition. Plant biomass is also influenced in the short-term by grazing, but there is little influence of grazing on community composition. Soil nutrients do not vary systematically across the floodplain and have little influence on species distributions. We conclude that reduced water availability due to water resource development will result in reduced productivity in the short-term and community composition changes in the long-term.     

Role of nurse shrubs in restoration of an arid rangeland: Effects of microclimate on grass establishment

A perennial forage grass, Agropyron desertorum was sown under the canopies of four shrub species or in open areas to test for facilitation during seedling establishment in an arid rangeland in Karnakh, Northeast Iran. Height, area and volume of shrubs were measured. Microclimate conditions and seedling establishment were assessed three times within two consecutive growing seasons. Near surface light intensity and air temperature were lower under shrubs, which led to initially higher soil moisture and grass establishment under the canopy of some shrub species. The leguminous shrub (Astragalus gossypinus) showed facilitation during moderate stress (summer 2009), but shifted to a negative effect during the severe drought (summer 2010). Competition, possibly for light, reduced the establishment of Agropyron seedlings under the cushion-like shrub (Acantholimon prostegium). Salsola arbusculiformis and Artemisia kopetdaghensis respectively showed a neutral and a facilitation effect in the first season, but a combined effect of allelopathy and drought led to the high mortality of Agropyron seedlings under their canopy. In conclusion in this arid rangeland, shrubs may facilitate establishment of understory plants under moderate drought stress, and for non-resource factors (light and temperature), but these positive effects are suppressed due to competition under severe drought conditions.     

Linking landscape and species: Effect of shrubs on patch preference of beetles in arid and semi-arid ecosystems

Linking individual behavior to spatial population processes, may clarify the complex link between species distribution and landscape properties. We asked how shrubs affect beetles in drylands and tested if we could explain distribution patterns of beetles by individual response to shrub landscape. We studied patch preference of ground-dwelling beetles segregated in a two-phase mosaic landscape, composed of shrub-covered and open patches and hypothesized that species richness and abundance are higher under shrubs due to the ameliorated microclimatic conditions and greater food resources. Pitfall trapping showed that shrub patches were preferred in shrub poor ecosystem because there was more food available under shrubs and cooler temperatures. However, similar conditions resulted in shrub preference only in an arid ecosystem, whereas in a semi-arid ecosystem, with high cover of shrubs, we found more beetles in the open patches. Observations in beetle movement patterns explained the contradicting effects of shrub patches in the two ecosystems. Beetle movement was affected by shrubs’ shading suggesting dependency on shrub structure rather than speciesdependency. Integrating analysis of beetle distribution in the population level with analysis of individual movement provides a robust framework for linking landscape properties to species behavior and distribution in a patchy landscape.     

区域可持续发展中的环境伦理案例分析:不同社会群体责任

环境伦理是对人与自然之间道德关系的认知,在区域发展中构建可持续发展的环境伦理观是实现人与环境协调的核心内容。从区域发展的案例入手,从哲学层面分析区域发展中人与环境产生冲突的原因,构建区域可持续发展环境伦理观,明确不同利益主体应承担的环境伦理责任与义务,是实现可持续发展的必要内容。本文对云南省林浆纸一体化工程进行环境伦理探讨,分析了桉树种植的土地资源、生态效应、纸浆生产的环境影响、经济效益、利益流向等一系列问题;从环境伦理角度对林浆纸工程进行分析,提出了可持续发展环境伦理观建立和环境伦理规范,认为在利益冲突的形势下,应该遵循"非人类中心"的环境伦理准则,贯彻人地和谐的自然观,综合考虑生态安全原则、综合效益原则、公平原则、共赢竞争原则,采取综合思维方法,构建可持续发展的环境伦理观;分析不同社会团体在区域可持续发展建设中的环境伦理责任,提出了决策者群体、企业家群体、媒介群体、科学家群体、公众群体等在环境伦理意识、环境伦理责任、环境伦理义务等方面所应起到的作用。     

放牧对准噶尔荒漠植物群落及土壤特性的影响

通过比较封育6年的围栏内外植物群落种类组成、结构差异,以及土壤特性,研究了家畜啃食对新疆准噶尔荒漠植物群落及土壤特性的影响.使用X2-test和U-test分析表明,围栏内外相比,植物种数(n=7.03)、半灌木种数(n=2.40)、草本植物种数(n=4.63)、植被盖度(35.77%)和生物量(144.19 g/m2)在围栏内显著增加,而植被密度在围栏外显著降低(87.93株/m2).灌木中,梭梭(Haloxylon ammodendron)在围栏内出现的频率和密度显著增加(X2=4.63,p＜0.05;z=2.56,p＜0.05).小半灌木中,博乐绢蒿(Seriphidium borotalense)在围栏内出现的频率和密度显著高于围栏外(X2=13.08,p＜0.01;Z=4.01,p＜0.01).4种多年生草本植物的密度在围栏内均显著升高,有3种在围栏内出现的频率也同时明显高于围栏外.二年生草本植物沙生婆罗门参(Tragopogon sabulosus)在围栏内出现的频率和密度显著高于围栏外(X2=4.71,p＜0.05;Z=2.51,p＜0.05).4种一年生草本植物在围栏内外出现的频率均无显著差异,其中3种在围栏内外的密度也无明显变化.研究结果表明,过度放牧导致灌木和半灌木衰败;多年生和二年生草本植物几近绝迹;一年生植物所受影响则较小.土壤理化特性中,围栏内土壤水分显著低于围栏外(Z=2.65,p＜0.01),HCO3、Cl-和速效K含量在围栏内外土壤中差异显著.作者建议在准噶尔荒漠建立一定数量和面积的永久性围栏以维系物种多样性.     

Is the analysis of plant community structure better than common species-diversity indices for assessing the effects of livestock grazing on a Mediterranean arid ecosystem?

Grazing in arid Mediterranean ecosystems brings about changes in species diversity, but the best way to measure such changes is unclear. In this study we compared various methods in order to identify indicators that might be useful for the management and conservation of grazed arid Mediterranean ecosystems.Changes in community structure and composition were compared along a previously studied grazing gradient in Cabo de Gata-Nijar Natural Park. Plant diversity was measured by calculating diversity (Shannon information index), evenness (Pielou index) and richness (species number). Rarefaction curves were used to measure plant species richness and the results were compared with traditional richness values. Community structure was measured as the percentage of bare ground and the coverage of overall perennial grasses, Stipa tenacissima L., perennial shrubs and annual plants. Our results showed that the proportion of bare ground, the cover of perennial shrubs and the relative abundance of S. tenacissima are good indicators of grazing effects on vegetation. Overall plant community structure was more sensitive to the grazing gradient than were the diversity indices. Finally, the adequacy of standardized methods for comparing species richness (i.e. rarefaction curves) along a grazing gradient are discussed.     

内陆干旱区土地利用变化的景观格局特征分析——以新疆白杨河流域为例

基于GIS/RS环境对两期Landsat7-ETM 影像数据进行土地利用分类处理,运用景观生态学原理和数理统计分析方法,从区域整体景观格局水平和土地利用类型水平两个角度,选取景观多样性指数等5个指数描述白杨河流域土地利用变化的景观格局特征。结果表明:研究区各土地利用类型面积都有不同程度的变化,除草地和未利用土地有所减少,其他土地利用类型都有不同程度的增加。从景观水平上看,区域景观异质性在增大,景观斑块的连通性降低,表现为多样性指数和均匀度指数呈增加,优势度指数减小;从类型水平上看,5年间人类对景观的干预程度较大,对人工景观的干扰强于半自然景观,体现在半自然景观类型的分离度较小,而人工景观类型的分离度较大。同时,景观周长-面积分维度指数的增长趋势说明景观斑块的自我相似性减小,几何形状趋于复杂化。总体上,是人类活动加剧破坏了自然绿洲内部的整体性和完整性,并且人类活动干扰还在增加。     

Climatic change and rainfall patterns: Effects on semi-arid plant communities of the Iberian Southeast

The structure and functioning of semi-arid ecosystems are strongly influenced by precipitation patterns. Water availability in such environments is highly pulsed, and discrete rainfall events interspersed with drought periods are important components of the annual water supply. Plant communities do not only respond to rainfall quantity, but also to variations in time, so that relatively small changes in rainfall frequency (i.e., pulsed inputs) may have strong effects on communities. Within the Mediterranean basin, climate change models forecast a decrease in mean annual precipitation and more extreme events (i.e., less rainy days and longer drought periods between events), along with seasonal changes. However, little is known on the consequences of these future precipitation changes on plant communities, especially in semi-arid environments. Here, we summarize the few experiments that have manipulated rainfall patterns in arid and semi-arid areas worldwide, and introduce the first results of a pioneer, long-term rainfall exclusion in the semi-arid southeast region of the Iberian Peninsula. The experiment is not only manipulating the amount of rainfall, but also its frequency and seasonal distribution in a grassland-shrubland in the Tabernas desert (Almería, Spain). This work monitored the effect of precipitation changes on different ecosystem processes for five years, at the species and community level, concluding that this plant community (as other communities studied in the same area) exhibited great resilience to changes in rainfall availability, likely caused by plant adaptation to large intra- and inter-annual precipitation variability.     

基于景观破碎度分析的传统地域文化景观保护模式——以浙江诸暨市直埠镇为例

传统地域文化景观空间的破碎度研究是在借鉴自然生态空间破碎度研究的基础上,吸收破碎度研究的经验、理论、观点和方法,以整体人文生态系统为对象,将传统地域文化景观看做是人类生存与发展的地方性生境,研究传统地域文化景观的时空过程与景观格局,目的在于探讨传统地域文化景观连续性和整体性保护的模式.以浙江省诸暨市直埠镇作为典型案例,...     

干旱区工业共生网络优化研究——以新疆石河子市为例

立足资源和环境约束,对干旱区工业共生过程中链条的设计、水资源的优化利用进行了定性探讨,提出两个观点:干旱区需在确定支柱产业和重点行业的基础上再进行纵向主导产业链与横向耦合共生链的设计;通过促进农业节水用于工业、工业共生反哺农业、提高工业重复用水率来解决工业用水不足的矛盾。继而运用模糊数学建立了多目标模糊优化模型,对共生网络的优化进行了定量研究。所建模型以共生网络经济效益、社会效益、资源效益和环境效益的综合最优作为目标函数,以非线性的相对优属度作为权重系数,将资源瓶颈、环境污染排放总量控制目标等作为约束条件,来求解多目标问题,既科学表达了共生系统的复杂性,又充分体现了工业共生追求经济-环境双赢的内涵。实例应用则表明以上思路、模型与方法具有理论价值和实践意义。     

论都市郊区游憩景观规划与景观生态保护——以北京市郊区游憩景观规划为例

城市化是我国21世纪经济社会全面发展的重要推动力量,城乡一体化整合发展是城市化发展的战略主题。面向都市圈的游憩产业和游憩景观成为郊区发展中最活跃的经济成分和景观要素。科学合理地利用郊区开放空间和进行游憩景观规划对保护都市圈景观生态环境具有重要意义。本文以北京市郊区为例,在典型研究郊区景观利用与景观生态破坏和定量评价景观行为相容度的基础上,论述了都市郊区景观开发与游憩景观规划的规律、游憩景观区域规划和乡村游憩景观规划,并提出了建设北京市郊区完善的游憩景观体系和景观生态保护的具体措施。     

城市景观对住宅价格的影响——以杭州市为例

优美的城市景观是人们日常生活休闲、娱乐的场所, 给人们带来心理上的愉悦和舒适感, 对城市的品质内涵也有重要影响。由于大多数景观效益是隐性的, 其舒适性价值难以用货币价格直接测量, 国内外学者广泛采用特征价格法进行实证研究。本文以杭州市为例, 从建筑、邻里、区位、景观四个维度选择25个解释变量构建特征价格模型, 定量评估了城市内部各类景观对住宅价格的影响。实证结果表明:住宅价格与到西湖和公园的距离呈负相关关系, 而与公园的面积呈正相关关系:其中, 到西湖和最近公园的距离每增加1%,住宅价格将分别下降0.240%和0.036%;公园的面积每增大1%,附近的住宅价格则提高0.012%;广场、山景、钱塘江等景观也对周边一定范围内房价具有显着的提升作用。     

Integration of InVEST-habitat quality model with landscape pattern indexes to assess mountain plant biodiversity change: A case study of Bailongjiang watershed in Gansu Province

Journal of Geographical Sciences - Mountains in western China, hosted rich biodiversity and millions of people and inhabitant with vital ecosystem services, had experienced the most serious...     

三维景观GIS几何建模方法——以无锡唐城为例

本文实现了以 4D测绘数据 (DEM、DOM、DLG、DRG)为基本数据源的无锡唐城古建筑三维数字景观GIS。同时 ,在三维GIS传统三维空间数据模型的基础上 ,提出面向对象的三维建模点对象的划分不同与二维GIS中的点对象 ;针对基于面状的三维GIS,提出有向曲线构建面状复杂单体的几何建模方法是较为简捷的途径。     

Desert detritivory: Nutritional ecology of a dung beetle (Pachysoma glentoni) subsisting on plant litter in arid South African sand dunes

Dry conditions limit microbial decomposition of plant litter in deserts, which leaves a primary role to detritivorous macroarthropods. In the sandy arid strip along the west coast of South Africa, such detritivores include the large scarabaeid dung beetle Pachysoma glentoni. Highly unusual among dung beetles, this species collects surface litter and drags it into an underground storage and feeding chamber which is abandoned after 6–7 days. Fresh stores for single beetles and for breeding pairs (mean depths: 30 and 39 cm) contained about 1.1 and 2.9 g organic matter, respectively. Using ergosterol as a biomarker for fungal biomass, we tested the hypotheses that (1) the dry detritus takes up water underground; (2) this promotes fungal growth on the detritus, and (3) fungi are the main food of the beetles. These hypotheses were disproved, but the stored litter, including floral remains, was shown to have relatively high quality (mean atomic C:N ratio: 35) and the beetles assimilated about 60% of it. Estimated weekly water gain per beetle, supplied entirely by the food, was about 0.6 g. Our results highlight unique nutritional adaptations to survival in deserts without the usual dung beetle food: wet dung of large herbivores.     

“亚喀斯特”概念与景观特征的初步探讨——以贵州为例

"亚喀斯特"作为贵州等地喀斯特生态环境的特殊组成部分,属典型的生态脆弱区,理清其概念内涵及景观特征是认识这一特殊环境的重要途径,本文拟对其概念内涵、景观特征进行初步探讨。分析认为,亚喀斯特是介于一般典型喀斯特与非喀斯特间的另一种地貌景观,三者在岩层特性、地貌发育、景观特征及生态环境效应若干方面均存在显著差异。构成亚喀斯特的岩性主要是不纯碳酸盐岩(如泥质白云岩、泥质灰岩)及碳酸盐岩与非碳酸盐岩组合的夹层,岩石含泥质成分高,洞穴分布极少,地下水资源模数较大;地貌以丘陵谷地、浅中丘、浅切割低中山为主,地形起伏较缓;成土母质丰富,土层较厚,宜农耕地较多,农用价值相对较大,但同等条件下土壤侵蚀量较高;植被生长茂盛、覆盖度高,生态环境相对较好。     

城市社区的邻里性本质及其影响机制研究——以广州15个社区为例

当前中国的城市与社会面临着多元的剧烈重构,存在种种问题与挑战,人本回归的发展命题下,社区更是一个意义深远的实践单元。中国社区研究多针对某一主题内容如治理、情感、环境等开展具体实证分析,而全面系统性的社区基础研究相对缺乏。本研究基于“人文”与“结构”的理论分析视角,结合社区的本质内涵辨析,对社区进行“内核-外核”的系统建构;具体选择广州15个样本社区,基于3302份问卷调研数据,采用结构方程模型剖析社区系统的运作逻辑,重点探究作为社区本质的邻里性的影响机制。研究发现：① 社区系统蕴含了多元的有机结构和丰富的运作逻辑。② 物质空间属性相较其他属性变量,对邻里性具有相对最强的正向效应力,同时又与其他维度属性紧密相关,体现其关键地位。③ 在社区系统中,四个维度属性对邻里性水平的影响呈现了差异化的特征,体现了相应的运作内涵。     

干旱对河西走廊植被净初级生产力的影响

干旱对生态系统碳循环具有重要影响,随着气候变暖,全球干旱事件频率不断上升,研究干旱对植被净初级生产力的影响具有重要意义.提高植被净初级生产力(NPP)的时间分辨率是认识干旱对其影响机制的重要途径.基于5天NDVI遥感数据,以河西走廊为研究区,利用CASA模型估算2010-2015年5天步长尺度的NPP,将5天降水为零定...     

基于社会交换理论的社区旅游支持度模型及应用——以黄山风景区门户社区为例

门户社区毗邻风景区且处于其出入口位置,在旅游发展中面临特殊的机遇和难题.依据社会交换理论,选择“社区参与度”、“居住区条件”、“对旅游机构信任度”、“旅游利益感知”、“旅游成本感知”、“社区满意度”和“旅游支持度”7 个结构变量构建社区旅游支持度测度模型,以黄山风景区的4 个门户社区为研究案例,对该模型进行检验,通过结构方程模型分析和因子分析,探讨模型内各变量对社区旅游支持度发挥作用的路径及造成同一风景区不同门户社区支持度差异的影响因素.研究结果表明:① 总体而言,旅游利益感知和社区满意度对旅游支持度有正向影响;居住区条件、对旅游机构信任度和社区满意度对旅游利益感知有正向影响;社区参与度、居住区条件和对旅游机构信任度对社区满意度有正向影响.社区参与度对旅游利益感知正向影响不显著,旅游成本感知这一变量与其他变量之间关系不大.②各地居民感知和旅游支持度存在差异,南门汤口各维度总体得分最高,北门甘棠-耿城次之,东门谭家桥第三,西门焦村得分最低.③ 门户社区与黄山风景区的空间关系、区位条件与交通格局、旅游经济发展水平等因素造成了各门户社区旅游支持度的差异.