中国生态脆弱带人地关系行为机制模型及应用

以农牧交错带为研究对象,通过建立人地关系行为机制模型,探讨外部社会经济因素影响土地退化的机制,并重点就当前正在实施的退耕还林还草政策所带来的生态经济效果进行分析。模型拟合结果显示,利用玉米及农作物秸秆作为饲料,扩大舍饲动物饲养,或者扩大种植葵花或油料作物等商品作物以替代自给性作物糜子,将可以在不加剧水土流失的前提下增加农户收入。模型结果还显示,非农就业机会增加时,农户会减少坡地垦殖。这表明推进农村工业化和城镇化发展,增加农民非农就业机会,鼓励农民进城的政策对于黄土高原的水土保持也是有促进作用的。     

Willingness and Participation of Local Communities to Manage Communal Grazing Lands in the Lake Tana Biosphere,Ethiopia

Sustainable management of communal grazing lands in Ethiopia is crucial to sustain livestock productivity and reduce land degradation. This study was conducted in Dera district, Ethiopia, to assess local communities’ perceptions of the degradation and their attitudes on the management of communal grazing lands. Household surveys, group discussions, and the contingent valuation method were used to gather data. Results indicated that local communities are aware of the degradation and are willing to participate in the management of communal grazing lands by contributing labor and cash. Labor contribution is positively and significantly correlated to total livestock units (TLU) and credit, and negatively correlated with household size and extension service. Significant correlation between the willingness to contribute cash and TLU was also detected. Community participation and discussions, demarcation of boundaries, equity in benefit sharing, and engaging both formal and informal institutions are crucial to sustain and enhance the effectiveness of grazing land management.     

Traditional intramontane mobility in Garhwal Himalaya: A survey of subsistence practices in the Pindar basin, Uttaranchal

This paper looks at the key resource interactions driving the current trend in intramontane mobility as a traditional subsistence practice in the Garhwal Himalaya region of Uttaranchal, India. For hundreds of years, the natural resource based mid-altitude villages in the Pindar River basin hinged on the annual summer migration to highland pastures. Where self-sufficiency has been obtained through an environmentally embedded tradition of crop and livestock farming, highland forests and alpine pastures continue to provide the human and animal requirements of fuelwood and fodder, as well as the forest products defining traditional diets and cottage industry. The paper reports the data from a rapid appraisal survey of resources obtained by households in selected mid-altitude villages from the seven highland locations that have sustained the centuries-old subsistence culture of the Pindar basin. While livestock have been the crucial link in a forest/fodder–manure–cultivation chain that has necessitated households' dependence on highland pastures and forests, over the last four decades there has been a decline in the numbers engaged in livestock raising and, concomitantly, the annual migration to summer pastures. Instead, there is a trend towards increased cultivation of cash crops and forest resource collection in the traditional highland encampment areas.     

普兰县农牧结合潜力分析（英文）

农牧结合是高寒牧区放牧系统的一项重要的实践,具有实现农业和牲畜业可持续生产的重大潜力。然而,目前青藏高原的农牧业分离已经导致集约化农业、草地退化和饲料短缺的问题产生。因此,为探索高山放牧系统中农牧结合的潜力,本研究以中国普兰县为例,基于多数据源,分析了牧草生产潜力和牲畜产量,并从饲草供给角度评估了农牧结合的潜力。结果表明:普兰县可用于人工种草的潜在边际土地约560公顷,基本位于环境条件较好的普兰镇周边。而积温是牧草种植的主要环境限制因子,今后牧草种植应注重品种的抗寒性和生长周期,同时也要注意人工草地建立后的退化和沙化问题。另外,虽然2012–2016年普兰县牲畜数量明显下降,但高寒草地放牧牲畜数量依然高于农牧景观的牲畜放牧数量。该地区目前放牧牲畜数量一般维持在约11万只羊单位,而人工草地和作物秸秆能够提供约1.1万只羊单位的饲料,约占农牧景观中牲畜数量的一半。普兰县农牧结合可以适当补充放牧条件下牲畜饲料的缺额,尤其是在农牧区的普兰镇。本研究结果对未来牧草生产和发展农牧结合具有重要的指导意义。     

Land degradation is not a necessary outcome of communal pastoralism in arid Namibia

In Otjimbingwe, a region of arid south-central Namibia, human population densities are high and these communal pastoralists own large numbers of livestock. Such situations are commonly perceived to lead to the ‘tragedy of the commons'. This region lends itself to a comparison of the effects of communal and commercial farming (with private land ownership) because the communal area is completely surrounded by commercial farms. In spite of far higher stocking densities on the communal areas and the absence of an overall grazing strategy, we found no evidence of the ‘tragedy of the commons' on Otjimbingwe. Indeed, the communal areas did not differ in a number of soil and vegetation parameters from the commercial farms. These results point both to the resilience of arid environments to high stocking levels and the over-riding influence of abiotic variables on environmental quality.     

Rangeland management impacts on the properties of clayey soils along grazing gradients in the semi-arid grassland biome of South Africa

The grassland biome of South Africa is a major resource for livestock farming; yet the soils of these rangelands are stressed differently by various management systems. The aim of this study was to investigate how basic soil properties respond to different management systems. For this purpose we sampled rangeland management systems under communal (continuous grazing), commercial (rotational grazing) and land reform (mixture of grazing systems) farming. Within each of these systems a grazing gradient was identified with decreasing grazing pressure with increasing distance to the water points. Results showed that communal farms with continuous grazing were generally depleted in the respective nutrient stocks. The depletion increased with rising grazing pressure. Along that line there was a breakdown of macroaggregates with losses of the C and N stored therein. However, the commercial farms also exhibited a decline of macroaggregates and their associated C content nearby the water points. Aggregate fractionation is a sensitive indicator for detecting the beginning of soil degradation in this biome; yet, degradation was less pronounced under the rotational grazing of the commercial farms than under communal property right conditions. Hence, soil analyses confirm that fences and appropriate grazing periods are needed to manage these rangelands sustainably.     

Impact of land cover types on the soil characteristics in karst area of Chongqing

The 26 plots including natural forestland, secondary forestland, shrub-grassland, sloping cropland, artificial forest and abandoned field, were selected to discuss the impact of land cover on the soil characteristics in the three karst districts of Chongqing. The results showed that: (1) After the vegetation turned into secondary vegetation or artificial vegetation, or reclamation, soil physical properties would be degraded. In the surface-layer soil of sloping cropland, the contents of > 2 mm water-stable aggregates decreased obviously with apparent sandification. (2) The contents of soil organic matter and total nitrogen are controlled completely by vegetation type and land use intensity. The increasing trend is rather slow in the early days when over-reclamation is stopped and the land is converted to forest and pasture. (3) Herbaceous species increase and woody plants species decrease with the increase of land use intensity, therefore, the soil seed banks degrade more seriously. (4) The soil degradation index has been set up to describe the relative soil degradation degree under the conditions of different vegetation types. (5) Land cover has a significant effect on karst soil characteristics, land degradation in the karst ecosystem is essentially characterized by the different degradation of soil functions that serve as water banks, nutrient banks and soil seed banks.     

重庆喀斯特地区土地覆被类型对土壤特征的影响

1 Introduction The karst region of Southwest China, with Guizhou Province as the center, extends across Yunnan Province, Guangxi Zhuang Autonomous Region, Sichuan Province, Chongqing, western Hunan Province, Hubei Province, and Guangdong Province, coveri…     

岩溶山区不同植被群落土壤生态系统特性研究

自然植被演替成为次生植被、人工林或人工开垦利用后,岩溶山地土壤物理性能退化;沙化现象明显;坡耕地土壤长时间持水供水性能、抗旱性能降低;土壤种子库中草本种子比例大,木本植物种子少,土壤种子库退化更严重。研究区土壤有机质和全N受植被类型和土地利用强度影响明显,坡耕地土壤有机质较林草地系统低,退耕还林还草后,土壤有机质含量稳定增加。与自然植被相比,人工林、次生林系统土壤有机质含量仍较低。从弃耕地→灌草坡→次生林地的演替过程中,土壤种子库生态优势度呈降低趋势,物种丰富度和多样性增加。研究结果认为,岩溶生态系统土地退化的实质是土壤作为水库、养分库和土壤种子库功能的差异退化。     

应对青藏高原东部的草地退化:政府和当地牧民有何差异(英文)

In the last decade, there has been increasing interest in climate change, pasture degradation and its driving forces, and innovations in nomadic pastoralism on the Tibetan Plateau. However, little is known of indigenous strategies of adaptation to pasture degradation, which limits the effectiveness of adaptation strategies planned by local government. This paper analyzes nomads’ strategies of adaptation to pasture degradation on the basis of a field survey of three townships of Dalag County in the source regions of the Yangtze and Yellow rivers. Pastures there have evidently degraded, with pastures in Wasai mainly in a state of slight or medium degradation and those in Manzhang and Jianshe in a state of medium or severe degradation. With the degradation of pasture, the grazing time is reduced, which affects the livelihoods of nomads. Although the Four-Package Project has commenced in this region, there is still severe fodder shortage in winter and spring. The traditional hay storage strategy does not work because of pasture degradation, and few nomads establish fenced and artificial pastures. Therefore, nomads have employed other strategies, such as renting pasture, providing supplementary feed, and diversifying their livelihoods. Local strategies taken by nomads can provide valuable insights into ecological restoration and livelihood improvement in the region and suggest changes to means promoted by local government. It is necessary to seek new means that combine the best aspects of nomadic pastoralism with modern stockbreeding technologies to help nomads adapt to pasture degeneration and improve their livelihoods.     

Soil degradation assessment in mixed farming systems of southern Africa: use of nutrient balance studies for participatory degradation monitoring

Soil degradation assessments for mixed farming systems of the Molopo Basin (North West Province, South Africa and Southern District, Botswana) are provided from farmer–based research, designed to quantify nutrient fluxes across the farming system and to analyze the social, economic, political and environmental factors affecting nutrient management practices. This paper discusses the practical difficulties of how to use participatory farmer–led studies to assess soil degradation extent and its causes, and of then disseminating this information to farming communities and policymakers. Nutrient balance studies show that land degradation is evident on arable fields as soil nutrient depletion (the main threat to poorer manure–reliant farmers) and soil acidification (the main threat to wealthier farmers who have become dependent on inorganic fertilizer additions). Integrated nutrient management strategies involving both compound fertilizer additions and regular manure inputs can mitigate most soil degradation even on the sandy infertile Kalahari soils, but remain infrequently practised. The need to retain nutrient flows through the livestock sector from rangeland to arable land is thus vital to environmental sustainability and offers an applicable entry point for agricultural development initiatives and support. Factors identified as threatening the flow of nutrients from rangelands to arable lands include policy settings in terms of the different support programmes offered to communal farmers, village–level extension advice, household poverty levels and labour constraints.     

海南岛中部山区热带天然林与人工橡胶林土壤特性对比研究

通过调查取样,对比分析了海南岛中部山区天然林地及林地转变为橡胶林后的土壤物理和化学性质差异.结果表明:(1)不同林地对砂、粉粒和黏土粒度分布的影响显著,天然林地0～30 cm、30～60 cm和60～120 cm三个深度的土壤的物理性黏粒含量均高于人工林地.(2)天然林地和人工橡胶林三层的土壤容重和田间持水量均存在显著差异,天然林地0～30 cm和30～60 cm的土壤田间持水量大于人工橡胶林.(3)两种林地的上、中、下三层土壤的有机质、全氮、碱解氮均有很大差异.天然林地土壤上层( 0～30 cm)有机质     

Spatial variability of selected soil properties in relation to land use and slope position in Gelana sub-watershed,Northern highlands of Ethiopia

Land degradation resulting from land-use changes and soil erosion has been a serious environmental problem in Ethiopia. This study addressed the effects of land use and slope position on soil physical and chemical properties in the Gelana sub-watershed, Northern highlands of Ethiopia. A total of 63 soil samples were collected and analyzed using a two-way ANOVA. Results showed that clay, soil pH, soil organic matter, total nitrogen, cation exchange capacity, and exchangeable base contents of the cultivated land were significantly (p < 0.001) lower than those of the forest land, while soil bulk density, available phosphorous, and percentage base saturation were higher for cultivated land than forest land. In general, soil fertility declines as land use changes from forest to grazing and cultivated lands. Sand, clay, bulk density, soil pH, organic matter, total nitrogen, carbon:nitrogen ratio, available phosphorous, cation exchange capacity, exchangeable cations, and percentage base saturation showed significant variation due to slope position differences. Therefore, the study reinforces the need for integrated watershed management for sustainable agricultural production in the study area.     

ONE LAST STAND? FORESTS AND CHANGE ON ECUADOR'S EASTERN CORDILLERA

ABSTRACT. Tropical montane forests are known for their ecological importance. Most montane forests in Ecuador have been converted to agriculture, and those that remain are concentrated on the eastern cordillera. Understanding of land‐use‐land‐cover change in this ecological zone is inadequate. Using remote sensing (Landsat tm, spot ) and fieldwork, we document land‐use‐land‐cover change in two watersheds on Ecuador's eastern cordillera (Cañar Province). During the 1990s the region experienced a 0.58 percent annual rate of deforestation, but two areas within it show active signs of re/afforestation. Although conversion of forest to pasture for cattle grazing continues, human migration to the United States is likely to affect the trajectory of future land‐use‐land‐cover change.     

西南地区山地不同土地退化类型特征及调控途径

土地退化不仅是目前全还需性的重大环境问题之一，而且也是重大的社会和经济问题之一，西南地区的土地退化是以水力侵蚀为主要动力形成的，文中简述了西南地区的土地退化状况，选择了4个（楚雄市、遂宁市，毕节地区及元谋县）山地不同土地退化类型进行分析，讨论了土 退化过程，提出了土地退化调控途径。     

放牧对高寒草甸地表特征和土壤物理性状的影响

在中国科学院海北高寒草甸生态系统定位站地区,选择五种处于不同放牧强度的高寒草甸为研究对象,进行放牧对高寒草甸植被演替规律和土壤对放牧压力的响应过程研究,为合理利用和提高草地生产力提供科学依据。结果表明:随着放牧强度的增加,高寒草甸地上生物量呈急剧下降趋势,由禾草草甸的646.24 g/m2下降到小嵩草草甸的328.16 g/m2,容重逐渐减小;在小嵩草草甸阶段地表逐渐出现塌陷和裂缝,0~10 cm土层中根土体积比逐渐变大;土壤的质地类型发生变化,由禾草草甸粘壤土转变为壤质粘土;放牧强度对牧草返青开始时间和生长期都没有影响,但在重牧处理时,非生长季地温降低程度很明显。     

Pastoral nomadism in the forest-steppe of the Mongolian Altai under a changing economy and a warming climate

The population structure, educational level and the livelihoods of 82 households of pastoral nomads, the organization of livestock husbandry and its impact on the grassland and forest ecosystems of the Dayan high valley (>2000 m a.s.l.) in the Mongolian Altai, western Mongolia, were surveyed using interviews and secondary information from official sources. Changes following the transition from centrally planned (before 1990) to market economy were analyzed. Two thirds of the monthly mean income of ca. 310 USD per nomad household is cash (ca. 55 USD) or non-cash (ca. 165 USD) income from livestock husbandry. Cashmere sale accounts for 70% of the cash income from livestock husbandry, which has led to a strong increase of goat numbers after 1990. Forests are used for livestock grazing, fuel wood collection, logging, and fruit collection. Livestock breeding and the seasonal migration of the nomad households are no longer organized by the government. To avoid transportation costs, two thirds of the families have reduced their seasonal migrations. This trend was favored by rising temperatures and earlier snowmelt during the last few decades, but resulted in a shortage of fodder and intensified forest use. Therefore, the use of grasslands and forests in the Mongolian Altai is no longer considered to be sustainable.     

Monitoring degradation in arid and semi-arid forests and woodlands: The case of the argan woodlands (Morocco)

Arid and semi-arid forests and woodlands (hereafter called «dryland forests»), in spite of their ecological and social importance, have received little attention in land change studies. Growing evidence shows that these forests have been receding at very high rates in many places, suggesting a need for a better understanding of the processes and causes of dryland forest degradation. Changes in the extent of dryland forests are debated in part because estimates of forest and woodland areas in drylands are uncertain. Causal explanations of the degradation tend to draw on the literature on desertification and tropical deforestation, and to emphasize either local or remote, and either social or biophysical drivers. This study contributes to a better understanding of dryland forest degradation as a basis for conservation policies. Firstly, we argue that monitoring arid and semi-arid forests and woodlands using area estimates may lead to an underestimation of the severity of change because tree density change often exceeds area change. Secondly, we argue that the analysis of degradation processes in these multifunctional landscapes should integrate both local and remote, and both social and biophysical factors. We use a case study of degradation in the argania woodlands in semi-arid to arid Southwest Morocco to test these two claims. We used gridded tree counts on aerial photographs and satellite images to estimate forest change between 1970 and 2007, and we tested several possible causes of change on the basis of original socio-economic field surveys and climatic and topographic data. We found that forest density declined by 44.5% during this period, a figure that is significantly underestimated if forest area change is used as a measure of degradation. Increasing aridity and, to a lesser extent, fuelwood extraction were related to forest decline. No effect of grazing by local livestock was found.     

Grazing itineraries and forage selection of goats in the Al Jabal al Akhdar mountain range of northern Oman

In view of the repeatedly reported overstocking of the high-altitude pastures on Al Jabal al Akhdar, northern Oman, plant species abundance, cover and frequency, and herbaceous mass yield were studied in ungrazed versus heavily grazed areas of this mountain range. In addition, plant species selection by goats along a gradient of 1000–2000 m and spatial extent of pasture areas were investigated after abundant rainfall and a subsequent 6-months dry spell by means of manual observation and GPS/GIS tools.The substantially higher species diversity and herbaceous mass yield in the ungrazed area illustrate the production potential of these mountain pastures or, respectively, the biodiversity and productivity loss resulting from continuous grazing. The concentration of goats' selection on only a dozen herbaceous and ligneous species favours pasture encroachment with poisonous shrubs such as Nerium mascatense in the lower and Dodonaea viscosa in the higher altitudes. Given the spatially limited extent of pasture areas, these are exposed to high stocking rates. Therefore, grazing and feeding schemes need to be developed which reduce livestock pressure on the pastures, taking into account local property rights, herding skills and the recovery potential of the vegetation, which heavily depends on unpredictable rainfall events.     

干旱半干旱区山地森林类型的土壤水文特征

处于中国西北干旱半干旱区的山地森林以独特的水文作用成为山前平原及川区绿洲生态经济系统稳定发展的基础。以无林地为对照,对典型山地森林祁连山水源涵养林区4种主要林分类型的土壤水文物理性状、土壤入渗特性及土壤贮水性能进行定位研究,结果表明:(1)不同林分类型的土壤容重、孔隙度和孔隙比等表征土壤水文物理性质的指标明显好于无林地,且0～20 cm土层好于20～40 cm。各指标林地间差异较大,其中青海云杉林和湿性灌丛林好于祁连圆柏林,干性灌丛林较差。(2)乘幂方程能较好的反映研究地区不同林分的土壤入渗过程,有林地入渗性能好于无林地,青海云杉林、湿性灌丛林、祁连圆柏林、干性灌丛林的平均渗透速率值分别是无林地(1.68 mm/min)的15.72,13.39,3.55,1.94倍。(3)有林地的土壤吸持、滞留贮水量、土壤涵蓄降水量、有效涵蓄量均表现为青海云杉林>湿性灌丛林>祁连圆柏林>干性灌丛林>无林地,且0～20 cm土壤贮水性能好于20～40 cm。说明在涵养水源和水分有效性方面,青海云杉林和湿性灌丛林优于祁连圆柏林和干性灌丛林。从涵蓄水分、涵养水源角度来考虑,可优先考虑青海云杉林和湿性灌丛林。