The Role of Soil Surface Crusting in Desertification and Strategies to Reduce Crusting

Soil crusting decreases infiltration, increases erosion, and impedes vegetation establishment, so reducing the impact of crusting is of major importance in combating desertification. Although surface crusting has been the subject of considerable research over the past 50 years or more, the practical management of soil crusts remains a challenge for many dryland communities. Crusting occurs in two steps, an initial aggregate breakdown period that occurs under rainfall and a subsequent hardening phase during drying. Several factors influence crust development, but the single most important one is soil aggregate stability. Strategies to reduce crusting can be based either on protecting the surface from raindrop impact or improving aggregate stability, or a combination of both. However, crust control is labor and/or capital intensive and must be thought out clearly in terms of the benefits to be achieved.     

Soil erosion in developing countries: a socio-economic appraisal

Soil erosion is the single most important environmental degradation problem in the developing world. Despite the plethora of literature that exists on the incidence, causes and impacts of soil erosion, a concrete understanding of this complex problem is lacking. This paper examines the soil erosion problem in developing countries in order to understand the complex inter-relationships between population pressure, poverty and environmental-institutional dynamics. Two recent theoretical developments, namely Boserup's theory on population pressure, poverty and soil erosion and Lopez's theory on environmental and institutional dynamics have been reviewed. The analysis reveals that negative impacts of technical change, inappropriate government policies and poor institutions are largely responsible for the continued soil erosion in developing countries. On the other hand, potential for market-based approaches to mitigate the problem is also low due to the negative externalities involved. A deeper appreciation of institutional and environmental dynamics and policy reforms to strengthen weak institutions may help mitigate the problem.     

Use of Soil and Water Protection Practices Among Farmers in Three Midwest Watersheds

Data were collected from 1011 farmers in three Midwestern watersheds (Ohio, Iowa, and Minnesota) to assess factors that influence the use of conservation production systems at the farm level. The “vested interests” perspective used to guide the investigation was derived from elements of social learning and social exchange theories. Respondents were asked to indicate their frequency of use for 18 agricultural production practices that could be adopted on Midwestern farms at the time of the study. Responses to the 18 items were summed to form a composite variable, termed “conservation production index,” for use as the dependent variable in multivariate analysis. Eleven independent variables were identified from the theory as likely predictors of conservation adoption, including respondents' perceptions about production costs, output and risks, and perceived importance of access to subsidies, technical assistance, and informational/educational programs. Regression analysis was used to assess the performance of the independent variables in explaining variance in the conservation production index. Explained variance in the three regression models ranged from 2% in the Minnesota watershed to 19% in the Ohio watershed. The researchers concluded that the model had limited utility in predicting adoption of conservation production systems within the three study watersheds. Findings are discussed in the context of conservation programs within the three areas.     

复合农林业的由来与兴起

由于人口的增长,人们对粮食、烧柴的需求与日俱增,致使森林面积减少,土壤等自然资源退化,生态环境恶化。对此于20世纪70年代提出了“复合农林业(Agroforestry)”,并发展成一门新兴的学科。它有意识地将多年生木本植物与农作物或家畜结合起来,在为农村提供烧柴、木材、饲料、粮食的同时,又可保持土壤肥力,达到持久农业的目的。它对我国大面积山丘地区自然资源的综合利用与保护有着重要的意义。     

河北省坝上地区气候与沙化关系的研究

本文利用坝上五县气象站近３０年资料进行数理统计，研究其与该区沙暴等自然灾害的关系。其结果表明：坝上地区近３０年来气温上升了０．７８℃；降雨量增加了１３．８ｍｍ；大风递减了２３．７个大风日和沙暴减少了９．２个沙暴日。同时根据不同介质的风蚀积沙观测资料，以及沙化与恢复指标，对该区的生态环境的初步恢复与改善进行了预测研究。     

ASSESSMENT OF GULLY-CONTROL STRUCTURES IN THE RIO NUTRIA WATERSHED,ZUNI RESERVATION,NEW MEXICO1

ABSTRACT: During the latter part of the 19th century and the early part of the 20th century, a major cycle of erosion, arroyo cutting, and gullying occurred in the southwestern United States. Since this erosion cycle began, many projects to control erosion, such as the Civilian Conservation Corps projects in the 1930s, were initiated. However, in the Southwestern United States few studies have documented the effect of these structures in reducing erosion or their effect on gully systems. As part of a watershed rehabilitation project on the Zuni Reservation, New Mexico, 47 structures made either of earth or rocks and 23 rock and brush structures were assessed. Sixty percent of the 47 earth or rock structures have breached and relative to dam height, 65 percent of 47 structures are more than 50 percent silted. Of the 23 rock and brush structures, 22 percent have breached or are close to breaching. Reasons for breaching of all structural types may be piping, scour immediately below the structures, large runoff and large drainage area, poor maintenance, headcutting, and active arroyo deepening and widening. In most cases, documentation does not exist on structure design, the specific purpose for a structure, or when these structures were built.     

SEDIMENT DEPOSITION ESTIMATION FROM CESIUM-137 MEASUREMENTS1

ABSTRACT The movement of fallout ¹³⁷Cs carried by soil particles was studied as an indicator of erosion and sedimentation in the Allerton watersheds and 4-H Memorial Lake located near Monticello, Illinois. Sediment deposition was greater in the waterway draining from watershed IB than in the waterway from watershed IA. At the average rate of 2.3 cm/yr of sediment deposition in the lake (from 1954 to 1979), there will be a loss of over 2 meters of water depth in the next century. However, there appears to be a decreasing rate of sediment deposition in the 4-H Memorial Lake as a result of improved conservation practices on the watersheds and the increased effectiveness of vegetated waterways and buffers for retaining sediment.     

开展新形势下环境保护宣传教育工作的几点思考

环境保护事业在发展，宣传教育工作也要与时俱进。环境保护不仅是一门专业，更重要的是一个理念，是新的文明和新的文化形态。宣传这种理念需要一种无私的奉献精神，更需要一种有效的手段。在强化公众的环保意识的同时，更要针对领导干部、企业负责人、消费者等不同群体开展环保教育，建立宣传教育的配套机制，依托多元主体，进行各有侧重的环境保护宣传教育。     

中小城市中学师生环保意识调查——以湖南省永州市为例

公众的环保意识对国家环境保护政策的制定与实施具有重要影响。最大限度地促进公众参与环保与和谐社会的创建,能有力地推进整个社会环保工作的开展。中学师生作为公众的关键性窗口群体,其环保意识的强弱直接关系到该地区或国家的民众环保意识、公众参与环保水平及未来环境可持续发展状况。本文通过对湖南省永州市城区中学师生环保意识随机抽样调查,分析了师生的环保意识水平。总体来看,大多数师生具备必要的环境知识,但其中相当一部分环境意识比较薄弱,而环保行为更是普遍不足,因此加强在校学生的环境教育和培养在职教师自身环保素质尤显重要。并提出相应的建议。     

茂名市高岭土开采生态破坏及污染调查与研究

茂名盆地蕴藏着大量的涂布级高岭土,能广泛应用于国民生产的各个领域,但目前的采选过程引起的水土流失对周围的生态环境造成了很大的破坏.通过分析采选过程中产生的污染物对茂名盆地生态环境的破坏,为茂名地区高岭土产业的可持续发展提供参考建议.