Organic matter characteristics and nutrient content in eroded soils

Twenty-one severely eroded soils of SE Spain (Torriorthent xeric soils) were studied. These soils form a fragile system characterized by soils with a low density of plant cover (<5%), are loamy and occur in a semiarid climate. The soils formerly were used for agricultural purposes but were abandoned at least 15 years ago. These eroded soils had a low total organic carbon content, and their humic substances, humic acid carbon, and carbohydrates were lower compared with soils that had never been cultivated (natural soils). The variables in which the effects of erosion were particularly noted were those related with the active organic matter (respiration and water-soluble organic matter). Those eroded soils with higher salt content showed lower organic matter and carbohydrate contents. Only total nitrogen was correlated with the carbon fractions in the eroded soils.     

Ground flora trampling studies: Five years after closure

Trampling as an ecological factor is a major concern of the management of park, forest, nature preserves, and wilderness areas as recreational resources. Of particular importance to the management concept of carrying capacity is the relative resistance of native plant communities, to trampling and the resilience or the capacity of impacted communities to recover. This information can be used by management to establish seasonal use limits to prevent irreversible degradation of these resources. The purpose of this study was to follow the recolonizaton of experimental trail surfaces barren of vegetative cover and hiked at three levels of use intensity. Results of this study indicate that soil compaction as measured by soil penetration resistance increased progressively with use level while the total number of species, species diversity, and dominant index scores declined. A major finding was that the greatest degree of change occurred at the first level of hiking, indicating that major floristic measures were most affected by the least amount of hiking. Recolonization of impacted areas that received 100 trampling passes as measured by plant cover, dominant indices, floristic dissimilarity, and species diversity was similar to areas receiving four and eight times more trampling, despite major differences in soil penetration resistance. These data suggest limited use delivered at one time can be as damaging as increasing levels of use delivered at over time.     

Environmental effects of soil property changes with off-road vehicle use

The effects of off-road vehicles (ORVs) on the physical and chemical properties of 6 soil series were measured at Hollister Hills State Vehicular Recreation Area in central California. Accelerated soil erosion and the alteration of surface strength, bulk density, soil moisture, temperature, and soil nutrients were quantified to gain an insight into the difficulty of revegetating altered, or modified, areas.Erosion is severe at Hollister Hills, particularly in coarse grained soils on steep slopes. Erosion displaced 0.5 and 3.0 metric tons per square meter on 2 trails on gravelly sandy loam, and 0.3 metric tons/m² from a trail on sandy loam. The surface strength and bulk density increased while the soil moisture decreased in gravelly sandy loam, coarse sandy loam, sandy loam, and clay. Clay loam had an increased surface strength with variably increased bulk density and no decrease in soil moisture. Diurnal temperature fluctuations increased and organic material and soil nutrients decreased in soil modified by vehicles.These property changes increase the erosion potential of the soil, impede germination of seedlings, and slow natural revegetation. Management methods in ORV-use areas should include planning trails by prior application of the universal soil loss equation and soil surveys, trail closure before complete loss of the soil mantle, and revegetation of closed areas.     

Nuclear magnetic resonance studies of interactions between organic pollutants and soil components,a review

This article presents a short overview of selected recent papers using nuclear magnetic resonance (NMR) to investigate interactions between organic pollutants and soil components such as organic matter, clays, whole soils, and sediments. First, we describe solid state cross polarisation magic angle spinning (CP-MAS) experiments as the main tools to investigate covalent bonds. Second, we report NMR approaches allowing us to assess molecule mobility and to characterise non-covalent interactions. Those approaches include correlations between K _oc values and soil organic matter functions determined by CP-MAS, ²H NMR fingerprints, relaxation time measurements, ¹⁹F and ¹H high resolution (HR)-MAS experiments.     

Assessing vulnerability to invasion by nonnative plant species at multiple spatial scales

Basic information on where nonnative plant species have successfully invaded is lacking. We assessed the vulnerability of 22 vegetation types (25 sets of four plots in nine study areas) to nonnative plant invasions in the north–central United States. In general, habitats with high native species richness were more heavily invaded than species-poor habitats, low-elevation areas were more invaded than high-elevation areas, and riparian zones were more invaded than nearby upland sites. For the 100 1000-m² plots (across all vegetation types), 50% of the variation in nonnative species richness was explained by longitude, latitude, native plant species richness, soil total percentage nitrogen, and mean maximum July temperature (n = 100 plots; P < 0.001). At the vegetation-type scale (n = 25 sets of four 1000-m² plots/type), 64% of the variation in nonnative species richness was explained by native plant species richness, elevation, and October to June precipitation (P < 0.001). The foliar cover of nonnative species (log) was strongly positively correlated with the nonnative species richness at the plot scale (r = 0.77, P < 0.001) and vegetation-type scale (r = 0.83, P < 0.001). We concluded that, at the vegetation-type and regional scales in the north–central United States, (1) vegetation types rich in native species are often highly vulnerable to invasion by nonnative plant species; (2) where several nonnative species become established, nonnative species cover can substantially increase; (3) the attributes that maintain high native plant species richness (high light, water, nitrogen, and temperatures) also help maintain nonnative plant species richness; and (4) more care must be taken to preserve native species diversity in highly vulnerable habitats.     

垫江土地资源可持续利用研究

通过对垫江县目前土地资源利用特点，存在问题及其原因的详细分析，结合垫法实际，提出了垫江县土地资源可持续利用分区的设想，针对各区不同的土地利用特点，提出了土地持续利用方向及主要措施。     

水力侵蚀对路基表面稳定性的影响研究

通过降雨试验和天然降雨水土流失调查 ,笔者首先探讨了风化花岗岩地区路基表面水力侵蚀的表现形式和规律 ,其中 ,基床表层已填筑级配碎石的易于发生级配碎石粗粒化 ,未填筑级配碎石的易于发生沟蚀 ;裸露的路堤边坡水力侵蚀发生发展规律一般为 :沟蚀→边坡滑坍 ;裸露的路堑边坡水力侵蚀发生发展规律一般为 :溅蚀→面蚀→沟蚀→坍塌 ;片石护坡的路堤和路堑边坡易于发生潜蚀。然后分析了水力侵蚀对路基表面稳定性的影响 ,认为溅蚀和面蚀对路基表面稳定性的影响较小 ;沟蚀对路堤边坡表面稳定性的影响程度随侵蚀程度和工程进度具体情况而定。最后 ,提出了施工期路基表面防护的建议     

呼吸性职业健康危害预防对策的研究

针对我国职业健康现状，依据预防为主的原则，论述了预防劳动疾病的重点和预防工作中的薄弱环节。提出了减少呼吸吸入引起的职业病的措施。     

Environmental impact of the Gulf War: An integrated preliminary assessment

This article provides an objective integrated environmental impact assessment of the Gulf War consequences. The environmental damage was evaluated and found to be significantly exaggerated by the media and speculators. The total amount of burned crude oil was calculated to be 52.5 million metric tons. Most air pollution field measurements were comparable to those found in Western cities. The health impact associated with such exposure was found to be minimal. The total amount of oil released into the marine environment ranged between 2 and 4 million barrels, much less than the early estimation of 12–14 million barrels. The marine environment is expected to recover much faster than earlier anticipations. Unlike water and air, soil pollution is likely to persist for some years to come.     

A SPATIAL DECISION SUPPORT SYSTEM FOR ASSESSING AGRICULTURAL NONPOINT SOURCE POLLUTION1

ABSTRACT: A spatial decision support system (SDSS) was developed to assess agricultural nonpoint source (NPS) pollution using an NPS pollution model and geographic information systems (GIS). With minimal user interaction, the SDSS assists with extracting the input parameters for a distributed parameter NPS pollution model from user-supplied GIS base layers. Thus, significant amounts of time, labor, and expertise can be saved. Further, the SDSS assists with visualizing and analyzing the output of the NPS pollution simulations. Capabilities of the visualization component include displays of sediment, nutrient, and runoff movement from a watershed. The input and output interface techniques/algorithms used to develop the SDSS, along with an example application of the SDSS, are described.