基于高精度DEM的元谋典型冲沟土壤侵蚀因子分析

为了探讨基于不同栅格分辨率DEM提取冲沟尺度土壤侵蚀因子形成的差异,选择金沙江干热河谷区典型冲沟为研究对象,基于Arc GIS平台,在0.5m、1.0m、1.5m和2.0m四种高精度数字高程模型的基础上提取冲沟的坡度、坡长、坡度坡长因子,分析了坡度、坡长、坡度坡长因子的分布特征、面积比例与损失量情况,以及不同分辨率的土壤侵蚀因子精度的差异。结果表明:1元谋冲沟陡坡较多,大于35°的面积占50%。当分辨率降低时,大于35°区域比例减少,15°—25°面积增加,地形趋缓。2区域坡长为0—30m的短坡。分辨率降低时,短坡长被合并,短坡坡长的面积减小,30m以上坡长的面积不同程度增加,坡长发生整体延伸。3区域坡度坡长因子主要集中在0—10。分辨率降低时,0—10的坡度坡长因子面积的比例减少,大于10的坡度坡长因子的面积比例增加。元谋干热河谷区陡峭的坡度对坡度坡长因子的影响较大,较短的坡长对其影响较小。     

沙湾荒漠生态区的土壤微生物监测

以土壤微生物为监测对象，对沙湾荒漠生态区农田、荒漠两大区系的微生物生态特征进行了综合分析与研究，初步确定真菌总数为荒漠生态区生态环境监测的微生物学指标生物。     

鲁西平原区荒地农业开发后表层土壤理化性质变化

荒地的农业开发利用可以有效缓解当前耕地减少的现状,了解荒地开发后土壤质量状况具有重要的现实意义.以山东省西部平原区为研究区域,通过代表性地块取样分析并与第二次土壤普查对比,初步结论如下:耕层土壤各项物理性质有不同程度的改良,个别地块改良效果不明显;养分含量增加明显,但速效养分含量偏高,产量仍属中低产水平.     

黑水河干旱河谷沿程土壤物理参数梯度变化特征研究

横断山区干旱河谷是具有典型的旱季和雨季的特殊气候特征的区域，本区域土壤退化和荒漠化极大制约了区域农业的发展。本文研究了金沙江干热河谷区支流黑水河从源头到河口未扰动土壤的物理参数变化特征。结果表明，沿河土壤物理呈现不同变化趋势，砾石在中游部分河段和河口段高，而〉5mm团聚体的变化则相反；5～1mm的团聚体变化不大；〈1mm团聚体河口和源头段高于其余地段；土壤容重沿程增大，非饱和导水率源头地段土壤最高。本研究初步揭示了干旱河谷土壤不均匀，不同水热条件及其组合可能对退化程度有至关重要的影响。这表明横断山区不同的干旱河谷地段土壤和植被退化途径、退化特征和退化过程不同，开发和治理途径与方式也应当不同。     

植被混凝土在官地水电站的试验分析

本文主要对官地水电站高陡边坡植被混凝土前期绿化试验成果进行分析,以寻求在干湿季节明显、雨量集中、干旱季节漫长、温度高、蒸发量大等干热河谷气候特征条件下的最佳生境构筑方法,为官地水电站乃至雅砻江流域水电工程高陡边坡生态恢复提供技术依据。     

浅谈竹浆原料林基地建设对土壤环境的影响——以四川省合江县、纳溪区竹浆原料林基地为例

土壤有机质和有效养分是评价土壤质量的重要指标,也是陆地生态系统物质循环的重要组成成分。本研究以四川省合江县、纳溪区2个区县12个乡镇的竹林地土壤作为研究对象,通过对土壤剖面的取样分析,对比分析了不同年份竹浆原料林基地与邻近土地的土壤有机质及速效养分含量特征,探讨竹子生长对土质有机含量的影响。结果表明,从土壤肥力情况看,种植竹林对土壤养分有一定的影响。与旱地相比,种植竹林会降低部分区域的土壤肥力,与多年竹林地相比,竹浆原料林基地土壤全磷、速效磷、速效钾明显升高。从土壤物理性质看,种植竹林对土壤团粒结构影响不大,对土壤容重有一定正影响,可在一定程度上改良土体结构。建议在生产实际中应结合土壤肥力监测结果,科学施肥、多施有机肥,尽可能做到平衡施肥,防止土壤养分的过度消耗。     

长江上游川江流域林业土壤资源评价

本文选取包括土壤物理、养分、化学性质的质地、全氮、pH 等10个土壤因子作为评价项目,并根据众多专家提供的指标强度分级和因素的权重分配标准,以模糊综合评判法对长江上游川江流域林业土壤资源分别进行分类和分区综合评价。按5级制以土壤亚类为单元的分类评价结果表明,在所研究的12.86万 km~2的土壤区域内,不同等级土壤面积分布比例约为Ⅱ:Ⅰ:Ⅲ:Ⅳ V=4:3:2:1。在土壤分类评价的基础上,进一步以土壤区(二级区)为评价单元进行土壤质量的分区评价,区域评价结果既以等级又以较精细的得分表示。     

高台位旱地石灰性紫色土培肥研究

本文研究了高台位旱地石灰性紫色土的肥力退化因子,并针对紫色母岩矿质养分丰富、易风化成土的特点,以一种培肥耕作法-聚土免耕耕作法培肥土壤。结果表明,采用此耕作法的土壤具有防蚀、抗旱、培肥和自调能力,能提高系统生产力。     

环渤海及其邻近地区引种常绿杜鹃花气候相似性研究——兼论加权欧几里得距离法在杜鹃花引种栽培区域预测中的应用

通过模糊数学方法,对环渤海及其邻近地区引种栽培"华西雨屏带"中山区常绿杜鹃的气候相似性进行了初步探讨和预测。研究提取了11项气象指标,其中5项作为"门槛指标",6项作为"有效样本集"考察指标,并根据专家经验对考察指标赋予了不同的权重和可控系数。在此基础上,通过数学建模对22个城市的有关气象要素进行了考察和计算。结果表明,8个城市进入上述"有效样本集",可分为3个适宜性等级,其中环渤海地区的日照、威海、青岛进入次高适宜等级,大连进入最低适宜等级。围绕研究结果,对被考察城市引种特定区域常绿杜鹃的适应性问题进行了分析,并对有关研究方法进行了探索性修订。     

施入城市生活垃圾堆肥对玉米植株重金属分布及土壤养分的影响

以玉米为供试作物,研究施入生活垃圾堆肥对土壤和玉米各器官重金属分布规律及对土壤养分的影响。结果表明：连续3年施肥,土壤速效养分的含量明显增加;土壤重金属呈现累积,但含量远远低于二级土壤标准（GB 15618—1995）;植株中重金属含量表现为根部〉茎秆〉叶片〉籽粒,Cd在植株根部富集,但未大量向其他部位转移,玉米植株地上部分重金属含量明显低于饲料卫生标准（GB 13078—2001）。由此推断,在短期内（3年）,年施入60 000 kg·hm^-2的垃圾堆肥能提高土壤肥力,且暂时不会引起土壤重金属污染,也不影响玉米植株的饲用;使用多年后应及时监测,以保证安全性。     

氮肥形态对坡耕地雨季土壤养分流失的影响

为了明确氮肥形态对土壤养分流失通量及途径的影响,采用随机区组试验设计,利用模拟径流小区观测的方法,研究在地膜覆盖与不覆盖情况下氮肥形态对坡耕地雨季土壤养分流失通量及途径的影响。研究结果表明：壤中流氮、磷和钾的流失量分别占总径流流失量的71.30%、6.36%和8.85%,说明磷和钾流失的主要途径是地表径流,而氮流失的主要途径是壤中流,地膜覆盖降低酰胺态氮肥和缓控释肥处理氮素流失量,其中酰胺态氮肥处理地膜覆盖较不覆盖壤中流氮流失浓度和径流氮素流失量分别降低40.40%和29.32%。在无覆盖条件下,各处理径流氮素流失顺序表现为：酰胺态氮肥〉铵态氮肥〉缓控释肥〉硝态氮肥,施用硝态氮肥氮素流失量最低,较施用酰胺态氮肥氮素流失少40.86%。在地膜覆盖条件下,各处理径流中氮素流失顺序表现为：铵态氮肥〉酰胺态氮肥〉硝态氮肥〉缓控释肥,施用缓控释肥氮素流失量最低,较施用铵态氮肥氮素流失少59.60%。结果表明在四川紫色丘陵区为了有效控制水土养分流失,在肥料形态的选择上,以无覆盖条件下施用硝态氮肥较好,以地膜覆盖条件下施用缓控释肥较好。     

Effects of stream channelization on exports of nitrogen and phosphorus from north Carolina coastal plain watersheds

Nitrogen and phosphorus exports from channelizedstream watersheds were elevated over those from nearby natural swamp-stream watersheds. Nitrate exports were significantly greater from channelized-stream watersheds, and higher exports were attributed to faster groundwater drawdown, continual streamflow, and transformation of former floodplain to croplands following channelization. Exports of total organic nitrogen and total nitrogen were also significantly greater from channelized-stream watersheds. Differences in the exports of ammonium, filterable reactive phosphorus, and filterable unreactive phosphorus between the two watershed types were not detectable. Particulate phosphorus exports were significantly higher from channelized-stream watersheds, presumably because of greater erosion potential of nearby croplands and steep channel banks in the altered watersheds. The presence of nonpoint sources of pollution increased watershed exports of nutrients regardless of stream morphology. Examination of nutrient budgets for a portion of swamp floodplain at the base of one natural-stream watershed revealed that changes in local groundwater hydrology and stream morphology associated with channelization appeared to have greater effect on nutrient exports than simply the loss of bordering forested floodplain.     

水磨河流域水土保持生态建设及其效益

水磨河流域是乌鲁木齐市水土流失最严重的地区,是工业发达的人口密集区,也是风景旅游区。但由于土壤侵蚀、暴雨成灾,每年造成很大经济损失。经过多年的生态和防洪工程建设,已使该流域生态环境大为改善,取得了生态经济效益。     

AN EXAMINATION OF LAND USE - NUTRIENT EXPORT RELATIONSHIPS1

ABSTRACT: Lake and watershed management strategies and recent environmental legislation dictate that nonpoht nutrient sources associated with storm water runoff must be assessed. Accordingly, a nutrient flu assessment for phosphorus and nitrogen is conducted through an extensive literature review of nutrient export studies. These studies are reevaluated. The nutrient export coefficients are screened according to sampling design criteria and compiled according to land use. The ecological mechanisms within each land use influencing the magnitude of nutrient flux are also discussed     

Using Ecological Risk Assessment to Identify the Major Anthropogenic Stressor in the Waquoit Bay Watershed,Cape Cod,Massachusetts

The Waquoit Bay Watershed ecological risk assessment was performed by an interdisciplinary and interagency workgroup. This paper focuses on the steps taken to formulate the analysis plan for this watershed assessment. The workgroup initially conducted a series of meetings with the general public and local and state managers to determine environmental management objectives for the watershed. The workgroup then decided that more information was needed on the impacts of six stressors: nutrient enrichment, physical alteration of habitat, altered freshwater flow, toxic chemicals, pathogens, and fisheries harvesting. Assessment endpoints were selected to establish the link between environmental management objectives, impacts of stressors, and scientifically measurable endpoints. The following assessment endpoints were selected: estuarine eelgrass cover, scallop abundance, finfish diversity and abundance, wetland bird distribution and abundance, piping plover distribution and abundance, tissue contaminant levels, and brook trout distribution and abundance in streams. A conceptual model was developed to show the pathways between human activities, stressors, and ecological effects. The workgroup analyzed comparative risks, by first ranking stressors in terms of their potential risk to biotic resources in the watershed. Then stressors were evaluated by considering the components of stressors (e.g., the stressor chemical pollution included both heavy metals and chlorinated solvents components) in terms of intensity and extensiveness. The workgroup identified nutrient enrichment as the major stressor. Nutrient enrichment comprised both phosphorus enrichment in freshwater ponds and nitrogen enrichment within estuaries. Because phosphorus impacts were being analyzed and mitigated by the Air Force Center for Environmental Excellence, this assessment focused on nitrogen. The process followed to identify the predominant stressor and focus the analyses on nitrogen impacts on eelgrass and scallops will serve as an example of how to increase the use of the findings of a watershed assessment in decision making.     

Changes in soil nitrogen and phosphorus under different broiler production systems

In a field study, soils of four conventional free-range and organic broiler runs were analyzed for N and P concentrations in the years 2000 and 2001. Zones of different use intensity by broilers were identified on the free runs and mean zonal nutrient contents were compared with each other. Intensity of use by birds and spatial distribution of soil nutrient concentrations were found to be related to each other. Fecal N input by broilers resulted in accumulation of soil mineral nitrogen (N(min)) contents down to a 90-cm sampling depth. In highly frequented "hot spots," plant requirement as defined by the German "N-Basis-Sollwert" (110 kg/ha N(min)) for grassland was exceeded in all four cases. This implies an increased environmental risk of ammonia volatilization and nitrate leaching. Fecal P input by broilers resulted in accumulation of plant-available and thus mobile soil P (phosphorus extracted with calcium-acetate-lactate [P(CAL)] and phosphorus extracted with water [P(w)]) in the most intensely used zones. In these areas, soil P contents exceeded 90 mg/kg P(CAL) (upper limit of soil test P defined in Germany for optimum plant yield) by as much as 217 mg/kg, which indicates an enhanced risk of P loss from the soil via runoff or leaching. The conclusion might be drawn that, with regard to nutrient loss from free-run soils, intensive indoor production in a closed system may be more environmentally neutral than conventional free-range or organic production. However, to put this into perspective, the scope of the environmental risk connected with spatially limited point accumulation of nutrients should be considered. Furthermore, an environmental evaluation must also account for the fate and environmental effects of the broiler litter produced inside the broiler house.     

Soil, water and nutrient conservation in mountain farming systems: case-study from the Sikkim Himalaya

The Khanikhola watershed in Sikkim is agrarian with about 50% area under rain-fed agriculture representing the conditions of the middle mountains all over the Himalaya. The study was conducted to assess overland flow, soil loss and subsequent nutrient losses from different land uses in the watershed, and identify biotechnological inputs for management of mountain farming systems. Overland flow, soil and nutrient losses were very high from open agricultural (cropped) fields compared to other land uses, and more than 72% of nutrient losses were attributable to agriculture land use. Forests and large cardamom agroforestry conserved more soil compared to other land uses. Interventions, like cultivation of broom grass upon terrace risers, N2-fixing Albizia trees for maintenance of soil fertility and plantation of horticulture trees, have reduced the soil loss (by 22%). Soil and water conservation values (> 80%) of both large cardamom and broom grass were higher compared to other crops. Use of N2-fixing Albizia tree in large cardamom agroforestry and croplands contributed to soil fertility, and increased productivity and yield. Bio-composting of farm resources ensured increase in nutrient availability specially phosphorus in cropped areas. Agricultural practices in mountain areas should be strengthened with more agroforestry components, and cash crops like large cardamom and broom grass in agroforestry provide high economic return and are hydroecologically sustainable.     

Development of the Chesapeake Bay Watershed Total Maximum Daily Load Allocation

Nutrient load allocations and subsequent reductions in total nitrogen and phosphorus have been applied in the Chesapeake watershed since 1992 to reduce hypoxia and to restore living resources. In 2010, sediment allocations were established to augment nutrient allocations supporting the submerged aquatic vegetation resource. From the initial introduction of nutrient allocations in 1992 to the present, the allocations have become more completely applied to all areas and loads in the watershed and have also become more rigorously assessed and tracked. The latest 2010 application of nutrient and sediment allocations were made as part of the Chesapeake Bay total maximum daily load and covered all six states of the Chesapeake watershed. A quantitative allocation process was developed that applied principles of equity and efficiency in the watershed, while achieving all tidal water quality standards through an assessment of equitable levels of effort in reducing nutrients and sediments. The level of effort was determined through application of two key watershed scenarios: one where no action was taken in nutrient control and one where maximum nutrient control efforts were applied. Once the level of effort was determined for different jurisdictions, the overall load reduction was set watershed‐wide to achieve dissolved oxygen water quality standards. Further adjustments were made to the allocation to achieve the James River chlorophyll‐a standard.     

Nonpoint Source Loading Rates From Selected Land Uses1

ABSTRACT: Loading rates derived from monitoring natural runoff from selected land uses are compared. Land uses selected for evaluation are construction sites, barnyards, and agriculture (dairying). Runoff volumes, sediment, and nutrient fractions were monitored and expressed as areal loadings for comparison purposes. Sediment yield and total phosphorus (total P) loss was directly proportional to runoff (m³/ha). In decreasing order, the loadings for sediment and total P were as follows: construction site > barnyard > general dairying. Runoff from the barnyard area was approximately 10 times higher in soluble phosphorus and ammonium nitrogen than the other land uses under investigation. Areal loss for nitrate nitrogen was highest from the construction site and was attributed to the higher volume of runoff per unit area. Results show that barnyards in a dairying watershed are potentially a major source of sediment and nutrients, especially those dissolved fractions which have the potential for immediate water quality impacts. Relative to general agricultural land, urban construction sites also appear to be a major source of sediment and nutrients. As with barnyard sites, however, the effect of such sites on water quality likely depends on proximity to surface water bodies and other watershed characteristics affecting delivery ratios of contaminants.     

Application of nutrient loading models to the analysis of trophic conditions in Lake Okeechobee,Florida

Lake Okeechobee (surface area = 1830 km², mean depth = 3.5 m), the largest lake in Florida, is eutrophic and has nitrogen and phosphorus loading rates in excess of nearly all established criteria. The lake is not homogeneous regarding trophic conditions, and spatial and temporal variations occur regarding nutrient limitation. Nonetheless, phosphorus loading rate and trophic state data fit reasonably well to various input-output models developed for temperate lakes. Modification of the models by regression analysis to fit data for Florida lakes resulted in improved predictions for most parameters. Analysis of nutrient management alternatives for the lake indicates that a 75% reduction of phosphorus loading from the largest source (the Taylor Creek-Nubbins Slough watershed) would reduce the average chlorophyll a concentration by less than 20%. Complete elimination of inputs from the largest nitrogen source (the Everglades Agricultural Area) would decrease the average nitrogen concentration in the lake by about 20%. Limitations of nutrient inputoutput models regarding analysis of trophic conditions and management alternatives for the lake are discussed.