DEM栅格分辨率对丘陵山地区定量土壤-景观模型的影响

基于数字高程模型（Digital Elevation Model,DEM）的定量土壤-景观模型的精度依赖于DEM栅格分辨率,而DEM栅格分辨率如何影响土壤-景观模型及其预测精度目前研究较少。以西南丘陵山地区一典型汇水盆地为研究对象,以该区2.5、5、10、20和30 m DEM为基础,利用逐步线性回归方法建立起研究区不同分辨率下的定量土壤-景观模型,并应用这些模型预测研究区内土壤表层碱解氮含量的空间分布,进而比较DEM不同分辨率下土壤-景观模型及其预测精度。结果表明,随着DEM栅格分辨率的降低,比汇水面积、地形湿度指数的均值逐渐增加;平均坡度逐渐降低;曲率变化的范围逐渐减小。地形指数的这一变化规律对土壤-景观模型及其预测结果产生显著影响,模型的校正决定系数、平均绝对误差和均方根误差都以5 m栅格分辨率为转折点,分辨率低于5 m,模型的校正决定系数显著减小,平均绝对误差和均方根误差显著增加。     

东北黑土区融雪径流对流域产沙的贡献及因素分析

[目的]揭示流域融雪期径流产沙特征及对全年总产沙的贡献,阐明东北黑土区影响融雪期产沙贡献的主控因素,并进而为东北黑土区流域综合治理提供科技支撑。[方法]基于东北地区203个气象站点数据以及15个流域水文站点径流泥沙资料,通过提取流域降水、地形、气候、土壤和土地利用等因子,采用多因素相关分析的方法,开展融雪期产沙贡献影响因素研究。[结果]东北黑土区不同流域年均降雪量占年均降水量的比例为3.7%～23.9%,空间分布差异较大,呈东南多、西北少的分布特点。融雪期径流深占全年径流深比例为13.7%～32.5%,融雪期产沙量对全年产沙量的贡献3.8%～23.47%,融雪期产沙模数占全年产沙模数的3.1%～35.9%,且它们空间分布规律性差。年均降水量、降雪量占降水量比例、融雪期径流深占全年径流深比例3个因素与融雪期产沙贡献在0.05的水平上呈显著相关。降雪量占降水量比例对流域融雪期产沙量和产沙模数的贡献率分别为25.41%和30.22%。最大高程对流域融雪产沙量和产沙模数的贡献率分别为24.36%和20.38%。[结论]东北区融雪期产沙对流域全年产沙有较大贡献,且受多重因素影响,未来应加强融雪期的侵蚀产沙观测研究。     

Reducing runoff by managing crop location at the catchment level,considering agronomic constraints at farm level

Runoff and erosion cause frequent damage through muddy floods in the loess belt of Northern Europe. One possibility for reducing damage is to lower runoff on agricultural land by spatially alternating different crops at the catchment level. But crop location results from decisions taken at the farm level. This study aimed to assess the existing leeway to modify crop location in the farms of a catchment, in order to reduce runoff at the catchment's outlet. The case study was the Bourville catchment (1086 ha), cultivated by 28 farmers and located in Pays de Caux, France. First, crop location rules in the 14 main farms of the catchment were analysed on the basis of surveys carried out with farmers, distinguishing spatial constraints from temporal ones. These rules made it possible to simulate crop location on each farm territory for the 2001–2002 crop year. Each field of the catchment was classified depending on whether one or several crops could be sown, taking into account both field history and farmer decision rules. Then two extreme scenarios of crop location in the Bourville catchment were built. Runoff simulation at the outlet with the STREAM model showed that runoff could be reduced while sticking to current farmer decision rules in terms of crop location. Depending on rainfall event characteristics, runoff reduction varied between 13·5 per cent and 4·5 per cent. Copyright © 2006 John Wiley & Sons, Ltd.     

云南省小江流域砂化土地整理研究

云南省小江流域地处小江断裂带,有百余条泥石流沟、造成大量泥沙下泄,使得河床宽敞、土地砂化、边滩发育。多年来东川人一直进行泥石流防治及河滩地开发工作,并取得明显效益。通过全面深入的调查、量测和分析研究,查明了小江滩地利用现状。提出不同类型和气候条件下滩地的种植方向和开发模式,对600多hm²河滩地制定了科学、合理、系统、高效的开发和保护规划。为同类型山区多泥沙河流滩地开发和保护提供借鉴。     

OPTIMAL FARM MANAGEMENT RESPONSES TO EMERGING SOIL SALINISATION IN A DRYLAND CATCHMENT IN EASTERN AUSTRALIA

Secondary salinisation of soil and water resources is an acute management issue over large parts of Australia. This paper focusses on the situation in the Liverpool Plains, where secondary soil salinity is on the increase due to rising saline groundwater tables. The Liverpool Plains are famous for the vast alluvial floodplains where self-mulching black clays provide the production basis for an extensive dryland cropping industry. The farmers there are asking how best to manage their resources under the present hydrological conditions, and are concerned whether their businesses will remain viable in the future. A multi-period programming model is applied to a model farm situation. The objective function reflects the economic paradigm of farming. The model includes a simulation sub-routine which links land use, rainfall and lateral groundwater flow into a point water balance and estimates the salt-affected area. A feedback relationship applies between soil salinity and land productivity. The results of the model suggest that the prevailing cropping practices that rely on long fallowing for soil moisture retention are sub-optimal. Increased cropping frequency increases farm income and reduces on-farm recharge to groundwater. Diversification into lucerne is favourable for the same reasons. Unless trees have commercial value, tree planting is not a favoured option except on salt-affected land. The farm achieves complete on-farm recharge control. However, assuming that the groundwater table rises at a rate of 10 cm per year independent of on-farm recharge, salinisation continues despite these land management changes. The subsequent land productivity losses render the model farm financially unviable in the medium term. Sustaining the productivity of the Liverpool Plains is an issue of reducing recharge to the groundwater system by changing land-use practices throughout the entire catchment. © 1997 John Wiley & Sons, Ltd.     

中国季风区土壤137Cs背景值研究

 通过测定山东沂蒙山区、江苏苏南丘陵区以及云南滇池流域背景点样品中土壤137Cs活度,探讨了土壤剖面中137Cs的分布状况,发现不同地区不同质地的土壤137Cs 的分布深度有所不同。非耕地137Cs活度呈指数型分布,且与分布深度表现出很强的相关关系;耕地中137Cs活度呈深度分异上的均一性。确定了这几个地区137Cs的背景值分别为1 737.1、1847.2和918.0 Bq/m2。地区土壤137Cs背景值的确定使得 137Cs示踪技术研究土壤侵蚀退化状况、侵蚀和沉积的空间分布成为可能,为土壤资源的可持续利用、土壤侵蚀的经济损益评估及水土保持措施评价等提供有力的技术支持。     

豫西山地生活用雨水集流系统的设计计算

生活用雨水集流系统设计计算的任务 ,就是确定最优的集流场面积和贮水窖容积 ,即满足生活供水需求的集流场面积和贮水窖容积的最小值。以频率为 75 %和 95 %的特征水文年为基本计算年份 ,以降雨期的降水量、间雨期持续日数、最大间雨期日数和人均日需水指标为参数 ,根据逐日降水资料 ,计算出豫西山地各代表站的最优贮水窖容积和最优集流场面积。     

Heavy‐Metal Losses from an Agroforestry Catchment

Abstract

Long‐term agricultural sustainability and water quality are impacted by different chemicals, including heavy metals. Heavy‐metal losses at the catchment scale depend largely on land‐management practices. Water‐quality indicators are required near soil‐quality indicators for different regions and farming systems. The purpose of this work is to analyze the heavy‐metal losses from a mixed agroforestry catchment. Iron (Fe), Magnesium (Mn), Zinc (Zn), and Copper (Cu) were measured in the drainage water of a 36.3 km² catchment located at the Valiñas River (Coruña, northwest Spain), and a total of 193 samples were collected during the course of 2003. The sampling strategy was a stratified point sampling involving more frequent sampling when flow was high. Water metal content was analyzed by inductively coupled plasma (ICP‐AES). The content ranges of dissolved heavy metals were as follows: Fe between 10 and 267 µg/L, Mn 0.2 and 77 µg/L, Zn 0.62 and 53.7 µg/L, and Cu 0.20 and 9.26 µg/L. Heavy metal content strongly varied along the study time, depending on storm flow but also on timing of animal‐waste applications.     

The CLIMEX soil-heating experiment: soil response after 2 years of treatment

 Most model predictions concerning the response of boreal forest ecosystems to climate change are inferred from small-scale experiments on artificial, simplified systems. Whole-ecosystem experiments designed to validate these models are scarce. We experimentally manipulated a small forested catchment in southern Norway by increasing soil temperature (+3  °C in summer to +5  °C in winter) using heating cables installed at 1 cm depth in the litter layer. Especially nitrification in the 0 to 10-cm soil layer increased as a result of the climate manipulation. Betula litter, produced after exposing trees for 2 years to ambient and elevated CO₂ in greenhouses, was incubated for 1 year in the manipulated catchment. Exposure to elevated CO₂ did not affect the C/N ratio or decomposition of the Betula litter, but lignin content decreased by 10%. We found no effect of elevated temperature on litter decomposition, probably due to desiccation of the litter. The heating cables caused a permanent increase in soil temperature in this soil layer, but when soils were dry, the temperature difference between control and heated plots decreased with increasing distance from the cables. When soils were wet, no gradients in temperature increase occurred. Received: 25 November 1997     

Temporal Oscillations of Calcium,Magnesium, Potassium,and Sodium Dissolved Contents in an Agroforestry Catchment from the Atlantic Galicia

There is an increasing awareness worldwide of the conveyance of sediment-associated nutrients across eroding soil surfaces into receiving waters. The objective of this study was to analyze the temporal oscillations of concentrations as well as the exportation of calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) at the outlet of an agroforestry catchment. These macronutrients were measured in the drainage waters of a 36.3-km² catchment located at the Valiñas River (Coruña, northwest Spain), where 560 samples were taken from 2003 to 2007. The water collection strategy was a stratified point sampling involving more frequent collections when flow was high. Element contents in the water were analyzed by inductively coupled argon plasma–mass spectrometry (ICP-MS). The dissolved content ranges were as follows: Ca between 4.47 and 20.7 mg L^–1, Mg between 2.4 and 7.3 mg L^–1, K between 1.13 and 8.6 mg L^–1, and Na between 8.9 and 27.2 mg L^–1. Significant correlations among all the analyzed elements were observed during the entire study period. Mostly, nutrient losses were related to degradation induced by soil erosion on the cultivated land portion of the catchment.