Anthropogenic influences on Zuni agricultural soils

Farmers in the Zuni area of the semiarid American Southwest have successfully cultivated maize and other crops for over three millennia without using artificial fertilizers. Zuni agricultural fields are among the oldest, more or less continuously cultivated areas in the United States. Traditional Zuni agriculture is based on runoff farming, a system whereby runoff and organic‐rich sediment generated in small watersheds are captured and directed onto fields for crop use. We conducted a study to compare soil properties associated with paired and unpaired cultivated, abandoned, and uncultivated fields to evaluate the long‐term effects of cultivation on soil quality. Sampling and analytical methods of this research are especially applicable to geoarchaeological studies of anthropogenic effects on soil fertility and agricultural sustainability in ancient and traditional historical farming systems. Results of the Zuni soil study indicate that cultivation has altered some soil properties, including bulk density, organic carbon, total nitrogen, and C:N ratios in paired fields, but there is no indication that agricultural soils are degraded. This assessment supports the perception of Zuni farmers that long‐term cultivation has not caused a decline in agricultural productivity. © 2005 Wiley Periodicals, Inc.     

Eolian Deposition and Soil Fertility in a Prehistoric Agricultural Complex in Central Arizona,USA

Prehistoric farmers in arid and semiarid ecosystems commonly used rock alignments to concentrate water and sediments on their fields. Previous research has emphasized the importance of runoff from organic matter‐rich uplands as a mechanism for soil nutrient replenishment. However, eolian inputs to these dryland ecosystems might also contribute substantially to mineral‐derived nutrient pools. We explored the relative importance of eolian deposition, prehistoric agriculture, and the presence of rock alignments on soil properties in a semiarid grassland in Arizona. Subsurface soils behind natural rock alignments are finer in texture than soils unbound by rock alignments, while subsurface soils behind agricultural rock alignments coarsen relative to unbound soils. Neither rock alignments nor estimated crop yields had detectable effects on mineral‐derived nutrient pools. In contrast, eolian deposition is an important source of soil mass and nutrients to modern soils. While dust deposition likely reduced soil heterogeneity across this landscape, it could have also contributed to the sustainability of prehistoric agriculture.     

概念性水文模型在出山径流预报中的应用

根据HBV水文模型的基本原理，建立了西北干旱区内陆河出山径流概念性水文模型。该模型反映了我国西部山区流域的径流形成特征，将山区流域划分为高山冰雪冻土带和山区植被带两个基本海拔景观带来对山区径流的形成和汇流过程进行模拟计算，以常规气象站的月气温和降水量为模型的初始输入，模拟计算月出山径流量。应用该模型对河西走廊黑河祁连山北坡的山区流域水量平衡进行了模拟计算，并对年径流和逐月分配进行了预报。结果表明，从枯水年到丰水年，降水量、蒸发量、径流量和径流系数均增加，而冰川融水和积雪融水对出山径流的补给比重则减少，这表明了冰雪融水对径流的具有调节作用。黑河山区流域径流系数远比干旱内流区的平均值大，但要小于全国的平均径流系数。所提出的内陆河山区流域出山径流的模拟和预报模型对年径流量和月分配的预报具有较好的精度，可用于黑河以及其他西北干旱区内陆河出山径流的预报，为内陆河流域中下游的水资源分配和开发利用提供依据。     

南方小型岩溶流域与非岩溶流域的释水过程及径流组分差异

我国南方岩溶流域和非岩溶流域下垫面条件和含水介质结构的差异造成了不同的产汇流过程及机制,进而导致不同释水时段径流组分的开发利用价值不同。为深入理解岩溶流域的产汇流机制并探索岩溶流域的水资源评价方法,文章对鄂西庙沟岩溶流域和高家坪非岩溶流域共31次洪水过程进行了流量衰减分析,对比分析了两个流域的标准衰减方程、典型次降雨的释水过程以及不同洪峰流量下的径流组分差异。结果表明:岩溶流域的释水过程快于非岩溶流域,其衰减系数比非岩溶流域大40％;两个流域的河流基流均来自裂隙介质释水,裂隙介质为流域的主要储水空间,但非岩溶流域的裂隙介质比例比岩溶流域高8.8％;随洪峰流量增加,两个流域的地表径流占比均呈对数形式增大,地下径流占比均呈对数形式减小;岩溶流域径流组分随洪峰流量变化比非岩溶流域更为敏感,其地表径流占比变幅为4％~40％,而非岩溶流域则始终小于10％。文章定量评价了管道和裂隙介质在流域中的导水及储水功能,在进一步刻画岩溶流域产汇流过程及机制方面进行了有益的探索,研究结果可为岩溶山区水资源评价和流域水文模型的改进提供科学依据。     

Modeling watershed rainfall–runoff relations using impervious surface-area data with high spatial resolution

A distributed object-based rainfall–runoff simulation (DORS) model with incorporation of detailed impervious surface-area (ISA) data, derived from digital true-color orthophotography data with high spatial resolution, was developed. This physically based model simulates hydrologic processes of precipitation interception, infiltration, runoff, evapotranspiration, change of soil moisture, change of water-table depth, runoff routing, groundwater routing, and channel-flow routing. The modeling processes take objects based on land-cover types as fundamental spatial units in order to reduce data volume, increase computational efficiency, strengthen representation of watersheds, and utilize the data in variable scales. US Geological Survey stream-gaging data were used to validate the temporal variation of simulated discharge within two watersheds in Rhode Island State. The ratio of absolute error to the mean and the Nash coefficient in the validation period are 7.2% and 0.90 for the first watershed, and 8.0% and 0.77 for the second watershed, respectively. The results indicate that the DORS model is able to capture the relationship between rainfall and runoff in the study area, and that it is applicable in the further study of ISA impacts on the water cycle and associated pollution problems. The results also demonstrate that the performance of the hydrologic simulation is improved with ISA data with high spatial resolution.     

Comparative analysis of heavy metal concentration in secondary treated wastewater irrigated soils cultivated by different crops

The use of treated urban wastewater for irrigation is a relatively recent innovation in Botswana and knowledge is still limited on its impact on soil heavy metal levels. The aim of this study is to analyze and compare heavy metal concentration in secondary wastewater irrigated soils being cultivated to different crops: olive, maize, spinach and tomato in the Glen Valley near Gaborone City, Botswana. The studied crop plots have been cultivated continuously under treated wastewater irrigation for at least 3 years. Most crop farms have sandy loam, loamy sand soils. Based on food and agriculture organization, heavy metal threshold values for crop production have been studied. Results showed that the wastewater irrigated soils in the Glen Valley have higher cadmium, nickel and copper than desirable levels, while the levels of mercury, lead and zinc are lower than the maximum threshold values recommended for crop production. The control sites show that the soils are naturally high in some of these heavy metals (e.g copper, zinc, nickel) and that crop cultivation under wastewater irrigation has actually lowered the heavy metal content. Comparing between the crops, mercury and cadmium levels are highest in soils under maize and decline linearly from maize to spinach to olive to tomato and control site. By contrast, concentrations of the other metals are at their lowest in maize and then increase from maize to spinach to olive to tomato and to control site.     

基于Erlang分布蓄水容量曲线的流域产流模型

蓄水容量曲线是反映流域缺水量空间分布不均匀性的特征曲线,对流域产流计算有直接影响。通过对多个典型流域蓄水容量空间分布的分析,发现Erlang分布能更好地拟合流域的蓄水容量曲线,进一步基于Erlang分布进行流域产流的推导,提出了基于Erlang分布蓄水容量曲线的流域产流模型。应用结果表明,基于Erlang分布的流域产流模型,增加了模型的适应性,模拟结果更接近流域实际的产流过程,比新安江模型能取得更高的模拟精度。此外,该产流模型的参数可由流域地形和土壤类型数据估算,为无资料地区的产流计算提供了一种可行的途径。     

Soil Erosion Susceptibility Assessment of the Lower Himachal Himalayan Watershed

Assessment of erosion status of a watershed is an essential prerequisite for integrated watershed management. It not only assists in chalking out suitable soil and water conservation measures to arrest erosion and conserve water but also helps in devising best management practices to enhance biomass production in watersheds. Keeping this in view, the present study has been undertaken by involving geospatial-statistical techniques to determine the critical and priority areas for soil and water conservation in Suketi watershed of the lower Himachal Himalayan region. A novel weighted sum analysis technique was used for ranking each of hydrological unit by obtaining the weightages from various morphometric parameters. This technique offers dynamic, effective and sustainable approach over traditional prioritization methods in which significance of each parameter were considered equally. Considering this approach, sub-watersheds were delineated into low, medium and high priority zones. The results illustrate that about 52 % of sub-watersheds of Suketi watershed are in moderate to high erosion and runoff susceptible zones. Therefore, these potential areas can be considered for preferential soil and water conservation planning. The results obtained from the study will be useful for various stakeholders such as agriculturists, water resource managers, conservation measures planners and decision policy makers for better management practices and decision making. The geospatial-statistical technique can be used for effective estimation of erosion status of watersheds leading to watershed prioritization for taking up soil and water conservation measures in watershed systems. Finally, this technique can be very useful in remote, rugged and inaccessible watersheds with absence of soil erosion and runoff monitoring.     

基于模块化建模方法的寒区水文过程模拟——在中国西北寒区的应用

中国西北高山、 高原广泛分布着冻土和积雪, 春季融雪和冻土融化是该地区重要的水文过程.基于模块化的寒区水文建模环境CRHM, 根据流域水文过程特征和观测数据约束, 选取描述不同寒区子水文过程的模块构建寒区水文模型, 并基于长期观测的两个典型寒区小流域来验证模块化的寒区水文模型.在冰沟流域, 主要模拟雪的积累/消融、 雪的升华、 融雪下渗和融雪径流过程. 结果显示: 冰沟流域积雪升华占降雪量(145.5 cm)的48%, 其中风吹雪引起的升华损失量(35 cm)占积雪升华(69 cm)的一半, 风速和辐射引起的积雪升华是该地区积雪物质平衡的重要组成; 构建的寒区水文模型可以再现春季积雪消融引起的径流过程.在左冒孔冻土流域, 主要模拟冻土下渗过程、 冻土坡面产流过程和土壤冻融对径流的影响. 结果显示: 构建的寒区水文模型可以捕捉到春季主要的冻土融化径流过程.两个流域的验证结果揭示: 模块化的建模方法在搭建模型结构的时候减少了模型的不确定性, 所以在未经率定的情况下, 具有在无资料和资料缺少地区模拟寒区水文要素和水文过程的能力.     

粤北石漠化地区土地利用优化配置及资源利用研究

以粤北典型石漠化地区秀水小流域为例,综合考虑流域地形、地貌、土地利用等因素,探讨土地利用时空优化布局及资源利用。研究表明:(1)流域内缺水比较严重,分别与地形指数＜4.702、4.702～8.05和＞8.05对应的土壤低、中、高含水区所占总面积比例依次为79.94%、10.72%、9.35%;（2）坡耕地是秀水小流域水土流失的重要区域。为此,对于流域土地利用配置,坡度＜10°的耕地宜采用等高耕作和覆盖耕作相结合的措施,坡度在10°～25°的耕地可采用植物篱措施,坡度＞25°的耕地则必须退耕还林。此外,受海拔高度和灌溉条件影响,玉米最好种植在海拔400～500 m 的区域;由于上半年降雨量多、下半年少,在缺乏灌溉条件的区域,耗水量较大的作物宜主要安排在上半年,下半年主要以种植玉米等耐旱作物为主。      

甘肃干旱与半T旱地区水资源可T持续开发利用对比分析

甘肃半干旱区天然降水是主要的水资源，而干旱区的水资源来自于南部祁连山以及阿尔金山的山区降水和冰雪融水.甘肃半干旱区在小麦生长需水关键期的5～6月，降水量离差系数大，农业生产易遭旱灾.河西干旱区出山径流较稳定，为灌溉农业的稳定提供了基础.甘肃半干旱地区的水资源持续开发利用应主要拦蓄大气降水，配合开发地下水，并合理规划利用地表水，其中雨水集流工程和旱作节水农业技术的推广政策和措施是关键.干旱区的水资源持续开发利用主要应通过水价调整来引导建立节水型经济结构和推广节水技术，政策支持重点领域是水资源的合理配置并完善绿洲资源保护与水源涵养林保护的法规体系     

Water content variations and respective ecosystems of sandy land in China

Soil water conservation is essential to the sustainability of sandy farming. In this paper, long-term observation of soil water, dry soil thickness and soil chemical changes are evaluated at eight locations in sandy soil. This paper subdivides the sandy lands and deserts of China into three climate zones: arid (hyperarid and extremely arid), semiarid, and humid (subhumid and subtropical humid), with respect to the bioclimatic zone, aridity, soil water content, and soil chemical characteristics. The water movement conditions, and chemical variations in each zone are analyzed. The paper also estimates the spatial and temporal correlation function of arid soil thickness and soil moisture. Sandy soils organic matter content, CaCO₃ content, soluble salts content are investigated. Afforestation and selection of tree species in different sandy areas are suggested to regulate sandy land soil moisture. Sandy land in China can be divided into the four sand stabilization regions according to the shifting sand conditions and the techniques advanced: regions I, II, III, and IV. These results have important implications for remote sensing of soil moisture and soil organic carbon, and soil moisture parameterization in climate models.     

降雨和地形地貌对水文模型模拟结果的影响分析

概念性水文模型数量众多,判断模型是否适合研究流域可以通过模拟结果来体现,但是熟悉流域的产汇流特性可以筛选模型,从根源上大量减少工作量,也可以解决相似流域无资料的问题。选取6种概念性水文模型,以马渡王、板桥和志丹这3个半湿润与半干旱流域为研究区域,探讨流域特性与模型结构之间的关系,并通过降雨和地形地貌分析其对模型模拟结果的影响。研究结果表明,流域地形及植被对产汇流过程有重要影响,由于局部产流现象严重,河道坡度影响大于流域平均坡度,当区域气候条件相差不大时,地形地貌比降雨对流域产汇流特性影响更大。因此对于水文模型的选择,可以在熟悉流域产汇流特性的基础上因地制宜,必要时可以增加适合研究流域的模块来获得更好的预报,在半干旱与半湿润流域,同时具有蓄满和超渗机制的模型能得到更好的应用。     

Early agriculture in the Eastern Grand Canyon of Arizona,USA

Abandoned fields in Colorado River alluvium in the eastern Grand Canyon show signs of primitive agriculture. Presence of maize pollen in association with buried soils near Comanche Creek suggests that farming began prior to 3130 yr B.P. Cotton pollen, identified in buried soils near Nankoweap Creek, dates to 1310 yr B.P., approximately 500 years earlier than previously reported anywhere on the Colorado Plateau. Farming spanned three millennia in this reach of the canyon. Entrenchment, starting approximately 700 yr B.P., making water diversion to fields infeasible, was likely responsible for field abandonment. © 2000 John Wiley & Sons, Inc.     

Assessing impact of urban impervious surface on watershed hydrology using distributed object-oriented simulation and spatial regression

In this study, we investigated the relationship between watershed characteristics and hydrology using high spatial resolution impervious surface area (ISA), hydrologic simulations and spatial regression. We selected 20 watersheds at HUC 12 level with different degrees of urbanization and performed hydrologic simulation using a distributed object-oriented rainfall and runoff simulation model. We extracted the discharge per area and ratio of runoff to base flow from simulation results and used them as indicators of hydrology pattern. We derived percentage of ISA, distance from ISA to streams, and stream density as the watershed characteristics to evaluate the relationship with hydrology pattern in watersheds using ordinary least square, spatial error and spatial lag regression models. The comparison indicates that spatial lag regression model can achieve better performance for the evaluation of relationship between ratio of runoff to base flow and watershed characteristics, and that three models provide similar performance for the evaluation of relationship between discharge per area and watershed characteristics. The results from regression analyses demonstrate that ISA plays an important role in watershed hydrology. Ignorance of spatial dependence in analyses will likely cause inaccurate evaluation for relationship between ISA and watershed hydrology. The hydrologic model, regression methods and relationships between watershed characteristics and hydrology pattern provide important tools and information for decision makers to evaluate the effect of different scenarios in land management.     

An approach to the ecological characterization of arid and semiarid basins

A morphometric study of 61 sub-basins of the River Segura basin (SE Spain) enables us to attribute ecological processes in streams of these arid and semiarid watersheds to altered patterns of discharge resulting from human activity. Methods used are compared to other, commonly used limnological indexes.     

风沙活动对陆地生态系统影响研究进展

风沙活动及其物质输移运动是关键的陆地地表过程,对全球生态环境有显著的影响。归纳了风沙运动中养分的释放、搬运和沉降机制;总结了目前风沙运动中的物质及养分组成,养分流失与沉降对植物生长的影响、养分在植被群落中的分配和利用机理等方面的研究进展;揭示了大区域尺度上风沙运动与地表养分的释放和输移的关系及植被群落对风沙活动的响应;指出了风沙活动在陆地生态系统演化中扮演的角色。在已有研究的基础上,提出揭示风尘物质在远源陆地区域的沉降机制、风尘物质中有效养分的组成和含量、风尘物质养分的主要传输路径,建立风尘物质养分的源—汇模式,构建植被对风沙活动的响应过程,综合集成风沙活动与植被演化之间的动态关系等是未来主要研究方向的建议。     

Contaminants from cretaceous black shale: II. Effect of geology,weathering, climate,and land use on salinity and selenium cycling,Mancos Shale landscapes,southwestern United States

The Cretaceous Mancos Shale (MS) is a known nonpoint source for a significant portion of the salinity and selenium (Se) loads in the Colorado River in the southwestern United States and northwestern corner of Mexico. These two contaminants pose a serious threat to rivers in these arid regions where water supplies are especially critical. Tuttle et al. (companion paper) investigates the cycling of contaminants in a Colorado River tributary watershed (Uncompahgre River, southwestern Colorado) where the MS weathers under natural conditions. This paper builds on those results and uses regional soil data in the same watershed to investigate the impact of MS geology, weathering intensity, land use, and climate on salt and Se storage in and flux from soils on the natural landscape, irrigated agriculture fields, areas undergoing urban development, and wetlands. The size of salinity and Se reservoirs in the MS soils is quantified. Flux calculations show that during modern weathering, natural landscapes cycle salt and Se; however, little of it is released for transport to the Uncompahgre River (10% of the annual salinity and 6% of the annual Se river loads). When irrigated, salinity and Se loads from the MS soil increase (26% and 57% of the river load, respectively), causing the river to be out of compliance with Federal and State Se standards. During 100 years of irrigation, seven times more Se has been removed from agricultural soil than what was lost from natural landscapes during the entire period of pedogenesis. Under more arid conditions, even less salt and Se are expected to be transported from the natural landscape. However, if wetter climates prevail, transport could increase dramatically due to storage of soluble phases in the non-irrigated soil. These results are critical input for water-resource and land-use managers who must decide whether or not the salinity and Se in a watershed can be managed, what sustainable mitigation strategies are possible, and what landscapes should be targeted. The broader implications include providing a reliable approach for quantifying nonpoint-source contamination from MS and other rock units elsewhere that weather under similar conditions and, together with results from our companion paper, address the complex interplay of geology, weathering, climate, and land use on contaminant cycling in the arid Southwest.     

黄土高原土壤裸露与景观格局关系——以延安市宝塔区为例

土壤裸露是水土流失具体的空间表现,同时又是导致进一步水土流失的重要因素。由人类和自然相互作用下形成的景观格局对土壤裸露具有深刻的影响。为深入探讨二者间的内部联系,文章选定位于黄土高原的延安市宝塔区为研究区,分别就景观格局的类型组成和空间结构,分析其与土壤裸露的关系。研究结果可知人为活动强度较大的区域土壤裸露程度较高,在景观类型上,表现出滩地、农村居民点、其他建设用地、低覆盖度草地及山区旱地等景观类型的土壤裸露值较高,另外,从景观组成来看,农牧组成为主的流域土壤裸露值明显高于其他流域;通过景观空间结构与土壤裸露的关系分析,可知个体单元型态、空间构型以及整体多样性等景观空间结构特征,均对土壤裸露程度具有不同大小的指示意义,其中又以景观聚集度及平均斑块面积与土壤裸露程度有强烈负相关。     

TOPMODEL在流域径流模拟中的应用研究

介绍了TOPMODEL的基本结构与理论。该模型结构简单、物理概念明确、优选参数少,在集总式和分布式流域水文模型之间起到了一个承上启下的作用。TOPMODEL在国外已被广泛研究,并认为是一个相当成功的流域水文模型。为了进一步拓宽该模型的应用,选择6个不同尺度、分布于不同区域和不同气候条件下的流域来应用研究该模型的径流模拟效果。结果表明,该模型在率定和校核两个阶段的模拟精度都比较高,基本上能达到新安江三水源模型的水平。