鄂尔多斯盐沼湿地土壤盐分特征对植物群落的影响

为研究内陆盐沼植物群落的分布对土壤盐分的响应特征,选取鄂尔多斯盐湖盐沼区作为研究区,筛选了肉质耐盐植物群落、苔草植物群落和禾草植物群落3类典型植物群落,开展了土壤含水量、pH、电导率以及Na⁺、K⁺、Mg²⁺、Ca²⁺、Cl^-、SO₄^2-、CO₃^2-和HCO₃^-测定,分析了区内典型植物群落对土壤水盐因子的响应规律。探讨了3类植物群落之间土壤因子含量的差异性;采用相关性分析和CCA分析,评价了3类植物群落多样性及物种分布随土壤因子的变化规律。结果表明,区内3类植物群落中,土壤盐分含量表现为肉质耐盐植物群落最高,苔草植物群落最低,禾草植物群落居中;植物多样性与土壤中含量最高的Na⁺和SO₄^2-的相关性最显著;植物分布同时受到土壤盐分、水分和pH的显著影响。研究结果可为鄂尔多斯盐湖区土壤盐...     

The use of caesium‐137 to estimate agricultural erosion on steep slopes in a tropical watershed

The estimation of erosion and sediment delivery rates in tropical mountain watersheds is difficult and most of the methods widely used for estimating soil erosion over large areas have serious limitations. The ¹³⁷Cs approach has potential for quantifying soil erosion because it can provide retrospective estimates of long‐term (since 1963) net sediment redistribution relatively quickly. Despite its great potential, ¹³⁷Cs has not yet been used in an extensive, reconnaissance level survey of erosion in complex tropical mountain environments. The objective of this study was to examine the applicability of the ¹³⁷Cs method to estimate erosion on steep tropical agricultural lands (23 to 80% slopes) in the Nizao watershed, a humid, tropical mountain area of the Dominican Republic. In this study we (i) examine the variation of ¹³⁷Cs in ten reference sites—eight coffee groves and two forested sites—and (ii) estimate erosion from 14 cultivated fields. The soil pool of ¹³⁷Cs ranged from to 150 to 192 mBq cm⁻² on reference sites with minimal erosion. Variability among reference sites was less than expected for such complex mountain terrain. The variability within coffee and forested reference (average CV=28%) sites was similar to the variability found on grassland and forested reference sites in the temperate zone. The estimated annual soil loss from 14 sampled fields ranged from 6 to 61 t ha⁻¹ year⁻¹ with an overall mean of 26 t ha⁻¹ year⁻¹. Overall, the soil erosion estimates found using the ¹³⁷Cs method were much lower than those often assumed for such steep tropical hillsides. These erosion estimates account for soil loss since 1963 only and it seems likely that soil losses may have been much higher in earlier decades immediately after initial forest clearing earlier in the 20th century. Copyright © 2000 John Wiley & Sons, Ltd.     

高泉沟流域产流产沙的降水特征因子分析

高泉沟流域属于黄土丘陵沟壑区。运用灰色关联与相关系数分析法,分析影响该流域坡面产流产沙的降水特征因子。结果表明对黄土丘陵沟壑区产生径流贡献最大的因子是降雨量;对土壤侵蚀量贡献最大的因子是降雨量半小时雨强复合因子。因此,降雨量的多少是影响本区产流产沙最关键的因素。     

盐城滨海港区防波堤建设对水下地形的影响研究

利用双频测深仪和声学多普勒流速仪对滨海港区附近海域进行了区域测深和定点全潮水文观测,通过与以往调查研究资料的对比,分析了防波堤建成前后海底冲淤变化特征。研究结果表明:近20年以来水下岸坡为侵蚀最剧烈的区域,海底平原则处于相对稳定状态;受自然侵蚀的影响,水下岸坡继续向岸内移,目前最强侵蚀区已内移至–8~–12 m水深的水下岸坡;近年来自然侵蚀明显减弱,年均侵蚀速率约为前10年的1/4;受防波堤挡流效应的影响,口门南侧已由往复流转变为旋转流;目前已出现三大淤积区域,其中以口门处淤积最严重,最大淤积厚达3.5 m,已造成口门处水深不足–10 m;防波堤对周边海域直接影响范围约13.4 km~2,最远可达废黄河口。分析认为,防波堤建设是引起港区海底冲淤格局发生变化的主因。该研究为防波堤的后续维护及滨海港区30万t级航道工程论证提供了基础资料。     

基于Sentinel-1和Sentinel-2协同反演干旱区地表土壤水分——以格尔木河中下游为例

土壤水分是全球水循环的重要组成成分,对研究水分的空间分布、农作物长势和产量、气候变化、水资源时空特征等有着重要意义。利用Sentinel(哨兵)系列主动微波雷达卫星SAR(Sentinel-1)结合光学卫星(Sentinel-2)对格尔木中下游低矮植被覆盖下的地表土壤水分进行反演研究,探讨不同极化组合方式和水云模型前后的土壤水分含量反演方法的适用性。结果表明,VV(VV Polarization)极化比VH(VH Polarization)极化更加适用该区域,VV极化结合归一化水指数(NDWI)反演地表土壤水分精度达到42.6%,拟合精度最高;VH极化仅为22.6%;利用水云模型去除植被覆盖后对地表土壤水分的反演精度有所提升,VV极化精度提高约3.5%,VH极化提高1.5%;Sentinel系列卫星影像对于干旱区的土壤水分的反演具有较好的适用性。探索了适用于该研究区乃至柴达木盆地土壤水分大面积实时监测的可靠手段和依据。     

A model of Cs activity profile for soil erosion studies in uncultivated soils of Mediterranean environments

A model to simulate ¹³⁷Cs profiles in soils during the time in which they are being eroded is proposed. The model uses one parameter to characterize the cesium transference in the soil and another to express the erosion rate. To test the model, ¹³⁷Cs profiles of stable and eroded soils were collected at sampling sites located on semi-arid and temperate slopes in the Central Ebro basin, Spain. The ¹³⁷Cs profiles, corresponding to uncultivated soils with natural vegetation cover, were simulated using this model. The ¹³⁷Cs inventories and profiles calculated with the model are very similar to those measured experimentally, and thus it is possible to calculate soil erosion rates in physiographically diverse Mediterranean environments.     

热惯量法在监测土壤表层水分变化中的研究

利用遥感方法监测一定层水深土壤水分变化，关键是建立卫星数据与地表水热变化关系，该文地遥感定量反演土壤水热变化的数值模拟系统及热惯量在其边界，初始条件确定中所起的作用进行的简述，并介绍了热惯量法求解表层水分含量的发展概况，为进一步提高定量化监测方法的地必琢计算精度，该文发展了地表能量平均方程的一种新的化简方法，经过这样的处理，可从遥感图象数据直接得到真实热惯量值，进而得到土壤水分含量分布，通过野外实     

章丘区北部土壤重金属地球化学特征及潜在生态风险

以山东省济南市章丘区北部表层土壤中As等8种重金属元素为研究对象,利用多元统计进行重金属来源分析,采用污染负荷指数法及潜在生态危害指数法进行污染评价,结果表明:研究区表层土壤重金属元素含量低于济南市土壤背景值,Cd和Hg元素含量为强度变异,在表层土壤产生一定的富集;不同土地利用类型下重金属元素含量具有差异性。土壤中Cr,Cu,Ni和Zn来源于土壤母质,Cd和Pb元素来源于人类活动,As元素来源复杂。土壤综合污染以轻度污染为主,重金属元素污染程度大小为AsNiPbZnCrCuCdHg。综合潜在生态风险以轻微和中度为主,潜在生态风险强弱程度为HgCdAsCuPbNiCrZn,建议防范Hg和Cd元素污染及生态风险。     

气候模式-农业气象模式集成系统的小麦灌溉管理新途径

首次采用区域数值预报模式与农业气象模型结合的技术途径, 构成一个气候模式-土壤水分模式-灌溉模式的系统模型。模型的数值天气预报部分采用大气过程与陆面过程耦合的区域气候模式; 农业气象模型采用适用于冬小麦区的土壤水分和灌溉管理预报模型。研究表明, 本模型较农业气象模型中一般用气候平均作为环境背景场的方法其预测能力有显著提高, 并提供覆盖整个小麦生长期的区域土壤水分定量预报和灌溉管理服务, 具有很好的使用和推广前景。     

Effectiveness of post-fire salvage logging stream buffer management for hillslope erosion in the U.S. Inland Northwest Mountains

Active wildfire seasons in the western U.S. warrant the evaluation of post-fire forest management strategies. Ground-based salvage logging is often used to recover economic loss of burned timber. In unburned forests, ground-based logging often follows best management practices by leaving undisturbed areas near streams called stream buffers. However, the effectiveness of these buffers has not been tested in a post-wildfire setting. This experiment tested buffer width effectiveness with a novel field-simulated rill experiment using sediment-laden runoff (25 g/L) released over 40 min at evenly timed flow rates (50, 100 and 150 L/min) to measure surface runoff travel length and sediment concentration under unburned and high and low soil burn severity conditions at 2-, 10- and 22-month post-fire. High severity areas 2-month post-fire had rill lengths of up to 100 m. Rill length significantly decreased over time as vegetation regrowth provided ground cover. Sediment concentration and sediment dropout rate also varied significantly by soil burn severity. Sediment concentrations were 19 g/L for the highest flow 2-month post-fire and reduced to 6.9–14 g/L 10-month post-fire due to abundant vegetation recovery. The amount of sediment dropping out of the flow consistently increased over the study period with the low burn severity rate of 1.15 g L⁻¹ m⁻¹ approaching the unburned rate of 1.29 g L⁻¹ m⁻¹ by 2-year post-fire. These results suggest that an often-used standard, 15 m buffer, was sufficient to contain surface runoff and reduce sediment concentration on unburned sites, however buffers on high burn severity sites need to be eight times greater (120 m) immediately after wildfire and four times greater (60 m) 1-year post-fire. Low burn severity areas 1-year post-fire may need to be only twice the width of an unburned buffer (30 m), and 2-year post-fire these could return to unburned widths.