岩溶流域典型农业区水体氢氧同位素的空间异质性及形成机制   总被引：1，自引：0，他引：1  

张金  韩志伟  吴攀  田永著  赵然  罗广飞 《中国农村水利水电》2021,(3)

分别于平水期和枯水期采集了花溪河流域典型农业区地表水和地下水样品。利用氢氧同位素示踪技术,结合土地利用类型对研究区不同水体的补给来源、季节变化及主要影响过程进行了分析,并对不同水体氢氧同位素值进行了空间插值分析,同时对其形成机制进行了分析,阐明了不同土地利用类型影响下的主要水文过程。结果表明:(1)研究区不同水体的主要补给来源为当地大气降水,月亮湖水库受蒸发作用影响明显,地表水和地下水的δD和δ~(18)O整体上呈现平水期高于枯水期的特征。(2)地下水的δD和δ~(18)O在枯水期与平水期均呈现明显的空间分异性特征,西部水田/水库集中区富集,东部旱地集中区贫化,土地利用对研究区环境水文过程影响明显。该研究结果有助于了解不同土地利用方式下地表水对地下水的影响,为流域管理提供科学依据。  相似文献   

Spatiotemporal patterns of mountain whitefish (Prosopium williamsoni) in response to a restoration of longitudinal connectivity          下载免费PDF全文

Peter M. Kiffney  Ben Cram  Paul L. Faulds  Karl Burton  Michele Koehler  Thomas P. Quinn 《Ecology of Freshwater Fish》2018,27(4):1037-1053

To examine the role of longitudinal connectivity on the spatial and temporal dynamics of mountain whitefish (Prosopium williamsoni), we quantified movement and population dynamics following installation of the Landsburg Dam fishway, Cedar River, WA, USA. Mountain whitefish is widely distributed, poorly studied and not the focus of restoration. Before the fishway, mountain whitefish were not observed above the dam. Here, we focus on snorkel counts collected at reach and mesohabitat (e.g. pools) scales over 11 summers on the 20‐km above‐dam segment following restoration. A camera within the ladder provided number, size and movement timing, thereby informing on behaviour and recolonisation. Segment‐scale abundance increased following fish passage reaching an asymptote in 7 years, and mountain whitefish were detected throughout the main stem in 10 years. Annual movement through the ladder increased over time and was positively correlated with instream abundance and discharge, but negatively correlated with water temperature. About 60% of fish movements occurred in spring and early summer, potentially for foraging opportunities. Reach‐scale abundance peaked between 7 and 10 km from the dam; deep, cool (~10.6 to 11.6°C) conditions characterised these reaches. At the mesohabitat scale, mountain whitefish detection increased with depth and velocity after accounting for distance from the dam. Our results show how restoring longitudinal connectivity allowed this nontarget species to colonise newly available habitat. Their response supports the critical roles of longitudinal connectivity and environmental conditions, that manifest at different spatial scales, in dictating how freshwater fish respond to habitat disturbance.  相似文献   

Digital mapping of soil ecosystem services in Scotland using neural networks and relationship modelling—Part 1: Mapping of soil classes     

Matt J. Aitkenhead  Malcolm C. Coull 《Soil Use and Management》2019,35(2):205-216

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Boundary-fitted grid in landscape modeling     

Kang-Ren Jin  Yegang Wu 《Landscape Ecology》1997,12(1):19-26

Landscape modeling requires the delineation of system boundaries and interior features. Quite often, these components are complex and difficult to accurately represent. A rectangular grid is used to represent the study and adjacent non-study areas in most cases. When the non-study area occupies a large portion of the grid, computer memory is wasted, and computational time increases. An elliptical grid generator for non-orthogonal curvilinear coordinates is used to generate a boundary-fitted grid for a landscape model. In a boundary-fitted grid coordinate system, one coordinate axis follows the landscape domain boundary and is non-orthogonal to the second axis. The boundary-fitted grid uses elliptic partial differential equations to distribute grid points inside the landscape domain. Although the boundary-fitted grid follows the domain boundary, the grid pattern and point allocation remain structured. Thus, a landscape model can use a boundary-fitted grid without changing the model’s data structure or the computational scheme. In this study, a boundary-fitted grid and a raster-based grid were applied to the Everglades Landscape Fire Model. Use of the boundary-fitted grid decreased model simulation time by about one fifth and computer storage by 58% relative to the raster-based grid. Also, the linear characteristics of interior geographical features such as rivers and airboat trails were preserved by the boundary-fitted grid, but not by the raster-based grid. This preservation provided a more reasonable base map for simulating ecological processes, such as fire across heterogenous landscapes.  相似文献   

Some Comments on Gerechte Designs     

R. A. Bailey    J. Kunert  R. J. Martin 《Journal of Agronomy and Crop Science》1991,166(2):101-111

In a companion paper we derived the correct analysis for gerechte designs with uncorrected errors. Here we show that this correct analysis cannot be justified by the usual randomization argument. However, when the regions are rectangular there is a randomization procedure which validates an analysis with three separate error terms. We also outline other developments in design and analysis that may be more satisfactory.  相似文献   

杉木扁长蝽若虫空间分布型的研究   总被引：1，自引：0，他引：1  

薛贤清  余荣卓 《福建林业科技》1996,23(4):48-50

本文采用聚集度指标检验法、回归分析法研究了杉木扁长蝽若虫的空间分布型。结果表明：在不同林地、不同虫口密度情况下，均呈聚集分布。若虫的聚集与栖息生境有直接关系。  相似文献   

Spatial distribution of Aspergillus flavus and its toxigenic strains on commercial cottonseed from south Texas and its relationship to aflatoxin contamination     

R. Jaime-Garcia  P. J. Cotty 《Plant pathology》2006,55(3):358-366

The structure of Aspergillus flavus communities associated with south Texas cottonseed was determined by analysing samples from 178 truckloads of commercial cottonseed from 35 gins, extending from Fort Bend County in the north to the Rio Grande Valley in the south, from September 1999 to October 2001. The number of colony-forming units (CFU) of A. flavus on the cottonseed, and the percentage of S strain (%S) were both correlated with aflatoxin contamination of cottonseed. The number of CFU differed between both regions and seasons, while %S differed only between regions. Comparison of maps of CFU and %S revealed that CFU shows a higher variation across years, while %S shows higher spatial variation. The Rio Grande Valley had significantly lower CFU and %S strain than the Coastal Bend and Upper Coast regions. Cottonseed produced in 1999 had significantly more A. flavus than that produced in either 2000 or 2001. Identification of factors dictating geographical variation in S-strain incidence may provide insights that will lead to improved aflatoxin management.  相似文献   

七星瓢虫幼虫空间分布型及抽样技术研究     

李定旭  张志勇  郭岩 《河南科技大学学报(农学版)》1991,(3)

采用颍次分布X~2检验、Iwao平均拥挤度m~*=a+βx和Taylor幂法则S~2=am~b等8种方法,分析了七块麦田中七星瓢虫幼虫的空间分布型,认为其分布型为负二项分布,且聚集的原因是由于个体之间存在着相互吸引,并确定了代表性较强的棋盘式抽样技术,最佳抽样数量为:Q=28.7088/+0.7552。  相似文献   

Change in spatial characteristics of forest openings in the Klamath Mountains of northwestern California,USA   总被引：4，自引：0，他引：4  

Carl N. Skinner 《Landscape Ecology》1995,10(4):219-228

Change in the spatial characteristics of forest openings was investigated in three forested watersheds in north-western Siskiyou County, California totalling approximately 24,600 hectares. Watersheds with minimal human disturbance were chosen for study. However, fire suppression has been pervasive throughout. Characteristics of forest openings (area, perimeter, distance between neighboring openings) were measured on aerial photographs taken 41 years apart. An index of regional form was determined for the landscape. Shape complexity for each opening was calculated using two indices based upon fractals. Significant differences were found using the Kolmogorov-Smirnov two-sample test between the perimeters, areas, distance from sample point to nearest opening, and distance between neighboring openings. The perimeters and areas became smaller, and the distances from the sample point to the nearest opening and between neighboring openings became greater over the 41 years between aerial photo sets. The estimated area occupied by openings decreased from 25.8 % to 15.6 % of the study area. No significant difference was found in the shape of the openings except as the shape indices were influenced by changes in size of the openings.This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright.  相似文献   

阜康绿洲土壤盐渍化特征及其与肥力的相关性分析   总被引：9，自引：0，他引：9  

顾峰雪  张远东  刘永强  初雨  潘晓玲 《干旱区资源与环境》2003,17(2):78-82

本文以电导、可溶性总盐含量和pH作为指标,将阜康绿洲的盐渍化类型划分为9种,其中以强盐渍土和盐土为主,在纬度梯度上从南至北,即从洪积扇下部到沙漠按照中盐渍土-强盐渍土-盐土-强盐渍土-盐土-非盐渍土的顺序依次分布。而土壤含水率却是从洪积下部至扇缘溢出带逐渐升高,在细土平原地区差异较大,在沙漠中又迅速降低。通过土壤剖面中有机质、全量N、P、K和速效N、P、K的分析,结果表明阜康荒漠自然状态下土壤肥力很低,各养分含量在空间上呈现规律性的变化,在纬度梯度上逐渐升高又在沙漠中降低。通过水盐与土壤肥力的相关性分析,结果表明:有机质、全N、P和速P与含水率、电导、总盐均具有显著和极显著正相关,而与pH成负相关,但相关性不显著。由于盐生植物的多样性,在盐渍土和盐土土壤肥力并无显著降低,只是土壤溶液的高盐浓度限制了植物对养分的吸收,因此防止和治理土壤盐渍化是发挥土地生产潜力的重要手段。  相似文献