滴灌下生物质改良材料对盐渍土水盐氮运移的调控效应   总被引：2，自引：0，他引：2  

姚荣江  李红强  杨劲松  陈强  郑复乐  尚辉 《农业机械学报》2020,51(11):282-291

为探究生物质改良材料对滴灌盐渍土水、盐、肥运移过程的调控效应，采用土箱模拟试验，研究了水肥一体化滴灌条件下，生物炭和腐殖酸两种改良材料对盐渍土水、盐、氮运移和再分布过程及其时空分布特征的影响规律。结果表明：在滴灌条件下，盐渍土壤水盐的时空动态变化表现出明显的水分入渗驱动的盐分运移过程和蒸发扩散驱动的水盐再分布过程；铵态氮含量在时间上表现出先增大、后减小的变化趋势，在空间上的运移再分布特征较弱；硝态氮含量初始时空分布表现出与水盐相似的运移特征，受铵态氮硝化作用的多重影响，后期空间分布与铵态氮空间分布相似；生物炭通过提高土壤饱和导水率，增大了入渗阶段土壤水、盐、氮的运移速率和分布范围；腐殖酸通过提高土壤田间持水率增大了再分布过程土壤水、盐、氮的分布范围和强度，同时其对尿素的水解和硝化过程表现出更强的抑制效果。应用生物质改良材料在改变土壤物理性状进而调控滴灌土壤水盐运移的同时，还影响土壤氮素转化运移过程及其分布，这为水肥一体化滴灌盐渍农田的节水、控盐、减肥治理提供了理论基础。  相似文献   

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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中西药结合预防肉鸡腹水综合征的临床试及防治机理探讨     

杨慧萍  岳治权  王建华 《中国家禽》2004,8(Z1):69-71

将一日龄艾维因肉仔鸡(雌雄各半)180只在同一舍内饲养,14日龄时将其随机分成4组,其中Ⅰ、Ⅱ组饲料按1％分别添加我们研制的方剂一和方剂二,连续用药15d,为药物预防组;Ⅲ组在饲料中按0.05％添加肾肿腹水消,连用7d(药品要求的预防剂量),为药物对照组;Ⅳ组饲料中不添加任何药物,为空白对照组。Ⅰ-Ⅳ组发病率分别为0、10％、3％和20％,42d时Ⅰ、Ⅳ组体重高于其它组,Ⅰ平均体重为1972.92g,Ⅳ组平均体重为1989.91g。试验表明方剂一为该试验条件下预防肉鸡腹水综合征最有效的方剂,其保护率可达100％,且不影响出栏重。对方剂一预防肉鸡腹水综合征的机理进行探讨。  相似文献   

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   

造纸工业必须走林纸一体化与可持续发展道路     

韩小红  王哓青  吴海平 《陕西林业科技》2005,(1):23-24,34

通过对我国造纸工业面临的现状和存在问题的调研、分析，并比较国内外造纸工业发展的现状，认为国内木材市场已经进入供不应求的紧缺阶段，而从国外进口木材，增加了企业的经营成本，又受市场的制约。所以企业通过自身营造集生态效益和经济效益为一体的原料林，是解决目前造纸工业瓶颈问题的现实而有效的途径。因此，造纸工业必须走林纸一体化与可持续发展的道路。  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