Correspondence between spatial patterns in fish assemblages in ohio streams and aquatic ecoregions

Land classification systems can be useful for assessing aquatic ecosystems if relationships among them exist. Because the character of an aquatic ecosystem depends to a large extent upon the character of the landscape it drains, spatial patterns in aquatic ecosystems should correspond to patterns in the landscape. To test this hypothesis, the US state of Ohio was divided into four aquatic ecoregions based on an analysis of spatial patterns in the combination of land-surface form, land use, potential natural vegetation, and soil parent material. During the period July–October 1983, fish assemblages were sampled in 46 streams that were representative of the ecoregions, and that had watersheds relatively undisturbed by human activities. Spatial patterns of the fish assemblages were examined relative to the ecoregions; distinct regional differences were identified. The assemblages differed most between the Huron/Erie Lake Plain region and the Western Allegheny Plateau region; assemblages in the Eastern Corn Belt Plains and the Erie/Ontario Lake Plain-Interior Plateau regions were intermediate. This pattern also reflects the gradient in landscape character as one moves from the northwest to the southeast of Ohio.     

WATER RESOURCES MANAGEMENT: INTERNATIONAL CHALLENGE AND OPPORTUNITIES1

The entire water resources field is not contemplated, although reference thereto will be registered. Water supply for potable and hygienic purposes will be presented as symbolic of the global issues confronting 4.8 billion people. Some two billion of these live in the so-called developing or less favored countries. They are either underserved or not served at all by utility systems of whatever grade. Targets for meeting their needs were exemplified by the international agencies in the International Water and Sanitation Decade of 1980-1990. Some successes are apparent, but, in general, hopes are not fulfilled. The pace of accomplishment is very slow. Constraints will be reviewed in some detail. Challenges for reducing these and increasing pace of installations are presented. The potential for a global public works program unprecedented in history is reviewed. Several issues will not be discussed in this paper. Their omission rests primarily upon the fact that their resolution is improbable for decades ahead, if ever. Economists have categorized water as any other economic commodity - and should always be subject to benefit-cost scrutiny. I do not share that view. People could well live without the telephone or the automobile, a destroyer. Without water, their survival is a matter of days. Cost-benefit seems unreal and singularly inappropriate under such circumstances. Secondly, the search for quantifying the health impact of safe water goes on forever. My view is that the results speak for themselves - while sturdy souls continue to seek out the exact correlation figure. Thirdly, the population explosion, although softened a bit, proceeds apace while I write. Lastly, the exposition herein is restricted to potable water and its associated sanitation aspects. Other major uses of water, obviously highly important, are not addressed.     

Irrigation development and its environmental consequences in arid regions of India

The present paper examines the nature and dimensions of environmental transformation induced by canal irrigation in the arid region of India. The case study pertains to the Indira Gandhi Canal comand area in Rajasthan where the density and area of vegetation cover have increased due to afforestation, and the cultivated area has expanded due to irrigation. Consequently, there has been a perceptible improvement in the structure and fertility of sandy soils, but it would require a herculean effort on the part of the canal authority and local people to reduce soil erosion and siltation in the lower parts of stage I and the entire command area of stage II. Moreover, the water table has been rising rapidly throughout the command area of stage I. About half of the command area and adjoining Ghaggar basin in Ganganagar District will be facing the danger of waterlogging by the turn of the century. The incidence of irrigation-induced alkalization is higher in the lower parts of stage I. Soil alkalinity has appeared within five years of the introduction of irrigation in the interdunal basins and is manifested as a strong salt regime or calcareous pans near surface. This calls for immediate reclamation of the affected area and prevention of its expansion by altering the strategy of irrigation development, by changing cropping patterns, and by providing soil drainage.     

水相中苯酚光催化降解的全额光子效率

为定量评价光催化反应器的性能,利用主辐射波长为207 nm的KrBr*准分子灯降解水相中的苯酚,测定了光解和光催化降解2种体系中苯酚和TOC去除率,并计算了苯酚降解的ξ_g(全额光子效率),探讨了其影响因素. 结果表明:①延长反应时间、加入适量催化剂、降低初始c(苯酚)能提高苯酚和TOC去除率. 采用动力学模型对苯酚的降解进行拟合,表明光解和光催化降解体系中苯酚的降解均符合准一级动力学模型. ②加入催化剂和提高初始c(苯酚)均可以获得较高的ξ_g,而光源的辐射功率与ξ_g没有线性相关性;在辐射功率为0.76 W、初始c(苯酚)为1.10 mmol/L、催化剂投加量(以ρ计)为0.8 g/L的条件下,ξ_g为5.56%. ③采用高效液相色谱对光催化降解体系中生成的中间产物的变化规律进行研究发现,4种中间产物表现为c(对苯二酚)＞c(邻苯二酚)＞c(对苯醌)＞c(间苯二酚);通过建立苯酚及中间产物的拟一级降解动力学模型,证实苯酚光催化降解历程为苯酚→芳香烃中间产物→最终产物.      

近30年青海三江源西部干旱区草地退化特征的遥感分析

使用自20世纪70年代末~2004年的3期遥感图像(70sMSS、90sTM和2004年TM/ETM),研究了近30年青海三江源西部干旱区草地退化的格局与过程,结果表明:整个研究时段内,草地退化发生面积占总草地面积的10%左右,且以草地覆盖度轻度下降为主,其退化面积占总草地退化面积的80%以上,其次是轻度沙化/盐化,相应比重占10%以上。草地退化面积呈东南向西北减少趋势,退化程度呈东南向西北降低格局,而退化类型也由复合型向单一型过渡。整个时段内,草地退化面积呈增加趋势,尤其是沙化面积增加较快。不同海拔、坡度和坡向间草地退化面积差异显著。海拔4 800~5 100m范围内为草地退化发生的主要分布区,4 500~4 800m和5 100m以上草地退化基本相当。退化率较高的坡度级别介于2~8°之间,类似于草地面积随坡度变化的基本趋势。不同坡向呈阴坡、半阴半阳坡高于阳坡的态势。脆弱的基底、极端气候年际间周期波动等限制性因子控制着草地退化的基本格局,人为扰动则决定草地退化的强度和速度。总体看来,研究区地带性自然条件决定的荒漠化草地已占据主导地位,人类活动相对较弱,草地退化程度增加趋势不明显,新的草地退化现象不十分突出。     

红壤丘陵区LAI与土壤侵蚀分布特征的关系

叶面积指数(LAI)是常用的一个用于描述植被覆盖的方面指数,土壤侵蚀的分布又与植被的覆盖状况息息相关,这就意味着LAI与土壤侵蚀有一定的相关性,目前有关这二者的相关性研究还鲜有文献报道。基于这此,本研究首先利用2000年的遥感影像(TM)解释出该年度的土壤侵蚀强度图,再利用该遥感影像通过图像的代数运算得出该地区的NDVI栅格图,通过实测该县不同典型植被条件的LAI值,得出实测的LAI与图像NDVI值之间的函数关系式,由图像的代数运算把NDVI图转换成LAI图,即实现了遥感图像的实测LAI纠正。在GIS软件的帮助下,通过将LAI栅格图与土壤侵蚀强度图的空间叠加分析,得到不同LAI条件下的土壤侵蚀分布。结果表明,LAI与土壤侵蚀的分布表现为:大致以LAI=2为分界线,当LAI<2时,土壤侵蚀并未随LAI的增加而迅速减少,LAI>2时,土壤侵蚀的分布随植被指数的增加而减少,当LAI=2左右时,土壤侵蚀的面积最大。这种情况对于轻度、中度及强度土壤侵蚀的影响是类似的,都呈类正态分布的曲线形式,但在曲线的两侧土壤侵蚀类型是有本质区别的,在曲线的左侧土壤侵蚀类型的分布是中度和强度为主,而在曲线右侧则以轻度为主。表明LAI这个指标与土壤侵蚀有很好的相关性,可以用于土壤侵蚀方面的相关研究工作。     

全球变化下有关卤代甲烷源汇的研究进展

大气中存在的卤代甲烷对臭氧层具有极强的破坏作用并参与其它气候现象，其动态变化对臭氧的恢复和地球生态系统有重要影响。文章概述了全球变化下卤代甲烷源汇的研究情况并简单探索其进一步的研究方向。几种卤代甲烷中，溴代甲烷源汇最复杂且对臭氧具有最强的破坏力，因此研究较多。已证明CH3Br的来源有：海洋、土壤、生物燃烧、陆地植物和沼泽地的释放等；CH3Br的汇包括：光化学分解、被土壤和植物吸收、在海洋中的化学和生物降解等。但事实上是已知汇远远大于已知源，且各个源汇的通量在不同研究中结果差异较大，归其原因是卤代甲烷释放与吸收机制的不确定性。虽然近几年的研究也应用了稳定同位素示踪技术，但卤代甲烷各源汇的具体贡献并不清楚。今后卤代甲烷源汇的研究重点应放在与气体产生机制最密切的地下部分即“地下生态学”对其通量的影响，而同位素技术的改进及其在痕量气体研究中的应用也将是未来的重点方向。     

Satellite image analysis of human caused changes in the tundra vegetation around the city of Vorkuta,north-European Russia

In this paper we present what kind of human impacted changes can be found in dwarf birch (Betula nana) dominated shrub tundra vegetation around the large industrial complex of Vorkuta in the north-European Russian tundra. Using fieldwork data and Landsat TM satellite image we could identify two impact zones: (1) Pollution zone (150-200 km2). In this zone most of the lichen species are absent. Changes in vegetation communities' species composition in all main plant groups are obvious. Willows especially are more dominant than in the unpolluted sites. (2) Slight pollution/disturbance zone (600-900 km2). Here vegetation changes are mainly similar but less so than the changes in the first zone. Particularly, the amount of herbs and grasses is increased when compared to unpolluted areas. The pollution zones are spatially connected to the main emission sources in the area. Zones spread furthest to the northeast, matching the prevailing winds during winter.     

Marine macroalgae in polar regions as natural sources for volatile organohalogens

Marine macroalgae species from the polar regions were investigated for their importance as natural sources of volatile halogenated compounds released into the biosphere. Several different halogenated C1 to C4 hydrocarbons were identified and their release rates determined. The compounds contained mainly bromine and iodine, and form was the dominant compound released. Although an annual atmospheric input of approximately 10(8)-10(10) g bromine and 10(7)-10(8) g iodine was calculated from the release rates, marine macroalgae are apparently not the major source on a global scale, as the release is up to four orders of magnitude lower than a presumed annual flow from the oceans. Despite this, macroalgae may be more important on a local scale due to their occurrence at a high biomass in the coastal regions. The present paper gives an overview about studies done on the release of volatile halocarbons by macroalgae from polar regions. Furthermore, the function of these compounds in the macroalgal metabolism is discussed.     

Syndromes of Global Change: a qualitative modelling approach to assist global environmental management

A novel transdisciplinary approach to investigate Global Change (GC) is presented. The approach rests on the decomposition of the intrigue dynamics of GC into patterns of civilization–nature interactions (syndromes) by an iterative scientific process of observations, data and system theoretical analyses, and modelling attempts. We illustrate the approach by a detailed analysis of the Sahel Syndrome, which describes the rural poverty driven overuse of natural resources. The investigation is performed by (i) identifying relevant symptoms and interlinkages which are characteristics for this pattern, and (ii) a qualitative model representing the internal dynamics of the essential flywheel. The geographical patchwork of the regions affected by the syndrome which is obtained by global data analysis, proves the high global relevance of this pattern. The qualitative model is employed for an evaluation of basic policy strategies debated in the context of rural poverty driven environmental degradation. It turns out that a mixed policy of combating poverty and introducing soil preserving agricultural techniques and practices is most promising to tackle the syndrome dynamics.