Atmospheric dust in modern soil on aeolian sandstone,Colorado Plateau (USA): Variation with landscape position and contribution to potential plant nutrients

Rock-derived nutrients in soils originate from both local bedrock and atmospheric dust, including dust from far-distant sources. Distinction between fine particles derived from local bedrock and from dust provides better understanding of the landscape-scale distribution and abundance of soil nutrients. Sandy surficial deposits over dominantly sandstone substrates, covering vast upland areas of the central Colorado Plateau, typically contain 5–40% silt plus clay, depending on geomorphic setting and slope (excluding drainages and depressions). Aeolian dust in these deposits is indicated by the presence of titanium-bearing magnetite grains that are absent in the sedimentary rocks of the region. Thus, contents of far-traveled aeolian dust can be estimated from magnetic properties that primarily reflect magnetite content, such as isothermal remanent magnetization (IRM). Isothermal remanent magnetization was measured on bulk sediment samples taken along two transects in surficial sediment down gentle slopes away from sandstone headwalls. One transect was in undisturbed surficial sediment, the other in a setting that was grazed by domestic livestock until 1974.Calculation of far-traveled dust contents of the surficial deposits is based on measurements of the magnetic properties of rock, surficial deposits, and modern dust using a binary mixing model. At the undisturbed site, IRM-based calculations show a systematic down-slope increase in aeolian dust (ranging from 2% to 18% of the surface soil mass), similar to the down-slope increase in total fines (18–39% of surface soil mass). A combination of winnowing by wind during the past and down-slope movement of sediment likely accounts for the modern distribution of aeolian dust and associated nutrients. At the previously grazed site, dust also increases down slope (5–11%) in sediment with corresponding abundances of 13–25% fines. Estimates of the contributions of aeolian dust to the total soil nutrients range widely, depending on assumptions about grain-size partitioning of potential nutrients in weathered bedrock. Nevertheless, aeolian dust is important for this setting, contributing roughly 40–80% of the rock-derived nutrient stocks (P, K, Na, Mn, Zn, and Fe) in uppermost soil over most of the sampled slope at the undisturbed site, which shows no evidence of recent wind erosion.     

Bird community structure across riparian buffer strips of varying width in a coastal temperate forest

Buffer strips are strips of forest retained along streamsides after harvesting to mitigate negative impacts of forestry on aquatic and riparian fauna and water quality. The capacity of riparian buffer strips of old-growth forest to maintain species richness and abundance of natural bird communities was explored in coastal montane forest on Vancouver Island, Canada. Breeding bird communities in buffer strips of varying widths along rivers were compared with controls of equivalent area in uncut old-growth riparian forest to identify shifts in species richness, diversity, abundance and composition. We observed that effects on riparian bird communities were greatest in very narrow buffers with high amounts of edge habitat. Several forest-interior species were found almost exclusively in wider buffers and abundances dropped dramatically between wide (125 m) and medium (41 m) width buffers with replacement by open-edge species in narrow buffers. Species composition of communities in wide buffers were very similar to controls while narrow buffers shared less than half of their species with controls. Species richness and diversity increased in buffers over the three years while remaining constant in controls. Increases in species richness and abundance within buffers were positively correlated with similar increases in the adjacent clearcuts, suggesting that regeneration in clearcuts may facilitate recolonization of forest in remnant buffers. For the forest-interior species found primarily in wide buffers, buffers >100 m may need to be retained.     

Riparian forest buffer system research at the coastal plain experiment station,Tifton, GA

Recent attention has focused on riparian forest buffer systems for filtering sediment, nutrients, and pesticides entering from upslope agricultural fields. Studies in a variety of physiographic areas have shown that concentrations of sediment and agrichemicals are reduced after passage through a riparian forest. The mechanisms involved are both physical and biological, including deposition, uptake by vegetation, and loss by microbiological processes such as denitrification. Current research by USDA-ARS and University of Georgia scientists at Tifton, GA is focusing on managing riparian forest buffer systems to alleviate agricultural impacts on the environment. The underlying concept for this research is that agricultural impact on streams is best protected by a riparian forest buffer system consisting of three zones. In consecutive upslope order from the stream these zones are (1) a narrow band of permanent trees (5–10 m wide) immediately adjacent to the stream channel which provides streambank stabilization, organic debris input to streams, and shading of streams, (2) a forest management zone where maximum biomass production is stressed and frees can be harvested, and (3) a grass buffer strip up to 10 m wide to provide control of coarse sediment and to spread overland flow. Several ongoing projects at Tifton, GA are focusing on using riparian forest buffer systems as filters. A forest management project is testing the effects of different management practices on surface and ground water quality. This project includes three different forest management practices: mature forest, selectively thinned forest, and clearcut. In a different study a natural wetland is being restored by planting frees. The effectiveness of this wetland on filtering nutrients from dairy wastes which are being applied upslope is being evaluated. At this same site, a pesticide study is being conducted on the side opposite to where dairy wastes are applied. An overland flow-riparian buffer system using swine lagoon waste is evaluating the effectiveness of different vegetative treatments and lengths of buffer zones on filtering of nutrients. In this study three vegetative treatments are compared: (1) 10 m grass buffer and 20 m riparian forest, (2) 20 m grass buffer and 10 m riparian forest, (3) 10 m grass buffer and 20 m of the recommended wetland species maidencane. Waste is applied at the upper end of each plot at either a high or low rate, and then allowed to flow downslope. The three zone riparian forest buffer system is being used for the Riparian Ecosystem Management Model (REMM). This model, which is currently under development at Tifton, GA, is a computer simulation model designed to reduce soil and water degradation by aiding farmers and land use managers in decision making regarding how best to utilize their riparian buffer system. Both information currently being collected in field studies and development of the REMM are innovative farm-level and forestry technologies to protect soil and water resources.     

Soil communities and plant litter decomposition as influenced by forest debris: Variation across tropical riparian and upland sites

Forest debris on ground surface can interact with soil biota and consequently change ecosystem processes across heterogeneous landscape. We examined the interactions between forest debris and litter decomposition in riparian and upland sites within a tropical wet forest. Our experiment included control and debris-removal treatments. Debris-removal reduced leaf litter decomposition rates in both the riparian and upland sites. Debris-removal also reduced soil microbial biomass C in the upland site, but had no effect on microbial biomass C in the riparian site. In contrast, debris-removal altered the density of selected arthropod groups in the riparian site. Litter decomposition rates correlated with both soil microbial biomass and the density of millipedes in a multiple stepwise regression model. Removal of forest debris can substantially reduce rates of leaf litter decomposition through suppressing soil activities. This influence can be further modified by landscape position. Forest debris plays an essential role in maintaining soil activities and ecosystem functioning in this tropical wet forest.     

Correlation between earthworms and plant litter decomposition in a tropical wet forest of Puerto Rico

Earthworms are recognized to play an important role in the decomposition of organic materials. To test the use of earthworms as an indicator of plant litter decomposition, we examined the abundance and biomass of earthworms in relation to plant litter decomposition in a tropical wet forest of Puerto Rico. We collected earthworms at 0–0.1 m and 0.1–0.25 m soil depths from upland and riparian sites that represent the natural variation in soils and decomposition rates within the forest. Earthworms were hand-sorted and weighed for both fresh and dry biomass. Earthworms were dominated by the exotic endogeic species Pontoscolex corethrurus Müller; they were more abundant, and had higher biomasses in the upland than in riparian sites of the forest. Plant leaf litter decomposed faster in the upland than riparian sites. We found that earthworm abundance in the upper 0.1 m of the soil profile positively correlated with decomposition rate of plant leaf litter. Ground litter removal had no effect on the abundance or biomass of endogeic earthworms. Our data suggest that earthworms can be used to predict decomposition rates of plant litter in the tropical wet forest, and that the decomposition of aboveground plant litter has little influence on the abundance and biomass of endogeic earthworms.     

Understory herb assemblages 25 and 60 years after clearcutting of a northern hardwood forest, USA

The abundance of understory herbs in 25- and 60-year old clearcuts was compared to adjacent old secondary stands to infer how herb assemblages change in space and time following clearcutting of secondary forest. Herb densities and environmental conditions were sampled along 100 m transects crossing the clearcut/old secondary forest boundary, at three sites with 25-year old clearcuts and three sites with 60-year old clearcuts. At the 25-year sites, species densities of the 23 most frequent species were compared between clearcuts and adjacent old secondary forest to classify species into response groups. Species were classed as “insensitive” if there was little or no difference in density (seven species), “sensitive” if densities were lower in the clearcuts (six species), “enhanced” if densities were higher in clearcuts (four species), and “edge-enhanced” if densities were highest near clearcut edges (six species). Densities of two of the six sensitive species declined significantly with distance from the edge into the clearcut. Further, when regression results for all 23 species were combined, the mean slope of density vs. distance was significantly negative, indicating an overall trend to lower density with distance into the clearcuts. Most species classed as sensitive at 25 years did not show similar sensitivity at the 60-year sites; only one species had lower density in 60-year clearcuts than adjacent old secondary stands. Overall, there were substantial residual effects of clearcutting on herb assemblages within 50 m of the historical edge at 25-year sites, but not at 60-year sites. This difference may be due to different logging practices at the two historical times, as well as the difference in time for recovery since logging.     

Origin of organic halogen in boreal lakes

Old (>100 years, situated below 15 cm depth) sediment layers, of two humic forest lakes contained 400 to 600 mg of solvent soluble organic halogen (EOX) (kg C)^-1. This was two to three fold more than in the most recent layers at the depth of 0 to 10 cm. Sediment accumulation of EOX in humic forest lakes correlated positively with the sediment accumulation of organic matter. Lake water concentration of adsorbable organic halogen (AOX) correlated positively with water concentration of total organic carbon (TOC) and with the water colour in the different strata, seasons and lakes. These facts suggest that organic halogen in boreal humic lakes originated from the drainage area. Paleolimnological study of diatom remains showed that sediment concentration of organic halogen correlated negatively with the historical pH of the lake water column. This fact supports a view that the presence of organic halogen was promoted by haloperoxidase type of enzyme, which is most active at low pH (3.5 to 4). The dates of forest management events (clear cutting, prescribed burning) matched with the observed changes in lake water column historical pH and decrease in sediment content organic halogen in dated sediment layers. Clear cutting and prescribed burning are known to increase soil pH. This may decrease the intrinsic formation of organic halogens in soil, thereby decreasing the flow of organic halogens from the runoff area to the forest lake. Our results support a conclusion that changes in natural organically bound halogen in the sediment were promoted by acidification, forest fires and forest management in the drainage area. The organic halogen content in the most polluted layer of the pulp mill recipient sediment was 10 to 100 fold as compared to forest lake sediments.     

腾格里沙漠南缘风积物粒度空间分布及物源指示

为探讨腾格里沙漠南缘风积物物源,基于粒度参数分析其空间分布,采用粒度端元分析并与潜在源区对比,结合常量元素法进行了多角度探究。结果表明:黄河北岸沉积物粒度较南岸粗,两岸沉积物粒度存在较明显的空间差异性。粒度空间分布差异结合风沙活动、地形特征,可表明腾格里沙漠南缘的黄河北岸为南岸沉积物的上风向源区之一; 就地球化学元素分析表明,沙漠南缘与祁连山区常量元素特征具有一定相似性,与沙漠腹地差异较大。提取4个端元,多角度分析表明端元1(峰值粒径范围是30～50 μm)为全由祁连山北麓风成沙所组成的沉积体,端元2(100～120 μm)主要由沿黄北岸风成沙和黄河二次搬运所组成。端元3(170～250 μm和15～25 μm)为沿黄以北就地起沙,端元4(300～600 μm和10～20 μm)由黄河搬运沉积物所组成。综上,可认为腾格里沙漠南部边缘区沙物质主要是由黄河、沿黄以北和祁连山北麓所提供。     

风水两相作用和人类活动对无定河粗泥沙输沙量的影响

风沙活动、降雨和人类活动是干旱-湿润过渡区影响粗泥沙(d>0.05mm)入黄的几个重要因素。粗泥沙输沙量的变化取决于全沙输沙量和粗泥沙在全沙中所占的比例。基于悬移质输沙量和泥沙粒径构成、降雨量、沙尘暴日数和水土保持面积等数据,分析了粗泥沙输沙量与影响因素之间的关系,利用Arc-GIS和SPSS软件定量分析了影响无定河流域代表自然过程的风水两相作用和人类活动对粗泥沙输沙量的影响,并通过回归分析确定了不同影响因素对全沙输沙量和粗泥沙比例的贡献。结果表明,影响全沙输沙量的主要因素是降雨量和水土保持措施,而影响粗泥沙比例的是风沙活动和水土保持措施。利用二元回归分析确定了各因素的贡献比例,认为降雨量的减少和人类活动对全沙量减少的贡献相当,人类活动对粗泥沙比例降低的贡献高于风沙活动的作用。     

太湖上游西苕溪近岸森林土壤氮磷养分差异特征

近岸森林土壤受到河水涨落等自然侵蚀和人类活动的双重扰动,增加了土壤养分流失威胁,从而增大了下游河流和湖泊富营养化的风险,影响森林作为河岸缓冲带作用的发挥。对河岸森林土壤养分的研究,可为河岸森林树种的选取、河岸带建设、经营与管理等提供依据。以太湖上游的西苕溪两岸1km范围内的森林为研究对象,选择典型竹林、经济林、纯林和混交林样地34块,分层采集土壤样品,实验室测定有效磷、碱解氮、全氮和全磷等养分含量,利用变异系数分析不同森林类型和不同深度土层中养分含量的变异性,并且采用单因素方差分析和多重比较的方法分析土壤养分含量在不同森林类型间同一深度土层的差异性。结果表明,竹林土壤有效磷、碱解氮、全氮和全磷均具有较高的变异性,经济林土壤中的有效磷和全氮的变异较大,纯林和混交林土壤养分的变异性总体上较低;土壤有效磷、碱解氮和全氮平均含量在不同林型中都表现为0-10cm〉10-30cm〉30-50cm,即随着土层的加深养分含量降低;土壤有效磷含量竹林显著高于纯林,不同土层竹林与经济林的碱解氮含量显著高于纯林和混交林的;经济林的全氮含量较其他林型的较低,而全磷的含量却较高。     

Dam construction and ecological change in the riparian forest of the Hadejia – Jama'are floodplain,Nigeria

Riparian forests in the Sahel zone of Africa are of considerable importance for human resource use and for their ecological and conservation value. Typical riparian forest tree species are dependent on river flows and a shallow aquifer, and the community and population structure of riparian forests is related to spatial and temporal patterns of flooding at a site. Therefore, changes in hydrology caused by dams cause changes in floodplain vegetation. This paper explores the spatio-temporal complexity of these changes through an analysis of regeneration in a Nigerian floodplain affected by dams built in the early 1970s. The study shows that under certain conditions, and given sufficient time, riparian forests may be changing to forest types more characteristic of unflooded, upland areas. The results of the study have implications for the way in which the sustainability of developments downstream of large dams are analysed, suggesting that assessment of impacts must take place within temporal parameters relevant to ecological processes and at spatial scales that encompass spatial variation in floodplain ecosystems.     

Agricultural Sediment Reduction by Giant Cane and Forest Riparian Buffers

The sediment filtering capabilities of giant cane (Arundinaria gigantea (Walt.) Chapm.) and forest riparian buffers were compared in a southern Illinois, USA non tile drained agricultural watershed. Giant cane, a bamboo species, serves as important wildlife habitat throughout its native range in the southeastern and lower midwestern United States. Overland flow samples were collected at the field edge and at 3.3 m, 6.6 m, and 10.0 m within the riparian buffers during 19 precipitation events over a 1-year period. On an annual basis, significant sediment reductions occurred by 3.3 m and 6.6 m in the cane and forest buffers, respectively. The giant cane buffer reduced incoming sediment mass by 94% within the first 3.3 m, while the forest buffer reduced sediment by 86% over 6.6 m. Within 10.0 m of the field edge, the cane and forest buffers reduced sediment mass by 100% and 76%, respectively. On a seasonal basis, the cane buffer outperformed the forest buffer. During each of the four seasons, the cane buffer reduced sediment masses within 3.3 m of the field edge, while the forest buffer showed initial reductions occurring at 6.6 m during the summer, fall, and winter. No detectable reductions occurred during the spring in the forested buffer. Reductions in sediment concentrations were less evident compared to mass basis, indicating that infiltration may be a more important sediment reduction mechanism than particle settling. Both the forest and giant cane buffers had relatively high measured soil infiltration rates. Study results indicate that giant cane is an appropriate species to include in riparian buffer restoration designs for sediment control.     

Rates of forest floor decomposition and soil forming processes as indicators of forest ecosystem functioning on a polluted dredged sediment landfill

Results of intensive monitoring of forest floor decomposition rates and soil forming processes after afforestation of a calcareous upland dredged sediment landfill with an oxidised surface soil are presented. Nutrient status of the sediment substrate favours tree growth and allows for afforestation and thus an integration in the landscape. Soil processes on the landfill resulted in small differences between the surface and the subsurface soil layer, although higher soil organic carbon and Cd concentrations in the surface soil were observed. So far, tree species had a minor impact on soil processes. Relative to the uncontaminated covered part of the site and to general references, forest floor decomposition was found to be relatively fast for sycamore maple and pedunculate oak. Despite the pollution status of the dredged sediment landfill, the sediment substrate was favourable for forest floor decomposition. This might indicate that the soil nutrition status and the high carbonate status override the negative impact of soil pollution with metals and other pollutants. Application of a covering layer composed of uncontaminated soil material resulted in lower Cd concentrations in earthworms, but concentrations were still higher than for references. We conclude from the observations that polluted but fertile soils allow for afforestation and for regular forest floor decomposition with normal or slightly elevated metal concentrations. Only long-term observations of such new forests will lead to a correct site-specific assessment of the actual ecological risks, but after 16 years of landfilling and 12 years of afforestation no adverse effects were observed.     

风沙冲蚀与碳化耦合作用下风积沙粉体混凝土耐久性能

该研究以风积沙粉体为水泥替代材料的风积沙粉体混凝土为研究对象,设计风沙冲蚀-碳化、碳化-风沙冲蚀2种工况,探讨其在风沙冲蚀、碳化环境下的劣化机理及耐久性能。结果表明,风沙冲蚀时,90o冲蚀角作用时以撞击作用为主,产生冲蚀坑洞,45°冲蚀角作用时以削切作用为主,产生冲蚀沟壑,且风沙冲蚀破坏混凝土表面水泥石结构,可使碳化深度增加3倍以上;碳化作用时,普通混凝土碳化时是由于氢氧化钙和水化硅酸钙发生脱钙反应,风积沙粉体混凝土则是由于氢氧化钙、水化硅酸钙和钙矾石发生脱钙反应,且由于碳化产物自身的膨胀作用使混凝土变的疏松,使风沙冲蚀后质量损失增加1.6倍以上;风积沙粉体混凝土内部孔径在20 nm以下的无害孔的比例多于普通混凝土21.37个百分点,200 nm以上多害孔少于普通混凝土13.93个百分点,其劣化显著性低于普通混凝土;相对于单一工况,风沙冲蚀、碳化耦合作用下劣化显著性更高,且风沙冲蚀-碳化耦合作用劣化显著性低于碳化-风沙冲蚀耦合作用,风沙冲蚀-碳化耦合作用后的10~15 mm范围内出现碳化区域、碳化产物发生变化(生成硫酸钙)及非碳化区域的混合区,且风沙冲蚀-碳化耦合作用后风积沙粉体混凝土孔隙度下降0.47%,20 nm以下的无害孔的比例高出普通混凝土25.15%。     

Modelling forest regeneration processes in clear-cut and burned areas in the Angara Region

A method to select measures for enhancing natural forest-regeneration process in areas under extensive management is discussed. Using available information on geomorphological site characteristics and stand parameters, indices are determined using a specific criterion that describes the forest regeneration process. Using these indices as model inputs, clearcuts and burns can be classified; within each stratum the natural forest regeneration process is similar. Analysing these strata, one can select a regime of forest treatment that is appropriate for a given stratum and, consequently, for the clearcuts (or burns) it includes.     

Plantation clearcut size and the persistence of early-successional wildlife populations

Plantation clearcuts represent an important habitat for many open-area wildlife species – including conservation-concern species – in landscapes dominated by industrial forests. However, due to the ephemeral nature of clearcuts, species using this type of environment face a “shifting mosaic” in which their ability to successfully relocate to another habitat patch may play a crucial role in the species’ persistence in the landscape. Although several studies have shown a positive effect of patch size on the persistence of open-habitat species, forest clearcutting represents a special case in which, on average, larger patches also tend to be more isolated from each other, likely creating a trade-off between area and isolation effects. We developed an individual-based spatially-explicit model to test the effect of clearcut size (a critical management variable in plantation forestry) on the persistence of generic early-successional wildlife species in a landscape dominated by forest plantations. We simulated a landscape covered with a plantation harvested regularly over a 25-year rotation and different versions of a wildlife population whose habitat was constituted only by 1–4 year-old patches. We observed that when the species could perceive the attributes of the neighboring pixels persistence time was higher at intermediate clearcut sizes agreeing with our prediction. Also, species with a high dispersal capacity were less limited by connectivity and reached their maximum persistence at higher clearcut sizes. Results also showed a positive effect of habitat lifetime on persistence. Our results suggest large clearcuts may be incompatible with the conservation of many early-successional vertebrates that have limited dispersal capacity, unless additional conservation measures, such as the use of corridors or special spatial arrangement of clearcuts, are taken to overcome the lack of connectivity.     

Distribution and background levels of mercury in sediment cores from selected wisconsin lakes

The vertical distribution of Hg in sediment cores from a range of hard- and soft-water lakes in Wisconsin was evaluated in terms of potential sources of Hg during the nineteenth and twentieth centuries. For the Madison lakes, the trends in Hg distribution were related to variations in sewage inputs during the last 80 yr. It is unlikely that either inputs of sewage or erosional products are responsible for the observed accumulation of Hg in the most recent sediments from three lakes in northeastern Wisconsin. Background levels varied from 0.01 to 0.24 ppm of Hg (intact sediment basis) in precultural sediments from the Wisconsin lakes investigated. There was no consistent relationship between the concentration of Hg and other sediment components of potential importance in the retention of Hg.     

Tillage techniques to reactivate aeolian erosion on inland drift-sand

The inland drift-sand areas in northern Europe are characterised by a rapid decline in both aeolian activity and areal size. Many former drift-sand surfaces have become immobilised by natural or man-induced processes, such as conversion into forest or other terrain for agricultural, economic or societal purposes. The sharp reduction of these areas automatically implies the disappearance in Western Europe of a unique landscape with a high natural and cultural-historic value. Therefore, it is necessary to investigate how drift-sand areas can be preserved, how the balance between the active areas and those colonised with drift-sand vegetation can be kept under control, and how introducing techniques that reactivate, or benefit, the aeolian processes can counteract irreversible immobilisation by subsequent colonisation. Four such techniques (rotary cultivator, beach sand cleaner, disk harrow and excavator) were evaluated during an 8-month experiment on drift-sand stabilised by grey hair grass and algae crusts at Kootwijkerzand, The Netherlands. The effect of the techniques was measured using five key-parameters: the raising and lowering of the surface due to aeolian activity, the horizontal sediment transport flux, the vertical sediment accumulation flux, changes in the grain size of the top layer due to aeolian processes, and changes in the organic matter content of the topsoil. The effect of each technique on soil compaction, surface roughness and the amount of plant residue left on the field is also discussed. The highest aeolian activity (horizontal and vertical flux, surface lowering) was observed on test fields treated with the beach sand cleaner and the rotary cultivator. The changes in grain size and organic matter content of the top layer were also highest in these fields. Of the four techniques tested, the beach sand cleaner and the rotary cultivator are thus the most recommendable methods to reactivate drift-sand stabilised by grey hair grass and algae crusts. The disk harrow and the excavator may also lead to a reactivation, but they are less effective and therefore less recommendable.     

Relating bat species presence to simple habitat measures in a central Appalachian forest

We actively sampled the bat community at 63 sites using detection and non-detection metrics on the Fernow Experimental Forest (FEF) in the central Appalachians of West Virginia using Anabat acoustical equipment May-June 2001-2003 to relate species presence to simple habitat measures such as proximity to riparian areas, forest canopy cover, forest canopy gap width, and forest canopy height. We acoustically detected eight species on the FEF, including the endangered Myotis sodalis. The presence of Lasiurus cinereus, M. lucifugus, M. sodalis, and Pipistrellus subflavus was associated more with riparian areas than upland areas. Both univariate comparisons and multiple logistic regression modeling showed that the probability that clutter-adapted foraging species such as M. septentrionalis and M. sodalis would be detected was greater as forest canopy cover increased or forest canopy gap size decreased, whereas the opposite was true for open-adapted foraging species such as Eptesicus fuscus and L. cinereus. The overall proportion of unidentifiable bat echolocation sequences to those identified to species was related to upland sites with increasing forest canopy cover indicating some sampling bias between cluttered and uncluttered habitats. However, given sufficient sample points, bat community surveys using acoustical detection show the ability to quickly develop generalized habitat associations for rugged areas such as the central Appalachians where traditional mist-net survey efforts often are logistically difficult and are lacking in scope. Moreover, these acoustical surveys also could lend themselves to species-specific predictive mapping of foraging habitat as well as allowing researchers to formulate testable hypotheses about detailed bat habitat relationships to be definitively tested with radio-telemetry techniques.     

滨岸缓冲带截留污染物机理和效果的研究进展

滨岸缓冲带是指与河流（包括湿地和湖泊）相邻的对污染物、沉积物和洪水具有一定缓冲功能的水陆生态系统交错带,是一种重要的控制面源污染和保护水体环境的方法。滨岸缓冲带的研究存在较多的方向和不同的立足点。为了更好地总结和梳理已有研究成果,该文通过大量的文献调研,构建了滨岸缓冲带的研究框架,从其作用机理、结构、功能与效果等方面对国内外的有关研究和实践进行了系统分析和总结,并提出了未来的研究展望。