Methods to prioritize placement of riparian buffers for improved water quality

Agroforestry buffers in riparian zones can improve stream water quality, provided they intercept and remove contaminants from surface runoff and/or shallow groundwater. Soils, topography, surficial geology, and hydrology determine the capability of forest buffers to intercept and treat these flows. This paper describes two landscape analysis techniques for identifying and mapping locations where agroforestry buffers can effectively improve water quality. One technique employs soil survey information to rank soil map units for how effectively a buffer, when sited on them, would trap sediment from adjacent cropped fields. Results allow soil map units to be compared for relative effectiveness of buffers for improving water quality and, thereby, to prioritize locations for buffer establishment. A second technique uses topographic and streamflow information to help identify locations where buffers are most likely to intercept water moving towards streams. For example, the topographic wetness index, an indicator of potential soil saturation on given terrain, identifies where buffers can readily intercept surface runoff and/or shallow groundwater flows. Maps based on this index can be useful for site-specific buffer placement at farm and small-watershed scales. A case study utilizing this technique shows that riparian forests likely have the greatest potential to improve water quality along first-order streams, rather than larger streams. The two methods are complementary and could be combined, pending the outcome of future research. Both approaches also use data that are publicly available in the US. The information can guide projects and programs at scales ranging from farm-scale planning to regional policy implementation.     

Nutrient Attenuation in Agricultural Surface Runoff by Riparian Buffer Zones in Southern Illinois,USA

Nutrients in overland flow from agricultural areas are a common cause of stream and lake water quality impairment. One method of reducing excess nutrient runoff from non-point sources is to restore or enhance existing riparian areas as vegetative buffers. A field scale study was conducted to assess the ability of remnant giant cane (Arundinaria gigantea (Walt.) Muhl.) and forest riparian buffer zones to attenuate nutrients in agricultural surface runoff from natural precipitation events. Two adjacent, 10.0 m wide riparian buffers were instrumented with 16 overland flow collectors to monitor surface runoff for nitrate, ammonium, and orthophosphate. Measurements were taken at 3.3 m increments within each buffer. The forest buffer significantly reduced incoming dissolved nitrate-N, dissolved ammonium-N, total ammonium-N, and total orthophosphate masses in surface runoff by 97, 74, 68, and 78 , respectively within the 10.0 m riparian buffer. Nutrient reductions within the cane buffer were 100 for all three nutrients due to relatively high infiltration rates. Significant reductions of total ammonium- N and total orthophosphate were detected by 3.3 m in the cane buffer and at 6.6 m in the forest buffer. Results suggest that both giant cane and forest vegetation are good candidates to incorporate into riparian buffer restoration designs for southern Illinois as well as in other regions within their native range with similar climatic and physiographic conditions.     

森林河溪植被带建设

森林河溪植被带对河流水质、水量,改善小气候、增加生物多样性和稳定性等方面起着非常重要的作用.文章从森林植被带的重要性出发,介绍了国外河岸植被缓冲带建设模式,提出了我国河溪植被带的建设原则、构建过程及其评价.     

长白山典型林区主要河流两岸森林资源变化研究

本文对两期遥感图像进行解译，并在GIS支持下提取露水河林业局主要河流两岸各缓冲区森林资源信息，经分析得到各类地物在1985年及1999年的变化趋势。结果表明：在河流沿岸对森林的采伐强度1999年较1985年明显减小，整体生态环境较1985年有所改善。在缓冲区1，2，3除中龄针叶林大幅度增加外，其它地物类型面积均减少，由此可以看出，在这三个缓冲区内针叶林得到了较好的恢复。在缓冲区4内，中龄针叶林、成熟针叶林、成熟阔叶林形成一个林龄梯队，有利于森林生态系统的稳定与功能的发挥，十五年间缓冲区4受到的干扰相对较小。湿地数量在四个缓冲区内均有所减少，虽然在缓冲区4内森林生态系统恢复的较好，但湿地面积仍有所减少，说明保护及恢复湿地资源是一件非常艰巨的任务，必须引起高度重视。图5表2参12。     

Comparing buffer zone alternatives in forest planning using a decision support system

Increased awareness of the connection between forest management activities and negative effects on water quality means that forestry needs to consider its potential impact on the aquatic environment when planning operations. Protective buffer zones are effective, but their design can vary. To be able to incorporate up-to-date scientific theory into practical applications easy-to-use planning tools are needed. In this study, we evaluate different buffer zone alternatives by using the freely available decision support system Heureka. The consequences on both economic and ecological values over a time period of 100 years were evaluated for two buffer zone approaches and three management alternatives within the buffer zones. Results indicated that there is a trade-off between economic and ecological values when managing the buffer zones. To be able to perform the analyses within Heureka, a new tool was developed. This software development provides access to a forest planning tool that can help improve nature conservation.     

Forest resources variation along with the main rivers in typical forest region of Changbai Mountain

The restoration of the riparian vegetation disturbed by human activities is one of the hotspots of watershed ecology. Through interpreting the images of Remote Sensing in 1985 and 1999, the basic information of forest resources of Lushuhe Forest Bureau, which is a typical forest area of Chanbai Mountain was obtained with support of GIS. By dividing Land covers of Lushuihe area into 10 types (water body, residential land, stump land, farming land, wetland, mature conifer forest, midlife conifer forest, mature broadleaf forest, midlife broadleaf forest, and man-made young forest) and dividing the riparian zone into four buffers (in turn 1000, 2000, 3000, 4000 m away from the river), the changes of riparian forest resources during 1985–1999 were analyzed. The results showed that the deforestation intension has obviously decreased and the whole environment has been evidently improved, but the riparian ecosystem was still flimsy. In buffer 1, 2, 3 the area of midlife conifer forest increased largely, but the areas of other types of land covers all decreased. Midlife conifer forest had a comparatively good status in the three buffers. In buffer 4, midlife conifer forest, mature conifer forest, and mature broadleaf forest formed a forest-age rank that is helpful to stabilize the forest ecosystem and exert its functions. Area percentage of wetland decreased in buffer 1, buffer 2, and buffer 3, even in buffer 4 in which forest ecosystem rehabilitated comparatively well, so protecting and rehabilitating wetland is a very difficult task. Foundation item: This study is supported by major projects of Knowiedge Innovation Program. Chinese Academy of Sciences (No. KZCX2-SW-320-3) and Institute of Applied Ecology (a grant SCXZD010-01), CAS. Biography: HAO Zhan-qing (1962-), Male, Ph. Doctor, Professor in Institute of Applied Ecology, Chinese Academy of Science, Shenyang 1100016, P.R. China Responsible editor: Chai Ruihai     

Forest-floor temperatures and soil moisture across riparian zones on first- to third-order headwater streams in southern New England,USA

Riparian zones along forest streams in the western United States have been repeatedly shown to be floristically and climatically different from adjacent upland forest, and to be important contributors to forest biodiversity. Similar evidence for the presence or function of riparian zones is lacking for forests of the northeastern U.S. We conducted seasonal surveys of forest-floor temperature and soil moisture across 30-m riparian transects on first- to third-order streams in southern New England. We were unable to detect any effect of distance from the stream channel on either temperature or soil moisture. These preliminary results indicate the absence of a unique riparian forest-floor microclimate within 30 m of low-order streams in southern New England. While this study failed to identify a distinctive riparian microclimatic zone, protection of a riparian buffer during forestry operations or other disturbance is essential for the protection of forest streams and their resources and the maintenance of forest biodiversity.     

Efficacy of riparian buffers in mitigating local population declines and the effects of even-aged timber harvest on larval salamanders

Headwater streams are an important and prevalent feature of the eastern North American landscape. These streams provide a wealth of ecosystem services and support tremendous biological diversity, which is predominated by salamanders in the Appalachian region. Salamanders are ubiquitous throughout the region, contributing a significant biomass that supports ecological and ecosystem processes. One of the greatest threats to salamanders is loss of headwater-riparian habitat through timber harvest. In this study, we measured larval salamander abundance at five headwater streams with different riparian buffer widths retained following logging. By sampling larval salamanders using leaf litter bags, we assessed the impacts of even-aged timber harvest on aquatic larval salamander abundances, where it was found that larvae are negatively impacted by increased stream sedimentation and a decrease in riparian buffer width. We found that retention of a 9-m buffer was effectively no different than complete removal of all riparian forest, and as such, current regulations to protect headwater streams are ineffectual. Furthermore, no significant differences were observed between the 30 m buffer treatment and uncut control treatments suggesting that a 30 m or larger riparian buffer may assuage the in-stream effects of riparian timber harvest. Management guidelines for Appalachian forests should be revised to accommodate the biology of plethodontid salamanders.     

Biodiversity management approaches for stream–riparian areas: Perspectives for Pacific Northwest headwater forests,microclimates, and amphibians

Stream–riparian areas represent a nexus of biodiversity, with disproportionate numbers of species tied to and interacting within this key habitat. New research in Pacific Northwest headwater forests, especially the characterization of microclimates and amphibian distributions, is expanding our perspective of riparian zones, and suggests the need for alternative designs to manage stream–riparian zones and their adjacent uplands. High biodiversity in riparian areas can be attributed to cool moist conditions, high productivity and complex habitat. All 47 northwestern amphibian species have stream–riparian associations, with a third being obligate forms to general stream–riparian areas, and a quarter with life histories reliant on headwater landscapes in particular. Recent recognition that stream-breeding amphibians can disperse hundreds of meters into uplands implies that connectivity among neighboring drainages may be important to their population structures and dynamics. Microclimate studies substantiate a “stream effect” of cool moist conditions permeating upslope into warmer, drier forests. We review forest management approaches relative to headwater riparian areas in the U.S. Pacific Northwest, and we propose scenarios designed to retain all habitats used by amphibians with complex life histories. These include a mix of riparian and upslope management approaches to address the breeding, foraging, overwintering, and dispersal functions of these animals. We speculate that the stream microclimate effect can partly counterbalance edge effects imposed by upslope forest disturbances, hence appropriately sized and managed riparian buffers can protect suitable microclimates at streams and within riparian forests. We propose one approach that focuses habitat conservation in headwater areas – where present management allows extensive logging – on sensitive target species, such as tailed frogs and torrent salamanders that often occur patchily. Assuming both high patchiness and some concordance among the distribution of sensitive species, protecting areas with higher abundances of these animals could justify less protection of currently unoccupied or low-density habitats, where more intensive forest management for timber production could occur. Also, we outline an approach that protects juxtaposed headwater patches, retaining connectivity among sub-drainages using a 6th-field watershed spatial scale for assuring well-distributed protected areas across forested landscapes. However, research is needed to test this approach and to determine whether it is sufficient to buffer downstream water quality and habitat from impacts of headwater management. Offering too-sparse protection everywhere is likely insufficient to conserve headwater habitats and biodiversity, while our alternative targeted protection of selected headwaters does not bind the entire forest landscape into a biodiversity reserve.     

The influence of timber harvest on the structure and composition of riparian forests in the Coastal Redwood region

The composition and structure of riparian forests in the coast redwood region were analyzed in relation to the length of time since timber harvest, and the width of riparian buffer zone. Ten sites were sampled in the central range of the coast redwood forest type within a variety of post-harvest age groups and riparian buffer zone widths. Data was collected using randomly selected sample plots adjacent to perennial coastal steams. Correlation Fisher's r to z tests and two-tailed t-test were used to examine the relationship between the sample variables and the experimental parameters “years since harvest”, and “width of buffer.” Results indicate that canopy cover was negatively correlated to “years since harvest” with the highest level of canopy cover found on the youngest sites and the lowest level found on the old-growth sites. The hardwood to conifer dominance ratio and the basal area of Alnus rubra (red alder) were correlated negatively to both “years since harvest” and “buffer width” indicating that timber harvest favored hardwood species. Late seral associates such as Oxalis oregana (redwood sorrel), Anthyrium filix-femina (lady fern), and Vaccinium parviflorum (billberry) were found preferentially in older forests and sites with wider buffer zones, while non-native species such as Hedera helix (English ivy), Pampas cortedaria (pampas grass), and Myosotis latifolia (forget-me-not) were found preferentially in younger forests and areas with smaller buffer zones.     

滨水植被缓冲带水质净化研究

滨水植被缓冲带兼具生态、社会和经济价值。对其研究以生态学和水文学为基础,涉及多种学科和技术。我国滨水植被缓冲带的理论与实践研究均较为薄弱。文中从滨水植被缓冲带的结构特征及作用、滨水植被缓冲带水质净化机理和滨水植被缓冲带水质净化的影响因素3个方面进行论述,同时探讨总结了滨水植被缓冲带在水质净化方面需要进一步研究的突出问题。随着人们对水污染关注的增加,滨水植被缓冲带的生态净水方式将备受重视。     

Stand carbon stocks and soil carbon and nitrogen storage for riparian and upland forests of boreal lakes in northeastern Ontario

The establishment of shoreline reserves (buffer strips) has guided riparian forest management in Ontario for many years. A riparian area is defined as the transitional zone between the aquatic and terrestrial environments and therefore is also known as the aquatic/terrestrial ecotone. While many functions of riparian forests have been recognized and well studied, less is known about their potential to sequester C and whether this potential differs from other areas in the boreal forest landscape. Increased harvesting pressure due to decreased wood supply in Ontario and debate about the effectiveness of the current reserve guidelines has resulted in a renewed interest in harvesting riparian forests. In this study riparian and upslope forest C and soil C and N storage were quantified for 21 lakes shorelines at the Esker Lakes Research Area, a boreal forest ecosystem in northeastern Ontario, Canada. Objectives were to compare the C and N storage potential of riparian forests with those of adjacent upland forests, and to examine the potential impacts of harvesting on C stocks in riparian zones of the boreal forest.Riparian forests did not differ from upslope stands in terms of total aboveground overstory C storage although there were significant differences in stocking density and species composition. However, a greater proportion of total site C in riparian areas was stored in the overstory tree layer (>5 cm dbh) compared to upslope areas. Forest floor layers were deeper and stored more C and N in riparian forest stands in comparison to upslope stands. In contrast, mineral soil in upslope stands had greater C and N storage than mineral soil horizons within the riparian forest. As a result, the riparian organic horizons comprise a larger percentage of the overall soil storage of C and N than upslope layers. Currently practiced full-tree harvesting would result in a removal of approximately 76% of total aboveground C (17% of the ecosystem C) in upslope stands compared to 98% of total aboveground C (35% of the ecosystem C) in riparian forests. Selective or modified harvesting in riparian zones could decrease C removal to levels equal to that obtained by full-tree harvesting in upslope areas.     

Integration of LiDAR and QuickBird imagery for mapping riparian biophysical parameters and land cover types in Australian tropical savannas

Riparian zones are exposed to increasing pressures because of disturbance from agricultural and urban expansion and overgrazing. Accurate and cost-effective mapping of riparian environments is important for baseline inventories and monitoring and managing their functions associated with water quality, biodiversity, and wildlife habitats. In this study, we integrate remotely sensed light detection and ranging (LiDAR) data and high spatial resolution satellite imagery (QuickBird-2) to estimate riparian biophysical parameters and land cover types in the Fitzroy catchment in Queensland, Australia. An object based image analysis (OBIA) was adopted for the study. A digital terrain model (DTM), a tree canopy model (TCM) and a plant projective cover (PPC) map were first derived from the LiDAR data. A map of the streambed was then produced using the DTM information. Finally, all the LiDAR-derived biophysical map products and the QuickBird image bands were combined in an OBIA to (1) map the following land cover types: riparian vegetation, streambed, bare ground, woodlands and rangelands; (2) determine the distribution of overhang vegetation within the streambed; and (3) measure the width of both the riparian zone and the streambed. The combined use of both datasets allowed accurate land cover mapping, with an overall accuracy of 85.6%. The estimated widths of the riparian zone and the streambed showed strong correlation with the actual field measurements (r = 0.82 and 0.98 respectively). Our results show that the combined use of LiDAR and high spatial resolution imagery can potentially be used for the assessment of the riparian condition in a tropical savanna woodland riparian environment. This work also shows the capacity of OBIA to assist in the assessment of the composition of the riparian environment from multiple image datasets.     

Linking physical, economic and institutional constraints of land use change and forest conservation in the hills of Nepal

This paper analyses the changes in spatial patterns of agricultural land use during the period 1976–2000 along the altitudinal gradients in a watershed in Nepal. Land change patterns during this period were examined using information on land use derived from satellite images from 1976, 1990 and 2000. During the 24-year period from 1976 to 2000 agricultural land use increased by 35% at a cost of loss of forestland. Agricultural expansion was most conspicuous at higher elevations (1150–2000-m). About 36%, 18% and 6% of forestland was converted into agricultural activities from higher, middle and lower elevations respectively in the period from 1990 to 2000. Spatial distribution of living standard parameters, including farm family income and, food availability obtained from family surveys, shows a decreasing trend as the elevation increases whereas percentage of food bought shows an increasing trend. In this way it was found that, lost forest areas were smaller when located around high-income areas with good quality agricultural land and near an administrative centre as compared to areas located around low-income areas with low quality agricultural land and far from an administrative centre. Additionally, a regression model is constructed, to link the socioeconomic variables with the conversion of forestland into agricultural activities, breaking the study area into smaller zones. The spatial trajectories of these zones are then contrasted, paying particular attention to the socioeconomic conditions and institutional arrangements governing access to land resources. The study finds that while overall land change patterns in the region are largely explained by elevation and the socioeconomic conditions of people living adjacent to the forestland, more specifically, in sub-regional areas, trajectories reflect the signatures of institutions governing access to land. As sustainability of the watershed is dependent on forests, continued depletion of forest resources will result in poor economic returns from agriculture for local people together with loss of ecosystem services.