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121.
Assessing Biotic Integrity of Streams: Effects of Scale in Measuring the Influence of Land Use/Cover and Habitat Structure on Fish and Macroinvertebrates 总被引:21,自引:2,他引:19
/ Fish and macroinvertebrate assemblage composition, instream habitat features and surrounding land use were assessed in an agriculturally developed watershed to relate overall biotic condition to patterns of land use and channel structure. Six 100-m reaches were sampled on each of three first-order warm-water tributaries of the River Raisin in southeastern Michigan. Comparisons among sites and tributaries showed considerable variability in fish assemblages measured with the index of biotic integrity, macroinvertebrate assemblages characterized with several diversity indexes, and both quantitative and qualitative measurements of instream habitat structure. Land use immediate to the tributaries predicted biotic condition better than regional land use, but was less important than local habitat variables in explaining the variability observed in fish and macroinvertebrate assemblages. Fish and macroinvertebrates appeared to respond differently to landscape configuration and habitat variables as well. Fish showed a stronger relationship to flow variability and immediate land use, while macroinvertebrates correlated most strongly with dominant substrate. Although significant, the relationships between instream habitat variables and immediate land use explained only a modest amount of the variability observed. A prior study of this watershed ascribed greater predictive power to land use. In comparison to our study design, this study covered a larger area, providing greater contrast among subcatchments. Differences in outcomes suggests that the scale of investigation influences the strength of predictive variables. Thus, we concluded that the importance of local habitat conditions is best revealed by comparisons at the within-subcatchment scale. KEY WORDS: Stream; Biomonitoring; Land use; Scale; Habitat; Fish; Macroinvertebrates 相似文献
122.
Hemlock Woolly Adelgid (Adelges tsugae) is spreading across forests in eastern North America, causing mortality of eastern hemlock (Tsuga canadensis [L.] Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.). The loss of hemlock from riparian forests in Great Smoky Mountains National Park (GSMNP) may result in significant
physical, chemical, and biological alterations to stream environments. To assess the influence of riparian hemlock stands
on stream conditions and estimate possible impacts from hemlock loss in GSMNP, we paired hardwood- and hemlock-dominated streams
to examine differences in water temperature, nitrate concentrations, pH, discharge, and available photosynthetic light. We
used a Geographic Information System (GIS) to identify stream pairs that were similar in topography, geology, land use, and
disturbance history in order to isolate forest type as a variable. Differences between hemlock- and hardwood-dominated streams
could not be explained by dominant forest type alone as forest type yields no consistent signal on measured conditions of
headwater streams in GSMNP. The variability in the results indicate that other landscape variables, such as the influence
of understory Rhododendron species, may exert more control on stream conditions than canopy composition. The results of this study suggest that the
replacement of hemlock overstory with hardwood species will have minimal impact on long-term stream conditions, however disturbance
during the transition is likely to have significant impacts. Management of riparian forests undergoing hemlock decline should,
therefore, focus on facilitating a faster transition to hardwood-dominated stands to minimize long-term effects on water quality. 相似文献
123.
We examined the effect of subsample size on the accuracy of information obtained from aquatic macroinvertebrate assemblage
samples. Subsamples containing 100 organisms or 300 organisms were compared on the bases of processing time and the ability
to discern ecological differences among samples. Independently of subsample size, assemblages differed between study streams,
primarily reflecting an intermittent vs. permanent stream difference, and between seasons at most streams. It required, on
average, two additional hours to process the larger subsamples. Larger subsamples gave significantly higher estimates of total
richness and Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, but the relative abundances of many assemblage subsets
(e.g., EPT organisms and most functional feeding groups) were similar using both subsample sizes. Larger subsamples did not
typically enhance the ability to discriminate between samples from different seasons, but did more accurately distinguish
among streams when differences were subtle. They also appeared to avoid Type I error in comparisons of compositionally similar
reaches within a study stream. 相似文献
124.
Addressing landscape-level threats to stream fishes such as habitat and hydrological alterations requires adequate watershed-level
species inventories. Where watershed-level ichthyofaunal surveys are prohibitively expensive, existing (historical) data sources
may provide an option for compiling species lists. However, it is critical that managers consider potential biases or limitations
of species lists compiled from existing data. Here we assess the suitability of species lists compiled from existing data
sources for making watershed-level fish management and conservation decisions. For nine Great Lakes watersheds, we developed
existing species lists by compiling all available federal and state agency and museum fish survey data. We then compared the
size and species composition of existing species lists to current species lists compiled from intensive field surveys, conducted
in 2002, of the same watersheds. Species lists compiled from commonly available existing data sources, such as state and federal
agency and museum data, missed many species detected during our 2002 field surveys. In most watersheds, more than 10 species
were missed (range 5–21) on existing lists. Sampling over multiple years and seasons increased the size of both current (field)
and existing species lists. Existing species lists compiled from surveys conducted over multiple years and seasons included
an average of 15 species not captured during the 2002 field surveys. However, such multiyear existing datasets are rare and
not available for many watersheds. In addition, species lists compiled from older existing surveys (e.g., before 1984) did
not accurately represent current species composition of the watersheds and our results indicate several apparent misidentifications
or errors on these lists. Lastly, while most game species were detected on existing lists, migratory species and recently
introduced species were commonly missed on these lists. We conclude with recommendations for using existing data for watershed-level
stream fish management and conservation decisions. 相似文献
125.
Pulp and paper mills are one of the major effluent generating industries in the world. In most cases, mill effluent (treated or raw) is discharged back into a river, creek, stream or other water body; resulting in negative environmental impacts, as well as social concerns, among the downstream users. Pulp and paper mill effluent management, which could result in zero discharge into downstream water bodies, would present the best management option to address socio-environmental concerns. This paper presents such an effort aimed at closing the water cycle by using treated effluent from the mill to irrigate forage and fodder crops for producing animals feed. The treated effluent is delivered from the mill through gravity into a winter storage dam of 490ML capacity. For irrigation applications on 110ha of farmland, which is 42% of the total farmland, the water is pumped from the winter storage dam to five individual paddocks with Centre Pivot (CP) irrigators and one rectangular paddock with a Soft Hose Travelling (SHT) irrigator. From October 2001 to June 2006, a total of 2651mm of wastewater was applied at the farm. The impact assessment results, obtained from field monitoring, investigations and analysis, indicated that the closed water cycle effluent management strategy described had resulted in a lessening of the impact on water resources usually associated with paper mills. However, social attitudes to the use of crops that have been irrigated with recycled waters and the resulting impact on market value of the produce may still be a major consideration. 相似文献
126.
Quantitative Identification of Disturbance Thresholds in Support of Aquatic Resource Management 总被引:3,自引:0,他引:3
The identification of disturbance thresholds is important for many aspects of aquatic resource management, including the establishment
of regulatory criteria and the identification of stream reference conditions. A number of quantitative or model-based approaches
can be used to identify disturbance thresholds, including nonparametric deviance reduction (NDR), piecewise regression (PR),
Bayesian changepoint (BCP), quantile piecewise constant (QPC), and quantile piecewise linear (QPL) approaches. These methods
differ in their assumptions regarding the nature of the disturbance-response variable relationship, which can make selecting
among the approaches difficult for those unfamiliar with the methods. We first provide an overview of each of the aforementioned
approaches for identifying disturbance thresholds, including the types of data for which the approaches are intended. We then
compare threshold estimates from each of these approaches to evaluate their robustness using both simulated and empirical
datasets. We found that most of the approaches were accurate in estimating thresholds for datasets with drastic changes in
responses variable at the disturbance threshold. Conversely, only the PR and QPL approaches performed well for datasets with
conditional mean or upper boundary changes in response variables at the disturbance threshold. The most robust threshold identification
approach appeared to be the QPL approach; this method provided relatively accurate threshold estimates for most of the evaluated
datasets. Because accuracy of disturbance threshold estimates can be affected by a number of factors, we recommend that several
steps be followed when attempting to identify disturbance thresholds. These steps include plotting and visually inspecting
the disturbance-response data, hypothesizing what mechanisms likely generate the observed pattern in the disturbance-response
data, and plotting the estimated threshold in relation to the disturbance-response data to ensure the appropriateness of the
threshold estimate. 相似文献
127.
The concentrations of sediment and turbidity in stream water were monitored during culvert removals to determine the short term effects of road obliteration. Sediment concentration was measured at 11 stream crossings among two locations in Idaho and one in Washington. Sediment concentration immediately below the culvert outlet exceeded levels above the culvert outlet by at least three orders of magnitude at all stream crossings. Sediment yields ranged from 170 to less than 1kg in the 24-h period following culvert removal. Turbidity exceeded the regulatory limits during culvert removal at all locations monitored in this study and remained above the limits beyond the monitoring periods of 24h at four of the locations. Sediment concentrations 100m downstream of the culvert outlet were reduced by an order of magnitude, but did not change the turbidity values sufficiently to meet regulatory limits. Sediment concentrations an average of 810m downstream of the culvert outlet were similar to sediment concentrations above the culvert for the entire excavation period and turbidity regulations were met. Mitigation consisting of two straw bales placed in the stream caused a significant reduction in sediment yield from an average of 67kg to an average of 1.6kg. 相似文献
128.
When native grassland catchments are converted to pasture, the main effects on stream physicochemistry are usually related
to increased nutrient concentrations and fine-sediment input. We predicted that increasing nutrient concentrations would produce
a subsidy-stress response (where several ecological metrics first increase and then decrease at higher concentrations) and
that increasing sediment cover of the streambed would produce a linear decline in stream health. We predicted that the net
effect of agricultural development, estimated as percentage pastoral land cover, would have a nonlinear subsidy-stress or
threshold pattern. In our suite of 21 New Zealand streams, epilithic algal biomass and invertebrate density and biomass were
higher in catchments with a higher proportion of pastoral land cover, responding mainly to increased nutrient concentration.
Invertebrate species richness had a linear, negative relationship with fine-sediment cover but was unrelated to nutrients
or pastoral land cover. In accord with our predictions, several invertebrate stream health metrics (Ephemeroptera–Plecoptera–Trichoptera
density and richness, New Zealand Macroinvertebrate Community Index, and percent abundance of noninsect taxa) had nonlinear
relationships with pastoral land cover and nutrients. Most invertebrate health metrics usually had linear negative relationships
with fine-sediment cover. In this region, stream health, as indicated by macroinvertebrates, primarily followed a subsidy-stress
pattern with increasing pastoral development; management of these streams should focus on limiting development beyond the
point where negative effects are seen. 相似文献
129.
Seasonal and spatial variations in major ion chemistry and isotope composition in the rural-urban catchment of the Shigenobu River were monitored to determine the influences of agricultural and urban sewage systems on water quality. Temporal patterns of biochemical oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), and suspended sediment (SS) were examined at four sites in the rural-urban catchment. Urban land cover, incorporating the effects of increased population, domestic water use, and industrial wastewater, was positively associated with increases in water pollution and was included as an important explanatory variable for the variations in all water quality parameters. Significant trends were found in each parameter. BOD concentrations ranged widely, and were high in urban regions, due to the presence of a waste water treatment plant. TN and SS showed various trends, but did not vary widely, unlike TP. TP concentrations varied greatly, with high concentrations in cultivated areas, due to fertilizer use. Local water quality management or geology could further explain some of the variations in water quality. Non-point-source pollution exhibited strong positive spatial autocorrelation, indicating that incorporating spatial dimensions into water quality assessment enhances our understanding of spatial patterns of water quality. Data from the Ministry of Land Infrastructure and Transport (MLIT) and Environment Ministry (EM) were used to investigate trends in land management. Stepwise regression analysis was used to test the correlation between specific management practises and substance concentrations in surface water and sediment. MLIT and EM data for 1981-2003 showed an increase in TN, TP, and SS concentrations in surface water. High levels of fertilizer in dormant sprays and domestic water use were associated with high pesticide concentrations in water and sediment. This paper presents a novel method of studying the environmental impact of various agricultural management practises and recommends a management strategy that combines the use of reduced-risk pesticides with irrigation and non-irrigation periods in paddy fields. 相似文献
130.
Bin He Taikan Oki Fubao Sun Daisuke Komori Shinjiro Kanae Yi Wang Hyungjun Kim Dai Yamazaki 《Journal of environmental management》2011
Artificial Neural Network (ANN) is a flexible and popular tool for predicting the non-linear behavior in the environmental system. Here, the feed-forward ANN model was used to investigate the relationship among the land use, fertilizer, and hydrometerological conditions in 59 river basins over Japan and then applied to estimate the monthly river total nitrogen concentration (TNC). It was shown by the sensitivity analysis, that precipitation, temperature, river discharge, forest area and urban area have high relationships with TNC. The ANN structure having eight inputs and one hidden layer with seven nodes gives the best estimate of TNC. The 1:1 scatter plots of predicted versus measured TNC were closely aligned and provided coefficients of errors of 0.98 and 0.93 for ANNs calibration and validation, respectively. From the results obtained, the ANN model gave satisfactory predictions of stream TNC and appears to be a useful tool for prediction of TNC in Japanese streams. It indicates that the ANN model was able to provide accurate estimates of nitrogen concentration in streams. Its application to such environmental data will encourage further studies on prediction of stream TNC in ungauged rivers and provide a useful tool for water resource and environment managers to obtain a quick preliminary assessment of TNC variations. 相似文献