Riparian influences on stream fish assemblage structure in urbanizing streams

We assessed the influence of land cover at multiple spatial extents on fish assemblage integrity, and the degree to which riparian forests can mitigate the negative effects of catchment urbanization on stream fish assemblages. Riparian cover (urban, forest, and agriculture) was determined within 30 m buffers at longitudinal distances of 200 m, 1 km, and the entire network upstream of 59 non-nested fish sampling locations. Catchment and riparian land cover within the upstream network were highly correlated, so we were unable to distinguish between those variables. Most fish assemblage variables were related to % forest and % urban land cover, with the strongest relations at the largest spatial extent of land cover (catchment), followed by riparian land cover in the 1-km and 200-m reach, respectively. For fish variables related to urban land cover in the catchment, we asked whether the influence of riparian land cover on fish assemblages was dependent on the amount of urban development in the catchment. Several fish assemblage metrics (endemic richness, endemic:cosmopolitan abundance, insectivorous cyprinid richness and abundance, and fluvial specialist richness) were all best predicted by single variable models with % urban land cover. However, endemic:cosmopolitan richness, cosmopolitan abundance, and lentic tolerant abundance were related to % forest cover in the 1-km stream reach, but only in streams that had <15% catchment urban land cover. In these cases, catchment urbanization overwhelmed the potential mitigating effects of riparian forests on stream fishes. Together, these results suggest that catchment land cover is an important driver of fish assemblages in urbanizing catchments, and riparian forests are important but not sufficient for protecting stream ecosystems from the impacts of high levels of urbanization.     

Spatial weighting of land use and temporal weighting of antecedent discharge improves prediction of stream condition

Land management to protect streams requires knowing which parts of the landscape most strongly influence stream condition. Understanding how flow through landscapes and along streams affects such land-use impacts requires knowing the period of antecedent discharge that most strongly influences condition. Both considerations require determination of optimal weighting schemes for predictors of stream condition. We calculated forest cover weighted by flow-path distance to 572 urban, peri-urban, and rural sites—in the Melbourne, Australia, region—sampled for macroinvertebrates, and antecedent discharge weighted by time preceding each of 1,723 samples. Using mixed linear models that accounted for spatial dependence, we aimed to determine the weighting curve shape and length that best predicted macroinvertebrate assemblage composition. The best model was a function of mean annual discharge, weighted forest cover, weighted imperviousness, weighted antecedent discharge, and their interactions. Optimal weightings were exponential—half-decay distance 35 m overland (plausible range 26–50 m), and 1.0 km in-stream (0.75–1.3 km) for forest cover—, and linear over ≥4 year for antecedent discharge. Model plausibility was more affected by weighting distance than the shape of the weighting function. Regardless of weighting curve shape, riparian forest effects on macroinvertebrate assemblages are strongest within 10¹–10² m from the stream, and 10³ m upstream. Although exponential weightings are only marginally more plausible, they are the most realistic representation of physical processes. While our conclusions should not be interpreted as recommendations for buffer widths, they provide valuable insight into the scales of influence in the region and could be used to inform management decisions.     

Scale-specific land cover thresholds for conservation of stream invertebrate communities in agricultural landscapes

Context

In agricultural landscapes, riparian forests are used as a management tool to protect stream ecosystems from agricultural activities. However, the ability of managers to target stream protection actions is limited by incomplete knowledge of scale-specific effects of agriculture in riparian corridor and catchment areas.

Objectives

We evaluated scale-specific effects of agricultural cover in riparian corridor and catchment areas on stream benthic macroinvertebrate (BMI) communities to develop cover targets for agricultural landscapes.

Methods

Sixty-eight streams assigned to three experimental treatments (Forested Riparian, Agricultural Riparian, Agricultural Catchment) were sampled for BMIs. Ordination and segmented regression were used to assess impacts of agriculture on BMI communities and detect thresholds for BMI community metrics.

Results

BMI communities were not associated with catchment agricultural cover where the riparian corridor was forested, but were associated with variation in catchment agriculture where riparian forests had been converted to agriculture. Trait-based metrics showed threshold responses at greater than 70% agricultural cover in the catchment. Increasing agriculture in the riparian corridor was associated with less diverse and more tolerant BMI communities. Eight metrics exhibited threshold responses ranging from 45 to 75% agriculture in the riparian corridor.

Conclusions

Riparian forest effectively buffered streams from agricultural activity even where catchment agriculture exceeds 80%. We recommend managers prioritize protection of forested riparian corridors and that restore riparian corridors where agricultural cover is near identified thresholds be a secondary priority. Adoption of catchment management actions should be effective where the riparian corridor has been converted to agriculture.

     

Local,landscape and regional factors structuring benthic macroinvertebrate assemblages in Swedish streams

A total of 694 streams were sampled for benthic macroinvertebrates in the autumn of 1995 as part of the Swedish national stream survey. After removal of sites considered as impacted, data from 428 streams as well as a large number of environmental variables were used to determine the relative importance of local, landscape, and large scale factors in explaining the variability in species composition of benthic stream macroinvertebrates. The environmental variables were divided into seven explanatory variable groups: local physical, local chemical, catchment land use/cover, catchment bedrock geology, Quaternary geology in catchment, regional factors (such as ecoregion) and spatial position. Partial Canonical Correspondence Analysis was used to partition the total explained variance in the species data into these variable groups. The pure (or unique) effects of the seven variable groups accounted for 69.1%, and combinations of variable groups (interaction terms) the remaining 30.9% of the total explained variability. Local scale variables such as in-stream substratum, vegetation in and near the stream (riparian zone), and some chemical variables were most strongly associated with the among-site variability. Local physical (24.4%) and local chemical (20.4%) variables explained the largest part of the among-site variability of community assemblages. These results are of importance when planning conservation and management measurements, implementing large-scale biomonitoring programs, and predicting how human alterations will affect running water ecosystems.This revised version was published online in May 2005 with corrections to the Cover Date.     

Landscape influences on stream biotic integrity assessed at multiple spatial scales

The biological integrity of stream ecosystems depends critically on human activities that affect land use/cover along stream margins and possibly throughout the catchment. We evaluated stream condition using an Index of Biotic Integrity (IBI) and a habitat index (HI), and compared these measures to landscape and riparian conditions assessed at different spatial scales in a largely agricultural Midwestern watershed. Our goal was to determine whether land use/cover was an effective predictor of stream integrity, and if so, at what spatial scale. Twenty-three sites in first-through third-order headwater streams were surveyed by electrofishing and site IBIs were calculated based on ten metrics of the fish collection. Habitat features were characterized through field observation, and site HIs calculated from nine instream and bank metrics. Field surveys, aerial photograph interpretation, and geographic information system (GIS) analyses provided assessments of forested land and other vegetation covers at the local, reach, and regional (catchment) scales. The range of conditions among the 23 sites varied from poor to very good based on IBI and HI scores, and habitat and fish assemblage measures were highly correlated. Stream biotic integrity and habitat quality were negatively correlated with the extent of agriculture and positively correlated with extent of wetlands and forest. Correlations were strongest at the catchment scale (IBI with % area as agriculture, r²=0.50, HI with agriculture, r²=0.76), and tended to become weak and non-significant at local scales. Local riparian vegetation was a weak secondary predictor of stream integrity. In this watershed, regional land use is the primary determinant of stream conditions, able to overwhelm the ability of local site vegetation to support high-quality habitat and biotic communities.     

Spatial scaling of core and dominant forest cover in the Upper Mississippi and Illinois River floodplains, USA

Different organisms respond to spatial structure in different terms and across different spatial scales. As a consequence, efforts to reverse habitat loss and fragmentation through strategic habitat restoration ought to account for the different habitat density and scale requirements of various taxonomic groups. Here, we estimated the local density of floodplain forest surrounding each of ~20 million 10-m forested pixels of the Upper Mississippi and Illinois River floodplains by using moving windows of multiple sizes (1?C100 ha). We further identified forest pixels that met two local density thresholds: ??core?? forest pixels were nested in a 100% (unfragmented) forested window and ??dominant?? forest pixels were those nested in a >60% forested window. Finally, we fit two scaling functions to declines in the proportion of forest cover meeting these criteria with increasing window length for 107 management-relevant focal areas: a power function (i.e. self-similar, fractal-like scaling) and an exponential decay function (fractal dimension depends on scale). The exponential decay function consistently explained more variation in changes to the proportion of forest meeting both the ??core?? and ??dominant?? criteria with increasing window length than did the power function, suggesting that elevation, soil type, hydrology, and human land use constrain these forest types to a limited range of scales. To examine these scales, we transformed the decay constants to measures of the distance at which the probability of forest meeting the ??core?? and ??dominant?? criteria was cut in half (S _1/2, m). S _1/2 for core forest was typically between ~55 and ~95 m depending on location along the river, indicating that core forest cover is restricted to extremely fine scales. In contrast, half of all dominant forest cover was lost at scales that were typically between ~525 and 750 m, but S _1/2 was as long as 1,800 m. S _1/2 is a simple measure that (1) condenses information derived from multi-scale analyses, (2) allows for comparisons of the amount of forest habitat available to species with different habitat density and scale requirements, and (3) can be used as an index of the spatial continuity of habitat types that do not scale fractally.     

Regional patterns of riparian characteristics in the interior Columbia River basin, Northwestern USA: applications for restoration planning

Recent declines in anadromous Pacific salmonids (Oncorhynchus spp.) have been attributed, in part, to degradation of freshwater habitat. Because riparian areas directly affect instream habitat, assessing riparian characteristics is essential for predicting salmon habitat quality and for prioritizing restoration projects. We quantified land use modification of anadromous fish-bearing streams in the interior Columbia River basin at multiple resolutions. We identified riparian areas in several land use and land cover classes using remotely sensed data. We then interpreted aerial photographs at random locations within each class to quantify riparian modifications at a local (stream reach) scale. Riparian areas in agricultural and urban areas were significantly narrower (~30 m, median) than those in forested or shrub/grass areas (~70 m). The largest proportion of modified riparian areas occurred in low-gradient streams with floodplains in semi-arid ecoregions. Riparian vegetation in these areas is unlikely to provide adequate in-stream functions, making these areas a natural starting point for restoration prioritization. We investigated how existing riparian restoration projects were spatially related to riparian land use and found that restoration effort varied among subwatersheds. Effective strategies for restoring high quality salmon habitat will be watershed-specific and must restore natural watershed processes. By using a hierarchical analysis to identify regional strategies, restoration or conservation activity can be focused in specific basins and thereby increase the likelihood that efforts will significantly improve habitat conditions for listed salmonids.     

Upstream-to-downstream changes in nutrient export risk

Nutrient export coefficients are estimates of the mass of nitrogen (N) or phosphorus (P) normalized by area and time (e.g., kg/ha/yr). They have been estimated most often for watersheds ranging in size from 10² to 10⁴ hectares, and have been recommended as measurements to inform management decisions. At this scale, watersheds are often nested upstream and downstream components of larger drainage basins, suggesting nutrient export coefficients will change from one subwatershed to the next. Nutrient export can be modeled as risk where lack of monitoring data prevents empirical estimation. We modeled N and P export risk for subwatersheds of larger drainage basins, and examined spatial changes in risk from upstream to downstream watersheds. Spatial (subwatershed) changes in N and P risk were a function of in-stream decay, subwatershed land-cover composition, and subwatershed streamlength. Risk tended to increase in a downstream direction under low rates of in-stream decay, whereas high rates of in-stream decay often reduced risk to zero (0) toward downstream subwatersheds. On average, increases in the modeled rate of in-stream decay reduced risk by 0.44 for N and 0.39 for P. Interactions between in-stream decay, land-cover composition and streamlength produced dramatic changes in risk across subwatersheds in some cases. Comparison of the null cases of no in-stream decay and homogeneously forested subwatersheds with extant conditions indicated that complete forest cover produced greater reductions in nutrient export risk than a high in-stream decay rate, especially for P. High rates of in-stream decay and complete forest cover produced approximately equivalent reductions in N export risk for downstream subwatersheds. This revised version was published online in August 2006 with corrections to the Cover Date.     

Does catchment geodiversity foster stream biodiversity?

Context

One approach to maintain the resilience of biotic communities is to protect the variability of abiotic characteristics of Earth’s surface, i.e. geodiversity. In terrestrial environments, the relationship between geodiversity and biodiversity is well recognized. In streams, the abiotic properties of upstream catchments influence stream communities, but the relationships between catchment geodiversity and aquatic biodiversity have not been previously tested.

Objectives

The aim was to compare the effects of local environmental and catchment variables on stream biodiversity. We specifically explored the usefulness of catchment geodiversity in explaining the species richness on stream macroinvertebrate, diatom and bacterial communities.

Methods

We used 3 geodiversity variables, 2 land use variables and 4 local habitat variables to examine species richness variation across 88 stream sites in western Finland. We used boosted regression trees to explore the effects of geodiversity and other variables on biodiversity.

Results

We detected a clear effect of catchment geodiversity on species richness, although the traditional local habitat and land use variables were the strongest predictors. Especially soil-type richness appeared as an important factor for species richness. While variables related to stream size were the most important for macroinvertebrate richness and partly for bacterial richness, the importance of water chemistry and land use for diatom richness was notable.

Conclusions

In addition to traditional environmental variables, geodiversity may affect species richness variation in streams, for example through changes in water chemistry. Geodiversity information could be used as a proxy for predicting stream species richness and offers a supplementary tool for conservation efforts.

     

Multi-scale assessment of human-induced changes to Amazonian instream habitats

Context

Land use change and forest degradation have myriad effects on tropical ecosystems. Yet their consequences for low-order streams remain very poorly understood, including in the world´s largest freshwater basin, the Amazon.

Objectives

Determine the degree to which physical and chemical characteristics of the instream habitat of low-order Amazonian streams change in response to past local- and catchment-level anthropogenic disturbances.

Methods

To do so, we collected field instream habitat (i.e., physical habitat and water quality) and landscape data from 99 stream sites in two eastern Brazilian Amazon regions. We used random forest regression trees to assess the relative importance of different predictor variables in determining changes in instream habitat response variables.

Results

Multiple drivers, operating at multiple spatial scales, were important in determining changes in the physical habitat and water quality of the sites. Although we found few similarities in modelled relationships between the two regions, we observed non-linear responses of specific instream characteristics to landscape change; for example 20 % of catchment deforestation resulted in consistently warmer streams.

Conclusions

Our results highlight the importance of local riparian and catchment-scale forest cover in shaping instream physical environments, but also underscore the importance of other land use changes and activities, such as road crossings and upstream agriculture intensification. In contrast to the property-scale focus of the Brazilian Forest code, which governs environmental regulations on private land, our results reinforce the importance of catchment-wide management strategies to protect stream ecosystem integrity.

     

Landscape configuration alters spatial arrangement of terrestrial-aquatic subsidies in headwater streams

Context

Freshwater ecosystems depend on surrounding terrestrial landscape for resources. Most important are terrestrial leaf litter subsidies, which differ depending on land use. We lack a good understanding of the variation of these inputs across spatial scales.

Objectives

We sought to determine: (1) the relative importance of local versus catchment-level forestation for benthic leaf litter biomass in streams, (2) how landscape configuration alters these relationships, and (3) how land use affects the quality and diversity of leaf litter subsidies.

Methods

We measured biomass and identity of benthic leaf litter in 121 reaches in 10 independent catchments seasonally over the course of a year. We assessed direct and indirect effects of forestation, reach position, and seasonality on leaf litter biomass using structural equation models, and assessed how leaf litter diversity varied with land use.

Results

In catchments with forested headwaters, the degree of forestation and reach position in the catchment influenced benthic leaf litter biomass indirectly through local reach-scale forestation. In catchments where forest was only located downstream, or with minimal forest, none of these factors influenced reach-level benthic leaf litter. Leaf litter diversity peaked in fall in all land use types, but was generally lowest in forested reaches.

Conclusions

Not only habitat amount, but its location relative to other habitats is important for ecosystem function in the context of cross-ecosystem material flows. Here, lack of upstream forest altered spatial patterns of leaf litter storage. Studies with high spatiotemporal resolution may further reveal effects of landscape configuration on other ecosystems.

     

Linking Land-use, Water Body Type and Water Quality in Southern New Zealand

Land-use and vegetation cover have been linked to the nutrient levels (nitrogen, phosphorus) of surface waters in several countries. However, the links generally relate to streams and rivers, or to specific types of standing water, for example shallow lakes in a geologically defined region. We measured physical variables and nutrient chemistry of 45 water bodies representative of the wide range of lentic wetland environments (swamps, riverine wetlands, estuaries, reservoirs, shallow lakes, deep lakes) in Otago, New Zealand, and related these to catchment variables and land-use in order to assess the potential influence of catchment modification on water quality of these diverse wetlands. Catchment boundaries and land cover were derived from maps using ArcView GIS software. Our predictions that concentrations of nutrients and other components of water quality would correlate positively with the nature and intensity of catchment modification were confirmed in multivariate analyses. Physical and chemical measures were positively related to the extent of modification in the catchment (percentage of the catchment in pasture, planted forest, scrub and urban areas), and negatively related to lack of catchment modification (more of the catchment in bare ground, tussock grassland and indigenous forest). The strong negative correlations between nutrient concentrations, suspended sediment, water colour and the percentage of tussock cover in the catchment imply that increased conversion of the␣native tussock grassland to pastoral farming in␣Otago will increase nutrient concentrations and␣reduce water quality of the diverse lentic ecosystems.     

Riparian habitat changes across the continental United States (1972–2003) and potential implications for sustaining ecosystem services

Riparian ecosystems are important elements in landscapes that often provide a disproportionately wide range of ecosystem services and conservation benefits. Their protection and restoration have been one of the top environmental management priorities across the US over the last several years. Despite the level of concern, visibility and management effort, little is known about trends in riparian habitats. Moreover, little is known about whether or not cumulative efforts to restore and protect riparian zones and floodplains are affecting the rates of riparian habitat change nationwide. To address these issues, we analyzed riparian land cover change between the early 1970s and the late 1990s/early 2000s using existing spatial data on hydrography and land cover. This included an analysis of land cover changes within 180 m riparian buffer zones, and at catchment scales, for 42,363 catchments across 63 ecoregions of the continental US. The total amount of forest and natural land cover (forests, shrublands, wetlands) in riparian buffers declined by 0.7 and 0.9%, respectively across the entire study period. Gains in grassland/shrubland accounted for the 0.2% lower percentage of total natural land cover loss relative to forests. Conversely, urban and developed land cover (urban, agriculture, and mechanically disturbed lands) increased by more than 1.3% within riparian buffers across the entire study period. Despite these changes, we documented an opposite trend of increasing proportions of natural and forest land cover in riparian buffers versus the catchment scale. We surmise that this trend might reflect a combination of natural recovery and cumulative efforts to protect riparian ecosystems across the US. However, existing models limit our ability to assess the impacts of these changes on specific ecosystem services. We discuss the implications of changes observed in this study on the sustainability of ecosystem services. We also recommend opportunties for future riparian change assessments.     

Land-use history and topographic gradients as driving factors of subalpine Larix decidua forests

European larch (Larix decidua Mill.) forests in the Alps are cultural landscapes that have been shaped by humans for centuries through traditional management. Biological and historical data sources were employed, and a multi-scale approach was adopted to capture the influence of factors affecting the structure of these forests. Landscape and stand scale dynamics were analyzed in four watersheds (c. 13,000 ha) of the western and central Italian Alps that have experienced different land-use intensities. Observed landscape changes were generalized using path analyses developed from a common conceptual model. Stand structure and a range of environmental variables were sampled in 203 circular plots, and land use and anthropogenic variables were derived from thematic maps and aerial photographs. We used multivariate statistical analyses (ordination and SEM models) to relate forest structure, anthropogenic influences, land uses, and topography. The most commonly observed land cover transition was an expansion of forests at the expense of open areas. All studied watersheds were dominated by larch forests, but their structure and spatial pattern differed greatly. Anthropogenic variables were less important at Ventina, the least accessible site, but emerged as fundamental to explain stand structure in the other study sites. Complexity of topography and proximity to roads had influenced past human activities mainly in the most accessible sites. Regeneration density was greatest at lower elevations and closer to human settlements. Quantification of the role played by forest harvesting and cattle grazing in past centuries is critical for understanding how global change factors may influence future dynamics of mountain forests in the European Alps and similar cultural landscapes worldwide.     

Parametric distance weighting of landscape influence on streams

We present a parametric model for estimating the areas within watersheds whose land use best predicts indicators of stream ecological condition. We regress a stream response variable on the distance-weighted proportion of watershed area that has a specific land use, such as agriculture. Distance weighting functions model the declining influence of landscape elements as a function of their flowpath distances, first to the stream channel (to-stream distance), and then down the channel to the location at which stream condition was sampled (in-stream distance). Model parameters specify different distance scales over which to-stream and in-stream influences decline. As an example, we predict an index of biotic integrity (IBI) for the fish communities in 50 small streams of the Willamette Basin of Oregon, USA, from distance-weighted proportions of agricultural or urban land use in their watersheds. The weighting functions of best-fitting models (R ² = 0.57) represent landscape influence on IBI as extending upstream tens of kilometers along the stream channel network, while declining nearly to zero beyond a distance of 30 m from the channel. Our example shows how parametric distance weighting can identify the distance scales, and hence the approximate areas within watersheds, for which land use is most strongly associated with a stream response variable. In addition, distance-weighting parameters offer a simple and direct language for comparing the scales of landscape influence on streams across different land uses and stream ecosystem components.     

Using remote-sensing data to assess habitat selection of a declining passerine at two spatial scales

Context

Detailed information on habitat needs is integral to identify conservation measures for declining species. However, field data on habitat structure is typically limited in extent. Remote sensing has the potential to overcome these limitations of field-based studies.

Objective

We aimed to assess abiotic and biotic characteristics of territories used by the declining wood warbler (Phylloscopus sibilatrix), a forest-interior migratory passerine, at two spatial scales by evaluating a priori expectations of habitat selection patterns.

Methods

First, territories established by males before pairing, referred to as pre-breeding territories, were compared to pseudo-absence control areas located in the wider forested landscape (first spatial scale, N_territories = 66, N_controls = 66). Second, breeding territories of paired wood warblers were compared to true-absence control areas located immediately close-by in the forest (second spatial scale, N_territories = 78, N_controls = 78). Habitat variables predominantly described forest structure and were mainly based on first and last pulse lidar (light detection and ranging) data.

Results

Occurrence of pre-breeding territories was related to vegetation height, vertical diversity and stratification, canopy cover, inclination and solar radiation. Occurrence of breeding territories was associated to vegetation height, vertical diversity and inclination.

Conclusions

Territory selection at the two spatial scales addressed was governed by similar factors. With respect to conservation, habitat suitability for wood warblers could be retained by maintaining a shifting mosaic of stand ages and structures at large spatial scales. Moreover, leaf-off lidar variables have the potential to contribute to understanding the ecological niche of species in predominantly deciduous forests.

     

Using Large Wood to Restore Streams in Central Europe: Potential use and Likely Effects

The potentials for the use of large wood (LW) in stream restoration projects were quantified for streams in Central Europe (total stream length assessed 44,880 km). Two different restoration methods were investigated: recruitment (passively allowing natural LW input) and placement (active introduction of large wood pieces into streams). The feasibility and potential effects of each method were studied for three different scenarios, according to the land-uses to be permitted on the floodplain: (a) only natural-non woody vegetation, forest, and fallow land occur on the floodplain, (b) including pasture and meadow, (c) including pasture, meadow, and cropland. Hydromorphological data were used to identify stream sections where LW recruitment or placement are feasible, and the likely effects of both restoration methods on channel hydromorphology were predicted. Passive recruitment is feasible for only a small percentage of the total channel length in the study area (~1% for all three scenarios). Active placement of LW can be used in much higher extent: 6.5% if only natural non-woody vegetation, forest, and fallow land can occur on the floodplain, 20.2% if stream segments bordered by pasture and meadow are included, and 32% if cropland is included in addition. There are differences between (1) the lower-mountainous area, where a large number of channel segments can be restored yielding an improvement from a moderate/good to a good/excellent morphological status and (2) the lowlands, where only a small number of channel segments can be restored yielding an improvement from a bad to a moderate morphological state. The latter upgrading might be sufficient to reach a ‘good ecological status’ as defined by the EU Water Framework Directive. The results of this study show the suitability of large wood recruitment and placement as appropriate methods to markedly improve the hydromorphological state of a large proportion of the streams in the study area.     

Living on the edge: quantifying the structure of a fragmented forest landscape in England

Forest ecosystems have been widely fragmented by human land use, inducing significant microclimatic and biological changes at the forest edge. If we are to rigorously assess the ecological impacts of habitat fragmentation, there is a need to effectively quantify the amount of edge habitat within a landscape, and to allow this to be modelled for individual species and processes. Edge effect may extend only a few metres or as far as several kilometres, depending on the species or process in question. Therefore, rather than attempting to quantify the amount of edge habitat by using a fixed, case-specific distance to distinguish between edge and core, the area of habitat within continuously-varying distances from the forest edge is of greater utility. We quantified the degree of fragmentation of forests in England, where forests cover 10 % of the land area. We calculated the distance from within the forest patches to the nearest edge (forest vs. non-forest) and other landscape indices, such as mean patch size, edge density and distance to the nearest neighbour. Of the total forest area, 37 % was within 30 m and 74 % within 100 m of the nearest edge. This highlights that, in fragmented landscapes, the habitats close to the edge form a considerable proportion of the total habitat area. We then show how these edge estimates can be combined with ecological response functions, to allow us to generate biologically meaningful estimates of the impacts of fragmentation at a landscape scale.     

How good are tropical forest patches for ecosystem services provisioning?

Native forests play an important role regarding ecosystem services related to biodiversity, water, and nutrient cycling, and the intensity of those services should be related to the amount, configuration and quality of the forest. However, in highly dynamic landscapes, such as some tropical regions, ecosystem services are potentially affected not only by the present landscape structure, but also by the historical land use. Here we propose a simple methodological framework to evaluate the contribution of past landscape dynamics and present landscape structure in the provision of ecosystem services. We applied this framework to a traditional agricultural landscape from the Brazilian Atlantic Forest hotspot, where natural forests cover has increased from 8 to 16 % in the last 60 years (1962–2008), and where old forests are being reduced while young forests are being regenerated. Forests of different ages, in association with current landscape structure, reveal a mosaic of forest patches under different conditions, implying different abilities to deliver ecosystem services. With the replacement of old-growth forests by young-regenerating forests and a high level of forest fragmentation, less than 1/4 of the current forest cover is able to fully satisfy the ecosystem service demands. To avoid such tendency, government policies should not only focus on increasing forest cover, but also in conserving old-growth forest fragments or increasing forest quality. The proposed methodology allows integrating historical land use and current landscape structure to evaluate ecosystem services provision and can be useful to establish programs of payment for ecosystem services.     

The relative influence of catchment and site variables on fish and macroinvertebrate richness in cerrado biome streams

Landscape and site-scale data analyses aid the interpretation of biological data and thereby help us develop more cost-effective natural resource management strategies. Our study focused on environmental influences on stream assemblages and we evaluated how three classes of environmental variables (geophysical landscape, land use and cover, and site habitat), influence fish and macroinvertebrate assemblage richness in the Brazilian Cerrado biome. We analyzed our data through use of multiple linear regression (MLR) models using the three classes of predictor variables alone and in combination. The four MLR models explained dissimilar amounts of benthic macroinvertebrate taxa richness (geophysical landscape R ² ≈ 35 %, land use and cover R ² ≈ 28 %, site habitat R ² ≈ 36 %, and combined R ² ≈ 51 %). For fish assemblages, geophysical landscape, land use and cover, site habitat, and combined models explained R ² ≈ 28 %, R ² ≈ 10 %, R ² ≈ 31 %, and R ² ≈ 47 % of the variability in fish species richness, respectively. We conclude that (1) environmental variables differed in the degree to which they explain assemblage richness, (2) the amounts of variance in assemblage richness explained by geophysical landscape and site habitat were similar, (3) the variables explained more variability in macroinvertebrate taxa richness than in fish species richness, and (4) all three classes of environmental variables studied were useful for explaining assemblage richness in Cerrado headwater streams. These results help us to understand the drivers of assemblage patterns at regional scales in tropical areas.