Riparian Vegetation Conditions Research Articles

Processes of lateral hyporhiec exchange and its eco-environment effects

Due to the occurrence of strong biogeochemical processes in the lateral hyporheic zone (LHZ), its unique and complex hydrodynamic characteristics play an important role in aquatic ecosystem and ecological environment. Through analysis and summarization of previous studies on the LHZ, the process and mechanism of hyporheic exchange in different directions are clarified, and the main factors (including topographic conditions, characteristics of sedimentary layers, hydrogeological conditions, river engineerings, and riparian vegetation conditions) that affect the lateral hyporheic exchange are analyzed in detail. Furthermore, the effects of lateral hyporheic exchange on solutes, grains, and ecological environments are discussed. Finally, some suggestions on this subject are given for future study.

Incorporating food web dynamics into ecological restoration: amodeling approach for river ecosystems.

Restoration is frequently aimed at the recovery of target species, but also influences the larger food web in which these species participate. Effects of restoration on this broader network of organisms can influence target species both directly and indirectly via changes in energy flow through food webs. To help incorporate these complexities into river restoration planning, we constructed a model that links river food web dynamics to in-stream physical habitat and riparian vegetation conditions. We present an application of the model to the Methow River, Washington, USA, a location of on-going restoration aimed at recovering salmon. Three restoration strategies were simulated: riparian vegetation restoration, nutrient augmentation via salmon carcass addition, and side channel reconnection. We also added populations of nonnative aquatic snails and fish to the modeled food web to explore how changes in food web structure mediate responses to restoration. Simulations suggest that side channel reconnection may be a better strategy than carcass addition and vegetation planting for improving conditions for salmon in this river segment. However, modeled responses were strongly sensitive to changes in the structure of the food web. The addition of nonnative snails and fish modified pathways of energy through the food web, which negated restoration improvements. This finding illustrates that forecasting responses to restoration may require accounting for the structure of food webs, and that changes in this structure, as might be expected with the spread of invasive species, could compromise restoration outcomes. Unlike habitat-based approaches to restoration assessment that focus on the direct effects of physical habitat conditions on single species of interest, our approach dynamically links the success of target organisms to the success of competitors, predators, and prey. By elucidating the direct and indirect pathways by which restoration affects target species, dynamic food web models can improve restoration planning by fostering a deeper understanding of system connectedness and dynamics.

Effects of Urban Sprawl on Riparian Vegetation: Is Compact or Dispersed Urbanization Better for Biodiversity?

AbstractCompact urbanization is the main strategy for sustainable urban development. However, it is yet unclear whether compact urban forms are ecologically more favourable than dispersed ones. In this paper, we studied the effects of urban sprawl on the riparian vegetation condition in one of the most degraded watersheds in the Buenos Aires metropolitan area, Argentina. We conducted random sampling of the riparian vegetation at sites along streams in the basin and assessed urban indicators at the reach and sub‐watershed scales for each of those sites in a geographic information system: urban area, impervious surface, population density and two landscape metrics of dispersion. The indicators assessed explained a high proportion of the variability of the vegetation response variables, thereby confirming the importance of urban sprawl pressure in shaping riparian communities in fluvial ecosystems. Dispersed urbanization had more positive than negative effects on the vegetation in the study area. Riverbanks associated with dispersed urbanization had more plant species, including exotics, when urban sprawl was assessed at the local scale. At the sub‐watershed scale, dispersed urbanized areas were richer in native plants and most of the functional groups, and poorer in exotic species. The model of the compact city, including bio‐corridors along watercourses, has been proposed for the Buenos Aires conurbation process for the next decades. Our results showed that the quality of existing river corridors across the compact matrix was not desirable and best practices for redesigning a more sustainable landscape structure are necessary, including the restoration of habitats for wetland species. Copyright © 2017 John Wiley & Sons, Ltd.

Mayfly bioindicator thresholds for several anthropogenic disturbances in neotropical savanna streams

Anthropogenic disturbances are widely recognized as major threats to terrestrial and aquatic biodiversity worldwide, including areas located in non-forest ecosystems. Headwater streams in the neotropical savanna are severely threatened by large-scale landscape changes that degrade local habitat characteristics and lead to biodiversity loss. The objective of our study was to evaluate Ephemeroptera assemblages as bioindicators of catchment land use and cover, local streambed and riparian vegetation conditions, and instream water quality. To do so, we sampled mayfly nymphs in 184 stream sites across a broad disturbance gradient in four hydrologic units of the Brazilian neotropical savanna. We selected seven metrics without significant co-variation with natural variability: % catchment urban, riparian vegetation condition index (RCOND), human disturbances of the stream channel and riparian zone (W1_HALL), substrate mean embeddedness (XEMBED), dissolved oxygen (mgL−1), pH, and total phosphorus (mgL−1). We ran threshold indicator taxa analysis (TITAN) for each disturbance metric to detect change points in mayfly genera responses (whether sensitive or tolerant) and assemblage turnover pattern. TITAN showed that 20 of the 39 genera found were robust bioindicators (based on purity and reliability values >0.95), sixteen of them being sensitive to increased disturbance. The most sensitive genera were Tricorythopsis (Leptohyphidae) and Camelobaetidius (Baetidae), showing decreased abundance to most disturbance metrics. We found a turnover pattern of mayfly genera in response to W1_HALL in a narrow variation range. For total phosphorus, the benchmark value defined in Brazilian Federal Legislation is higher than the turnover threshold of several mayfly genera. This indicates that we will lose many sensitive genera even within the limits imposed by national environmental legislation. The indicator taxa approach, based on multiple taxa rather than univariate metrics or single indicator species, demonstrates the value of quantitative ecological information for conserving and managing freshwater ecosystems globally.

Riparian vegetation as an indicator of riparian condition: Detecting departures from historic condition across the North American West

Floodplain riparian ecosystems support unique vegetation communities and high biodiversity relative to terrestrial landscapes. Accordingly, estimating riparian ecosystem health across landscapes is critical for sustainable river management. However, methods that identify local riparian vegetation condition, an effective proxy for riparian health, have not been applied across broad, regional extents. Here we present an index to assess reach-scale (500 m segment) riparian vegetation condition across entire drainage networks within large, physiographically-diverse regions. We estimated riparian vegetation condition for 53,250 km of perennial streams and rivers, 25,685 km in Utah, and 27,565 km in twelve watersheds of the interior Columbia River Basin (CRB), USA. We used nationally available, existing land cover classification derived from 30 m Landsat imagery (LANDFIRE EVT) and a modeled estimate of pre-European settlement land cover (LANDFIRE BpS). The index characterizes riparian vegetation condition as the ratio of existing native riparian vegetation cover to pre-European settlement riparian vegetation cover at a given reach. Roughly 62% of Utah and 48% of CRB watersheds showed significant (>33%) to large (>66%) departure from historic condition. Riparian vegetation change was predominantly caused by human land-use impacts (development and agriculture), or vegetation change (native riparian to invasive or upland vegetation types) that likely resulted from flow and disturbance regime alteration. Through comparisons to ground-based classification results, we estimate the existing vegetation component of the index to be 85% accurate. Our assessments yielded riparian condition maps that will help resource managers better prioritize sites and treatments for reach-scale conservation and restoration activities.

Riparian vegetation condition is associated with invertebrate assemblage composition in intermittent and humic streams

Riparian vegetation is known to provide environmental benefits for aquatic ecosystems and is commonly used in the restoration of agricultural catchments. However, little information exists on the influence of riparian vegetation on the fauna of intermittent or humic (coloured) streams. We examined the ecological condition of riparian vegetation and its influence on stream fauna amongst humic and non-humic intermittent and perennial stream reaches in the Ellen Brook catchment, south west Western Australia. Permutation-tests showed that flow regime (Global R = 0.444, P < 0.001) and the presence/absence of riparian vegetation (Global R = 0.407, P < 0.001) were the most influential factors associated with invertebrate assemblage composition. Riparian vegetation influenced invertebrate assemblages through the provision of organic matter for food and habitat, and by shading stream channels, thereby limiting light and algal growth. This was illustrated by a higher proportion of algal grazers (Chironominae and Physidae) in unvegetated streams and more detritivores (Leptoceridae, Gripopterygidae, Ceinidae) in vegetated streams. Humic intermittent streams showed different invertebrate assemblages to non-humic intermittent streams; having fewer Cladocera and Chironomidae and more grazing gastropods (Physidae and Lynceidae). A significant proportion of the variation in invertebrate assemblages was associated with stream width, salinity and NOx-N concentrations because intermittent streams were narrower, more brackish and less enriched than with nitrogen than perennial streams. Riparian vegetation benefited invertebrate assemblages in all stream types, showing that revegetation is as effective a restoration action in intermittent and humic streams as it is in perennial streams.

Is the Sosiani River Healthy? Investigating the Relationship between Water Quality Indicators and Macroinvertebrate Assemblages in the Sosiani River

The health of rivers is of great concern to governments and communities worldwide due to their important ecological functions. Numerous studies have established that water quality indicators have a positive effect on river health. However, only a few studies have examined equatorial rivers, and, to date, there has been no study on the Sosiani River in Kenya. As such, this study explored the health of the Sosiani River by considering how its aquatic macroinvertebrate assemblages were affected by various water quality parameters. The research considered whether there was a relationship between water quality indicators and macroinvertebrate assemblages in the Sosiani River. This knowledge is of paramount importance to the communities and decision makers of the Sosiani catchment, and Kenya as a whole, since there is need to understand the relationship between the water quality indicators and the health of the river in order to allocate resources for its rehabilitation and maintenance. This study examined 10 sites, nine being “test” sites and one a “reference” site. The study established a significant relationship between water quality parameters and macroinvertebrate assemblages. The sites with natural riparian zone vegetation conditions were found to have more Ephemeroptera, Plecoptera, and Trichoptera macroinvertebrates when compared to those without or with exotic vegetation. In terms of absolute numbers of surface aquatic macroinvertebrates, sites characterised by dense stream bank vegetation had more macroinvertebrates than those characterised by forest with eroded, bare stream banks. From the study, it was therefore concluded that Sosiani River is healthier at head waters where there was natural forests compared to downstream where there was plantations, intensive farming and urban area. The study recommends that more detailed studies classify macroinvertebrates to gunus level and include microinvertebrates, since this may give a more accurate assessment of the river’s health. The study further recommends that identification keys for East African macroinvertebrates be developed.

Diversity and composition of Trichoptera (Insecta) larvae assemblages in streams with different environmental conditions at Serra da Bocaina, Southeastern Brazil

Abstract: Aim The goal of this study is to examine the composition and richness of caddisfly assemblages in streams at the Serra da Bocaina Mountains, Southeastern Brazil, and to identify the main environmental variables, affecting caddisfly assemblages at the streams with different conditions of land use. Methods The sampling was conducted in 19 streams during September and October 2007. All sites were characterized physiographically by application of environmental assessment protocol to Atlantic Forest streams and by some physical and chemical parameters. Of the 19 streams sampled, six were classified as reference, six streams as intermediate (moderate anthropic impact) and seven streams as poor (strong anthropic impact). In each site, a multi-habitat sampling was taken with a kick sampler net. The sample was composed by 20 units, each one corresponded to 1 m2 of collected substrate, corresponding 20 m2 of sampling area. The material was placed in a plastic container (500 µm of mesh), washed, homogenized and sub-sampled. For each stream, 6 subsamples were randomly sorted. Results Were collected 2,113 caddisfly larvae, belonging to 12 families and 28 genera. Hydropsychidae and Leptoceridae were the most abundant families, and Smicridea was the most abundant genus. Sorensen’s index results showed that the streams studied were grouped according to environmental integrity. The Indicator Species Analysis showed only characteristic taxa to reference streams. Canonical Correspondence Analysis showed that caddisfly assemblage was strongly influenced by nitrate concentration, pH and condition of riparian vegetation. Multiple regression analysis indicated significant correlations to five genera with some environmental parameters, besides total abundance of Trichoptera. Conclusions Ours results showed that degree of environmental impact, mainly the nitrate concentration, pH, and condition of cover vegetation acted as a major factor in determining the Trichoptera assemblages present in the stream of the Serra da Bocaina, separating streams along an environmental gradient.

A new empirical river pattern discriminant method based on flow resistance characteristics

A new empirical river pattern classification system is established based on the generalization of the famous Darcy–Weisbach equation. A parameter representing river shape is derived and defined as the river pattern discriminant criteria. After transformation, a couple of discriminant thresholds are determined and expressed as dimensionless forms relating the resistance factor to the relative roughness factor of the channel, which reflect the integrative effects of channel slope, sediment size, bank strength and channel geometry. A threshold function is used to separate single-thread channels (including straight and meandering) from multi-thread channels, and another one is employed to distinguish stable and unstable multi-thread channels (i.e., anabranching and braided) in this paper. A novel bank strength impact factor (μ) is proposed and turns out to be rather representative. Some channel patterns are reasonably redefined using this method. Analysis of various data sets reveals that riparian vegetation condition is a sensitive part of this classification system, in particular for single-thread channels, but not braided channels, because an overlarge width–depth ratio (W/d) could strongly weaken this impact. The definition of anabranching and braided channels herein is actually consistent with the traditional braided channels to some extent. It is also trustworthy that transient anabranching or braiding pattern could occur in a single-thread typical zone following external disturbance, but would eventually return to dynamic equilibrium state. Despite some potential limitations in the construction mechanism, the proposed discriminant method is supported by the selected existing datasets and could effectively distinguish three distinct types of channels by just a few river hydraulic parameters.

Riparian vegetation as indicator of channel adjustments and environmental conditions: the case of the Panaro River (Northern Italy)

Disturbances affecting flow and sediment transport regimes (e.g. dams, diversions, gravel mining, weirs, bank reinforcements, climate changes) can promote riverbed degradation and channel narrowing, and thus influence vegetation dynamics and composition. This study investigates the relationships and feedbacks between channel adjustments and riparian vegetation dynamics by combining an analysis of morphological channel changes with a wider phytosociology analysis of existing vegetation within the river corridor. These relationships were illustrated by using the case study of the Panaro River (located in the Northern Apennines, Italy), being a representative case of a deeply incised and narrowed river. More specifically we analyzed: (1) the relations between landforms and distributional patterns of vegetation types and characteristic plant species (index species): these provided information about the hydrogeomorphic condition of fluvial landforms and about channel adjustments; (2) the distance of riparian vegetation conditions from expected conditions as a consequence of human impact, based on the fact that each species and vegetation type has a given tolerance for specific disturbance regimes or stresses. Although some expected relations between landforms and vegetation types were found, we recorded significant deviations from the typical correlation pattern existing between morphology and vegetation, and this could be used to infer the intensity and the typology of human disturbances. In particular, the index species can indicate present ecological conditions and on past channel evolution. With this knowledge it might be possible to develop botanical recovery models in the future and, even more importantly, enable the recognition of the differences between temporal and spatial diversity.

Assessing the importance of the riparian zone for stream fish communities in a sugarcane dominated landscape (Piracicaba River Basin, Southeast Brazil)

In the Neotropics, the effect of agriculture on freshwater habitats is still poorly understood, particularly with respect to sugarcane expansion to meet increased ethanol demands. The variation in taxonomic composition, community attributes and trophic structure of fish assemblages from streams under different riparian zone preservation conditions were studied. Nine stream reaches under the following riparian vegetation conditions were selected: Native Forest (NF), with mostly primary forest; Secondary Forest (SF), which included sites with vegetation in an advanced stage of regeneration surrounded by sugarcane plantations; and Sugarcane sites (SC), located in areas without riparian vegetation, adjacent to sugarcane crops. Forty-one species were collected. The variance partitioning and partial Redundancy Analysis (pRDA) indicated that community composition and trophic structure were significantly explained by riparian condition and spatial variations, while diversity, richness, abundance and biomass were only explained by season and space, with higher diversity and richness at the SF sites. Abundance-Biomass curves (ABC curves) suggested that sugarcane plantations destabilized fish assemblages, especially at the more intensively managed sites, which seem to influence stream integrity and associated fish fauna. We concluded that both physical conditions of streams and some attributes of fish communities reflected the different levels of preservation of the riparian buffers, but given the influence of regional processes which have a pervasive role in shaping local assemblages, land use at the watershed scale seemed to be important especially to explain the higher richness and diversity found at the SF sites.

Making sense of landscape change: Long-term perceptions among local residents following river restoration

• Long-term perceptions among local residents following river restoration investigated. • Cultural values framework applied, based on forms, relationships and practices. • Nine key influences on public perception identified. • Idealised perceptual frameworks based on interactions between influences mapped. • Outcomes are of theoretical and applied relevance for future river restoration. Efforts to restore rivers are increasingly concerned with the social implications of landscape change. However, the fundamental issue of how people make sense of local riverine environments in the context of restoration remains poorly understood. Our research examined influences on perception among local residents 14 years after a restoration scheme on the River Dearne in the north of England. Human-landscape relationships emerging from semi-structured interviews with 16 local residents were analysed using an interpretive research framework. Nine recurring factors influenced perception among local residents: scenic beauty; the condition of riparian vegetation and of river channel morphology; opportunities to observe flora and fauna; cleanliness of the riverine environment; access available to the river; connections between the river and the surrounding landscape; disturbance and change in the familiarity of the landscape following restoration. These factors were not solely related to tangible outcomes of the restoration scheme, but were also influenced by history, memories, traditions and practices associated with the river. Critically, these factors also interacted rather than operating in isolation and two idealised perceptual frameworks were developed to map these interactions. Our research contributes to theoretical understanding of the relationships between humans and landscape change, whilst also considering how restoration practice may better reflect these relationships. The importance of a social dimension to the template of possibilities for restoring any given river emerges, underpinning place-based design and implementation of river restoration schemes.

Palynological investigations at the Late Bronze–Early Iron Age lakeshore settlement of Luokesa 1 (Moletai District, Lithuania): a contribution to the Middle-Late Holocene vegetation history of the south-eastern Baltic regions

Today, the settlement site of Luokesa 1 (L1) lies under water at the northern edge of Lake Luokesa in the Baltic Uplands, south-eastern Lithuania. Its 60 cm-thick Late Bronze–Early Iron Age cultural layer lies on top of lake marl. During excavations in 2008 and 2009, core samples at L1 were taken for the purpose of multidisciplinary investigations. From this material, five on-site pollen diagrams were created in parallel with geo-archaeological investigations and the examination of the botanical macro-remains. Two of these cores mainly comprised the cultural layer, another two consisted largely of the underlying lake marl and the fifth contained primarily the transition from the lake marl to the cultural layer. The chronological sequence was established through 11 AMS dates. The woodland history, starting from the Late Atlantic period, was recorded. The Quercetum mixtum values are quite low in the Subboreal, with the coniferous forest consisting mainly of Pinus and, though significantly less, Picea. At the transition to the cultural layer (Subatlantic) the pollen curves are highly variable, showing peaks in the curves for Betula and Alnus. Pollen from aquatic plants is also present. Changes in riparian vegetation and turbulent sedimentation conditions are to be expected and can be explained by a drop in the water level. As L1 was located on damp ground at that time, water influxes alternating with dry episodes were observed. In the area around L1 the sedge belt was less pronounced, and riparian woodland extended all the way to the shores of the lake. Pollen analyses of four sheep/goat dung samples provide information on the grazing season and pasture location of these domestic animals. The paper also discusses layer formation processes such as water level fluctuations and hiatuses.

Divergent patterns of riparian cottonwood recovery after the return of wolves in Yellowstone, USA

AbstractUnderstanding the potential effect apex predators may have on riparian plant communities, via a trophic cascade, represents an important research challenge in Rocky Mountain ecosystems. In the northern ungulate winter range of Yellowstone National Park where grey wolves (Canis lupus) were historically present, absent for seven decades, and recently reintroduced, our objective was to evaluate patterns of cottonwood (Populus spp.) recruitment for two adjacent reaches of the Lamar Valley. Results indicated that recruitment was common in both reaches when wolves were historically present and declined because of intensive herbivory from elk (Cervus elaphus) after wolves were extirpated in the early 1900s. By the 1970s, cottonwood recruitment along both reaches had essentially ceased. Wolves were reintroduced in the mid‐1990s, and by 2012, some 4660 young cottonwoods ≥2 m in height (the general upper browse level of elk) had become established within the 2‐km‐long upper Lamar study reach, consistent with re‐establishment of a tri‐trophic cascade involving wolves, elk, and cottonwoods. However, within the 8‐km‐long lower Lamar study reach, only 22 young cottonwoods had attained a height of ≥2 m because of high levels of herbivory, especially from bison (Bison bison). Top–down trophic interactions involving wolves and elk, as well as reach characteristics and browsing by bison, appear to explain the strongly contrasting patterns of recent riparian cottonwood recruitment currently underway in the northern Yellowstone – one reach represented by a recovering riparian ecosystem and the other an alternative stable state with highly altered riparian vegetation and channel conditions. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Defining and Testing Targets for the Recovery of Tropical Streams Based on Macroinvertebrate Communities and Abiotic Conditions

Here, we set target values to measure the ecological improvement of streams, based on invertebrate communities, riparian vegetation, instream habitat conditions and water chemistry. The study area is a large tropical catchment (Rio das Velhas, Minas Gerais, Brazil) affected by pastures, mining areas and a large urbanized area but also includes natural protected areas. Two stream types were found in the catchment, based on stream size, elevation, climate and geology with significantly different macroinvertebrate communities. In spite of a marked wet/dry seasons' climatic pattern, that does not result in the segregation of communities. Four classes of global degradation (IV—bad to I—good condition) were defined based on the available abiotic information, corresponding to a gradient in structure and biotic metrics of macroinvertebrate communities, matching the current knowledge on taxa sensitivity to pollution and general disturbance. Class I corresponds to target conditions to be achieved under restoration programmes. Using this approach, we were able to detect an improvement of abiotic conditions in four urban streams that benefited from enhancement measures in 2007–2008. However, invertebrate communities improved clearly in only one site (biotic metrics and community structure). Our study highlighted that good water quality alone is not enough and that only the combined effect of water quality, riparian vegetation and instream habitat condition enhancement resulted in the improvement of invertebrate communities. An important limiting factor for macroinvertebrate communities' recovery may be the distance to source populations. We concluded that the combined use of biological and abiotic target values for measuring the recovery of streams is needed to fully achieve an ecological restoration. This approach can also be valuable in the regular monitoring of streams to assess stream degradation. Target values based on other biological elements, such as fishes and algae, and functional processes could also contribute to define more global and realistic goals. Copyright © 2013 John Wiley & Sons, Ltd.

The influence of native replanting on stream ecosystem metabolism in a degraded landscape: can a little vegetation go a long way?

Summary The effectiveness of revegetation is usually gauged by responses in biodiversity, which may differ between isolated replanted patches. The ecological value of revegetation may be detected more effectively by monitoring ecosystem processes. In‐stream metabolism has been much modified by the degradation of riparian vegetation in agricultural landscapes around the world. We sought to determine whether the spatial scale typical of most riparian replanting projects (i.e. &lt;1 km long) influences stream metabolism. Metabolism is a functional measure that incorporates gross primary production (GPP), ecosystem respiration (ER) and the difference between them [net ecosystem productivity (NEP)]. We hypothesised that replanted reaches would have lower GPP (due to greater canopy shading) and greater ER (governed by larger terrestrial energy inputs) compared with pasture reaches. We measured metabolism in paired reaches within four agricultural streams. Two streams had an untreated pasture reach contrasted with a reach replanted with native woody vegetation &gt;17 years ago. The other two streams had similar riparian vegetation condition adjacent to both reaches, to act as reference sites. Mean daily GPP (0.27–4.9 g O2 m−2 day−1) and ER (1.1–22 g O2 m−2 day−1) were within the range of values recorded previously in agricultural streams elsewhere. Replanted reaches had rates of NEP lower than upstream untreated reaches at treatment sites, but NEP was similar between reaches at reference sites. The effects of replanting on stream ecosystem processes are detectable even when the spatial scale of restoration is relatively small in a whole‐of‐catchment context. Land managers can protect and restore vegetation at feasible spatial scales and benefit ecosystem processes. Ecosystem metabolism should be included in the range of responses that need to be monitored to provide a complete picture of the effectiveness of stream restoration.

Distribution and biometry of native and alien crayfish in Trentino (Italian Alps)

To fill the existing gaps in the knowledge of the crayfish species distribution in Trentino region (North-East Italy), we surveyed fourteen lakes, six ponds and sixty-nine creeks and streams in 2010-2012. We recorded four populations of the invasive alien species Orconectes limosus in four lakes and twenty of the native Austropotamobius pallipes complex from four lakes, three ponds and thirteen creeks; three of these populations went extinct during the three years of our survey. Crayfish populations were monitored in spring, summer and early autumn, to assess the distribution, density and seasonal dynamics of the two species. Statistical analysis of morphometric data showed differences in body size and growth rates among sampling sites, possibly related to local environmental factors, with higher growth rates in males of both species; A. pallipes grew faster in creeks than in lakes. The extinction of twenty-two native populations of A. pallipes complex in the last century was likely due to habitat modifications, in particular to the loss of riparian habitat, in few cases to overfishing, and, more recently, to the spread of alien species and the related transmission of their parasite Aphanomyces astaci . Some populations of A. pallipes complex were infested with the parasite Thelohania sp ., and only one population with ectosymbiotic Branchiobdellida. In Trentino, small creeks with well developed riparian vegetation and good hydromorphological conditions, flowing through mountain slopes, can represent potential refuge and recruitment areas for of A. pallipes complex, without significant management intervention, although a sustainable management of piedmont water bodies would allow preserving or increasing the number and density of the relict populations.

Fire as a disturbance in mediterranean climate streams

Mediterranean climate ecosystems are among the most fire-prone in the world; however, little is known about the effects of fire on mediterranean streams (med-streams). Fire impacts on med-streams are associated with increased runoff and erosion from severely burned landscapes during storms, particularly the first intense rains. Increased inputs of water, solutes, nutrients, sediment, organic matter, and ash to streams after fires are usually observed for months to up to 4 years. Return to pre-fire conditions is associated with vegetation recovery. Benthic algae, invertebrates, and fish are reduced to low levels by scouring floods after wildfire. If riparian zones are burned, benthic algae increase, and invertebrate communities become dominated by r-strategist species. Fishes are eradicated from reaches affected by intense wildfire and often do not re-colonize quickly because of downstream barriers. In general, med-stream communities appear to be more resilient to fire compared to streams in other ecosystems because of the rapid recovery of mediterranean upland and riparian vegetation and geomorphological conditions (1–4 years in med-streams vs 5–10 years in non-med streams). However, drought or mass sediment movements after fire can prolong fire effects. Studies of the long-term effects of fire and the consequences of fire management practices are still needed.

Water Quality Degradation of Coastal Waterways in the Wet Tropics, Australia

The Wet Tropics region of north Queensland has outstanding environmental values, contains the highest biological diversity in Australia, and borders the Great Barrier Reef. Comparable to other tropical areas worldwide, increasing urban and agricultural development in the Wet Tropics has caused concerns with respect to ecosystem degradation due to poor water quality in freshwater reaches and marine environments. Key issues currently identified in the Wet Tropics include erosion and subsequent stream turbidity and sedimentation, nutrients from erosion and fertiliser use and pesticide residue contamination. Issues such as reduced dissolved oxygen, acid sulfate soil runoff, and biological factors such as weed infestation, reduced and degraded riparian vegetation condition, and flow modification have also been identified. These issues mainly arise from agricultural activities with lesser effects from urban development. Management of pollution to improve in-stream water quality requires a long-term monitoring program to characterize water quality conditions over different flows and seasons. This type of monitoring program is underway; however, the focus is on the Great Barrier Reef and does not fully consider freshwater ecosystem health. Another major issue is the lack of a fully developed conceptual framework that links changed land use to water quality and subsequently to aquatic ecosystem health. In this paper, we establish the current level of water quality knowledge in the Wet Tropics while outlining a conceptual framework connecting changing land management practices and their effects to water quality and to ecosystem health.

Is Catchment Imperviousness a Keystone Factor Degrading Urban Waterways? A Case Study from a Partly Urbanised Catchment (Georges River, South-Eastern Australia)

The extent of catchment impervious surface is recognised to be an important factor associated with the condition of urban freshwater streams. We tested the hypothesis that the degree of catchment imperviousness predicted the relative ecological condition of freshwater reaches within the network of streams and rivers in the partly urbanised Georges River catchment in temperate south-eastern Australia. The 2-year study involved two spring and two autumn assessments of water quality (chemical and physical) and ecological condition, using benthic macroinvertebrates, riparian vegetation and calculation of catchment imperviousness. The study revealed that highly urbanised streams had strongly degraded water quality and macroinvertebrate communities, compared to clean non-urban reference streams. We found three clear groups of sites with varying degrees of ecological condition, being categorised according to the level of catchment effective imperviousness (low 18.0 %). Water pollution also varied according to these categories. A combination of two water chemistry attributes (total nitrogen and calcium), along with catchment imperviousness and riparian vegetation condition, were identified as being the factors most strongly associated with variation of macroinvertebrate communities. Based on our results, we recommend that protection of the ecological condition of streams should focus on not only water quality but also include catchment imperviousness and riparian vegetation condition.