Vegetation Encroachment Research Articles

HABITAT UTILIZATION BY THE TEXAS HORNED LIZARD (PHRYNOSOMA CORNUTUM) FROM TWO SITES IN CENTRAL TEXAS

The Texas Horned Lizard (Phrynosoma cornutum) is found in a variety of habitats. Although several studies have been conducted on habitat use by this species, none have been performed in central Texas, a more mesic habitat than most of those previously studied. This area is of special interest because horned lizard populations have been experiencing sharp declines in central Texas over the last approximately 50 years. We collected habitat data at two sites in central Texas, Camp Bowie and Blue Mountain Peak Ranch. Microhabitat data included canopy cover and ground cover from digitized photographs of Daubenmire quadrats; macrohabitat variables included vegetation height and length, cactus height, soil penetrability, woody plant species richness, tree density, tree diameter at breast height (DBH), and density of ant mounds collected along 100-m by 2-m transects. Similar patterns of habitat use were observed between the two sites. At Blue Mountain Peak Ranch, lizards appeared to be located in areas with a diversity of ground cover types, as observed in previous studies. At Camp Bowie, vegetation encroachment limited lizards in some areas to the use of roads and road margins. Implementation of prescribed burns or other vegetation management could create the preferred ground cover mosaic at such sites.

Quantifying meso‐mammal cave use in central Texas

Knowledge of meso‐mammal cave use is essential for natural resource managers, particularly in the management of endangered cave invertebrates. Scat left by meso‐mammals represents significant nutrient inputs into the oligotrophic cave environment which can disrupt the invertebrate species composition and ecology. Since little is known about what constitutes typical timing or frequency of meso‐mammal visitation, current management practices are largely speculative. Central Texas caves were historically associated with raccoons Procyon lotor, but with the loss of large predators and encroachment of woody vegetation, the now naturalized North American porcupine Erethizon dorsatum has become an established part of the local ecosystems whose effect on cave biology remains unknown. Our objective with this study was to quantify meso‐mammal cave use according to seasons, time of day, weather conditions, as well ecological and physical cave characteristics. We monitored 30 caves by placing trail cameras at cave entrances for one year on Joint Base San Antonio‐Camp Bullis military base just north of San Antonio, Texas. North American porcupines, raccoons, and Virginia opossums Didelphis virginiana were the three most commonly photographed meso‐mammals (>87%). All meso‐mammal groups showed significantly different cave use according to season, weather, and cave characteristics. Data suggested most meso‐mammals were using caves for denning while raccoons and Virginia opossums also were feeding on resident invertebrate and rodent populations. In particular, Virginia opossum and raccoon, both potential predators of endangered species, showed greater use of caves containing endangered species. The results from our study represent an initial step in understanding meso‐mammal cave use in central Texas.

Effect of shrub encroachment on vegetation communities in Brazilian forest-grassland mosaics

Woody vegetation encroachment in natural grasslands is a concern in many parts of the world. We evaluated the effect of Baccharis uncinella (Asteraceae) encroachment on grassland vegetation in southern Brazil, in terms of plant composition and richness. We conducted a vegetation survey in 12 plots of 10×10m. The study site was a forest-grassland mosaic where management practices have been excluded since 1994. Six plots were located in areas without B. uncinella and the remaining six in different densities of it. Within each plot, we randomly placed three subplots of 1×1m where we identified plant species and estimated their cover. Vegetation height, total plant cover and standing dead biomass were also estimated. We recorded 46 species belonging to 15 families; 34 of them were in plots with B. uncinella (29% grasses, 44% shrubs, 24% forbs and 3% trees) and 37 in plots without it (27% grasses, 35% shrubs and 38% forbs). B. uncinella affected grassland community by reducing total plant richness and decreasing the number of forb species. B. uncinella may alter the availability of resources, affecting the ability of forbs to establish and grow. The capacity of B. uncinella to occupy adjacent open-canopy ecosystems and to suppress grassland plants indicates that, without any management practice, plant richness in Brazilian highland grasslands may decrease. This study presents empirical data that may contribute to conservation efforts of forest-grasslands mosaics in southern Brazil.

Paleohydraulic Reconstruction of Modern Large Floods at Subcritical Speed in a Confined Valley: Proof of Concept

The present study aims to show the accuracy of paleoflood reconstruction techniques based on two-dimensional (2D) hydraulic modelling of a large flood. Using this reconstruction technique, we determined trends in flood stages over time in a regulated river. A stretch of the Guadalquivir River (Southern Spain) was selected as the study site. High-resolution orthophotos and LiDAR (Light Detection and Ranging) elevations were acquired just after modern floods. They were used for the identification and location of stage indicators. In addition, water gradients were estimated from gauging records, documentary information and paleostage indicators (PSIs) in two situations: (i) pre-vegetation encroachment; and (ii) post-vegetation encroachment due to upstream impoundment. Standard two-dimensional, flow depth-averaged equations over fixed beds were used in the hydraulic modelling. In a first stage, long records of instrumental data at gauging stations and documentary evidence of flood levels served to calibrate the input parameters of the hydraulic model. In a second stage, paleoflood signatures within sedimentary and botanical sequences served to verify the flood stages in the numerical simulations not only at the river reach where instrumental data exist but also in the downstream river reach. Interestingly, the rating curve obtained from the combined use of documentary information and imagery was nearly as accurate as gauging measurements. The thoughtful comparison of 2D modelled hydraulic variables against inferred values from PSIs and instrumental data supports the paleoflood reconstruction method over fixed beds. Vegetation encroachment provoked 10% deeper floods at the water discharge of 2000 m3 · s−1, which implied an increase of Manning’s roughness coefficient from 0.04 to 0.055 s · m−1/3 in less than 15 years.

Impacts of Mesquite Distribution on Seasonal Space Use of Lesser Prairie-Chickens

Loss of native grasslands by anthropogenic disturbances has reduced availability and connectivity of habitat for many grassland species. A primary threat to contiguous grasslands is the encroachment of woody vegetation, which is spurred by disturbances that take on many forms from energy development, fire suppression, and grazing. These disturbances are exacerbated by natural- and human-driven cycles of changes in climate punctuated by drought and desertification conditions. Encroachment of honey mesquite (Prosopis glandulosa) into the prairies of southeastern New Mexico has potentially limited habitat for numerous grassland species, including lesser prairie-chickens (Tympanuchus pallidicinctus). To determine the magnitude of impacts of distribution of mesquite and how lesser prairie-chickens respond to mesquite presence on the landscape in southeastern New Mexico, we evaluated seasonal space use of lesser prairie-chickens in the breeding and nonbreeding seasons. We derived several remotely sensed spatial metrics to characterize the distribution of mesquite. We then used these data to create population-level resource utilization functions and predict intensity of use of lesser prairie-chickens across our study area. Home ranges were smaller in the breeding season compared with the nonbreeding season; however, habitat use was similar across seasons. During both seasons, lesser prairie-chickens used areas closer to leks and largely avoided areas with mesquite. Relative to the breeding season, during the nonbreeding season habitat use suggested a marginal increase in mesquite within areas of low intensity of use, yet aversion to mesquite was strong in areas of medium to high intensity of use. To our knowledge, our study is the first to demonstrate a negative behavioral response by lesser prairie-chickens to woody encroachment in native grasslands. To mitigate one of the possible limiting factors for lesser prairie-chickens, we suggest future conservation strategies be employed by land managers to reduce mesquite abundance in the southern portion of their current range.

Squeezed out: the consequences of riparian zone modification for specialist invertebrates

While anthropogenic biodiversity loss in fresh waters is among the most rapid of all ecosystems, impacts on the conservation of associated riparian zones are less well documented. Riverine ecotones are particularly vulnerable to the combined ‘squeeze’ between land-use encroachment, discharge regulation and climate change. Over a 3-year period of persistent low discharge in a regulated, temperate river system (River Usk, Wales, UK; 2009–2011), specialist carabid beetles on exposed riverine sediments (ERS) were used as model organisms to test the hypotheses that catchment-scale flow modification affects riparian zone invertebrates more than local habitat character, and that this modification is accompanied by associated succession among the Carabidae. Annual summer discharge during the study period was among the lowest of the preceding 12 years, affecting carabid assemblages. The richness of specialist ERS carabids declined, while generalist carabid species’ populations either increased in abundance or remained stable. Community composition also changed, as three (Bembidion prasinum, B. decorum and B. punctulatum) of the four dominant carabids typical of ERS increased in abundance while B. atrocaeruleum decreased. Despite significant inter-annual variation in habitat quality and the encroachment of ground vegetation, beetle assemblages more closely tracked reach-scale variations between sites or catchment-scale variations through time. These data from multiple sites and years illustrate how ERS Carabidae respond to broad-scale discharge variations more than local habitat character. This implies that the maintenance of naturally variable flow regimes is at least as important to the conservation of ERS and their dependent assemblages as are site-scale measures.

A Closer Look: Stream Geomorphology and Ecohydrological Interactions in the Minnesota River Basin

A Closer Look: Stream Geomorphology and Ecohydrological Interactions in the Minnesota River Basin

LANDSAT-BASED WOODY VEGETATION COVER MONITORING IN SOUTHERN AFRICAN SAVANNAHS

Mapping woody cover over large areas can only be effectively achieved using remote sensing data and techniques. The longest continuously operating Earth-observation program, the Landsat series, is now freely-available as an atmospherically corrected, cloud masked surface reflectance product. The availability and length of the Landsat archive is thus an unparalleled Earth-observation resource, particularly for long-term change detection and monitoring. Here, we map and monitor woody vegetation cover in the Northwest Province of South Africa, an area of more than 100,000 km<sup>2</sup> covered by 11 Landsat scenes. We employ a multi-temporal approach with dry-season data from 7 epochs between 1990 to 2015. We use 0.5 m-pixel colour aerial photography to collect > 15,000 point samples for training and validating Random Forest classifications of (i) woody vegetation cover, (ii) other vegetation types (including grasses and agricultural land), and (iii) non-vegetated areas (i.e. urban areas and bare land). Overall accuracies for all years are around 80 % and overall kappa between 0.45 and 0.66. Woody vegetation covers a quarter of the Province and is the most accurately mapped class (balanced accuracies between 0.74-0.84 for the 7 epochs). There is a steady increase in woody vegetation cover over the 25-year-long period of study in the expense of the other vegetation types. We identify potential woody vegetation encroachment 'hot-spots' where mitigation measures might be required and thus provide a management tool for the prioritisation of such measures in degraded and food-insecure areas.

LANDSAT-BASED WOODY VEGETATION COVER MONITORING IN SOUTHERN AFRICAN SAVANNAHS

Abstract. Mapping woody cover over large areas can only be effectively achieved using remote sensing data and techniques. The longest continuously operating Earth-observation program, the Landsat series, is now freely-available as an atmospherically corrected, cloud masked surface reflectance product. The availability and length of the Landsat archive is thus an unparalleled Earth-observation resource, particularly for long-term change detection and monitoring. Here, we map and monitor woody vegetation cover in the Northwest Province of South Africa, an area of more than 100,000 km2 covered by 11 Landsat scenes. We employ a multi-temporal approach with dry-season data from 7 epochs between 1990 to 2015. We use 0.5 m-pixel colour aerial photography to collect > 15,000 point samples for training and validating Random Forest classifications of (i) woody vegetation cover, (ii) other vegetation types (including grasses and agricultural land), and (iii) non-vegetated areas (i.e. urban areas and bare land). Overall accuracies for all years are around 80 % and overall kappa between 0.45 and 0.66. Woody vegetation covers a quarter of the Province and is the most accurately mapped class (balanced accuracies between 0.74-0.84 for the 7 epochs). There is a steady increase in woody vegetation cover over the 25-year-long period of study in the expense of the other vegetation types. We identify potential woody vegetation encroachment 'hot-spots' where mitigation measures might be required and thus provide a management tool for the prioritisation of such measures in degraded and food-insecure areas.

Geomorphic and vegetation changes in a meandering dryland river regulated by a large dam, Sauce Grande River, Argentina

This paper investigates post-dam geomorphic and vegetation changes in the Sauce Grande River, a meandering dryland river impounded by a large water-conservation dam. As the dam impounds a river section with scarce influence of tributaries, sources for fresh water and sediment downstream are limited. Changes were inspected based on (i) analysis of historical photographs/imagery spanning pre- (1961) and post-dam (1981, 2004) channel conditions for two river segments located above and below the dam, and (ii) field survey of present channel conditions for a set of eight reference reaches along the river segments. Whilst the unregulated river exhibited active lateral migration with consequent adjustments of the channel shape and size, the river section below the dam was characterized by (i) marked planform stability (93 to 97%), and by (ii) vegetation encroachment leading to alternating yet localized contraction of the channel width (up to 30%). The present river displays a moribund, stable channel where (i) redistribution of sediment along the river course no longer occurs and (ii) channel forms constitute a remnant of a fluvial environment created before closing the dam, under conditions of higher energy. In addition to providing new information on the complex geomorphic response of dryland rivers to impoundment, this paper represents the very first geomorphic assessment of the regulated Sauce Grande and therefore provides an important platform to underpin further research assessing the geomorphic state of this highly regulated dryland river.

Eastern redcedar dendrochronology links hill prairie decline with decoupling from climatic control of fire regime and reduced fire frequency1

Abstract Human-caused decreased fire frequency allows a shift toward woody vegetation in North American grasslands. Since the 1960s, Midwest hill prairies have declined in area due to invasion by Juniperus virginiana L. (eastern redcedar) and encroachment of deciduous woody vegetation. This process has been thought to result from reduced fire frequency but supportive data have not been available. We used tree-ring analysis of J. virginiana to develop chronologies of tree growth and fire scars since the mid-1800s at Fults Hill Prairie Nature Preserve, Monroe County, IL, and used them to understand effects of historical climate and changing fire regimes on loss of prairie habitat. Tree-ring analysis indicated spread of J. virginiana from escarpment habitat into prairie after 1960. Linear regression of time series data from aerial photos projected 80–100% loss of prairie cover before the year 2040. The J. virginiana fire scar chronology revealed a < 2-yr median fire return interval between 1850 and 1959. The...

La pérdida de biodiversidad por abandono rural en el LTER Montseny cuantificada a partir del monitoreo de aves

Herrando, S., Anton, M., Brotons, Ll., Guinart, D. 2016. Biodiversity loss for rural abandonment in LTER Montseny measured by bird surveys. Ecosistemas 25(1): 58-64. Doi.: 10.7818/ECOS.2016.25-1.07 The abandonment of traditional farmland practices in the mountain areas of the Mediterranean Basin is producing a general vegetation encroachment and a decrease on open habitats. The protected mountain areas of the LTER (Long Term Ecological Research) network are privileged zones to study in detail this process by means of long-term monitoring projects. In the particular case of the nodule LTER Montseny the impact of afforestation on birds is been monitorised during more than a decade in the framework of the Catalan Common Bird Survey. This scheme has allowed developing indicators that determine the shifts in bird communities associated to the open and forest habitats of this natural park. In this work we used multispecies indicators based on the geometric means of yearly population indices to determine the change that, as a whole, the birds are undergoing in these environments. Results show that the impact of vegetation encroachment is noticeable in the populations of open-space species (44% population decrease between 2002 and 2014). Following these results, park managers, together with local socioeconomic stakeholders, are promoting practices to recover and improve open pastures

Fluvial Corridor Changes Over Time in Regulated and Non‐Regulated Rivers (Upper Esla River, NW Spain)

AbstractOver the last decades, rivers and fluvial corridors have been noticeably modified from their natural conditions. In general, damming and other in‐channel human interventions have been traditionally considered as the main drivers of change. However, recent studies highlight the influence of climate, hillslope and floodplain cover changes over fluvial corridor dynamics. The present study illustrates the channel morphology and riparian vegetation responses observed in three gravel bed rivers located in the Upper Esla River, north‐west of Spain. The entire study catchment was exposed to afforestation changes and farmland abandonment during the last decades, and two of the rivers are regulated by large dams. Analysis of historical orthophotos at different periods between 1956 and 2011 allowed quantifying channel narrowing, reduction of braiding index and vegetation encroachment along the three rivers. Field reconnaissance of landforms and vegetation structure along transects showed significant differences in species composition and age structure between the non‐regulated reach, where recruitment of Salicacea pioneer species existed, and the regulated reaches where mature and late‐seral species were much more abundant. These responses were consistent with reductions in mean annual discharge in all rivers and with flood disturbance decrease and summer minimum flow increase that were observed in the regulated rivers. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Fuzzy cognitive mapping for predicting hydromorphological responses to multiple pressures in rivers

Summary Different pressures often co‐occur in rivers and act simultaneously on important processes and variables. This complicates the diagnosis of hydromorphological alterations and hampers the design of effective restoration measures. Here, we present a conceptual meta‐analysis that aims at identifying the most relevant hydromorphological processes and variables controlling ecological degradation and restoration. For that purpose, we used fuzzy cognitive mapping based on conceptual schemes that were created according to 675 scientific peer‐reviewed river hydromorphology studies. A model generated from this approach predicts responses that are consistent with common understanding of the direct interactions between hydromorphological pressures, processes and variables. However, it also leads to new knowledge beyond traditional hydromorphological models by dealing with the complex interactions of hydromorphology, vegetation, water chemistry and thermal regime. Water flow dynamics appeared as the most important of all hydromorphological processes affected by simultaneously interacting pressures. Relevant processes such as vegetation encroachment and sediment entrainment are closely linked to water flow. Synthesis and applications. Our results demonstrate the relevance of natural flow regime rehabilitation for river management. Hence, we suggest focusing primarily on rehabilitating the natural flow regime before carrying out extensive habitat restoration works. This challenging target in river rehabilitation could strongly increase the success of additional habitat restoration.

Abundance of Invasive, Non-Native Riparian Herbs in Relation to River Regulation

River regulation is associated with vegetation encroachment and invasions of some non-native species in the semi-arid west. Shifts in the abundance of native and non-native woody riparian species are an interplay of regulation, life history traits and an array of flow and physical environmental variables. We sought to compare plant densities and per cent cover of several invasive species over two time periods in a paired river study, contrasting three different degrees of regulation along reaches of the Green and Yampa rivers in Colorado and Utah, USA. We censused patches of non-native plants and recorded per cent cover in quadrats along 171 river km. The upper Green (10.1 patches ha−1) had the highest invasive plant patch density followed by the lower Green (4.4 per ha) and the Yampa (3.3 per ha). Invasive species were present in 23%, 19% and 4% of sample quadrats, and an average of 0.28, 0.22 and 0.04 invasive species detected per square metre was recorded along the upper Green, lower Green and Yampa Rivers, respectively. Most species had significantly (p ≤ 0.02) higher percent cover on the upper Green than either or both the lower Green and the Yampa River. Whereas the less regulated river reaches maintain lower densities of invasive species than the most regulated reach, long-term persistence of this pattern is still in question as some species patches showed notable increases on the Yampa and lower Green Rivers from 2002–2005 to 2010–2011. Although invasion is enhanced by flow regulation, life history traits of some species suggest invasion is likely, regardless of flow regulation. Published 2015. This article is a U.S. Government work and is in the public domain in the USA

Diagnosing problems produced by flow regulation and other disturbances in Southern European Rivers: the Porma and Curueño Rivers (Duero Basin, NW Spain)

This research presents an analysis of river responses to flow regulation and other disturbances over time. The study was conducted in the Porma and Curueno rivers, using the hierarchical multi-scale process-based framework developed within the European REFORM Project. The characterisation of the rivers at the landscape unit, segment and reach scales under current and past conditions by different hydro-morphological indicators has provided a useful approach to (1) identify where and how main channel adjustments have occurred, (2) establish causal relationships at different scales and (3) discuss potential future scenarios and restoration strategies. Reduction of mean annual flow at the catchment scale has been observed and associated with forest expansion in the uplands. Channel narrowing, braiding reduction and riparian vegetation encroachment have occurred along both rivers, although with variable intensity among the reaches as a result of their landscape setting. Damming and flow regulation of the Porma River have been directly associated with locally accelerated narrowing, vertical bank profiles, the absence of bare gravel bars and no Salicaceae recruitment observed in certain reaches. The vertical bank profiles and the absence of in-channel bare gravel deposition forms are good indicators of sediment starvation downstream from the dam. The findings from this study suggest the importance of multi-scale approaches to assess the impacts of human-induced, short-term changes (e.g., flow regulation by dams and reservoirs) in the context of other disturbances at broader scales (e.g., climate and land cover changes) and their utility in the diagnosing problems and the proposal of restoration measures.

Predicting the future effectiveness of protected areas for bird conservation in Mediterranean ecosystems under climate change and novel fire regime scenarios

AbstractAimGlobal environmental changes challenge traditional conservation approaches based on the selection of static protected areas due to their limited ability to deal with the dynamic nature of driving forces relevant to biodiversity. The Natura 2000 network (N2000) constitutes a major milestone in biodiversity conservation in Europe, but the degree to which this static network will be able to reach its long‐term conservation objectives raises concern. We assessed the changes in the effectiveness of N2000 in a Mediterranean ecosystem between 2000 and 2050 under different combinations of climate and land cover change scenarios.LocationCatalonia, Spain.MethodsPotential distribution changes of several terrestrial bird species of conservation interest included in the European Union's Birds Directive were predicted within an ensemble‐forecasting framework that hierarchically integrated climate change and land cover change scenarios. Land cover changes were simulated using a spatially explicit fire‐succession model that integrates fire management strategies and vegetation encroachment after the abandonment of cultivated areas as the main drivers of landscape dynamics in Mediterranean ecosystems.ResultsOur results suggest that the amount of suitable habitats for the target species will strongly decrease both inside and outside N2000. However, the effectiveness of N2000 is expected to increase in the next decades because the amount of suitable habitats is predicted to decrease less inside than outside this network.Main conclusionsSuch predictions shed light on the key role that the current N2000 may play in the near future and emphasize the need for an integrative conservation perspective wherein agricultural, forest and fire management policies should be considered to effectively preserve key habitats for threatened birds in fire‐prone, highly dynamic Mediterranean ecosystems. Results also show the importance of considering landscape dynamics and the synergies between different driving forces when assessing the long‐term effectiveness of protected areas for biodiversity conservation.

Demographic responses of piping plovers to habitat creation on the Missouri river

ABSTRACTThe piping plover (Charadrius melodus) was listed under the United States Endangered Species Act (ESA) because of habitat loss and excessive predation. The Missouri River provides important habitat for the Great Plains population of the species, some of which nest and forage on river sandbars deposited naturally during high river flows. The United States Army Corps of Engineers (USACE) operates a series of dams on the river that affect water level and the size, number, distribution, and vegetative cover of these sandbars. As a federal agency, USACE is required by the ESA to have a program to conserve the piping plover, and is prohibited from engaging in activities that jeopardize the plover's continued existence. Pursuant to these obligations, the USACE implemented a habitat creation program on the Gavins Point Reach (GVP) and Lewis and Clark Lake (LCL) on the Missouri River from 2004 to 2011. This habitat creation provided an opportunity to study the piping plover's demographic response to several habitat types, and in particular to habitat creation. The goal of this study was to assess the effects of management on plovers using the Missouri River. We studied the changes in engineered and natural habitats, and compared the effects of newly engineered habitat versus naturally created habitat on plover demography during 2005–2011. To this end, we estimated changes in nesting habitat (open or sparsely vegetated dry sand) and examined the factors affecting nest success, chick survival from hatching to fledging, survival, and movement (between and among engineered and natural sandbars) of hatch‐year and adult birds, fidelity of plovers to the study area, and immigration of plovers into engineered habitat. We used demographic estimates to determine overall and habitat‐specific reproductive output and overall population growth rate. Under the assumption that plovers are habitat limited on the Missouri River, we predicted that they would respond positively to the creation of engineered habitat, that their demographic rates would be higher at those sites than on older, natural sandbars, and that over time, the rates would resemble those on older, natural habitats. Engineered sandbars had proportionally more plover nesting habitat than natural sandbars, but the proportion of nesting habitat decreased through vegetation encroachment and erosion as the sandbars aged. Adult and hatch‐year plovers immigrated to engineered sandbars, but immigration slowed as nesting density increased. Nesting density on engineered sandbars increased soon after sandbar construction, peaked 2–3 years later, and then declined to levels similar to those on older, natural sandbars. Birds that nested on engineered sandbars had higher nest success, and those nesting on LCL had higher chick survival than those that nested on GVP sandbars. Adult survival did not differ between engineered or natural habitat, but apparent survival was lower for birds that were not known to nest, indicating higher emigration or mortality rates for non‐nesters. Adult and hatch‐year plovers had high fidelity to the study area (&gt;60% for hatch‐year birds, &gt;90% for adults), and hatch‐year fidelity was highest (&gt;80%) when habitat availability increased. We estimated that given observed survival rates, the reproductive output needed for a stationary population was 1.25 chicks fledged per pair, a rate which was equaled or exceeded in 3 of 4 years on LCL, in 2 of 5 years on engineered sandbars on GVP, and in 1 of 5 years on natural sandbars on GVP. Our results support the hypothesis that piping plovers were habitat‐limited before and during the study. Although nest exclosure and predator control sometimes can improve reproductive output, we predict that these interventions will do little to increase population size unless there is additional habitat to capture enhanced productivity. Based on high fidelity rates and short distances between subsequent nesting attempts (median = 12 km for adults), we suggest that habitat construction be widely distributed within approximately 12 km of a source population to maximize the efficiency of the population‐building process. © 2015 The Wildlife Society.

An ecological perspective on floods in Canada

This review presents a summary of the influences of floods on river ecology, both instream and on the adjacent floodplain, mostly in a Canadian context. It emphasizes that ecological impacts and benefits can be highly dependent on flood-generation processes and their magnitude and timing. In Canada, floods can occur under open-water or ice-influenced river conditions. The ecological impacts of floods generated from ice jamming are particularly relevant in Canadian ecosystems due to the potentially higher water levels produced and suspended sediment concentrations that can be detrimental to instream aquatic habitat, but beneficial to floodplains. Large floods provide a major source of physical disturbance. Moderate floods with shorter return periods can be beneficial to aquatic habitats by providing woody debris that contributes to habitat complexity and diversity, by flushing fine sediments and by providing important food sources from terrestrial origins. Floods also influence water-quality variables such as sediment loads, metals and pH, which further influence river ecology. This review points out important links between floods and habitat connectivity and refugia, and the ability of aquatic resources to recover from flood disturbances. The floodplain vegetation also influences bank erosion and channel configuration, as well as many processes contributing to the river ecology, such as allochthonous inputs of carbon, preventing bank erosion, food-web dynamics and other effects. Many species of riparian trees are dependent on floods for reproduction, and floods can limit competitive encroachment of upland vegetation. Floods play a critical role in deltaic environments where high flows provide nutrient supplies and overflows maintain water balances within these environments. Two substantial factors that will likely influence future flood regimes in Canada are climate change and flow regulation. Future research should focus on enhancing our understanding of how floods affect river ecology, including under winter conditions, to better manage important natural resources.

Biogeomorphic responses to flow regulation and fine sediment supply in Mediterranean streams (the Guadalete River, southern Spain)

Summary Geomorphic responses to damming are primarily determined by the magnitude of sediment transport and sediment supply alteration and by the resulting change in the balance between the two. The former change is caused by alterations in the flow regime that are caused by reservoir operations. Flow regime changes also affect the distribution and amount of riparian vegetation that, in turn, also may enhance geomorphic responses. The latter change is caused by sediment trapping in reservoirs and by the magnitude of sediment supply from watersheds that are downstream from the dam. We examined the bio-geomorphic responses to flow regulation along a Mediterranean stream located in an agricultural area of southern Spain where there is significant fine sediment erosion from adjacent hillsides. We measured changes in active channel width and riparian corridor features during the last fifty years, based on field work and aerial photographs surveys from 1956, 1984 and 2004. We assessed the hydrological alteration and sediment delivery trends linked to dam operation and land use changes. Channel narrowing of nearly 75% and 30% reduction in total corridor area, together with average accretion rates of 0.045 m y −1 and vegetation encroachment with a 305% increase of mature forest occurred between 1956 and 2004. Causal linkages were attributed to the strong reduction of peak flows and transport capacity of flows, together with land-use changes that likely promoted increased fine sediment delivery. Vegetation overgrowth favored by increased summer flows could contribute to the narrowing and aggradation processes. Our results differ from channel responses to damming in Mediterranean regions dominated by steep gradient gravel bed rivers, and highlight the relevance of topography and land-use affecting the sediment regime downstream from the dams. We argue for a more holistic approach of water resources and land-use management at the catchment scale in order to understand the synergistic effects of dams, sediment supply, and vegetation growth, and to design appropriate flow regulation schemes to cope with irrigation demands and flood risk management in Mediterranean streams.