Linking fish trait responses to in‐stream habitat in reconstructed valley‐plugged stream reaches of the Coastal Plain,U.S.A.

Valley‐plug formation is a challenging consequence of stream channelization especially in physiographic regions with highly erodible soils. Upstream channel degradation and incision results in accelerated sediment delivery processes wherein downstream aggradation decreases stream power and creates sand‐clogged channels. Channel reconstruction is now meeting hydrogeomorphic goals related to valley‐plug remediation, yet there exists a need to understand how this practice also facilitates ecological restoration. We evaluated fish trait response to in‐stream habitat conditions in channelized, recently restored, and “least‐disturbed” reference reaches of Coastal Plain streams in West Tennessee. Restored reaches were ecologically similar to channelized reaches, having higher proportions of nest‐guarding omnivores that were correlated with higher percentages of pool habitats and lower wetted width:depth ratios compared to reference reaches. Reference reaches had higher proportions of fast‐water dwelling and specialized insectivores that were correlated with high abundance of large woody debris, high‐wetted width:depth ratios, and low percentages of pool habitats. We conclude that in‐stream habitats in reconstructed channels have yet to promote reach‐scale ecological restoration relative to fish assemblage organization because trait‐habitat associations were not similar to reference conditions. However, our results lend to the development of ecological restoration targets that can be incorporated in future channel reconstruction projects in valley‐plugged, channelized streams of the Coastal Plain.     

Treatment by glyphosate-based herbicide allowed recovering native species after Oxalis pes-caprae L. invasion: indications from a Mediterranean island

Biological invasions represent a global threat to biodiversity. Particular attention should be devoted to the management of alien plants, focusing on the opportunity to obtain a rapid response to invasion and restoration of the invaded areas. In this study we aimed to evaluate five different methods for controlling Oxalis pes-caprae, a well-known invasive plant native to South Africa, also focusing on the restoration of the native flora. We set an experiment on the island of Montecristo (central Mediterranean). Treatment methods varied from chemical to low risk methods, including manual removal, covering with mulching sheets, and foliar spraying with acetic acid (30% solution) and two different concentrations of glyphosate (3 and 5% solutions, respectively). The total cover of O. pes-caprae and of other native plants was sampled before treatments, and then several times during the subsequent year; while the plant species composition was sampled in late winter (March 2015–2016) and late spring (May 2015–2016). The use of glyphosate was found to be the only efficient control method, leading to a significant decrease in O. pes-caprae cover as well as to a recovery in native species cover and richness. The effect of the other control methods was negligible.     

Tools for <Emphasis Type="Italic">Carex</Emphasis> revegetation in freshwater wetlands: understanding dormancy loss and germination temperature requirements

Carex is a globally distributed genus with more than 2000 species worldwide and Carex species are the characteristic vegetation of sedge meadow wetlands. In the mid-continental United States, Carex species are dominant in natural freshwater wetlands yet are slow to recolonize hydrologically restored wetlands. To aid in Carex revegetation efforts, we determined the dormancy breaking and temperature germination requirements of 12 Carex species. Seeds were cold stratified at 5/1°C for 0–6 months and then incubated in light at 5/1°C, 14/1°C, 22/8°C, 27/15°C, or 35/30°C. We found that all Carex species produced conditionally dormant seeds. The optimal temperature for germination for all but three species was 27/15°C. As is the case in other species with physiological dormancy, cold stratification increased germination percentages, broadened the temperature range suitable for germination, and increased germination rates for most species, but the magnitude of the effects varied among species. Many species germinated to 80% at 27/15°C without cold stratification and at 22/8°C with ≤1 month of stratification but required much longer stratification (up to 6 months depending on the species) to germinate to 80% at 14/1°C and 35/30°C. Our findings illustrate how a stratification pretreatment can greatly benefit Carex seed sowing efforts by triggering rapid germination to higher percentages. We recommend that cold stratification be targeted towards species with strong dormancy or used across a wider range of species when seed supplies for restoration are limiting. For Carex revegetation, establishing Carex canopies rapidly may help to prevent the invasion of undesirable species such as Phalaris arundinacea.     

Positive Feedbacks in Seagrass Ecosystems: Implications for Success in Conservation and Restoration

Abstract Seagrasses are threatened by human activity in many locations around the world. Their decline is often characterized by sudden ecosystem collapse from a vegetated to a bare state. In the 1930s, such a dramatic event happened in the Dutch Wadden Sea. Before the shift, large seagrass beds (Zostera marina) were present in this area. After the construction of a large dam and an incidence of the “wasting disease” in the early 1930s, these meadows became virtually extinct and never recovered despite restoration attempts. We investigated whether this shift could be explained as a critical transition between alternative stable states, and whether the lack of recovery could be due to the high resilience of the new turbid state. We analyzed the depth distribution of the historical meadows, a long-term dataset of key factors determining turbidity and a minimal model based on these data. Results demonstrate that recovery was impossible because turbidity related to suspended sediment was too high, probably because turbidity was no longer reduced by seagrass itself. Model simulations on the positive feedback suggest indeed the robust occurrence of alternative stable states and a high resilience of the current turbid state. As positive feedbacks are common in seagrasses, our findings may explain both the worldwide observed collapses and the low success rate of restoration attempts of seagrass habitats. Therefore, appreciation of ecosystem resilience may be crucial in seagrass ecosystem management.     

Genetic effects of habitat restoration in the Laurentian Great Lakes: an assessment of lake sturgeon origin and genetic diversity

Lake sturgeon (Acipenser fulvescens) have experienced significant habitat loss, resulting in reduced population sizes. Three artificial reefs were built in the Huron‐Erie corridor in the Great Lakes to replace lost spawning habitat. Genetic data were collected to determine the source and numbers of adult lake sturgeon spawning on the reefs and to determine if the founder effect resulted in reduced genetic diversity. DNA was extracted from larval tail clips and 12 microsatellite loci were amplified. Larval genotypes were then compared to 22 previously studied spawning lake sturgeon populations in the Great Lakes to determine the source of the parental population. The effective number of breeders (N_b) was calculated for each reef cohort. The larval genotypes were then compared to the source population to determine if there were any losses in genetic diversity that are indicative of the founder effect. The St. Clair and Detroit River adult populations were found to be the source parental population for the larvae collected on all three artificial reefs. There were large numbers of contributing adults relative to the number of sampled larvae. There was no significant difference between levels of genetic diversity in the source population and larval samples from the artificial reefs; however, there is some evidence for a genetic bottleneck in the reef populations likely due to the founder effect. Habitat restoration in the Huron‐Erie corridor is likely resulting in increased habitat for the large lake sturgeon population in the system and in maintenance of the population's genetic diversity.     

Do not neglect surroundings in restoration of disturbed sites

We examined the influence of surroundings, i.e. proximity effects, on the course of spontaneous vegetation succession using two data sets. In the first data set, we tested the effects of surrounding vegetation (woodlands, wetlands, grasslands, and synanthropic) on succession in various disturbed habitats in the Czech Republic by comparing successional sites with more natural vegetation within 100 m and at 1 km from each site. The habitats included old fields, gravel‐sand pits, spoil heaps from black coal mining, industrially extracted peatlands, and acidic stone quarries. We found that, with the exception of wetlands, the influence of the vegetation types on seral vegetation was nearly always significant using marginal and partial Canonical Correspondence Analyses. In the second data set, which included 27 limestone quarries, we compared species lists outside (up to 100 m apart) and inside the quarries using Detrended Correspondence Analysis and the Sørensen similarity index. We found much higher species similarity between outside and inside particular limestone quarries than among the quarries themselves and among their surroundings, which also indicates that the seral vegetation is decisively influenced by the surroundings. We argue that restoration ecologists should carefully consider the nature of the surroundings of disturbed sites because of its profound impact on restoration processes. They should conduct inventories and prescribe some restoration measures not only inside a restored site, but also in its surroundings.     

Density‐dependent effects on initial growth of a branching coral under restoration

Coral reef restoration aims to help threatened coral ecosystems recover from recent severe declines. Here we address whether coral fragments should be out‐planted individually or in larger aggregations. Theory suggests alternative possible outcomes: whereas out‐plants within aggregations might suffer from heightened negative interactions with neighbors (e.g. competition for space), they may alternatively benefit from positive interactions with neighbors (e.g. buffering wave disturbances). On a degraded reef in the Caribbean (St. Croix, USVI), using out‐plants of the critically endangered staghorn coral Acropora cervicornis, we experimentally tested how aggregation density (1–20 out‐planted coral fragments spaced at approximately 5 cm) influenced initial coral growth (over 3 months). Coral growth declined as a function of aggregation size, and out‐plants within larger aggregations had fewer and shorter secondary branches on average, indicative of horizontal competition for space. Our results therefore suggest that wide spacing of individuals will maximize the initial growth of out‐planted branching corals.     

Plant community response following the removal of the invasive Lupinus arboreus in a coastal dune system

The removal of invasive species is common in restoration projects, yet the long‐term effects of pest management programs are seldom assessed. We present results of a long‐term program to remove the invasive species Lupinus arboreus (lupin) from sand dunes in New Zealand. We evaluate the response of plant communities to lupin removal, by comparing total plant cover, the cover of non‐native and native plant species, and species richness between sand dune sites where lupin removal has occurred, not occurred, and where lupin has never been present. Neither lupin presence nor removal had a significant impact on the foredune environment. Following removal, total and other non‐native plant cover remained higher, and the cover of several native sand dune species remained lower compared with uninvaded sites in the deflation and backdune environments. These changes can be attributed to persistent effects associated with the invasion of lupin, but have also developed in response to lupin removal. The results of this study have implications for restoration projects in sand dunes. Pest management alone is unlikely to be sufficient to restore plant communities. Given the difficulties in restoring plant communities once an invasive species has established, managers should prioritize actions to prevent the spread of invasive species into uninvaded areas of sand dunes. Finally, the response to lupin invasion and removal differed between dune habitats. This highlights the importance of tailoring a pest management program to restoration goals by, for example, prioritizing areas in which the impacts of the invading species are greatest.     

Scale‐dependent effects of forest restoration on Neotropical fruit bats

Neotropical fruit bats (family Phyllostomidae) facilitate forest regeneration on degraded lands by dispersing shrub and tree seeds. Accordingly, if fruit bats can be attracted to restoration sites, seed dispersal could be enhanced. We surveyed bat communities at 10 sites in southern Costa Rica to evaluate whether restoration treatments attracted more fruit bats if trees were planted on degraded farmlands in plantations or island configurations versus natural regeneration. We also compared the relative influence of tree cover at local and landscape spatial scales on bat abundances. We captured 68% more fruit bat individuals in tree plantations as in controls, whereas tree island plots were intermediate. Bat activity also responded to landscape tree cover within a 200‐m radius of restoration plots, with greater abundance but lower species richness in deforested landscapes. Fruit bat captures in controls and tree island plots declined with increasing landscape tree cover, but captures in plantations were relatively constant. Individual species responded differentially to tree cover measured at different spatial scales. We attribute restoration effects primarily to habitat structure rather than food resources because no planted trees produced fruits regularly eaten by bats. The magnitude of tree planting effects on fruit bats was less than previous studies have found for frugivorous birds, suggesting that bats may play a particularly important role in dispersing seeds in heavily deforested and naturally regenerating areas. Nonetheless, our results show that larger tree plantations in more intact landscapes are more likely to attract diverse fruit bats, potentially enhancing seed dispersal.     

Culvert replacements: improvement of stream biotic integrity?

Roads and associated stream crossings can modify and degrade natural hydrology of a system and alter organism movement. Culvert replacement and stream crossing improvements are extremely common and often done with the intent to improve biotic integrity of a system. We evaluated 3 sites where poor road‐stream crossings were improved by replacing improper culverts with full‐span natural bottom structures. We used a before‐after‐control‐impact paired series (BACIPS) design to determine if there was evidence of associated improvement in biotic integrity of the stream communities. Biotic integrity indices developed for coldwater fish and macroinvertebrates in the Northern Lakes and Forests Ecoregion were used to estimate responses of the biotic communities adjacent to culvert replacements. With poor to fair fish and macroinvertebrate communities prior to culvert replacement, we predicted communities would show improvement into the good range of the indices. With 2–4 years of pre‐data and 3–5 years of postdata, we were not able to detect improvements in overall biotic integrity utilizing fish or macroinvertebrate index scores. Road crossing improvements may synergistically restore stream ecosystems, restore natural sediment dynamics, and improve passage; however, in these cases local biotic integrity scores were not significantly improved. Culvert replacements are often developed based on the potential, or the perception, that they will restore ecological integrity and biological communities or fisheries; however, as restoration practitioners, researchers, and managers, assessing these claims and learning from prior restoration attempts is necessary.