Climate and density influence annual survival and movement in a migratory songbird

Assessing the drivers of survival across the annual cycle is important for understanding when and how population limitation occurs in migratory animals. Density‐dependent population regulation can occur during breeding and nonbreeding periods, and large‐scale climate cycles can also affect survival throughout the annual cycle via their effects on local weather and vegetation productivity. Most studies of survival use mark–recapture techniques to estimate apparent survival, but true survival rates remain obscured due to unknown rates of permanent emigration. This is especially problematic when assessing annual survival of migratory birds, whose movement between breeding attempts, or breeding dispersal, can be substantial. We used a multistate approach to examine drivers of annual survival and one component of breeding dispersal (habitat‐specific movements) in a population of American redstarts (Setophaga ruticilla) over 11 years in two adjacent habitat types. Annual survival displayed a curvilinear relation to the Southern Oscillation Index, with lower survival during La Niña and El Niño conditions. Although redstart density had no impact on survival, habitat‐specific density influenced local movements between habitat types, with redstarts being less likely to disperse from their previous year's breeding habitat as density within that habitat increased. This finding was strongest in males and may be explained by conspecific attraction influencing settlement decisions. Survival was lowest in young males, but movement was highest in this group, indicating that apparent survival rates were likely biased low due to permanent emigration. Our findings demonstrate the utility of examining breeding dispersal in mark–recapture studies and complement recent work using spatially explicit models of dispersal probability to obtain greater accuracy in survival estimates.     

Ecological differentiation between the Sardinian endemic Maniola nurag and the pan-European M. jurtina

Recently refined evolutionary theories have highlighted that ecological interactions and environmental gradients can play a major role in speciation. This paper reports on a 3‐year field study, in which the ecology of two congeneric butterfly species was used to explore and compare the environmental factors determining their spatial distribution. These data are discussed in the context of possible speciation scenarios between the Sardinian populations of Maniola nurag and M. jurtina. M. nurag is endemic to the island of Sardinia, while M. jurtina is widespread over Europe. In Sardinia, the two species are locally sympatric. Mark–release–recapture experiments were combined with measures of environmental variables in 15 1‐ha plots, established in areas of potential habitat for the butterflies. Constrained linear models were parameterized from mark–recapture data to estimate both individual (survival and capture probabilities) and population (population size and recruitment) parameters. The two species had similar demography, movement patterns, life history, and behaviour. Population sizes developed in a parabolic fashion from beginning to end of the flight season. Differences included local population size, adult phenology, and habitat requirements. Long‐distance movements larger than 1.5 km were observed, suggesting a substantial amount of gene‐flow between populations of the endemic as well as the widespread species. Multivariate analyses revealed four main environmental gradients responsible for the abundance of the butterflies in an area. Both species responded similarly to environmental variables. However, each species’s abundance was correlated with a different environmental gradient determined by vegetation cover and structure. When sympatric, the two species responded to subtle differences in microhabitat structure. This might originally have induced their divergence. This study is an example of how empirical field data on population dynamics, dispersal, and habitat characteristics of two sympatric congeners can further our understanding of how species differentiate despite existing gene‐flow. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89 , 561–574.     

Relationship between topographic heterogeneity and vegetation patterns in a Californian salt marsh

Questions: Are species richness and species abundances higher in the presence of tidal creeks? Do species richness and species abundances vary with plot size? Location: Intertidal plain of Volcano Marsh, Bahia de San Quintin, Mexico. Methods: We analysed vegetation patterns in large areas (cells) with tidal creeks (+creek) and without (‐creek). We surveyed vegetation cover, microtopography, habitat type, and distance to creeks in nested plots of five sizes, 0.1, 0.25, 1, 2.5, and 10 m². Results: Species richness, frequency, cover, and assemblages differed between ±creek cells. Richness tended to be higher in +creek cells, and cover and frequency of individual species differed significantly between ±creek cells. We found consistent patterns in vegetation structure across plot sizes. We encountered 13 species that occurred in 188 unique assemblages. The most common assemblage had six species: Batis maritima, Frankenia salina, Salicornia bigelovii, S. virginica, Salicornia spec. and Triglochin concinna. This assemblage occurred in ±creek cells and at all spatial scales. Of the most common assemblages all but one were composed of multiple species (3–9 species/plot). Conclusions: The persistence of vegetation patterns across a 100‐fold range in spatial scale suggests that similar environmental factors operate broadly to determine species establishment and persistence. Differences in assemblage composition result from variation of frequency and cover of marsh plain species, particularly Suaeda esteroa and Monanthochloe littoralis. The recommendation for restoration of Californian salt marshes is to target (and plant) multi‐species assemblages, not monocultures.     

Aboveground and Belowground Impacts Following Removal of the Invasive Species Baby's Breath (Gypsophila paniculata) on Lake Michigan Sand Dunes

The removal of invasive species is often one of the first steps in restoring degraded habitats. However, studies evaluating effectiveness of invasive species removal are often limited in spatial and temporal scale, and lack evaluation of both aboveground and belowground effects on diversity and key processes. In this study, we present results of a large 3‐year removal effort of the invasive species, Gypsophila paniculata, on sand dunes in northwest Michigan (USA). We measured G. paniculata abundance, plant species richness, plant community diversity, non‐native plant cover, abundance of Cirsium pitcheri (a federally threatened species endemic to this habitat), sand movement, arbuscular mycorrhizal spore abundance, and soil nutrients in fifteen 1000 m² plots yearly from 2007 to 2010 in order to evaluate the effectiveness of manual removal of this species on dune restoration. Gypsophila paniculata cover was greatly reduced by management, but was not entirely eliminated from the area. Removal of G. paniculata shifted plant community composition to more closely resemble target reference plant communities but had no effect on total plant diversity, C. pitcheri abundance, or other non‐native plant cover. Soil properties were generally unaffected by G. paniculata invasion or removal. The outlook is good for this restoration, as other non‐native species do not appear to be staging a “secondary” invasion of this habitat. However, the successional nature of sand dunes means that they are already highly invasible, stressing the need for regular monitoring to ensure that restoration progresses.     

Dynamic landscapes shape post‐wildfire recolonisation and genetic structure of the endangered Hermes copper (Lycaena hermes) butterfly

1. The coastal sage scrub vegetation community experiences frequent fires, so the long‐term survival of species depends on the rate of recolonisations exceeding the rate of local extinctions. Recolonisation of these post‐wildfire habitats probably requires long‐distance dispersal events. These movements can also counter detrimental impacts associated with inbreeding. 2. The Hermes copper (Lycaena hermes) is an extremely rare butterfly inhabiting coastal sage scrub adjacent to San Diego, California, USA. Habitat loss due to urbanisation and impacts of recent wildfires has greatly restricted its range, prompting the United States Fish and Wildlife Service to list the Hermes copper as a Candidate Species in 2011. 3. Surveys for Hermes copper butterflies in 2010–2013 documented only two recolonisation events following wildfires in 2003 and 2007. Larger populations were readily detected each year, but detection of smaller populations was inconsistent. 4. Amplified fragment length polymorphism was used to identify potential genetic discontinuities within this species across the landscape. Results indicated that movements across much of the landscape were possible historically. However, individuals from three peripheral populations exhibited a higher degree of differentiation, suggesting more restricted dispersal in these regions. 5. From the results, it can be concluded that historically Hermes copper butterflies were able to move among habitat patches prior to recent changes in the landscape. However, low post‐fire recolonisation rates suggest limited contemporary dispersal, probably due to recent habitat fragmentation. This fragmentation is a relatively new event, as the human population in San Diego County experienced substantial growth in the late 20th Century.     

Potential metapopulation structure and the effects of habitat quality on population size of the endangered False Ringlet butterfly

The False Ringlet (Coenonympha oedippus) is a European butterfly species, endangered due to the severe loss and fragmentation of its habitat. In Hungary, two remaining populations of the butterfly occur in lowland Purple Moorgrass meadows. We studied a metapopulation occupying twelve habitat patches in Central Hungary. Our aim was to reveal what measures of habitat quality affect population size and density of this metapopulation, estimate dispersal parameters and describe phenology of subpopulations. Local population sizes and dispersal parameters were estimated from an extensive mark–release–recapture dataset, while habitat quality was characterized by groundwater level, cover of grass tussocks, bush cover, height of vegetation and grass litter at each habitat patch. The estimated size of the metapopulation was more than 3,000 individuals. We estimated a low dispersal capacity, especially for females, indicating a very low probability of (re)colonization. Butterfly abundance and density in local populations increased with higher grass litter, lower groundwater level and larger area covered by tussocks. We suppose that these environmental factors affect butterfly abundance by determining the microclimatic conditions for both larvae and adult butterflies. Our results suggest that the long-term preservation of the studied metapopulation needs the maintenance of high quality habitat patches by appropriate mowing regime and water regulation. Management also should facilitate dispersal to strengthen metapopulation structure with creating stepping-stones or gradually increase habitat quality in present matrix.     

Variation in fine‐scale genetic structure and local dispersal patterns between peripheral populations of a South American passerine bird

The distribution of suitable habitat influences natal and breeding dispersal at small spatial scales, resulting in strong microgeographic genetic structure. Although environmental variation can promote interpopulation differences in dispersal behavior and local spatial patterns, the effects of distinct ecological conditions on within‐species variation in dispersal strategies and in fine‐scale genetic structure remain poorly understood. We studied local dispersal and fine‐scale genetic structure in the thorn‐tailed rayadito (Aphrastura spinicauda), a South American bird that breeds along a wide latitudinal gradient. We combine capture‐mark‐recapture data from eight breeding seasons and molecular genetics to compare two peripheral populations with contrasting environments in Chile: Navarino Island, a continuous and low density habitat, and Fray Jorge National Park, a fragmented, densely populated and more stressful environment. Natal dispersal showed no sex bias in Navarino but was female‐biased in the more dense population in Fray Jorge. In the latter, male movements were restricted, and some birds seemed to skip breeding in their first year, suggesting habitat saturation. Breeding dispersal was limited in both populations, with males being more philopatric than females. Spatial genetic autocorrelation analyzes using 13 polymorphic microsatellite loci confirmed the observed dispersal patterns: a fine‐scale genetic structure was only detectable for males in Fray Jorge for distances up to 450 m. Furthermore, two‐dimensional autocorrelation analyzes and estimates of genetic relatedness indicated that related males tended to be spatially clustered in this population. Our study shows evidence for context‐dependent variation in natal dispersal and corresponding local genetic structure in peripheral populations of this bird. It seems likely that the costs of dispersal are higher in the fragmented and higher density environment in Fray Jorge, particularly for males. The observed differences in microgeographic genetic structure for rayaditos might reflect the genetic consequences of population‐specific responses to contrasting environmental pressures near the range limits of its distribution.     

Habitat use and dispersal characteristic by <Emphasis Type="Italic">Stethophyma grossum</Emphasis>: the role of habitat isolation and stable habitat conditions towards low dispersal

Species in a highly fragmented environment, such as the intensively used agricultural landscapes of Europe, are expected to be in danger of extinction. We hypothesize according to Kisdi’s theory (Am Nat 159:579–596, 2002) that species in fragmented landscapes with isolated habitats in general tend to possess low dispersal. In order to verify this hypothesis we studied the movement patterns of Stethophyma grossum, a hygrophilous species of wetlands, by mark–release–recapture techniques in a landscape with scattered suitable habitats over 3 years. The study focused on the major population in this landscape (site #1) as dispersal behaviour was assumed to be greatest. Actually, marked individuals of S. grossum were never found in any further suitable habitats in close vicinity to site #1. Despite that the peatland meadow of study site #1 was all over covered with homogenous vegetation only 6% (1.8 ha) of the whole area (30 ha) were occupied by S. grossum. The mean recapture rate over 3 years amounted to 39% with no significant differences between males and females. Both covered little distances within their mean range size of 1.8 ha; the median distances were 36.91 m for males and 26.65 m for females. We confirm the hypothesis that sub-populations of species in longstanding naturally isolated habitats, which habitat conditions have been stable; evolved low dispersal with little movements which are routine movements to find mating partners or food.     

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.     

If you build it,will they come? Use of restored dunes by beach mice

Restoration of coastal habitat fragmented, degraded, or destroyed by development and climate‐related processes such as sea level rise and storm surge usually involves planting native plants to restore habitat structure, but whether and how restored areas benefit taxa other than plants is rarely reported. Installing restoration plantings is one method used to build habitat such as beach dunes where dunes have been lost, potentially creating habitat for dune‐dependent species. We compared use of natural vegetated dunes, open sand gaps, and restoration plantings (habitat treatment) by Perdido Key beach mice (Peromyscus polionotus trissyllepsis) over 3 years using tracking tubes to assess the value of restoration plantings for beach mice. Tubes were monitored in two seasons (early and mid‐summer), and under new and full moon conditions. Mice used restoration plantings less than natural vegetated dunes but more than open sand gaps, which suggests restoration plantings may facilitate movement of mice across fragmented areas. Both season and moon phase influenced the effect of habitat treatment, interactions which may be attributable to perceived risk associated with movement under a combination of different conditions of ambient light, vegetation cover, and habitat novelty. Our results show restoration plantings provide habitat for movement and foraging, and may ameliorate some consequences of sea level rise and storms for beach mice and potentially other dune‐dependent species into the future.     

Dominant plant species shape soil bacterial community in semiarid sandy land of northern China

Plant species affect soil bacterial diversity and compositions. However, little is known about the role of dominant plant species in shaping the soil bacterial community during the restoration of sandy grasslands in Horqin Sandy Land, northern China. We established a mesocosm pots experiment to investigate short‐term responses of soil bacterial diversity and composition, and the related soil properties in degraded soils without vegetation (bare sand as the control, CK) to restoration with five plant species that dominate across restoration stages: Agriophyllum squarrosum (AS), Artemisia halodendron (AH), Setaria viridis (SV), Chenopodium acuminatum (CA), and Corispermum macrocarpum (CM). We used redundancy analysis (RDA) to analyze the association between soil bacterial composition and soil properties in different plant species. Our results indicated that soil bacterial diversity was significantly lower in vegetated soils independent of plant species than in the CK. Specifically, soil bacterial species richness and diversity were lower under the shrub AH and the herbaceous plants AS, SV, and CA, and soil bacterial abundance was lower under AH compared with the CK. A field investigation confirmed the same trends where soil bacteria diversity was lower under AS and AH than in bare sand. The high‐sequence annotation analysis showed that Proteobacteria, Actinobacteria, and Bacteroidetes were the most common phyla in sandy land irrespective of soil plant cover. The OTUs (operational taxonomic units) indicated that some bacterial species were specific to the host plants. Relative to bare sand (CK), soils with vegetative cover exhibited lower soil water content and temperature, and higher soil carbon and nitrogen contents. The RDA result indicated that, in addition to plant species, soil water and nitrogen contents were the most important factors shaping soil bacterial composition in semiarid sandy land. Our study from the pot and field investigations clearly demonstrated that planting dominant species in bare sand impacts bacterial diversity. In semiarid ecosystems, changes in the dominant plant species during vegetation restoration efforts can affect the soil bacterial diversity and composition through the direct effects of plants and the indirect effects of soil properties that are driven by plant species.     

The Role of Habitat and Herbivory on the Restoration of Tidal Freshwater Submerged Aquatic Vegetation Populations

Submerged aquatic vegetation (SAV) has declined precipitously throughout coastal areas and its reestablishment has long been an important objective of coastal management. We investigated restoration success of Vallisneria americana (wild celery) using seeds, seed pods, and whole shoot transplants at sites in the Chesapeake Bay in the United States where historical aerial photography has indicated that the species once grew. In addition, we evaluated habitat conditions and established herbivore exclosures to assess the impacts of water quality, sediment conditions, and grazers on planting success. Whole shoot transplants resulted in the most rapid cover of the bottom, but required greater planting effort. Direct dispersal of individual seeds was generally more successful than dispersal of intact seed pods, resulting in more rapid initial seedling growth. Overall, 100% bottom cover of whole shoot transplant plots could be reached in approximately 3 years, despite light attenuation coefficients (K_d) of 3.0 to 4.0. Transplants at shallow depths (<0.5 m) were able to rapidly grow and elongate to the surface at mid‐to‐low tidal heights. Transplants were successful in both muddy (8% organic) and sandy (<2%) substrates. Using mesh exclosures to protect the plants from herbivory was critical to restoration success. Although water quality and other habitat conditions are important for SAV growth and survival, restoration in the unvegetated areas studied here was limited by grazing of initial recruits. The establishment of protected founder colonies of sufficient size to withstand initial grazing pressures may be required to reestablish SAV in similar areas.     

Mark–recapture on large spatial scale reveals long distance dispersal in the Marsh Fritillary,Euphydryas aurinia

1. Long distance dispersal (LDD), or movements far beyond the occupied habitat borders, maintains the integrity of metapopulations in fragmented landscapes. Recent studies on butterflies increasingly reveal that LDD exists even in species that were long regarded as sedentary. Mark–recapture (MR) studies covering larger study areas typically reveal movements among distant colonies. 2. We studied dispersal of the EU‐protected, regionally endangered Euphydryas aurinia Rottemburg butterfly in the Czech Republic, using two complementary MR approaches. The single system study was carried out for eight seasons within 30 habitat patches covering 28 ha. The multiple populations study was carried out for a single season, but covering almost all Czech colonies of the species (82 colonies, 110 distinct patches, total area 324 ha within ca 1500 km²). 3. Single system mean lifetime movements were consistently higher for males, but slopes of dispersal kernel power functions were shallower for females, implying that higher proportions of females crossed distances of several kilometres. 4. The multiple populations study allowed detection of 51 lifetime movements exceeding 5 km (41 males, 10 females) and 14 movements exceeding 10 km (13 males, 1 female). Both mean lifetime movements and slopes of the dispersal kernels varied among systems, with no consistent pattern between sexes. All Czech Republic populations are within 0.1% movement probability of both sexes, whereas 1% movement probability delimits three separate management units. 5. Dispersal predictions from local data underestimate total mobility, warning against the use of local MR data for extrapolating long‐distance movements. Local dispersal data, however, remain useful for analysing finer details of insect mobility.     

Spontaneous vegetation dynamics and restoration prospects for limestone quarries in Lebanon

Abstract. In terms of restoration planning, the analysis of natural regeneration processes represents a valuable starting point for the selection of suitable species to be used. This paper aims to identify colonizing key species among the pioneer vegetation of limestone quarries in Lebanon, to identify potential restoration strategies in terms of reconstitution of the pre‐mining vegetation cover. Characteristics of the major ground colonizers after disturbance were identified in a representative quarry in the thermo‐Mediterranean biozone. The floristic inventories resulted in a matrix of cover values of 107 species × 14 plots. Correspondence analyses were used to pinpoint similarities in the distribution of key species among the different environmental characteristics of sites. The main results reveal a heterogeneous floristic composition along the regeneration gradient, where annual R‐strategy taxa such as Inula viscosa and Ainsworthia cordata dominate on very perturbed and degraded sites. Less degraded areas within the quarry were rich in herbaceous perennial or shrub species such as Geranium dissectum, Stachys distans, Salvia triloba and Ptilostemon chamaepeuce. On relatively non‐degraded areas woody and shrub perennials such as Pinus brutia, Pistacia palaestina and Quercus calliprinos dominate, along with less stress tolerant taxa such as Arbutus andrachne and Cistus creticus. Species to be used in restoration projects should be chosen from among the local vegetation, according to frequency of occurrence during the whole succession process which will reflect their adaptability to local conditions and their relevance to restoration objectives.     

Restoring Sage‐grouse nesting habitat through removal of early successional conifer

Conifer woodlands have expanded into sagebrush (Artemisia spp.) ecosystems and degrade habitat for sagebrush obligate species such as the Greater Sage‐grouse (Centrocercus urophasianus). Conifer management is increasing despite a lack of empirical evidence assessing outcomes to grouse and their habitat. Although assessments of vegetation recovery after conifer removal are common, comparisons of successional trends with habitat guidelines or actual data on habitat used by sage‐grouse is lacking. We assessed impacts of conifer encroachment on vegetation characteristics known to be important for sage‐grouse nesting. Using a controlled repeated measures design, we then evaluated vegetation changes for 3 years after conifer removal. We compared these results to data from 356 local sage‐grouse nests, rangewide nesting habitat estimates, and published habitat guidelines. We measured negative effects of conifer cover on many characteristics important for sage‐grouse nesting habitat including percent cover of forbs, grasses, and shrubs, and species richness of forbs and shrubs. In untreated habitat, herbaceous vegetation cover was slightly below the cover at local nest sites, while shrub cover and sagebrush cover were well below cover at the nest sites. Following conifer removal, we measured increases in herbaceous vegetation, primarily grasses, and sagebrush height. Our results indicate that conifer abundance can decrease habitat suitability for nesting sage‐grouse. Additionally, conifer removal can improve habitat suitability for nesting sage‐grouse within 3 years, and trajectories indicate that the habitat may continue to improve in the near future.     

Plant recovery techniques do not ensure biological soil‐crust recovery after gypsum quarrying: a call for active restoration

Biological soil crusts (biocrusts) are a key component of dryland ecosystems worldwide. However, large extensions of biocrusts are disturbed by human activities, gypsum quarry being an outstanding example. Restoration techniques applied have offered satisfactory results for vascular plants but they could greatly differ in promoting biocrust recovery. A basic question remains unaddressed: can measures for plant recovery accelerate or promote the recovery of biological crusts? We have examined eight different situations: undisturbed natural habitat, five treatments with no restoration measures (overgrazed area, abandoned quarry, topsoil removal from natural habitat, and two areas filled with gypsum mining spoil), and 2 areas receiving restoration measures (manual sowing and hydroseeding). We took 40 soil cores to determine cover of lichen, moss, and cyanobacteria. Biocrust richness and cover were higher in the undisturbed habitat, with remarkable differences for the different components among treatments. Cyanobacteria were well represented in all the cores (restored and non‐restored). Mosses were promoted the most by hydroseeding. Lichen cover was remarkably higher in undisturbed samples, very low in the quarry abandoned in 1992, and 0 in the rest. Complete spontaneous recovery of biocrusts was inefficient in the 25‐year period examined. Plant restoration measures could speed up its recovery comparing with non‐restored areas. Cyanobacteria and mosses can spontaneously recover fairly well. However, promoting them would accelerate the appearance of lichen. For lichen, inoculation or translocation of lichen thalli might be proposed. Therefore, our results call for the inclusion of active restoration measures of biocrust components in recovery plans, especially for lichens.     

Recovery of Foredune and Blowout Habitats in a Freshwater Dune Following Removal of Invasive Austrian Pine (Pinus nigra)

Invasive species removal is an important first step toward restoring invaded ecosystems; however, restoration following removal may be hindered by (1) unintended consequences of management, such as habitat destabilization, and/or (2) legacy effects of the invader, such as persistent alterations of soil structure or plant community composition. During 1956–1972, approximately 26,000 individuals of the non‐native pine, Pinus nigra, were planted into multiple freshwater sand dune habitats as a stabilization measure on the eastern shore of Lake Michigan in Allegan County, MI, U.S.A. From 2004 to 2010, we evaluated the recovery of foredune and blowout habitats following P. nigra removal in 2003–2005. We compared sand movement and plant community structure, composition, and richness between removal and control sites over the 6 years following pine removal. In addition, we evaluated the impact of litter removal on recolonization of native graminoids in foredunes. Sand movement patterns never differed between removal and control sites in foredunes; however, accumulation was more common in removal sites in blowouts 1 and 6 years following pine removal. Vegetation cover in removal sites became indistinguishable from control sites in both foredunes and blowouts, but species richness for both forb and woody species was higher in removal sites in blowouts. Removal sites in both foredunes and blowouts had higher cover by forbs and lower cover by graminoids. Pine litter did not inhibit recolonization of foredunes by native graminoids. These results suggest that high disturbance habitats, such as sand dunes, have the potential to recover from invasion if the mechanism of disturbance is restored and pioneer species are present to recolonize the system.     

Spontaneous and initiated succession on unvegetated slopes in the abandoned lignite‐mining area of Goitsche,Germany

Abstract. In this study, we examined the colonization of unvegetated, dry slopes in the lignite‐mining area of Goitsche, Germany. The plots, characterized by different habitat conditions, were studied from 1994–2000. The vegetation development on treated plots was compared to untreated plots showing spontaneous succession. For initial treatments we used fresh plant clippings from a species‐rich sandy grassland (Armerion elongatae) mowed at the end of July. Soil seed bank samples, taken at the beginning of the experiments and cultivated for 18 months, confirmed that the vegetation development on the slopes started with primary succession. Because seed rain is considered to be an important factor in primary succession, we also studied the diaspore input during the first year. The hospitable Quaternary substrate of Site I (pH = 4.1–4.7, 92 % sand) supports fast vegetation development on treated and untreated plots. On treated plots, we have identified plant assemblages similar to initial stages of the Armerion elongatae community. On control plots, Coryne‐phorion communities have established spontaneously. At Site II (mixed Quaternary and Tertiary substrate, pH = 3.0–3.5,40 % sand) the total cover and number of psammophytic species was low. Treated plots showed development towards ruderal sandy grassland, but the establishment of Calamagrostis epigejos would eventually lead to monodominant stands. Untreated control plots showed basically the same pattern, however the development was slower. At Site III (pH = 1.8–2.8, 34 % sand), the hostile Tertiary substrate impeded the succession on both treated and untreated plots because low pH and therefore high amounts of Al³⁺ produced elemental toxicity to plants. The application of plant clippings accelerated the vegetation development in sites with a pH exceeding 3. On plots with the initial treatment, vegetation cover and total number of species were higher than on untreated plots. The application of fresh plant clippings from areas with similar habitat conditions appears to be a viable alternative to traditional restoration methods.     

Avian Habitat Preference in Tropical Forest Restoration in Southern Costa Rica

An important question for tropical forest restoration is whether degraded lands can be actively managed to attract birds. We censused birds and measured vegetation structure at 27 stations in young (6–9‐yr old) actively and passively restored pasture and old growth forest at Las Cruces Biological Station in southern Costa Rica. During 481 10‐min point counts, we detected a high diversity—186 species—of birds using the restoration area. Surprisingly, species richness and detection frequency did not differ among habitats, and proportional similarity of bird assemblages to old growth forest did not differ between restoration treatments. Bird detection frequency was instead explained by exotic grass cover and understory stem density—vegetation structures that were not strongly impacted by active restoration. The similarity of bird assemblages in actively and passively restored forest may be attributed to differential habitat preferences within and among feeding guilds, low structural contrast between treatments, or the effect of nucleation from actively restored plots into passively restored areas. Rapid recovery of vegetation in this recently restored site is likely due to its proximity to old growth forest and the lack of barriers to effective seed dispersal. Previous restoration studies in highly binary environments (i.e., open pasture vs. tree plantation) have found strong differences in bird abundance and richness. Our data contradict this trend, and suggest that tropical restoration ecologists should carefully consider: (1) when the benefits of active restoration outweigh the cost of implementation; and (2) which avian guilds should be used to measure restoration success given differential responses to habitat structure.     

Application of harmonic radar technology to monitor tree snail dispersal

Abstract. Planned conservation efforts for tree snails of the endangered genus Achatinella, endemic to the island of O'ahu, Hawai'i, will include translocations among the remaining wild and captive‐bred populations. In order to establish optimal levels of artificial migration among neighboring groups of snails within fragmented populations, efforts to determine natural dispersal rates through direct observation were initiated. Capture–mark–recapture (CMR) efforts have proved inadequate for obtaining the requisite dispersal estimates, due to low recapture probabilities. In addition, snail dispersal beyond the boundaries of a finite CMR study site was indistinguishable from mortality. In the preliminary study reported here, both the low recapture probability and dispersal detection problems of past CMR efforts were addressed by using harmonic radar tracking. This approach yielded rough dispersal estimates that were unattainable using CMR alone by providing 100% recapture rates even beyond the normal survey area boundaries. Extensive snail movements within clusters of connected trees were frequently observed after tracking for merely a few hours, although movements between unconnected trees were rare and recorded only after monthly survey intervals. Just 11 out of 40 tracked snails made between‐tree movements (average distance of 4.94±1.52 m) during the entire 7‐month study, and provided the only data utilizable for inferring gene flow in and out of subpopulations. Meteorological data loggers were deployed when tracking began to look for an association between such snail movement and weather fluctuations. The resultant data indicate that increases in both wind gusts and humidity facilitate dispersal (R²=0.77, p‐value <0.001), and that passive wind dispersal alone may be responsible for many snail movements (R²=0.59, p‐value=0.0014). Despite having provided coarse estimates of short‐term dispersal and corresponding wind influences, the limitations of the radar method can be substantial.