River restoration success depends on the species pool of the immediate surroundings

Previous studies evaluating the success of river restorations have rarely found any consistent effects on benthic invertebrate assemblages. In this study, we analyzed data from 24 river restoration projects in Germany dating back 1 to 12 years and 1231 data sets from adjacent river reaches that lie within 0-5, 5-10, and 10-15 km rings centered on the restored sites. We calculated restoration success and recolonization potential of adjacent river reaches based on stream-type-specific subsets of taxa indicative for good or bad habitat quality. On average, the restorations did not improve the benthic invertebrate community quality. However, we show that restoration success depends on the presence of source populations of desired taxa in the surrounding of restored sites. Only where source populations of additional desired taxa existed within a 0-5 km ring around the restored sites were benthic invertebrate assemblages improved by the restoration. Beyond the 5-km rings, this recolonization effect was no longer detected. We present here the first field results to support the debated argument that a lack of source populations in the areas surrounding restored sites may play an important role in the failure to establish desired invertebrate communities by the means of river restorations. In contrast, long-range dispersal of invertebrates seems to play a subordinate role in the recolonization of restored sites. However, because the surroundings of the restored sites were far from good ecological quality, the potential for improvement of restored sites was limited.     

Predicting Plant Extinction Based on Species-Area Curves in Prairie Fragments with High Beta Richness

Abstract:  Species-area relationships and island biogeography theory are commonly used to predict how species richness will decline with fragmentation. There are a variety of largely untested assumptions in these approaches, including the assumptions that populations are distributed uniformly before fragmentation, and that local extinctions are due to effects of small population sizes. If populations are not distributed uniformly, then populations can be abundant locally but rare globally. This would cause extinction rates to be smaller than predicted. We tested extinction theory by developing estimates of the number of plant species that should be present in small tallgrass prairie fragments and then testing the uniformity assumption by partitioning species richness into α (within site) and β (among site) components in Iowa prairies. Many more native prairie plant species were present in surveys of prairie fragments (491) than was predicted based on theory (27–207). A large proportion (75%) of the total species richness was β richness. We suggest that the high proportion of β richness was responsible for the shallow species-area slopes and the lower than expected number of species losses and that a better understanding of what determines β diversity will improve predictions of fragmentation effects on richness of plants. We also suggest that plants in prairie remnants may be best conserved by protecting different prairie types rather than by protecting a few large areas containing a single prairie type.     

Patterns of Area Sensitivity in Grassland-Nesting Birds

Abstract: Between 1995 and 1997, we studied breeding birds in fragments of native tallgrass prairie in southwestern Missouri to determine the effect of habitat fragmentation on grassland bird populations. Data on density and nesting success collected in 13 prairie fragments of various sizes revealed three levels of area sensitivity. The most area-sensitive species, Greater Prairie-Chicken ( Tympanuchus cupido ), was absent from small prairie fragments. An intermediate form of area sensitivity was apparent in only one species, Henslow's Sparrow ( Ammodramus henslowii ), which occurred in lower densities in small than in large prairie fragments. Based on census (i.e., distributional) data, only those two species were area-sensitive (i.e., negatively affected by habitat fragmentation) in southwestern Missouri. A species can be sensitive not only on a distributional level, however, but also by having lower nesting success in small than in large prairie fragments. The Dickcissel ( Spiza americana ) was the only species that was area-sensitive on such a demographic level. These data indicate that we cannot rely solely on census data to describe the sensitivity of grassland-nesting species to habitat fragmentation, but that we also need to investigate demographic data (e.g., nesting success). Whereas it has previously been shown that density measures of forest-nesting birds do not reliably reflect nesting success in habitat fragments of various sizes, ours is the first study that describes this pattern for grassland-nesting species.     

Habitat edge, land management, and rates of brood parasitism in tallgrass prairie.

Bird populations in North America's grasslands have declined sharply in recent decades. These declines are traceable, in large part, to habitat loss, but management of tallgrass prairie also has an impact. An indirect source of decline potentially associated with management is brood parasitism by the Brown-headed Cowbird (Molothrus ater), which has had substantial negative impacts on many passerine hosts. Using a novel application of regression trees, we analyzed an extensive five-year set of nest data to test how management of tallgrass prairie affected rates of brood parasitism. We examined seven landscape features that may have been associated with parasitism: presence of edge, burning, or grazing, and distance of the nest from woody vegetation, water, roads, or fences. All five grassland passerines that we included in the analyses exhibited evidence of an edge effect: the Grasshopper Sparrow (Ammodramus savannarum), Henslow's Sparrow (A. henslowii), Dickcissel (Spiza americana), Red-winged Blackbird (Agelaius phoeniceus), and Eastern Meadowlark (Sturnella magna). The edge was represented by narrow strips of woody vegetation occurring along roadsides cut through tallgrass prairie. The sparrows avoided nesting along these woody edges, whereas the other three species experienced significantly higher (1.9-5.3x) rates of parasitism along edges than in prairie. The edge effect could be related directly to increase in parasitism rate with decreased distance from woody vegetation. After accounting for edge effect in these three species, we found evidence for significantly higher (2.5-10.5x) rates of parasitism in grazed plots, particularly those burned in spring to increase forage, than in undisturbed prairie. Regression tree analysis proved to be an important tool for hierarchically parsing various landscape features that affect parasitism rates. We conclude that, on the Great Plains, rates of brood parasitism are strongly associated with relatively recent road cuts, in that edge effects manifest themselves through the presence of trees, a novel habitat component in much of the tallgrass prairie. Grazing is also a key associate of increased parasitism. Areas managed with prescribed fire, used frequently to increase forage for grazing cattle, may experience higher rates of brood parasitism. Regardless, removing trees and shrubs along roadsides and refraining from planting them along new roads may benefit grassland birds.     

Evidence for ecological matching of whole AM fungal communities to the local plant-soil environment

The range of ecological roles exhibited by arbuscular mycorrhizal (AM) fungi depends on functional differences among naturally occurring local assemblages of AM species. While functional differences have been demonstrated among AM fungal species and among geographic isolates of the same species, almost nothing is known about functional differences among whole communities of naturally occurring AM fungi. In the greenhouse, we reciprocally transplanted whole AM fungal communities between plant-soil systems representing a serpentine grassland and a tallgrass prairie, using as hosts two grasses common to both systems. For Sorghastrum nutans, native fungi consistently enhanced plant growth more than fungi switched from the alternate system. For Schizachyrium scoparium, foreign and native fungi promoted plant growth similarly in both the serpentine and prairie systems. Thus, the use of foreign inoculum in restoration could change the relative performance, and potentially the competitive abilities, of co-occurring plant species. Moving AM fungal inocula into foreign environments also caused changes in the taxonomic composition of the resultant spore communities, demonstrating their response to environmental influences. These results provide strong evidence for functional differences among naturally occurring AM communities and suggest that a particular AM fungal community may be better matched ecologically to its local habitat than communities taken from other locations.     

Managing Species Diversity in Tallgrass Prairie: Assumptions and Implications

Conservation and restoration ecology efforts may conserve or restore a particular image of a community, a variety of plausible images, or maximum biological diversity. The choice is a policy decision that should reflect relevant history and sound science. Here I argue that common methods of conserving and restoring tallgrass prairie have a weak scientific rationale, are not consistent with plausible history, and threaten prairie biodiversity. Dormant-season burns and grazer exclusion are human interventions that may promote artificially consistent dominance of large grasses utilizing the C₄ photosynthetic pathway, thereby relegating hundreds of other prairie plants to small populations that are vulnerable to local extinction. I recommend an experimental approach to large remnant conservation and restoration in which varied conditions alter dominance, thereby increasing short-term species richness. I also recommend prescribed burning during the summer, to simulate the timing of lightning fire, and light-to-moderate grazing by different ungulates, to simulate historical grazing history. Both should favor plants that are consistently infrequent or rare in many managed prairies. Varied regimes of burn season, burn interval, and large-mammal grazing should promote greater overall species diversity and should more realistically represent varied conditions under which grassland taxa evolved.     

Temporal changes in C and N stocks of restored prairie: implications for C sequestration strategies

The recovery of ecosystem C and N dynamics after disturbance can be a slow process. Chronosequence approaches offer unique opportunities to use space-for-time substitution to quantify the recovery of ecosystem C and N stocks and estimate the potential of restoration practices for C sequestration. We studied the distribution of C and N stocks in two chronosequences that included long-term cultivated lands, 3- to 26-year-old prairie restorations, and remnant prairie on two related soil series. Results from the two chronosequences did not vary significantly and were combined. Based on modeling predictions, the recovery rates of different ecosystem components varied greatly. Overall, C stocks recovered faster than N stocks, but both C and N stocks recovered more rapidly for aboveground vegetation than for any other ecosystem component. Aboveground C and N reached 95% of remnant levels in only 13 years and 21 years, respectively, after planting to native vegetation. Belowground plant C and N recovered several decades later, while microbial biomass C, soil organic C (SOC), and total soil N recovered on a century timescale. In the cultivated fields, SOC concentrations were depleted within the surface 25 cm, coinciding with the depth of plowing, but cultivation apparently led to redistribution of soil C, increasing SOC stocks deeper in the soil profile. The restoration of prairie vegetation was effective at rebuilding soil organic matter (SOM) in the surface soil. Accrual rates were maintained at 43 g C x m(-2) x yr(-1) and 3 g N x m(-2) x yr(-1) in the surface 0.16 Mg/m2 soil mass during the first 26 years of restoration and were predicted to reach 50% of their storage potential (3500 g C/m2) in the first 100 years. We conclude that restoration of tallgrass prairie vegetation can restore SOM lost through cultivation and has the potential to sequester relatively large amounts of SOC over a sustained period of time. Whether restored prairies can retain the C apparently transferred to the subsoil by cultivation practices remains to be seen.     

Should heterogeneity be the basis for conservation? Grassland bird response to fire and grazing.

In tallgrass prairie, disturbances such as grazing and fire can generate patchiness across the landscape, contributing to a shifting mosaic that presumably enhances biodiversity. Grassland birds evolved within the context of this shifting mosaic, with some species restricted to one or two patch types created under spatially and temporally distinct disturbance regimes. Thus, management-driven reductions in heterogeneity may be partly responsible for declines in numbers of grassland birds. We experimentally altered spatial heterogeneity of vegetation structure within a tallgrass prairie by varying the spatial and temporal extent of fire and by allowing grazing animals to move freely among burned and unburned patches (patch treatment). We contrasted this disturbance regime with traditional agricultural management of the region that promotes homogeneity (traditional treatment). We monitored grassland bird abundance during the breeding seasons of 2001-2003 to determine the influence of altered spatial heterogeneity on the grassland bird community. Focal disturbances of patch burning and grazing that shifted through the landscape over several years resulted in a more heterogeneous pattern of vegetation than uniform application of fire and grazing. Greater spatial heterogeneity in vegetation provided greater variability in the grassland bird community. Some bird species occurred in greatest abundance within focally disturbed patches, while others occurred in relatively undisturbed patches in our patch treatment. Henslow's Sparrow, a declining species, occurred only within the patch treatment. Upland Sandpiper and some other species were more abundant on recently disturbed patches within the same treatment. The patch burn treatment created the entire gradient of vegetation structure required to maintain a suite of grassland bird species that differ in habitat preferences. Our study demonstrated that increasing spatial and temporal heterogeneity of disturbance in grasslands increases variability in vegetation structure that results in greater variability at higher trophic levels. Thus, management that creates a shifting mosaic using spatially and temporally discrete disturbances in grasslands can be a useful tool in conservation. In the case of North American tallgrass prairie, discrete fires that capitalize on preferential grazing behavior of large ungulates promote a shifting mosaic of habitat types that maintain biodiversity and agricultural productivity.     

An Edge Effect Caused by Adult Corn-Rootworm Beetles on Sunflowers in Tallgrass Prairie Remnants

Abstract: The once-extensive tallgrass prairie community of North America has been reduced to small remnants, many of which are surrounded by intensive corn (   Zea mays ) agriculture. We investigated adult corn-rootworm beetles (Chrysomelidae : Diabrotica spp.), important pests of corn, on sunflowers (Asteraceae : Helianthus spp . ) in prairie remnants in southeast Minnesota. Large numbers of beetles invaded the prairie from surrounding corn fields in late summer. D. barberi and D. virgifera were captured on sticky traps in all locations in the prairie, but abundance was much greater near the edge adjacent to corn. We observed D. barberi ( but not D. virgifera ) feeding extensively on sunflower pollen and occasionally on other flower parts, such as petals. Sunflowers located nearer corn fields sustained more floral damage than those farther from corn. To determine the effect of beetle damage on seed set, we enclosed sunflower heads in bags with either zero, two, or four D. barberi adults. Seed set was reduced in heads enclosed with D. barberi . Thus, this agricultural pest may interfere with the successful reproduction of sunflowers and possibly other prairie composites that flower in late summer. Given the small size of most prairie remnants and the abundance of this flower-feeding beetle in landscapes dominated by corn agriculture, D. barberi may affect the sustainability of prairie plant populations.     

The Prairie Dog and Biotic Diversity

Since the turn of this century, prairie dog populations have declined as much as 98% throughout North America, largely as a result of prairie dog eradication programs. The prairie dog is a keystone species that plays an important role in maintaining the biotic integrity of the western grasslands that stretch from southern Canada to northern Mexico. The fragmentation of prairie dog distribution has degraded diversity on those prairies, and several species depending on prairie dogs have achieved listing status under the Endangered Species Act. We propose that managing the praire dog would provide an effective avenue from single-species management to management of a system. Because prairie dogs have declined so profoundly, some form of legal protection will be required. In addition, protected areas can preserve habitat and integrate ecologically sound agricultural opportunities. Positive incentives for ranchers to manage in the interests of both livestock and wildlife will enhance the attitude change necessary for grassland conservation. These management options hinge critically on an end to U.S. government subsidies for prairie dog eradication programs. The subsidies are financially and ecologically unsound, and they only contribute to the prevailing misconceptions about the role of the prairie dog on the grasslands.     

Grassland Bird Responses to Land Management in the Largest Remaining Tallgrass Prairie

Abstract: Extensive habitat loss and changing agricultural practices have caused widespread declines in grassland birds throughout North America. The Flint Hills of Kansas and Oklahoma—the largest remaining tallgrass prairie—is important for grassland bird conservation despite supporting a major cattle industry. In 2004 and 2005, we assessed the community, population, and demographic responses of grassland birds to the predominant management practices (grazing, burning, and haying) of the region, including grasslands restored under the Conservation Reserve Program (CRP). We targeted 3 species at the core of this avian community: the Dickcissel (Spiza americana), Grasshopper Sparrow (Ammodramus savannarum), and Eastern Meadowlark (Sturnella magna). Bird diversity was higher in native prairie hayfields and grazed pastures than CRP fields, which were dominated by Dickcissels. Although Dickcissel density was highest in CRP, their nest success was highest and nest parasitism by Brown‐headed Cowbirds (Moluthrus ater) lowest in unburned hayfields (in 2004). Conversely, Grasshopper Sparrow density was highest in grazed pastures, but their nest success was lowest in these pastures and highest in burned hayfields, where cowbird parasitism was also lowest (in 2004). Management did not influence density and nest survival of Eastern Meadowlarks, which were uniformly low across the region. Nest success was extremely low (5–12%) for all 3 species in 2005, perhaps because of a record spring drought. Although the CRP has benefited grassland birds in agricultural landscapes, these areas may have lower habitat value in the context of native prairie. Hayfields may provide beneficial habitat for some grassland birds in the Flint Hills because they are mowed later in the breeding season than elsewhere in the Midwest. Widespread grazing and annual burning have homogenized habitat—and thus grassland‐bird responses—across the Flint Hills. Diversification of management practices could increase habitat heterogeneity and enhance the conservation potential of the Flint Hills for grassland birds.     

The influence of aridity and fire on holocene prairie communities in the eastern Prairie Peninsula

The role of climate and fire in the development, maintenance, and species composition of prairie in the eastern axis of the tallgrass Prairie Peninsula intrigued early North American ecologists. However, evaluation of the long-standing hypotheses about the region's environmental history has been hampered by the scarcity of paleorecords. We conducted multiproxy analyses on early and middle Holocene sediments from two Illinois, USA, lakes to assess long-term climatic, vegetational, and fire variability in the region. Sediment mineral composition, carbonate delta18O, ostracode assemblages, and diatom assemblages were integrated to infer fluctuations in moisture availability. Pollen and charcoal delta13C were used to reconstruct vegetation composition, and charcoal influx was used to reconstruct fire. Results indicate that fire-sensitive trees (e.g., Ulmus, Ostrya, Fraxinus, and Acer saccharum) declined and prairie taxa expanded with increased aridity from 10,000 yr BP to 8500 yr BP. Between approximately 8500 yr BP and approximately 6200 yr BP, aridity declined, and prairie coexisted with fire-sensitive and fire-tolerant (e.g., Quercus and Carya) trees. After approximately 6200 yr BP, prairie taxa became dominant, although aridity was not more severe than it was around 8500 yr BP. Along with aridity, fire appears to have played an important role in the establishment and maintenance of prairie communities in the eastern Prairie Peninsula, consistent with the speculations of the early ecologists. Comparison of our data with results from elsewhere in the North American midcontinent indicates that spatial heterogeneity is a characteristic feature of climatic and vegetational variations on millennial time scales.     

Use of data on avian demographics and site persistence during overwintering to assess quality of restored riparian habitat

Monitoring responses by birds to restoration of riparian vegetation is relatively cost-effective, but in most assessments species-specific abundances, not demography, are monitored. Data on birds collected during the nonbreeding season are particularly lacking. We captured birds in mist nets and resighted banded birds to estimate species richness and diversity, abundance, demographic indexes, and site-level persistence of permanent-resident and overwintering migrants in remnant and restored riparian sites in California. Species richness in riparian remnants was significantly higher than in restored sites because abundances of uncommon permanent residents were greater in remnants. Species richness of overwintering migrants did not differ between remnants and restored sites. Responses among overwintering migrants (but not permanent residents) to remnant and restored riparian sites differed. Capture rates were higher in remnant or restored riparian sites for 7 of 10 overwintering migratory species. For Lincoln's Sparrows (Melospiza lincolnii) and White-crowned Sparrows (Zonotrichia leucophrys) proportions of older birds were significantly higher in remnants, even though capture rates of these species were higher in restored sites. Overwinter persistence of 4 migrant species was significantly higher in remnant than in restored sites. A higher proportion of Hermit Thrushes (Catharus guttatus, 56.3%), older Fox Sparrows (Passerella iliaca, 57.1%), Lincoln's Sparrows (59.7%), and White-crowned Sparrows (67.8%) persisted in remnants than restored sites. Our results suggest restored riparian sites provide habitat for a wide variety of species in comparable abundances and diversity as occurs in remnant riparian sites. Our demographic and persistence data showed that remnants supported some species and age classes to a greater extent than restored sites.     

Butterfly community shifts over two centuries

Environmental changes strongly impact the distribution of species and subsequently the composition of species assemblages. Although most community ecology studies represent temporal snap shots, long‐term observations are rather rare. However, only such time series allow the identification of species composition shifts over several decades or even centuries. We analyzed changes in the species composition of a southeastern German butterfly and burnet moth community over nearly 2 centuries (1840–2013). We classified all species observed over this period according to their ecological tolerance, thereby assessing their degree of habitat specialisation. This classification was based on traits of the butterfly and burnet moth species and on their larval host plants. We collected data on temperature and precipitation for our study area over the same period. The number of species declined substantially from 1840 (117 species) to 2013 (71 species). The proportion of habitat specialists decreased, and most of these are currently endangered. In contrast, the proportion of habitat generalists increased. Species with restricted dispersal behavior and species in need of areas poor in soil nutrients had severe losses. Furthermore, our data indicated a decrease in species composition similarity between different decades over time. These data on species composition changes and the general trends of modifications may reflect effects from climate change and atmospheric nitrogen loads, as indicated by the ecological characteristics of host plant species and local changes in habitat configuration with increasing fragmentation. Our observation of major declines over time of currently threatened and protected species shows the importance of efficient conservation strategies.     

Habitat Fragmentation and Species Loss across Three Interacting Trophic Levels: Effects of Life-History and Food-Web Traits

Abstract:  Not all species are likely to be equally affected by habitat fragmentation; thus, we evaluated the effects of size of forest remnants on trophically linked communities of plants, leaf-mining insects, and their parasitoids. We explored the possibility of differential vulnerability to habitat area reduction in relation to species-specific and food-web traits by comparing species–area regression slopes. Moreover, we searched for a synergistic effect of these traits and of trophic level . We collected mined leaves and recorded plant, leaf miner, and parasitoid species interactions in five 100-m² transects in 19 Chaco Serrano woodland remnants in central Argentina. Species were classified into extreme categories according to body size, natural abundance, trophic breadth, and trophic level . Species–area slopes differed between groups with extreme values of natural abundance or trophic specialization. Nevertheless, synergistic effects of life-history and food-web traits were only found for trophic level and trophic breadth: area-related species loss was highest for specialist parasitoids. It has been suggested that species position within interaction webs could determine their vulnerability to extinction. Our results provide evidence that food-web parameters, such as trophic level and trophic breadth, affect species sensitivity to habitat fragmentation .     

Diversity and cover of a sessile animal assemblage does not predict its associated mobile fauna

Habitat-forming organisms often determine the structural properties and food resources available to a wide diversity of associated mobile species. Sessile invertebrate assemblages on marine hard substrates support an abundant fauna of mobile invertebrates whose associations with traits of their host assemblages are poorly known. To assess how changes to habitat-forming species are likely to affect their associated mobile fauna, the relationships between abundance, diversity and composition of mobile invertebrates and the diversity, cover and composition of the sessile assemblages they use as habitat were quantified in Sydney Harbour, Australia (33°50′S, 151°16′E). Similar compositions of sessile species were more likely to share a similar composition of mobile species, but univariate measures of the habitat (percent cover, species and functional diversity, prevalence of non-indigenous species) did not predict variation in associated mobile assemblages. These results demonstrate that in this habitat it is difficult to predict the diversity of marine assemblages based on common surrogate measures of biodiversity.     

Ecological Correlates of Extinction Proneness in Australian Tropical Rain Forest Mammals

Abstract. There is a dire need to predict the vulnerability of tropical forest biotas to habitat fragmentation I tested the efficacy of seven ecological traits (body size Iongeuity, fecundity, trophic level, dietary specialization, natural abundance in rain forest and abundance in the surrounding habitat matrix) for predicting responses of 16 nonflying mammal species to rain forest fragmentation in tropical QueenslaM Australia An ordination analysis revealed that most (84%) of the variation in traits was described by two axes, the first separating rand K-selected species, and the second discriminating rare species with specialized diets from common species with generalized diets.
Using multiple regression analysis, the two ordination axes explained 51.7% of variation in mammal extinction proneness (F = 9.96 P = 0.009). Howem, univariate tests revealed tbat a single trait abundance in the mawas a betterpredictor of vulnerability (r²= 63.8%, F = 24.69, P < 0.001). Partial correlations demonstrated that once the effects of matrix abundance tuete remove4 no other traits or ordination axes were significant predictors of extinction proneness.
These results highlight the importance of tolerance of modijied habitats in determining survival of nonpying mammals in tropical forest fragments. Species tbat traverse or exploit modaxied habitats tend to remain stable or inmase in fragments whereas those tbat avoid these habitats often disappem The implications of these findings for hopical forest conservation are discussed.     

Change in avian functional fingerprints of a Neotropical montane forest over 100 years as an indicator of ecosystem integrity

Ecologically relevant traits of organisms in an assemblage determine an ecosystem's functional fingerprint (i.e., the shape, size, and position of multidimensional trait space). Quantifying changes in functional fingerprints can therefore provide information about the effects of diversity loss or gain through time on ecosystem condition and is a promising approach to monitoring ecological integrity. This, however, is seldom possible owing to limitations in historical surveys and a lack of data on organismal traits, particularly in diverse tropical regions. Using data from detailed bird surveys from 4 periods across more than a century, and morphological and ecological traits of 233 species, we quantified changes in the avian functional fingerprint of a tropical montane forest in the Andes of Colombia. We found that 78% of the variation in functional space, regardless of period, was described by 3 major axes summarizing body size, dispersal ability (indexed by wing shape), and habitat breadth. Changes in species composition significantly altered the functional fingerprint of the assemblage and functional richness and dispersion decreased 35–60%. Owing to species extirpations and to novel additions to the assemblage, functional space decreased over time, but at least 11% of its volume in the 2010s extended to areas of functional space that were unoccupied in the 1910s. The assemblage now includes fewer large-sized species, more species with greater dispersal ability, and fewer habitat specialists. Extirpated species had high functional uniqueness and distinctiveness, resulting in large reductions in functional richness and dispersion after their loss, which implies important consequences for ecosystem integrity. Conservation efforts aimed at maintaining ecosystem function must move beyond seeking to sustain species numbers to designing complementary strategies for the maintenance of ecological function by identifying and conserving species with traits conferring high vulnerability such as large body size, poor dispersal ability, and greater habitat specialization. Article impact statement: Changes in functional fingerprints provide a means to quantify the integrity of ecological assemblages affected by diversity loss or gain.     

Plant-soil feedback: testing the generality with the same grasses in serpentine and prairie soils

Plants can alter soil properties in ways that feed back to affect plant performance. The extent that plant-soil feedback affects co-occurring plant species differentially will determine its impact on plant community structure. Whether feedback operates consistently across similar plant communities is little studied. Here, the same grasses from two eastern U.S. serpentine grasslands and two midwestern tallgrass prairie remnants were examined for plant-soil feedback in parallel greenhouse experiments. Native soils were homogenized and cultured (trained) for a year with each of the four grasses. Feedback was evaluated by examining biomass variation in a second generation of (tester) plants grown in the trained soils. Biomass was lower in soils trained by conspecifics compared to soils trained by heterospecifics in seven of 15 possible cases; biomass was greater in conspecific soils in one other. Sorghastrum nutans exhibited lower biomass in conspecific soils for all four grasslands, so feedback may be characteristic of this species. Three cases from the Hayden prairie site were explained by trainer species having similar effects across all tester species so the relative performance of the different species was little affected; plants were generally larger in soils trained by Andropogon gerardii and smaller in soils trained by S. nutans. Differences among sites in the incidence of feedback were independent of serpentine or prairie soils. To explore the causes of the feedback, several soil factors were measured as a function of trainer species: nutrients and pH, arbuscular mycorrhizal (AM) spore communities, root colonization by AM fungi and putative pathogens, and functional diversity in bacterial communities as indicated by carbon substrate utilization. Only variation in nutrients was consistent with any patterns of feedback, and this could explain the greater biomass in soils trained by A. gerardii at Hayden. Feedback at Nottingham (one of the serpentine sites) differed, most notably for A. gerardii, from that of similar past studies that used different experimental protocols. To understand the consequences of feedback for plant community structure, it is important to consider how multiple species respond to the same plant-induced soil variation as well as differences in the feedback detected between greenhouse and field settings.     

Assessing hypotheses about nesting site occupancy dynamics

Hypotheses about habitat selection developed in the evolutionary ecology framework assume that individuals, under some conditions, select breeding habitat based on expected fitness in different habitat. The relationship between habitat quality and fitness may be reflected by breeding success of individuals, which may in turn be used to assess habitat quality. Habitat quality may also be assessed via local density: if high-quality sites are preferentially used, high density may reflect high-quality habitat. Here we assessed whether site occupancy dynamics vary with site surrogates for habitat quality. We modeled nest site use probability in a seabird subcolony (the Black-legged Kittiwake, Rissa tridactyla) over a 20-year period. We estimated site persistence (an occupied site remains occupied from time t to t+1) and colonization through two subprocesses: first colonization (site creation at the timescale of the study) and recolonization (a site is colonized again after being deserted). Our model explicitly incorporated site-specific and neighboring breeding success and conspecific density in the neighborhood. Our results provided evidence that reproductively "successful" sites have a higher persistence probability than "unsuccessful" ones. Analyses of site fidelity in marked birds and of survival probability showed that high site persistence predominantly reflects site fidelity, not immediate colonization by new owners after emigration or death of previous owners. There is a negative quadratic relationship between local density and persistence probability. First colonization probability decreases with density, whereas recolonization probability is constant. This highlights the importance of distinguishing initial colonization and recolonization to understand site occupancy. All dynamics varied positively with neighboring breeding success. We found evidence of a positive interaction between site-specific and neighboring breeding success. We addressed local population dynamics using a site occupancy approach integrating hypotheses developed in behavioral ecology to account for individual decisions. This allows development of models of population and metapopulation dynamics that explicitly incorporate ecological and evolutionary processes.