Spatial variation in filters imposed by the abiotic environment causes variation in functional traits within and among plant species. This is abundantly clear for plant species along elevational ...gradients, where parallel abiotic selection pressures give rise to predictable variation in leaf phenotypes among ecosystems. Understanding the factors responsible for such patterns may provide insight into the current and future drivers of biodiversity, local community structure and ecosystem function. In order to explore patterns in trait variation along elevational gradients, we conducted a meta‐analysis of published observational studies that measured three key leaf functional traits that are associated with axes of variation in both resource competition and stress tolerance: leaf mass:area ratio (LMA), leaf nitrogen content per unit mass (Nₘₐₛₛ) and N content per unit area (Nₐᵣₑₐ). To examine whether there may be evidence for a genetic basis underlying the trait variation, we conducted a review of published results from common garden experiments that measured the same leaf traits. Within studies, LMA and Nₐᵣₑₐ tended to decrease with mean annual temperature (MAT) along elevational gradients, while Nₘₐₛₛ did not vary systematically with MAT. Correlations among pairs of traits varied significantly with MAT: LMA was most strongly correlated with Nₘₐₛₛ and Nₐᵣₑₐ at high‐elevation sites with relatively lower MAT. The strengths of the relationships were equal or greater within species relative to the relationships among species, suggesting parallel evolutionary dynamics along elevational gradients among disparate biomes. Evidence from common garden studies further suggests that there is an underlying genetic basis to the functional trait variation that we documented along elevational gradients. Taken together, these results indicate that environmental filtering both selects locally adapted genotypes within plant species and constrains species to elevational ranges based on their ranges of potential leaf trait values. If individual phenotypes are filtered from populations in the same way that species are filtered from regional species pools, changing climate may affect both the species and functional trait composition of plant communities.
Global change is altering species distributions and thus interactions among organisms. Organisms live in concert with thousands of other species, some beneficial, some pathogenic, some which have ...little to no effect in complex communities. Since natural communities are composed of organisms with very different life history traits and dispersal ability it is unlikely they will all respond to climatic change in a similar way. Disjuncts in plant-pollinator and plant-herbivore interactions under global change have been relatively well described, but plant-soil microorganism and soil microbe-microbe relationships have received less attention. Since soil microorganisms regulate nutrient transformations, provide plants with nutrients, allow co-existence among neighbors, and control plant populations, changes in soil microorganism-plant interactions could have significant ramifications for plant community composition and ecosystem function. In this paper we explore how climatic change affects soil microbes and soil microbe-plant interactions directly and indirectly, discuss what we see as emerging and exciting questions and areas for future research, and discuss what ramifications changes in these interactions may have on the composition and function of ecosystems.
Urban green spaces, such as forest fragments, vacant lots, and community gardens, are increasingly highlighted as biodiversity refuges and are of growing interest to conservation. At the same time, ...the burgeoning urban garden movement partially seeks to ameliorate problems of food security. Arthropods link these two issues (conservation and food security) given their abundance, diversity, and role as providers of ecosystem services like pollination and pest control. Many previous studies of urban arthropods focused on a single taxon (e.g. order or family), and examined either local habitat drivers or effects of landscape characteristics. In contrast, we examined both local and landscape drivers of community patterns, and examined differences in abundance, richness, and trophic structure of arthropod communities in urban forest fragments, vacant lots, and community gardens. We sampled ground-foraging arthropods, collected data on 24 local habitat features (e.g., vegetation, ground cover, concrete), and examined land-cover types within 2 km of 12 study sites in Toledo, Ohio. We found that abundance and richness of urban arthropods differed by habitat type and that richness of ants and spiders, in particular, varied among lots, gardens, and forests. Several local and landscape factors correlated with changes in abundance, richness, and trophic composition of arthropods, and different factors were important for specific arthropod groups. Overwhelmingly, local factors were the predominant (80 % of interactions) driver of arthropods in this urban environment. These results indicate that park managers and gardeners alike may be able to manage forests and gardens to promote biodiversity of desired organisms and potentially improve ecosystem services within the urban landscape.
Quality of the agricultural matrix profoundly affects biodiversity and dispersal in agricultural areas. Vegetatively complex coffee agroecosystems maintain species richness at larger distances from ...the forest. Epiphytes colonize canopy trees and provide resources for birds and insects and thus effects of agricultural production on epiphytes may affect other species. We compared diversity, composition, and vertical stratification of epiphytes in a forest fragment and in two coffee farms differing in management intensity in southern Mexico. We also examined spatial distribution of epiphytes with respect to the forest fragment to examine quality of the two agricultural matrix types for epiphyte conservation. We sampled vascular epiphytes in a forest fragment, a shade polyculture farm, and a shade monoculture farm at 100 m, 200 m, and 400 m from the forest. Epiphyte and orchid richness was greater in the forest than in the monoculture but richness was similar in the forest and polyculture farm. Epiphyte species composition differed with habitat type, but not with distance from the forest. In the forest, epiphytes were distributed throughout tree canopies, but in the farms, epiphytes were primarily found on trunks and larger branches. Epiphyte richness and species similarity to forest species declined with distance from the forest fragment in the monoculture, but richness and similarity to forest species did not decline with distance from forest in the polyculture. This suggests polyculture coffee has greater conservation value. In contrast, monoculture coffee is likely a sink habitat for epiphytes dispersing from forests into coffee. Coffee farms differ from forests in terms of the habitat they provide and species composition, thus protecting forest fragments is essential for epiphyte conservation. Nonetheless, in agricultural landscapes, vegetatively complex coffee farms may contribute to conservation of epiphytes more than other agricultural land uses.
Past research on plant-soil feedbacks (PSF), largely undertaken in highly controlled greenhouse conditions, has established that plant species differentially alter abiotic and biotic soil conditions ...that in turn affect growth of other conspecific and heterospecific individuals in that soil. Yet, whether feedbacks under controlled greenhouse conditions reflect feedbacks in natural environments where plants are exposed to a range of abiotic and biotic pressures is still unresolved. To address how environmental context affects PSF, we conducted a meta-analysis of previously published studies that examined plant growth responses to multiple forms of competition, stress, and disturbance across various PSF methodology. We asked the following questions: (1) Can competition, stress, and disturbance alter the direction and/or strength of PSF? (2) Do particular types of competition, stress, or disturbance affect the direction and/or strength of PSF more than others? and (3) Do methods of conducting PSF research (i.e., greenhouse vs. field experiments and whether the source of soil inoculum conditioning is from the field vs. greenhouse) affect plant growth responses to PSF or competition, stress, and disturbance, or their interactions? We discovered four patterns that may be predictive of what future PSF studies conducted under more realistic conditions might reveal. First, relatively little is known about how PSF responds to environmental stress and disturbance compared to plant-plant competition. Second, specific types of competition enhanced negative effects of soil microbes on plant growth, and specific environmental stressors enhanced positive effects of soil microbes on plant growth. Third, whether PSF experiments are conducted in the field or greenhouse can change plant growth responses. And, fourth, how the soil conditioning phase is conducted can change plant growth responses. With more detail than previously shown, these results confirm that environmental context writ large can change plant growth responses in PSF experiments. These data should aid theory and predictions for conservation and restoration applications by showing the relative importance of competition, stress, and disturbance in PSF studies over time. Lastly, these data demonstrate how variation in experimental methods can alter interpretation and conclusions of PSF studies.
Urbanization negatively affects biodiversity by increasing disturbance and habitat fragmentation. We compared three different urban habitats (vacant lots, gardens and forests) to examine differences ...in spider communities. We selected four sites of each habitat type and sampled spiders with pitfall traps. We collected a total of 547 individuals from 19 families. The most common families were Lycosidae, Corinnidae, Liocranidae, Cybaeidae, and Dictynidae. Spider activity-density overall and for males and females was higher in vacant lots than in forests, and female spiders had greater activity-density in gardens than in forests. Observed species richness did not differ with habitat type. Spider family composition differed significantly between urban habitat types, female morphospecies composition differed in forests and gardens and male morphospecies composition differed in forests and lots. The site characteristics differed significantly with habitat, and these habitat differences explained a large fraction (53.3% to 90.9%) of the variation in composition and richness. Yet, bare ground was the only factor that significantly correlated with declines in female richness. Thus, spider communities, aspects of specifically activity-density and composition, differ between habitats in urban green spaces with potentially important implications for conservation and trophic interactions within urban areas.
Herbivores modify their environment by consuming plant biomass and redistributing materials across the landscape. While small mammalian herbivores, such as rodents, are typically inconspicuous, their ...impacts on plant community structure and chemistry can be large. We used a small mammal exclosure experiment to explore whether rodents in a southeastern old field directly altered the aboveground plant species composition and chemistry, and indirectly altered the belowground soil community composition and activity. In general, when rodents were excluded, C3 graminoids increased in cover and biomass, contributing toward a shift in plant species composition relative to plots where rodents were present. The plant community chemistry also shifted; plant fiber concentration and carbon : nitrogen were higher, whereas plant nitrogen concentration was lower in exclosure plots relative to access plots. While microbial community enzyme activity increased when rodents were excluded, no significant changes in the fungal : bacterial or potential nitrogen mineralization occurred between treatments. Our results show that rodents can rapidly influence aboveground plant community composition and chemistry, but their influence on belowground processes may require plant inputs to the soil to accumulate over longer periods of time.
Wildfires are increasing in frequency and intensity as drier and warmer climates increase plant detrital fuel loads. At the same time, increases in urbanization position 9% of fire-prone land within ...the United States at the wildland–urban interface. While rarely studied, the compounded effects of urbanization and wildfires may have unknown synergistically negative effects on ecosystems. Previous studies at the wildland–urban interface often focus on aboveground plant communities, but belowground ecosystems may also be affected by this double disturbance. In particular, it is unclear how much fire and urbanization independently or interactively affect nutritional symbioses such as those between arbuscular mycorrhizal (AM) fungi and the majority of terrestrial plants. In November 2016, extreme drought conditions and long-term fire suppression combined to create a wildfire within the Great Smoky Mountains National Park and the neighboring exurban city of Gatlinburg, TN. To understand how the double disturbance of urbanization and fire affected AM fungal communities, we collected fine roots from the 5 dominant understory species in September 2018 at each of 18 sites spanning 3 burn severities in both exurban and natural sites. Despite large variation in burn severity, plant species identity had the largest influence on AM fungi. AM fungal colonization, richness, and composition all varied most among plant species. Fire and urbanization did influence some AM fungal metrics; colonization was lower in burned sites and composition was more variable among exurban locations. There were no interactions among burn severity and urbanization on AM fungi. Our results point to the large influence of plant species identity structuring this obligate nutritional symbiosis regardless of disturbance regime. Therefore, the majority of AM fungal taxa may be buffered from fire-induced ecosystem changes if plant community composition largely remains intact, plant species life history traits allow for AM fungal persistence after fire disturbance, and/or nearby undisturbed habitat can act as an inoculum source for recolonization following fires. Thus, it is critical to maintain natural, undisturbed habitats interspersed within the wildland–urban interface.
Urbanization negatively affects biodiversity by increasing disturbance and habitat fragmentation. We compared three different urban habitats (vacant lots, gardens and forests) to examine differences ...in spider communities. We selected four sites of each habitat type and sampled spiders with pitfall traps. We collected a total of 547 individuals from 19 families. The most common families were Lycosidae, Corinnidae, Liocranidae, Cybaeidae, and Dictynidae. Spider activity-density overall and for males and females was higher in vacant lots than in forests, and female spiders had greater activity-density in gardens than in forests. Observed species richness did not differ with habitat type. Spider family composition differed significantly between urban habitat types, female morphospecies composition differed in forests and gardens and male morphospecies composition differed in forests and lots. The site characteristics differed significantly with habitat, and these habitat differences explained a large fraction (53.3% to 90.9%) of the variation in composition and richness. Yet, bare ground was the only factor that significantly correlated with declines in female richness. Thus, spider communities, aspects of specifically activity-density and composition, differ between habitats in urban green spaces with potentially important implications for conservation and trophic interactions within urban areas.
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