Abundance Of Exotic Species Research Articles

Management of invasive Pinaceae is imperiled by the lack of invasive ungulate control: successful restoration requires multiple-species management

The magnitude and direction of an invasive species’ impact may be determined by its co-existence and interaction with other species. In Argentina, wild boar, red deer, and fallow deer are introduced mammals that have important negative impacts on ecosystems. In Patagonia, nonnative Pinaceae removal programs have been promoted since the 1980s to control exotic conifers and restore native vegetation. The consequences of removing exotic trees without continued management intervention may be unexpected due novel interactions between nonnative species. We evaluate habitat use of introduced ungulates, interactions with native and exotic plants, and their implications for restoration objectives in areas where pines have been removed. Exotic plant species richness and abundance was greater in clear-cuts than native forest or pine plantations. In contrast, richness and abundance of native plants was highest in native forests. Clear-cuts had the highest plant species diversity, primarily driven by high numbers of exotics, relative to native forests. Boar and deer were recorded in clear-cuts, native forests, and pine plantations, but deer were more frequently observed in clear-cuts. Removal of pines created a suitable habitat for deer. The herbivory pressure of deer, coupled with the presence and abundance of invasive plants, can prevent or hinder the establishment and development of native shrubs and trees that are required for the structure and function of the native ecosystem. Although the conditions in clear-cuts present complex challenges for natural regeneration, these sites could be an excellent opportunity for active restoration strategies, by excluding ungulates and controlling exotic plants to promote native species recovery.

Influence of Groundcover Vegetation, Soil Physicochemical Properties, and Irrigation Practices on Soil Fungi in Semi-arid Vineyards

Although plants are known to have a strong influence on soil biota, the effect of groundcover vegetation in perennial cropping systems on soil fungi has been little explored. We surveyed extensively managed vineyards to determine how plant community functional characteristics, soil factors, and irrigation management related to the abundance of two guilds of soil fungi that may play a role in plant-soil feedback (entomopathogenic fungi represented by Beauveria bassiana, and the pathogenic species complex, Ilyonectria spp.). We found that plant community characteristics were related to fungal abundance for both fungi assayed. Beauveria bassiana increased with native species, annual plants, and legumes consistently across sampling periods. Ilyonectria spp. increased with the abundance of forbs and exotic species, though only the relationship with forbs was consistent across sampling periods. Both fungal guilds increased with increasing soil organic matter. The use of dual or sprinkler irrigation systems also increased Beauveria bassiana and Ilyonectria spp. in vineyard soils. Overall, groundcover vegetation played a significant role in driving abundance of these important groups of soil fungi. Groundcover management may therefore be a viable tool to manipulate soil fungi with the potential for improving ecosystem services such as conservation biological control of soil dwelling insect pests and deterring pathogens in perennial cropping systems.

Drought in Southern California coastal sage scrub reduces herbaceous biomass of exotic species more than native species, but exotic growth recovers quickly when drought ends

Semi-arid regions with Mediterranean-type climates harbor exceptional biodiversity, but are increasingly threatened by invading exotic annual species and climatic changes, including drought. In semi-arid ecosystems, antecedent conditions often influence plant growth, but the role of antecedent conditions for drought response and recovery of native versus exotic species remains largely unexplored. From 2013 to 2016, we imposed experimental rainfall treatments (average rainfall, moderate or severe drought) in plots under a native shrub canopy and in inter-spaces dominated by herbaceous vegetation, and quantified growth (peak biomass) and abundance (cover) of native and exotic herbaceous species. The following year, we quantified recovery from the drought treatments (2017). Exotic biomass was less resistant to drought (declined more than native biomass), but was more resilient (increased more than native biomass in the year following drought), especially in unshaded inter-spaces between shrubs. These responses were associated with life history; annual species responded more negatively to drought in the inter-spaces than perennial species. Current years' rainfall was a better predictor of biomass than prior rainfall, but antecedent factors were also important. After four years of rainfall treatments, exotic species had the highest growth recovery in the severe drought treatment, while growth of natives had the opposite response. In contrast, litter was positively associated with plant growth regardless of origin. This study demonstrates that when native and exotic species differ in life history, as they do in Mediterranean climate ecosystems, they may respond differently to antecedent factors, and hence differ in recovery from climate extremes such as drought.

Calliphoridae (Diptera) in Human-Transformed and Wild Habitats: Diversity and Seasonal Fluctuations in the Humid Chaco Ecoregion of South America.

A temporal study of the Calliphoridae fauna was conducted in five different types of habitats in the Humid Chaco ecoregion: an urban settlement, a cattle farm, an alfalfa crop, a savanna, and a forest. Research was carried out to analyze 1) how the species composition of blow fly communities changes across different types of human-modified and wild environments, 2) their seasonal fluctuations, and 3) the influence of climatic factors (relative humidity, temperature, and precipitations) on the temporal dynamics of these communities. In each habitat, five sites were selected for the collection of blow flies using bait traps, and flies were collected for 1 yr. In total, 32,100 blow flies were collected, distributed in five genera and 11 species. The native species Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae) was the most abundant, followed by the exotic Chrysomya putoria (Wiedemann) (Diptera: Calliphoridae). The abundance of exotic species represented 59.9% of the total sample, showing a reduction toward less disturbed sites. The Calliphorid communities were compared in terms of species richness, composition, and abundance between habitats and seasons. Our results showed that the habitat type and season affect the composition of blow fly communities. The alfalfa crop and the forest showed the highest diversity of species. In general, there was a decrease in blow fly activity during winter in all habitats. The climatic factors did not greatly affect the diversity of these flies. This study provides a first understanding of several ecological aspects of the Calliphoridae assemblages of the previously unsurveyed Humid Chaco ecoregion of South America.

Classification of South Brazilian grasslands: Implications for conservation

AbstractAimsWe offer a first classification of South Brazilian grasslands (Campos Sulinos) based on quantitative vegetation data and describing grassland types in terms of dominant and indicator species.LocationSouth Brazilian grasslands (Paraná, Santa Catarina, Rio Grande do Sul states).MethodsWe described vegetation plots in 167 sampling units throughout the region using a stratified nested design, totalizing 1,502 1 m² quadrats. We classified vegetation using cluster analysis based on Bray–Curtis dissimilarities, establishing three vegetation types and ten subtypes. We conducted indicator species analysis within the resulting subtypes, and for all possible combinations of subtypes.ResultsIn the cluster analyses, a clear separation of poorly drained grasslands from the drier sites appeared. Further, a clear distinction between grasslands in the South Brazilian highland region, situated in the Atlantic Forest biome, and the grasslands of the Pampa biome, to the south, emerged, reflecting climatic and management differences. Highland grasslands showed lower species cover dominance, while in the Pampa, Paspalum notatum clearly was the most important species and the abundance of exotic species was higher.ConclusionsOur study provides the first classification of South Brazilian grasslands based on quantitative vegetation data recorded in a standardized sampling design. The data support the division of grasslands into the main phytogeographic units of the region (Brazilian biome classification). Grasslands in these two regions also differ in terms of species dominance pattern (higher dominance in Pampa grasslands, likely also due to higher grazing levels) and in terms of conservation state (low presence of exotic species in highland grasslands). Our results are important for conservation policies, which can now consider the presence of different grassland types in different region, but more data will be necessary for a more detailed classification that considers different abiotic features in more detail.

Along urbanization sprawl, exotic plants distort native bee (Hymenoptera: Apoidea) assemblages in high elevation Andes ecosystem.

Native bees contribute a considerable portion of pollination services for endemic as well as introduced plant species. Their decline has been attributed to several human-derived influences including global warming as well as the reduction, alteration, and loss of bees’ habitat. With human expansion comes along the introduction of exotic plant species with negative impacts over native ecosystems. Anthropic effects may even have a deeper impact on communities adapted to extreme environments, such as high elevation habitats, where abiotic stressors alone are a natural limitation to biodiversity. Among these effects, the introduction of exotic plants and urbanization may have a greater influence on native communities. In this work, we explored such problems, studying the relationship between the landscape and its effect over richness and abundance of native bees from the subandean belt in the Andes mountain chain. Furthermore, we investigated the effects of exotic plant abundance on this high-altitude bee assemblage. Despite the landscape not showing an effect over bee richness and abundance, exotic plants did have a significant influence over the native bee assemblage. The abundance of exotic plants was associated with a relative increase in the proportion of small and medium bee species. Moreover, Halictidae was the only family that appeared to be favored by an increase in the abundance of exotic plant species. We discuss these results and the urgent need for further research of high-altitude environments due to their vulnerability and high endemicity.

An Introduction and Practical Guide to Use of the Soil-Vegetation Inventory Method (SVIM) Data

Long-term vegetation dynamics across public rangelands in the western United States are not well understood because of the lack of large-scale, readily available historic datasets. The Bureau of Land Management’s Soil-Vegetation Inventory Method (SVIM) program was implemented between 1977 and 1983 across 14 western states, but the data have not been easily accessible. We introduce the SVIM vegetation cover dataset in a georeferenced, digital format; summarize how the data were collected; and discuss potential limitations and biases. We demonstrate how SVIM data can be compared with contemporary monitoring datasets to quantify changes in vegetation associated with wildfire and the abundance of exotic invasive species. Specifically, we compare SVIM vegetation cover data with cover data collected by BLM’s Assessment, Inventory, and Monitoring (AIM) program (2011–2016) in a focal area in the northern Great Basin. We address issues associated with analyzing and interpreting data from these distinct programs, including differences in survey methods and potential biases introduced by spatial and temporal variation in sampling. We compared SVIM and AIM survey methods at 44 plots and found that percent cover estimates had high correspondence for all measured functional groups. Comparisons between historic SVIM data and recent AIM data documented significant declines in the occupancy and cover of native shrubs and native perennial forbs, and a significant increase in exotic annual forbs. Wildfire was a driver of change for some functional groups, with greater change occurring in AIM plots that burned between the two time periods compared with those that did not. Our results are consistent with previous studies showing that many native shrub-dominated plant communities in the Great Basin have been replaced by exotic annuals. Our study demonstrates that SVIM data will be an important resource for researchers interested in quantifying vegetation change through time across public rangelands in the western United States.

Human land use promotes the abundance and diversity of exotic species on Caribbean islands.

Human land use causes major changes in species abundance and composition, yet native and exotic species can exhibit different responses to land use change. Native populations generally decline in human-impacted habitats while exotic species often benefit. In this study, we assessed the effects of human land use on exotic and native reptile diversity, including functional diversity, which relates to the range of habitat use strategies in biotic communities. We surveyed 114 reptile communities from localities that varied in habitat structure and human impact level on two Caribbean islands, and calculated species richness, overall abundance, and evenness for every plot. Functional diversity indices were calculated using published trait data, which enabled us to detect signs of trait filtering associated with impacted habitats. Our results show that environmental variation among sampling plots was explained by two Principal Component Analysis (PCA) ordination axes related to habitat structure (i.e., forest or nonforest) and human impact level (i.e., addition of man-made constructions such as roads and buildings). Several diversity indices were significantly correlated with the two PCA axes, but exotic and native species showed opposing responses. Native species reached the highest abundance in forests, while exotic species were absent in this habitat. Human impact was associated with an increase in exotic abundance and species richness, while native species showed no significant associations. Functional diversity was highest in nonforested environments on both islands, and further increased on St. Martin with the establishment of functionally unique exotic species in nonforested habitat. Habitat structure, rather than human impact, proved to be an important agent for environmental filtering of traits, causing divergent functional trait values across forested and nonforested environments. Our results illustrate the importance of considering various elements of land use when studying its impact on species diversity and the establishment and spread of exotic species.

Managed Fire Frequency Significantly Influences the Litter Arthropod Community in Longleaf Pine Flatwoods.

Frequent prescribed burns are essential to pine forest restoration and management. Research studies have assessed effects of prescribed fire and burn frequency on plants and vertebrates, but impacts of fire on terrestrial invertebrate communities are still poorly understood. This case study investigated effects of burning frequency on species richness and community composition of social insects (ants, Hymenoptera: Formicidae and termites, Blattodea: Isoptera) in fire-managed Southern longleaf pine flatwoods in central Florida. Community response to different fire frequencies was assessed: burned annually, every 2 yr, or every 3 yr, 30 yr unburned and 75 yr unburned. Richness was similar across all treatments, but ant community composition and species density significantly differed between frequently burned (1, 2, and 3 yr) and long-unburned (30 and 75 yr) treatments. Long-unburned treatments had higher ant abundance, but the species present were less characteristic of open canopy longleaf pine habitat than ants in frequently burned treatments. The annual burn treatment differed from 2-yr burn in species density, but to a lesser degree. Exotic species abundance was highest in frequently burned sites; only native species were detected in the 75-yr unburned plot. The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), was detected in all regularly burned plots but not in long-unburned sites. Frequent burning at this site increased habitat suitability for ant species adapted to the sunny, open canopy, and diverse niches characteristic of longleaf pine forest; however, regular fire disturbance also increased the likelihood of exotic ant species establishment.

Effects of an atypical drought on the benthic macroinvertebrate community in a tropical reservoir

Abstract Atypical drought events have increasingly occurred in Brazil over the last years due to global climate changes. However, their consequences on aquatic biota in reservoirs are poorly known. We tested the hypothesis that macroinvertebrate communities are negatively affected by atypical drought events, given the sensitivity of many taxa to environmental changes. We predicted that: (a) there would be changes in limnological and sediment parameters between a regular year and an atypical year, (b) abundance and richness of the genera of Chironomidae and of exotic species would be higher due to the enhanced ability of these organisms to adapt to changes in the physical environment, and (c) community structure metrics (i. richness; ii. % richness; iii. abundance; iv. % abundance) would be affected by disturbance indices (i. Buffer Disturbance Index-BDI; ii. Local Disturbance Index-LDI; iii. Integrated Disturbance Index-IDI) in both years. The study was carried out in the reservoir of the Nova Ponte Hydroelectric Power Plant, state of Minas Gerais, comparing two sampling periods: a regular climatological year (2010) and an atypical drought year (2014). A total of 40 sampling sites were defined along the shore of the reservoir, and types of land use in the surrounding area of each site were measured, as well as physical habitat conditions, sediments, and benthic macroinvertebrate communities. Sampling was performed at these sites in the end of the rainy season in both years. The intensity of anthropogenic modifications was assessed at local scale and in the areas (buffers) surrounding the sampling sites using quantitative disturbance indices. There were striking differences in limnological parameters and sediment characteristics between sampling periods. Taxonomic richness was significantly lower in the drought year. As opposed to our predictions, richness and abundance of Chironomidae and exotic species did not increase with the atypical drought event. Besides, most community structure metrics showed a significant relationship with disturbance indices only during the regular climatological year, thus indicating that the large-scale effects of water stress may override the conditions of local habitats and the surrounding landscape. Therefore, in addition to a correct political-environmental management of water resources at local-scale, which includes maintaining the water quality and the riparian and landscape integrity, addressing large-scale climate issues is required for the maintenance of the ecological integrity of tropical reservoirs.

Distribution of fishes in the Río Guayalejo-Río Tamesí system and relationships with environmental factors in northeastern Mexico

A priority issue in ecology and biogeography is understanding the patterns in species diversity and the causal factors of their distribution, which allows the generation of information for conservation strategies. The longitudinal distribution of fishes and their relationships with environmental variables were studied in the Guayalejo-Rio Tamesi system (northeastern Mexico) from February 2000 to July 2001. A total of 5918 fish were caught in 27 collections along an altitudinal gradient in the main river course, from high mountain (1500 masl) to coastal plain near Tampico. Forty-three native and five exotic species, belonging to 35 genera in 23 families, were identified. Cluster analyses identified four major fish habitats in the river system. A distinctive euryhaline marine fish habitat (1) occurs near the mouth with native and two exotic species. Two other habitats consist essentially of freshwater fish species that are distributed along the longitudinal gradient. One of these habitats (habitat 4) shows greater diversity, as per the Shannon index value, and also includes amphidromous fish, in addition to two exotic freshwater fish; the other (habitat 2) includes freshwater, euryhaline and three exotic species. The changes in the frequency of occurrence and the abundance of Gambusia vittata, Astyanax mexicanus, and Xiphophorus variatus contribute to explaining differences between these habitats. Another habitat (3) is represented by two sampling sites located near the mouth and consist of freshwater and euryhaline fish and three exotic cyprinids with broad salinity tolerance. The low abundance and richness of exotic species suggest little impact on native fish fauna in this river. The fish assemblage of the Guayalejo-Tamesi river system species changes along a longitudinal gradient with the addition, replacement and presence of indicator species. Upstream fish fauna is mostly composed of freshwater species, some of them generalists that inhabit the entire longitudinal gradient, others that are restricted to certain sites, and the remainder of species is an assemblage composed of a mixture of euryhaline freshwater and marine species near the mouth.

The role of fertile anthropogenic soils in the conservation of native and exotic agrobiodiversity in Amazonian homegardens

Amazonian dark earths (ADE) are anthropogenic soils mostly created between 500 and 2500 years ago by pre-Columbian populations. ADE are currently used by local people for different agricultural and agroforestry systems. Because of their high fertility they may play an important role in the conservation of non-native agrobiodiversity. This study aimed to investigate the variation in richness and abundance of exotic and native species in homegardens along the ADE-background soil continuum. We conducted floristic inventories in 70 homegardens located in 7 riverside communities along the lower and middle Madeira River, Central Amazonia. Each species sampled was classified according to its origin: native Amazonian, American (from outside Amazonia) and non-American, and each individual was classified according to its form of establishment: cultivated or spontaneous. The floristic diversity was significantly related to soil fertility, texture and homegarden size. We found a positive relationship between soil fertility and richness of species and landraces. Homegardens on more fertile soils tended to have a higher richness and abundance of cultivated non-American species, as well as a higher richness and abundance of spontaneously established American species. Homegardens at the fertile end of the fertility gradient provided conditions for the establishment and growth of many species, especially exotic species, that are generally more nutrient-demanding than Amazonian species. Our results show that homegarden agroecosystems on ADE favour experimentation with the introduction of a wide range of species from various regions of the globe.

Nutrient addition shifts plant community composition towards earlier flowering species in some prairie ecoregions in the U.S. Central Plains.

The distribution of flowering across the growing season is governed by each species’ evolutionary history and climatic variability. However, global change factors, such as eutrophication and invasion, can alter plant community composition and thus change the distribution of flowering across the growing season. We examined three ecoregions (tall-, mixed, and short-grass prairie) across the U.S. Central Plains to determine how nutrient (nitrogen (N), phosphorus, and potassium (+micronutrient)) addition alters the temporal patterns of plant flowering traits. We calculated total community flowering potential (FP) by distributing peak-season plant cover values across the growing season, allocating each species’ cover to only those months in which it typically flowers. We also generated separate FP profiles for exotic and native species and functional group. We compared the ability of the added nutrients to shift the distribution of these FP profiles (total and sub-groups) across the growing season. In all ecoregions, N increased the relative cover of both exotic species and C3 graminoids that flower in May through August. The cover of C4 graminoids decreased with added N, but the response varied by ecoregion and month. However, these functional changes only aggregated to shift the entire community’s FP profile in the tall-grass prairie, where the relative cover of plants expected to flower in May and June increased and those that flower in September and October decreased with added N. The relatively low native cover in May and June may leave this ecoregion vulnerable to disturbance-induced invasion by exotic species that occupy this temporal niche. There was no change in the FP profile of the mixed and short-grass prairies with N addition as increased abundance of exotic species and C3 graminoids replaced other species that flower at the same time. In these communities a disturbance other than nutrient addition may be required to disrupt phenological patterns.

Structure and floristic composition as indicators of restoration success in an urban riparian forest along the Das Velhas river in Southeastern Brazil

ABSTRACTThis study evaluated a 5-year-old riparian forest in an anthropogenically affected region along the Das Velhas River in southeastern Brazil, restored with the purposes of erosion control and other ecosystem functions and to monitor indicators of structure and composition. The forest was monitored via data collection of the diameter and height of trees for phytosociological analysis, including the identification of species and their classification with regard to life form, origin, weed-status, and successional stage. The forest was not very structurally developed and, overall, 111 species were recorded consisting of 65.8% herbs, 24.3% trees, and 9.9% other types of life forms. About 70.9% of species were natives, 29.1% exotics, and 65% weeds. The high abundance of exotic species and weed species (some aggressive such as Leucaena leucocephala) of various life forms may negatively affect the restoration success in terms of seedling recruitment and diversity of native species, but may constitute a neutral or even positive accomplishment for erosion control (with species composition as a secondary effect). Results also reinforce the knowledge that choice of species for restoration must be in accordance with major local filters (e.g., floods), and areas within urban matrices may deserve special attention, including periodic management actions to control undesirable species.

Origin of EL3 chondrites: Evidence for variable C/O ratios during their course of formation—A state of the art scrutiny

AbstractMineral inventories of enstatite chondrites; (EH and EL) are strictly dictated by combined parameters mainly very low dual oxygen (fO2) and sulfur (fS2) fugacities. They are best preserved in the Almahata Sitta MS‐17, MS‐177 fragments, and the ALHA 77295 and MAC 88136 Antarctic meteorites. These conditions induce a stark change of the geochemical behavior of nominally lithophile elements to chalcophile or even siderophile and changes in the elemental partitioning thus leading to formation of unusual mineral assemblages with high abundance of exotic sulfide species and enrichment in the metallic alloys, for example, silicides and phosphides. Origin and mode of formation of these exotic chondrites, and their parental source regions could be best scrutinized by multitask research experiments of the most primitive members covering mineralogical, petrological, cosmochemical, and indispensably short‐lived isotopic chronology. The magnitude of temperature and pressure prevailed during their formation in their source regions could eventually be reasonably estimated: pre‐ and postaccretionary could eventually be deduced. The dual low fugacities are regulated by the carbon to oxygen ratios estimated to be >0.83 and <1.03. These parameters not only induce unusual geochemical behavior of the elements inverting many nominally lithophile elements to chalcophile or even siderophile or anthracophile. Structure and mineral inventories in EL3 and EH3 chondrites are fundamentally different. Yet EH3 and EL3 members store crucial information relevant to eventual source regions and importantly possible variation in C/O ratio in the course of their evolution. EL3 and EH3 chondrites contain trichotomous lithologies (1) chondrules and their fragments, (2) polygonal enstatite‐dominated objects, and (3) multiphase metal‐rich nodules. Mineralogical and cosmochemical inventories of lithologies in the same EL3 indicate not only similarities (REE inventory and anomalies in oldhamite) but also distinct differences (sinoite‐enstatite‐graphite relationship). Oldhamite in chondrules and polygonal fragments in EL3 depict negative Eu anomaly attesting a common cosmochemical source. Metal‐dominated nodules in both EL3 and EH3 are conglomerates of metal clasts and sulfide fragments in EH3 and concentrically zoned C‐bearing metal micropebbles (≥25 μm ≤50 μm) in EL3 thus manifesting a frozen in unique primordial accretionary metal texture and composition. Sinoite‐enstatite‐diopside‐graphite textures reveal a nucleation and growth strongly suggestive of fluctuating C/O ratio during their nucleation and growth in the source regions. Mineral inventories, sulfide phase relations, sinoite‐enstatite‐graphite intergrowth, carbon and nitrogen isotopic compositions of graphite, spatial nitrogen abundance in graphite in metal nodules, and last but not least 129I/129Xe and 53Mn/53Cr systematics negate any previously suggested melting episode, pre‐accretionary or dynamic, in parental asteroids.

Frequent inundation helps counteract land use impacts on wetland propagule banks

AbstractQuestionHow do contrasting influences of inundation and historical land uses affect restoration of soil propagule bank composition in floodplain wetlands?LocationNorthern Nature Reserve (large ephemeral floodplain), Macquarie Marshes, New South Wales, Australia.MethodsWe conducted germination assays on soil samples collected from fields with different land‐use histories, stratified along an inundation gradient. We used GLM to determine whether native and exotic species richness and abundance varied along gradients of inundation and land use.ResultsSpecies richness and plant abundance in soil propagule banks were positively related to inundation and negatively related to intense historic land use. The abundance of native species was significantly higher in more frequently inundated areas. Abundances of exotic and ruderal species were higher in areas of intense prior land use. Overall species richness was generally similar across land‐use histories.ConclusionsLand‐use legacies compromised the ability of propagule banks to rejuvenate native vegetation in this floodplain wetland, especially in less frequently flooded parts of the floodplain, which harboured more ruderal and exotic species. Negative effects of prior land use may be alleviated by increased inundation. Native soil propagule banks were remarkably intact, providing a reservoir for restoration of wetland vegetation, even in soils highly disturbed by up to 20 yr of agricultural cropping. With appropriate inundation, soil propagule banks in less degraded areas of the Macquarie Marshes can provide diverse mixtures of desired species in high abundance but, in highly degraded areas, full restoration may be delayed.

Exotic trees contribute to urban forest diversity and ecosystem services in inner-city Cleveland, OH

Vacant land, a product of population and economic decline resulting in abandonment of infrastructure, has increased substantially in shrinking cities around the world. In Cleveland, Ohio, vacant lots are minimally managed, concentrated within low-income neighborhoods, and support a large proportion of the city’s urban forest. We quantified abundance, richness, diversity, and size class of native and exotic tree species on inner-city vacant lots, inner-city residential lots, and suburban residential lots, and used i-Tree Eco to model the quantity and economic value of regulating ecosystem services provided by their respective forest assemblages. Inner-city vacant lots supported three times as many trees, more exotic than native trees, and greater tree diversity than inner-city and suburban residential lots, with the plurality of trees being naturally-regenerated saplings. The urban forest on inner-city vacant lots also had two times as much leaf area and leaf biomass, and more tree canopy cover. The quantity and monetary value of ecosystem services provided by the urban forest was greatest on inner-city vacant lots, with exotic species contributing most of that value, while native taxa provided more monetary value on residential lots. The predominately naturally-regenerated, minimally managed exotic species on vacant land provide valuable ecosystem services to inner-city neighborhoods of Cleveland, OH.

Effects of exotic annual grass litter and local environmental gradients on annual plant community structure

Exotic annual grasses have been introduced into many semi-arid ecosystems worldwide, often to the detriment of native plant communities. The accumulation of litter from these grasses (i.e. residual dry biomass) has been demonstrated to negatively impact native plant communities and promote positive feedbacks to exotic grass persistence. More targeted experiments are needed, however, to determine the relative impact of exotic grass litter on plant community structure across local environmental gradients. We experimentally added exotic grass litter to annual forb-dominated open woodland communities positioned along natural canopy cover gradients in southwest Western Australia. These communities are an important component of this region’s plant biodiversity hotspot and are documented to be under threat from exotic annual grasses. After a one-year treatment period, we measured the effects of exotic grass litter, soil properties, and canopy cover on native and exotic species richness and abundance, as well as common species’ biomass and abundances. Plant community structure was more strongly influenced by soil properties and canopy cover than by grass litter. Total plant abundances per plot, however, were significantly lower in litter addition plots than control plots, a trend driven by native species. Exotic grass litter was also associated with lower abundances of one very common native species: Waitzia acuminata. Our results suggest that exotic grass litter limits the establishment of some native species in this system. Over multiple years, these subtle impacts may contribute substantially to the successful advancement of exotic species into this system, particularly in certain microenvironments.

Are conservation units in the Caatinga biome, Brazil, efficient in the protection of biodiversity? An analysis based on the drosophilid fauna

Biodiversity is believed to be low in regions with vegetation that has adapted to water stress. Additionally, there is little interest by authorities in establishing and expanding conservation units in these areas. In Brazil, the Caatinga and the Cerrado biomes comprise this xerophilous vegetation. In both, climate is tropical and the dry season is long and well-defined. The Caatinga is the Brazilian biome with the smallest area protected by conservation units. This study evaluates the efficacy of conservation units in the Caatinga biome based on abundance and richness of drosophilids. Flies were collected inside and outside these areas. In total, approximately 23,000 flies of 32 species were collected in six conservation and six non-conservation sites. Two non-described species occurred exclusively inside protected areas, underlining the importance of conservation efforts in the maintenance of biodiversity. Other species were recorded exclusively outside conservation areas, which emphasizes the importance of establishing and expanding conservation units in the Caatinga. Native species were significantly more abundant inside conservation units, though the richness was similar in protected and non-protected areas. Abundance of exotic species outside conservation areas was statistically different in comparison with that of native ones.

Initial soil amendments still affect plant community composition after nine years in succession on a heavy metal contaminated mountainside

AbstractMany efforts to restore disturbed landscapes seek to meet ecological goals over timescales from decades to centuries. It is thus crucial to know how different actions available to restoration practitioners may affect ecosystems in the long term, yet few such data exist. Here, we test the effects of seed and compost applications on plant community composition 9 years after their application, by taking advantage of a well‐controlled restoration experiment on a mountainside severely degraded by over 80 years of zinc smelting emissions. We asked whether plots have converged on similar plant communities regardless of initial seed and compost treatments, or if these initial treatments have given rise to lasting differences in whole plant communities or in the richness and abundance of native, exotic, and planted species. We found that compost types significantly affected plant communities 9 years later, but seed mix species composition did not. Observed differences in species richness and vegetative cover were negatively correlated, and both were related to the differences in plant communities associated with different compost types. These observed differences are due primarily to the number and abundance of species not in original seed mixes, of which notably many are native. Our results underscore the importance of soils in shaping the aboveground composition of ecosystems. Differences in soil characteristics can affect plant diversity and cover, which are both common restoration targets. Even in highly polluted and devegetated sites, compost and seed application can reinstate high vegetative cover and allow continued colonization of native species.