Globally, biological invasions can have strong impacts on biodiversity as well as ecosystem functioning. While less conspicuous than introduced aboveground organisms, introduced belowground organisms ...may have similarly strong effects. Here, we synthesize for the first time the impacts of introduced earthworms on plant diversity and community composition in North American forests. We conducted a meta‐analysis using a total of 645 observations to quantify mean effect sizes of associations between introduced earthworm communities and plant diversity, cover of plant functional groups, and cover of native and non‐native plants. We found that plant diversity significantly declined with increasing richness of introduced earthworm ecological groups. While plant species richness or evenness did not change with earthworm invasion, our results indicate clear changes in plant community composition: cover of graminoids and non‐native plant species significantly increased, and cover of native plant species (of all functional groups) tended to decrease, with increasing earthworm biomass. Overall, these findings support the hypothesis that introduced earthworms facilitate particular plant species adapted to the abiotic conditions of earthworm‐invaded forests. Further, our study provides evidence that introduced earthworms are associated with declines in plant diversity in North American forests. Changing plant functional composition in these forests may have long‐lasting effects on ecosystem functioning.
We evaluated the efficacy of a mixture of ground hot mustard and water as a sampling method for earthworms (Lumbricina) in research projects involving citizen scientists. To do so we conducted a ...field experiment to determine if sampling earthworms using mustard-powder would reveal similar patterns of earthworm abundance and community composition as relying on the more difficult to prepare, and possibly hazardous, allyl isothiocyanate (AITC) solution. Earthworms were sampled using either mustard or AITC in four pairs of 0.25-m2 plots located in each of four woodland sites that were predicted to exhibit a range of earthworm densities. Soil gravimetric water content (GWC) of each plot was quantified as a covariate. For analyses of changes in abundance and community structure, earthworms were classified as belonging to one of five groups based on where they occur in the soil profile, developmental stage, and level of taxonomic identification. The two sampling techniques revealed similar earthworm abundances and community composition across the four sites (all Ps > 0.16) and across the range in GWC (all Ps > 0.36). We conclude that using the mustard-water mixture to sample earthworms at our study site appears to be just as effective and reliable as using AITC. The mustard-water mixture, which is easier to prepare and is less hazardous than AITC solution, should, therefore, be considered as an appropriate tool to be utilized by researchers who collaborate with citizen scientists to help collect the large datasets needed to reveal how woodland management and restoration programs affect earthworms.
Urbanized and post‐industrial sites often host considerable biodiversity but are too frequently dismissed by conservation professionals, in part because current species assemblages differ from the ...site's natural history. Given the dramatic and often irreversible changes to these sites, we conclude that historic ecosystems do not provide a useful reference for restoration. However, seen through a novel ecosystem lens, these landscapes already have conservation value and thus require nuanced restoration planning that recognizes their current and potential community composition. We highlight slag‐dominated sites in the brownfields of the Calumet region as an example of a post‐industrial landscape that may serve both as a recreational area for humans and a refuge for native biodiversity.
We summarize the factors that shaped the biodiversity of Chicago and its hinterland and point out the conservation significance of these ecological systems, addressing why conservation of Chicago’s ...biodiversity has importance locally and beyond. We highlight Chicago Wilderness (CW), a regional biodiversity conservation alliance committed to protecting nature and enriching the lives of the region’s residents. Chicago Wilderness, with over 250 institutional members, has for over a decade coordinated the efforts of diverse institutions, including federal, state, and local agencies, public land-management agencies, conservation organizations, and scientific and cultural institutions. Chicago Wilderness is committed to using science and emerging knowledge as a foundation for its conservation work. CW has several specialist teams that promote an interdisciplinary approach to conservation; we focus on the work of the CW Science Team, the one team with a research mission. The scientific investigations that are undertaken to provide a knowledge base for the work of Chicago Wilderness have drawn upon a wide variety of conservation paradigms, including that of resilience thinking, which we illustrate in a series of case studies.
We conducted a three-year field experiment to determine if amending soils with mulched European buckthorn (Rhamnus cathartica) can limit reinvasion, and whether two methods of incorporation—tilling ...or surface application—produce similar results. Mulch (a high carbon: nitrogen C:N material) may reduce reinvasion by stimulating soil microbial immobilization of N. Converting the woody waste generated during buckthorn removal into mulch would also eliminate both the need to remove this waste from restoration sites and the expense of acquiring amendments from elsewhere. We found that adding buckthorn mulch to soils, whether tilled or not, did not decrease either buckthorn reinvasion or soil N availability. The mechanical disturbance of tilling, however, caused a large, prolonged reduction in reinvasion by killing a previously unrecognized but major contributor to reinvasion—small buckthorn individuals (most < 5 cm tall) that were undetected during initial removal. Recruitment of new individuals occurred during the experiment, but recruitment rate decreased rapidly over time, suggesting that buckthorn seeds are short-lived. Three major recommendations emerge: (1) buckthorn mulch should not be used to limit reinvasion; (2) tilling can greatly reduce reinvasion by killing buckthorn individuals that are undetected during initial removal; and (3) because buckthorn seeds appear to be short-lived, reinvasion can be reduced by repeated, annual follow-up control of undetected and newly recruited individuals.
•We examined how comprehensive vegetation management alters woodland arthropods.•Activity-densities of non-native isopods were highest in unmanaged woodlands.•Springtails (entomobryid Collembola) and ...wolf spiders were highest in managed sites.•The shift in arthropod community structure was correlated with invasive-plant cover.•We conclude that woodland vegetation management also restores arthropod communities.
Restoration of woodlands that have been invaded by exotic plants has primarily focused on restoring vegetation structure by removing invaders and planting native species that have declined in abundance. Management practices to date continue to focus on plant communities, but if restoring ecosystem integrity is the goal of restoration, knowledge of how the fauna has recovered is essential. We examined the impact of vegetation restoration and management on the surface-active arthropod community across a spectrum of 22 woodland sites in the greater metropolitan Chicago region. Sites were grouped into three categories based on existing condition. Invaded sites had never been restored or managed (“Control”, n=5); had been undergoing restoration for 3–21years (“Managed-int”, n=12) but were not yet near the management goal; or were restored plots (11–21years of management) that land managers identified as representative of their restoration target based upon the vegetation present (“Managed-REF”, n=5). Each site was a one-ha plot containing four pitfall traps used to assess activity-densities of 35 taxa of epigeic arthropods. Permutational analysis of variance (PERMANOVA) and subsequent canonical analysis of principal coordinates (CAP) revealed that arthropod community structure varied between Control and Managed-REF sites, with the Managed-int sites demonstrating convergence toward the Managed-REF. The activity-densities of non-native isopods (detritivores) were nearly twice as high in Control sites compared to Managed-REF sites, whereas traps in Managed-REF sites had four times the number of Collembola (fungivores). Distance-based redundancy analysis (dbRDA) revealed that invasive woody plant cover and rates of uptake of soil P and NO3− by root simulators explained over 40% of the variation in arthropod community structure. Our findings suggest that restoration management targeted at the vegetation also restores the arthropod community in woodlands to a composition that has fewer non-native arthropods.
Electrophilic trisubstituted ethylenes (TSE), halogen ring-substituted ethyl 2-cyano-1-oxo-3-phenyl-2-propenylcarbamates, RC
6
H
4
CH˭C(CN)CONHCO
2
C
2
H
5
(where R is 3-Br, 4-Br, 3-Cl, 4-Cl, 2-F, ...3-F, and 4-F) were prepared and copolymerized with styrene (ST). The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and N-cyanoacetylurethane, and characterized by CHN analysis, IR,
1
H, and
13
C NMR. All the ethylenes were copolymerized with ST (M
1
) in solution with radical initiation (AIBN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR,
1
H, and
13
C NMR. The order of relative reactivity (1/r
1
) for the monomers is 2-F (3.81) > 3-Cl (1.36) > 4-Br (1.31) > 3-Br (1.13) > 4-F (0.90) > 3-F (0.63) > 4-Cl (0.37). Higher T
g
of the copolymers in comparison with that of polystyrene indicates decrease in chain mobility of the copolymer due to the high dipolar character of the TSE structural unit. Gravimetric analysis indicated that the copolymers decompose in the range 303-319°C.
European buckthorn (
Rhamnus cathartica), a prevalent invasive shrub in relict woodlands throughout Northeastern Illinois, alters certain soil properties in a manner that may have importance for the ...long-term conservation management of these systems. We found that soil in areas of the woodland where buckthorn dominates have higher percentage of nitrogen (N) and carbon (C), modified nitrogen mineralization rates, elevated pH, and higher soil moisture than those areas where buckthorn was not present. Although there were small C:N ratio differences at two of the three sites, there was no overall difference in C:N ratios between the sites. Since the long-term management for these systems often calls for restoration to pre-invaded conditions, the likelihood that the invasive shrub is creating a legacy effect of altered ecosystems properties may call for reassessed management strategies.
Ecological restoration is a land management tool for biological conservation in areas where ecosystems are subject to a suite of natural and anthropogenic disturbances. This approach is particularly ...critical in urban areas where disturbances are often frequent and substantial. Restoration projects aim to re-establish an entire ecosystem, including the native organisms as well as the ecological processes and biotic interactions of those ecosystems for long-term sustainability. In practice, ecological restoration has primarily focused on establishing a diverse plant community while largely ignoring the belowground components of ecosystems. Surprisingly little is known about the complex relationships between soil factors, plant communities, and ecosystem processes in pristine systems, and even less is known about these relationships in restored or urban systems. In my dissertation, I ask: how do aboveground-focused management practices influence plant communities and belowground processes in the Chicago region? I address this question using research that spans spatial and temporal scales and includes different terrestrial habitats. I examine ecological patterns of restoration activities at sites replicated across a large landscape, plant-soil interactions at the site level, and interactions between plant tissues and fungal communities using molecular techniques. I also address these questions across temporal scales. Using a restoration chronosequence, I use a space for time substitution to investigate ecological patterns over large periods of time. In a manipulative field study, I examine plant-soil dynamics over a period of 4 years. My study sites include private and publicly owned lands that represent a range of upland terrestrial habitats in the Midwestern U.S. and are managed by citizen scientists, government agencies, and professional contractors and combinations therein. My highly replicated, regionally comprehensive, and ecologically and politically representative experimental approach ensures that conclusions from my research have direct and immediate impacts on the understanding these ecosystems and how they are managed. In Chapter 1, I describe the development of a collaborative network of protected sites that capitalize on the shared best management practices in the Chicago region. This network links on-the-ground restoration and land management activities with ecological research. This chapter provides the conceptual and experimental framework as well as experimental methods for collecting baseline data used in the subsequent studies. In Chapter 2, I describe how patterns in plant community structure and soil nutrient levels in woodlands and prairies differ with management duration and relate to each other. I found that in prairies, land use history is the most important factor in determining plant community assemblage followed by more recent land management activities. In woodlands, the initial action of removing woody invasive taxa is critical to initiating ecosystem restoration, while on-going management maintains community composition. In Chapter 3, I used geo-spatial analysis to develop a model of woodland degradation that integrates invasive shrub density, exotic earthworm biomass, and soil nitrogen (N) availability. Using this model, I found that unrestored sites have significantly higher invasive shrub cover, exotic earthworm biomass, and soil nitrogen availability than managed sites, regardless of their time under management. I also identified notable exceptions to these patterns that may be used to direct and prioritize future investigations and ultimately, lead to more cost-effective restoration efforts. In Chapter 4, I examine the decomposition rates of leaf litter in remnant and former row-crop agricultural prairie ecosystems across the restoration chronosequence and describe the functional and community composition of the decomposer fungal communities. I found that leaf chemistry was a more important driver of litter mass loss than either land use history or management duration. I also found that although fungal communities differed in composition, they remained functionally similar across all sites. In Chapter 5, I conducted a manipulative field experiment exploring traditional and novel methods of restoration following the invasion of a non-native shrub (Rhamnus cathartica). I determined that amending soils with woody mulch following buckthorn removal significantly reduced reinvasion over the four-year field study period but that these results are not due to a reduction in soil N availability. Manipulative studies in the greenhouse similarly showed that mulch-amended soils significantly reduced buckthorn germination, seedling growth, and transplanted sapling growth. The results of this study suggest that incorporation of ground woody material into the soil following aboveground removal may facilitate restoration following European buckthorn invasion. (Abstract shortened by ProQuest.)
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