Between Dec 19, 2024 and Jan 2, 2025, datasets can be submitted to DRUM but will not be processed until after the break. Staff will not be available to answer email during this period, and will not be able to provide DOIs until after Jan 2. If you are in need of a DOI during this period, consider Dryad or OpenICPSR. Submission responses to the UDC may also be delayed during this time.

Browsing by Subject "Restoration ecology"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Is fertilization essential for taking care of the next generation of tropical trees?
    (2022-12) Toro-Gonzalez, Laura
    Regrowing tropical forest is one of the main challenges of this decade. However, thischallenge goes beyond tree planting at small scales, ensuring that this practice can be scaled up, that the planted trees will grow, that native species will colonize, and that these plantations will become a functional forest is the main goal. Understanding plant-soil interactions in restoration settings can aid accelerate the regeneration process in degraded areas where active restoration initiatives are needed (tree planting or apply nucleation), and it can also help implement more costeffective restoration strategies. Some studies have found that P is the only nutrient limiting plant performance, while other nutrient manipulation studies and meta-analyses suggest that at the ecosystem scale there is colimitation by N, P, and other macronutrients. However, plant species from different functional groups respond in different ways to P availability. N-fixing species for example have higher responses to P addition, while non-N-fixing species have higher responses when the combination of NP is added. Even though, several nutrient manipulation experiments and meta-analysis have tested these hypotheses at the tree level, few studies have extensively evaluated how this costly practice influences seedling growth and survival across the tropics and how variable the cost-effectiveness of this practice is across species. Therefore, the main goal of this research was to determine how nutrient addition impacts the growth and survival of tree seedling species (i.e., Nitrogen (N)-fixing and non-N-fixing species) across the tropics. To do that, I first investigated how tropical dry forest N-fixing and non-N-fixing seedlings growing in shade house conditions in Costa Rica respond to P addition and how P acquisition strategies vary with P addition. I found that N-fixing seedlings had higher responses to P addition compared to non-Nfixers, and that P acquisition strategies were not down-regulated with P addition. Then, I tested this hypothesis at a larger scale where I established a 7-hectare tropical dry forest active restoration project in Southwestern Colombia. There I tested if P or the combination of multi-nutrients (N, P, and potassium) and water had an impact on seedling growth and survival. I also calculated the costeffectiveness of the different management practices implemented after two years of plant establishment. I found that the management strategies implemented did not have an effect on seedling growth and survival, instead the species identity had the highest influence over these two variables. Additionally, the most cost-effective management strategy was the unamended control. Finally, I conducted a meta-analysis to look at how nutrient addition impacts seedling growth and survival in shade-house and field studies across the tropics and explored the responses of N-fixing and non-N-fixing seedlings. This analysis showed that nutrient addition impacts the growth but not the survival of seedlings growing in both field and shade house studies. Additionally, seedlings grown in shade houses had higher responses to nutrient addition than seedlings growing in the field. v The magnitude of the increase in growth in shade houses double the one reported in field studies. Finally, non-N-fixers were more responsive to nutrient addition than N-fixer seedlings in shade houses and field studies. Collectively, these three studies help us to understand how nutrient addition impacts the survival and growth of N-fixing and non-N-fixing seedlings across the tropics and provide insight into when this practice should be implemented in restoration settings.
  • Thumbnail Image
    Item
    Restoring Oak Savannas with Multiple Disturbances: Thinning, Burning, and Targeted Cattle Grazing
    (2023-06) Yantes, Austin
    Temperate savannas are one of the rarest and most imperiled ecosystems in the world. In the Upper Midwest (USA), over 99% of pre-colonial oak savanna area has been lost due to extensive habitat conversion and altered disturbance regimes. In this region, savannas were characterized by a grass-sedge-forb ground layer and widely-spaced oaks (e.g., Quercus macrocarpa). This open structure was maintained historically by frequent disturbances including fires (primarily Indigenous burning) and grazing by megaherbivores (e.g., Bison bison). Due to fire suppression and the near extinction of native grazers, savannas often persist today in a degraded, woody-encroached state. Restoring savanna remnants is challenging because we don’t know how to best apply contemporary restoration tools to mimic historic disturbances. To that end, my dissertation evaluated the response of oak savanna vegetation and wildlife to a gradient of restoration actions: 1) no management, 2) tree thinning, 3) thinning + burning, and 4) thinning + burning + cattle grazing. I found that thinning and burning successfully increased canopy openness, herbaceous cover and diversity, and savanna-associated plant species such as Ceanothus americanus, Andropogon gerardii, Galium boreale, and Agastache scrophulariifolia. Bird abundance and species richness also responded positively to thinning and burning, while butterfly abundance/richness and the activity of most bat species did not differ across the restoration treatments. Thinning and fire had the unwanted effect of increasing shrub density, particularly Corylus americana. I then evaluated if shrub density could be reduced using short-duration targeted cattle grazing under high stocking density. The results suggest that targeted grazing with Angus/Angus cross cattle can be an effective tool to reduce shrub density in the short-term, but repeated management is needed to prevent resprout. I documented no negative impact of cattle grazing on birds, butterflies, or bats throughout the duration of this study. Overall, the results of my dissertation suggest that combining multiple restoration strategies partially achieves vegetation goals and improves bird habitat without negatively affecting butterfly and bat communities. A key takeaway from this work is that restoration outcomes are not dictated by how many management approaches are applied, but rather, the nuances of how they are applied.
  • Thumbnail Image
    Item
    Using functional traits to understand community assembly, responses to drought, and restoration in tropical dry forests
    (2017-12) Werden, Leland Kendall
    Tropical forests have been extensively degraded and deforested. Recent global restoration initiatives, such as the Bonn challenge, have emerged in an attempt to reverse these trends. To ensure these initiatives are effective, continued effort must be made to integrate ecological theory with restoration practice. It is imperative that some of this effort is focused on tropical dry forests (TDFs), as they are critically endangered and their restoration is understudied. Conservation efforts in NW Costa Rica have been effective in passively regenerating extensive areas of TDF, but the presence of degraded Vertisols in this region present a unique challenge and requires an active restoration approach. Furthermore, functional traits have been used to predict the outcomes of applied restoration of tropical wet forests, but their utility had not been evaluated in TDF. The goal of this research was therefore to determine how tree species in passively and actively restored TDFs use different functional strategies, to cope with stressful environmental conditions such as extreme drought and growing in degraded soils. In Chapters 1 and 2 I focused on determining how the functional strategies of tree species drive patterns in passively restored TDFs. In Chapter 1, I studied how abiotic and biotic gradients predict the landscape scale occurrence of TDF tree species, and I found that functional traits clarify community assembly mechanisms along these gradients in passively regenerating TDFs. In Chapter 2, I focused on the hydraulic responses of woody species to extreme drought and I found that trees and lianas have overlapping water-use strategies, but different in their leaf economic traits. In Chapters 3 and 4 I focused on using a similar functional trait-driven approach to actively restore TDF on degraded Vertisols. In Chapter 3, I implemented a 32 species trial to select native TDF species for Vertisol restoration. My results suggest that functional traits most predictive of survivorship and growth in TDF restoration correspond to how species capture carbon and tolerate drought. Finally, for Chapter 4, I used a 6 hectare Vertisol restoration project to conduct the first empirical test of how species with contrasting functional strategies perform at different TDF successional stages. The results from this study suggest that resource acquisition strategies of TDF tree species can be used to predict species’ responses to changes in microclimatic conditions over succession. Collectively these four studies contribute significantly to our understanding of how functional strategies of TDF tree species dictate their responses to drought and gradients in abiotic conditions in both passively and actively restored TDF.
  • Thumbnail Image
    Item
    Wet Meadow Revegetation Following Invasive Plant Control
    (Minnesota Department of Transportation, 2008-01) Iannone III, Basil V.; Galatowitsch, Susan M.
    Phalaris arundinacea invades sedge meadow restorations, forming persistent monotypes that prevent community establishment. Eradicating Phalaris, however, leaves restored ecosystems prone to reinvasion. In order to restore desired plant communities, methods to control Phalaris are needed. To determine if reducing light by sowing cover crops and reducing nitrogen by incorporating soil-sawdust amendments would prevent Phalaris invasions, a study was conducted under conditions similar to a restored wetland in two experimental basins with controlled hydrology. Seeds of a 10-species target community and Phalaris were sown in plots with high diversity, low diversity, or no cover crops in soils with or without sawdust amendments. Nitrogen, light, tissue C:N ratios, firstyear seedling emergence, establishment, and growth, and second-year above ground biomass were measured. Only high diversity cover crops reduced light and sawdust reduced nitrogen for about 9 weeks. Similar trends in firstyear seedling data and second-year biomass data suggested Phalaris control efforts should focus on establishing perennial communities rather than implementing separate resource-limiting strategies. Sowing high diversity cover crops resulted in Phalaris-dominated communities, making cover crops an ineffective Phalaris control strategy. Using sawdust amendments did not reduce Phalaris invasion much beyond what the target community did but resulted in a community similar to those of natural sedge meadows by increasing the abundance of seeded species from the Cyperaceae family and colonization of non-seeded wetland species. The target community apparently reduced Phalaris invasion by reducing both light and nitrogen. Regardless, no treatment fully prevented invasion, making follow-up Phalaris control necessary to ensure community recovery.