MacDonald, SuzanneZuliani, Mario2024-11-072024-11-072024-05-302024-11-07https://hdl.handle.net/10315/42404In recent decades, facilitative interactions have been the focus of ecological studies, specifically those with foundational shrubs within drylands. However, little has been done to analyze how the density of shrubs influence the frequency of these interactions. Here, I aim to establish shrub density as a crucial measure in ecology and facilitative interactions. I begin with a systematic review and meta-analysis (Chapter 2) to quantify the current understanding of shrub density on local animal abundance. A full text review of shrub density and animal abundance was conducted with 113 unique observations utilized in the meta-analysis. Shrub density positively predicted animal abundance, specifically within grassland and desert ecosystems. I conducted a greenhouse experiment to examine the effects of temperature on native and invasive plant species germination (Chapter 3). Temperatures were manipulated to simulate cooler microclimates and high temperature extremes. Increasing temperatures reduced germination, establishment, and biomass of all plant species, with the invasive species suffering more than natives. I conducted a telemetry experiment to determine the effects of shrub densities on an endangered species (Chapter 4). Telemetry data was combined with satellite-based counts of shrub density. Increasing shrub densities positively predicted the presence of G. sila individuals above ground. A field experiment comparing high and no shrub densities across aridity ecosystems in Southern California was conducted (Chapter 5). Camera traps were used at distinct ecosystems across southern California to determine vertebrate association. Areas of high shrub density influenced the richness and evenness of vertebrate species, while increasing temperatures negatively impacted vertebrate abundance, richness, and evenness. Finally, I tested if facilitative associations could be replicated with artificial structures (Chapter 6). Mimics were deployed within California drylands. Camera traps were utilized to estimate vertebrate communities, with temperature pendants used to contrast microclimates. Shrubs and mimics had similar microclimates, reducing the temperature underneath their canopy. Mimics displayed a higher vertebrate abundance and richness than open areas. These findings illustrate that facilitation between shrubs and dryland communities are crucial interactions. These findings suggest that shrub density is a critical measure, increasing the likelihood of interactions and possible benefits associated with shrubs.Author owns copyright, except where explicitly noted. Please contact the author directly with licensing requests.EcologyBiologyConservation biologyElectronic Thesis or Dissertation2024-11-07Shrub densityFacilitationArtificial structuresDrylandMimicDesertAridSemi-aridCommunity compositionFoundation speciesPlant-animal interactionsResourceConservationRestorationGambelia silaEphedra californicaMeta-analysisSystematic reviewGreenhouseNativeInvasivePlantAnimal