Life Sciences Commons^™

Landscape Scale: Inter- And Intraspecific Variation In Plant Interactions Along A Stress Gradient In The Sheep Range Of Nevada, Jordan Dowell

UNLV Theses, Dissertations, Professional Papers, and Capstones

Impending threats to shrubland ecosystems, posed by climate change, necessitate niche modeling efforts to project vegetation range shifts. However, efforts often remain unguided by individual-scale interspecific plant interactions. The stress gradient hypothesis posits that facilitation should increase in areas of high abiotic stress, only if the individuals are able to ameliorate the surrounding area via functional traits. The Sheep Range of Nevada was used to assess the role of functional traits as predictors of plant association. Larrea tridentata, Coleogyne ramosissima, and Artemisia nova were selected as shrubs with variable life history strategies and ranges in order to identify general patterns …

Watching Grass Grow: How Soil Moisture Affects Vesicular-Arbuscular Mycorrhizae And Growth In Little Bluestem, Laura M. Jones

Honors Scholar Theses

Vesicular-arbuscular mycorrhizae (VAM) are an ancient mutualism in which soil-dwelling fungi enhance plant absorption of phosphorus and nitrogen in exchange for photosynthates. VAM are sensitive to changes in soil moisture and nutrient content, fluctuating between mutualism and parasitism depending on conditions of drought stress and nutrient deficiency. Understanding how VAM respond to precipitation changes is crucial for both conservation and agricultural purposes. To test how soil moisture changes the effects of VAM colonization and growth in little bluestem (Schizachyrium scoparium), a common prairie grass, I planted 300 seeds in a greenhouse in sterilized soil and soil inoculated with …

Effects Of Elevated Temperature And Elevated Co2 On Leaf Carbon Fluxes In Boreal Conifers: Lab And Field Studies, Mirindi Eric Dusenge

Electronic Thesis and Dissertation Repository

Rising CO₂ may warm northern latitudes up to 10 °C by the end of the century. However, responses of plant physiological processes (such as photosynthesis and respiration) and growth to climate change remain uncertain. Seedlings and mature trees of tamarack (a deciduous species) and black spruce (an evergreen species), North America dominant conifers, were exposed to combined warming (up to +9 ˚C) and elevated CO₂ (up to +300 ppm). In seedlings, stomatal conductance (g_s) tended to increase with warming in tamarack seedlings, while g_sdeclined with warming in spruce. In both species, CO₂ had …

Diffuse Light And Wetting Differentially Affect Tropical Tree Leaf Photosynthesis, Z. Carter Berry, Gregory R. Goldsmith

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

‐Most ecosystems experience frequent cloud cover resulting in light that is predominantly diffuse rather than direct. Moreover, these cloudy conditions are often accompanied by rain that results in wet leaf surfaces. Despite this, our understanding of photosynthesis is built upon measurements made on dry leaves experiencing direct light.

‐Using a modified gas exchange setup, we measured the effects of diffuse light and leaf wetting on photosynthesis in canopy species from a tropical montane cloud forest.

‐We demonstrate significant variation in species‐level response to light quality independent of light intensity. Some species demonstrated 100% higher rates of photosynthesis in diffuse light …

Warming Up: Climate Change Related Shifts Of Mycorrhizal Fungal Communities In High Latitude Ecosystems, Megan Rae Devan

Biology ETDs

This dissertation examines how climate change affects mycorrhizal fungal communities in boreal and arctic ecosystems. In chapter one, I revealed that increases in fire severity and related increases in deciduous tree dominance result in greater Ascomycota relative abundance (RA) and subsequent declines in Basidiomycota RA. In chapter two I analyzed the effects of post-fire mycorrhizal fungal communites on host growth. There were trends at the fungal genus level that were largely reflected at the guild level across all hosts; however, there were some fungal genera that had the opposite effect on different host species. In chapter three, I found host …