Spatial Pattern In Invasive Grasses Of California

Author : Meghan J. Skaer Thomason
Publisher :
ISBN 13 : 9781339066332
Total Pages : pages
Book Rating : 4.0/5 (663 download)

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Download or read book Spatial Pattern in Invasive Grasses of California written by Meghan J. Skaer Thomason and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Invasive species may alter their environment in ways that influence their distribution patterns. In particular, positive feedbacks between plant traits and resource use can lead to distinct pattern formation. Plant traits that might interact with their environment include litter chemistry and developmental phenology. The degree to which invasive species may benefit from positive feedback is unknown. Furthermore, there is little detailed information about how demography might be affected by positive feedbacks, or how demography might influence distribution pattern formation. Climate change will likely influence the spread and impact of biological invasions, and interact with distribution pattern. It is important to predict which invasive species will benefit from future changes in climate, and thereby identify those problematic invaders that may need particular attention and prioritization of management efforts. Population demographics are a major indicator of invasion status and a key component needed to develop effective invasive species management strategies or to predict invasive species response to climate change. In the heavily invaded annual grasslands of the California Floristic Province, a biodiversity hotspot, two introduced invasive annual grasses, Elymus caput-medusae and Aegilops triuncialis, form dense stands (patches) interspersed across the landscape. These species have the potential to interact with their environment because of unique, recalcitrant litter chemistry as well as extended phenology that sets them apart from other annual competitors. I investigated the interaction between these invasive annual grasses, their competitors, and their environment with three studies, using observation, modeling, and a field experiment. The observational study aims to understand if E. caput-medusae interacts with its environment in forming patches, or instead responds passively to extant edaphic patterns. To address this aim, I measured demography across two generations, evaluated xylem water stress in E. caput-medusae, and measured edaphic factors across transects within and beyond established E. caput-medusae patches. Findings from this study indicate that demographic parameters vary across a small spatial scale and that E. caput-medusae phenology may lead to spatial "resource banking" of water in dense patches. I developed model based on the Tilman resource competition framework focusing on two groups of species: the invasive Mediterranean cool-season annual grasses and a pair of more recent invaders with a 2-4 week longer growing season (E. caput-medusae and A. triuncialis). I modeled litter feedback as a potential driver of invasion dynamics in California grasslands. Litter feedback in the model was a critical aspect for accurately modeling species range limits because actual species distribution was not modeled well until litter feedback effects were included. For areas with higher annual precipitation, there may be a period of time where restoration techniques like seeding might be especially important for long-term invader control. Finally, I developed a field experiment to understand the interaction of climate change and local-scale patterning on the demography of A. triuncialis. I manipulated rainfall (reduced, ambient, or augmented), seed density (300 or 600 seeds/m2), and local-scale seeding pattern in a full factorial experiment. Demographic and environmental data were collected for three years following initial establishment. Pattern and scale figure prominently in the demographic response of A. triuncialis to rainfall manipulation, where aggregated plantings led to increased reproductive output at two of three scales of observation. These results indicate that increasing the probability of interspecific interactions would likely be detrimental to A. triuncialis infestations, and should factor into developing management strategies.