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Linking community and ecosystem dynamics in invasion biology: An experimental approach in coastal sage scrub.

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Call No.	QH105.C2 W65 2009
Author	Wolkovich, Elizabeth Mary.
Title	Linking community and ecosystem dynamics in invasion biology: An experimental approach in coastal sage scrub.
Date	2009
Abstract	Though the science of invasion biology has over a 50-year history it still struggles with clearly documenting the mechanisms and impacts of plant invasions. Numerous observational studies find associations between plant invasions and largescale ecosystem and community changes but fail to document mechanistic causal links. The result is that identifying which changes are caused by plant invasions or occur due to other contemporaneous, confounding landscape alterations is often impossible. At the same time almost all studies of plant invasions focus on effects of the invader's living biomass, ignoring the changes in plant litter associated with invasion. Here I use a field manipulation of non-native litter to characterize both the impacts and the mechanisms of invasive grass litter in coastal sage scrub (CSS), a semi-arid shrub habitat of southern California undergoing the invasion of several non-native annual grasses. Addition of grass litter facilitated non-native grass growth, revealing a positive feedback likely to enhance invasion success. Surprisingly, I found similar positive responses of the shrubs to litter: they grew most with litter addition and least with litter removal. Thus, contrary to a major paradigm of invasion biology--that invasive plants compete with and to the detriment of native species--I found invasive grasses, via their litter, enhanced growth of the native dominant shrub. Non-native litter also greatly benefited shrub arthropod communities, but produced idiosyncratic effects on ground arthropod communities. For shrub arthropods a simple bottom-up effect of litter on shrub growth lead to increased herbivore and arthropod communities with no changes in the species composition. In contrast, ground arthropod communities showed a variety of responses to litter. Total arthropods decreased with the addition of litter, due predominantly to declines of the two dominant arid-specialist native ant species. Further, the major detritivore and predator taxa did not respond to manipulation, indicating the increased food provided by litter did not benefit the detrital web. Finally, I found grass litter greatly increased carbon and nitrogen storage in plant litter, aboveground native and non-native biomass, and soil. My results have widespread implications for changes in ecosystem and community properties of semi-arid systems undergoing grass or shrub invasions.
Description	xi, 201 leaves : ill. ; 28 cm
Format	application/pdf
Advisor	Bolger, Douglas T., Cottingham, Kathryn L., Virginia, Ross A., Moore, John C., Ayres, Matthew P.
Subject	Invasive plants -- Ecology -- California, Southern. Shrubland ecology -- California, Southern. Chaparral ecology -- California, Southern. Coastal plants -- California, Southern. Grasses -- Ecology -- California, Southern. Plant litter -- California, Southern. Arthropoda -- Ecology -- California, Southern
College	Dartmouth College. Dept. of Biological Sciences
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Copyright	All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means without permission in writing from the author.
DOI	http://dx.doi.org/10.1349/ddlp.295

Title	Page 1
Format	application/pdf
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D.)--Dartmouth College.
Full Text	LINKING COMMUNITY AND ECOSYSTEM DYNAMICS IN INVASION BIOLOGY: AN EXPERIMENTAL APPROACH IN COASTAL SAGE SCRUB A Thesis Submitted to the Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biological Sciences by Elizabeth Mary Wolkovich DARTMOUTH COLLEGE Hanover, New Hampshire, USA August 2009 Examining Committee: ____________________________ (Co-Chair) Douglas T. Bolger ______________________________ (Co-Chair) Kathryn L. Cottingham ______________________________ Matthew P. Ayres ______________________________ John C. Moore ______________________________ Ross A. Virginia _____________________________ Brian W. Pogue, Ph.D. Dean of Graduate Studies

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