Within Mediterranean ecosystems, conservation and restoration action is becoming increasingly necessary to preserve biological diversity within these working landscapes. Many of these systems have been managed to increase forage production through the removal of canopy trees and shrubs, resulting in understories dominated by herbaceous species. In California, woody plant regeneration can be constrained by exotic annual grasses, particularly in the presence of grazing. Quercus douglasii and other oak species are known to indirectly facilitate and provide spatial refuges to native plants through competitive suppression of herbaceous productivity. Mature trees can also compete with understory recruits and shrub species, limiting their occurrences to interstitial canopy gaps and resulting in reduced competition for resources. This study surveyed the overstory composition of 34 study plots at the Sierra Foothill Research and Extension Center to determine the effects of tree canopies on the occurrence and distribution of native woody species in the undergrowth. Because other studies have shown safesites, which include rock outcroppings, woodpiles, and nurse plants to facilitate woody plant establishment in this system, the microsites containing individual plants were recorded to determine the distribution of different woody species. Multivariate regressions showed that understory plant richness and abundance increased with higher levels of canopy cover, suggesting that mature trees play a role in maintaining understory diversity. The majority of stems were found growing directly underneath the canopy, with only one species established primarily in interstitial areas. Restoration strategies can utilize the natural distributions of woody species in the understory in order to increase the survival of plantings while continuing to manage these systems for multiple ecosystem services.
|Commitee:||Latimer, Andrew, Rice, Kevin|
|School:||University of California, Davis|
|School Location:||United States -- California|
|Source:||MAI 52/03M(E), Masters Abstracts International|
|Subjects:||Plant biology, Ecology, Conservation, Plant sciences|
|Keywords:||Oak savanna, Oak woodland, Quercus douglasii, Shrub recruitment|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be