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NWoods-Dissertation 2015.pdf (1.29 MB)

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The Relative Importance of Abiotic and Biotic Factors for Seedling Establishment in the Colorado Desert, CA

Woods, Natasha Nicole
http://rave.ohiolink.edu/etdc/view?acc_num=osu1429882344

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Evolution, Ecology and Organismal Biology.
Drought combined with warmer temperatures has caused extensive mortality in US southwest desert ecosystems. Disproportional mortality among long-lived shrub species can have dire consequences for community regeneration if novel recruitment is dependent on facilitated establishment. However, regeneration niches can be under biotic or abiotic control. My dissertation research examines mechanisms that control juvenile recruitment in the Colorado Desert, CA. Specifically I examine, seed and seedling responses to resources by partitioning those resources that are under direct biotic control based on the production and consumption patterns of standing vegetation, and those that are under abiotic control due to the effects of temperature and precipitation. By examining the relative importance of abiotic and biotic factors that affect plant recruitment, I can anticipate community stability in the face of natural or anthropogenic disturbance and if necessary offer strategies to mitigate species loss by identification of relevant variables to promote recruitment of target species. In chapter 1 I characterize the spatial and temporal distribution of nitrogen for three years at a long-term study site in the Colorado Desert. In chapter 2, I examine the capacity for dominant shrubs to serve as plant facilitators for seed establishment and use a greenhouse experiment to identify the distinct roles of light and nitrogen on seed germination. In a third experiment, I examine the roles of neighboring species identity, frequency and density on seedling performance when water and light are limiting. I found that each focal species distinctly influenced nitrogen availability, which is generally higher near plant canopies. I also found higher levels of nitrogen under Ambrosia dumosa compared to the other focal species and the interspace. These results were highly dependent upon season and year (Chapter 1). Adult shrubs did not uniquely impact germination but beneficiary species identity was the main factor for germination. In the greenhouse, differences in percent germination were strongest at full light, and canopy light and nitrogen levels did not affect beneficiary germination (Chapter 2). Using average rainfall, temperature and nitrogen concentrations from canopy microhabitats of Ambrosia dumosa from 2011-2012, I found that competition influenced early performance of A. dumosa, and Eriogonum fasciculatum, but not Larrea tridentata. Reduced growth of L. tridentata seedlings was not attributable to competition (Chapter 3). Given these results, seed germination is not strongly regulated by abiotic or biotic factors; however, shrub canopies may be important for seedling growth and survival. If seedling persistence responds to nitrogen resources, A. dumosa may be instrumental in facilitating the establishment of perennial species. Nevertheless, all facilitators are important for providing increased heterogeneity in the landscape, which may increase regeneration niches for species not examined in my research. Nitrogen levels under shrub control would diminish without shrubs and subsequently, regeneration niches would also decrease. However, relative competitive abilities can influence future community composition at the study site.
Maria Miriti, Ph.D. (Advisor)
Peter Curtis, Ph.D. (Committee Member)
Kristin Mercer, Ph.D. (Committee Member)
113 p.
Ecology
Colorado Desert, plant facilitation, seedling recruitment, drought recovery

Recommended Citations

Citations

  • Woods, N. N. (2015). The Relative Importance of Abiotic and Biotic Factors for Seedling Establishment in the Colorado Desert, CA [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429882344

    APA Style (7th edition)

  • Woods, Natasha. The Relative Importance of Abiotic and Biotic Factors for Seedling Establishment in the Colorado Desert, CA. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1429882344.

    MLA Style (8th edition)

  • Woods, Natasha. "The Relative Importance of Abiotic and Biotic Factors for Seedling Establishment in the Colorado Desert, CA." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429882344

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.