Author ORCID Identifier
Document Type
Dissertation
Date of Award
2024
Degree Name
Doctor of Philosophy (PhD)
Department
Biology
First Advisor
Mark Dixon
Abstract
Dam construction, flow regulation, and reduced peak flows along the Missouri River have altered fluvial geomorphic processes, leading to a decline in suitable environments for cottonwood regeneration and increased opportunities for recruitment and survival of invasive woody species like eastern redcedar (Juniperus virginiana). Additionally, environmental changes and anthropogenic activities that disrupt the shallow groundwater table essential for cottonwood's growth, such as water diversion, groundwater pumping, channel incision, and severe drought affect the health of existing cottonwood forests. The establishment of eastern redcedar, a native upland species, in the floodplain further threatens cottonwood forest health by intensifying competition for water and other resources. The expansion of redcedar may also reduce the diversity of native plant species, alter floodplain forest structure, disrupt forest successional trajectories, and wildlife habitats. In this study I mapped spatial and temporal changes in redcedar biomass along the Missouri National Recreational River (MNRR) using lidar and NDVI from satellite imagery and analyzed basal area increment from tree rings to understand the effects of flooding and climate on redcedar growth (Chapter 1). I also used lidar and aerial imagery to map cottonwood mortality from 2012 to 2020 along the Gavins Point segment of MNRR, aiming to discern the impact of environmental variables (temperature, precipitation, Palmer Drought Severity Index and flow data) on cottonwood mortality (Chapter 2). Finally, I examined the influence of redcedar cover and floodplain forest structure on breeding (Chapter 3) and wintering (Chapter 4) bird richness and abundance. Redcedar biomass more than tripled from 2005 to 2020, although tree growth was slowed during periods of stress from prolonged flooding or severe drought. The 2011 flood and ensuing severe drought also intensified localized cottonwood mortality, highlighting its vulnerability to extreme events. Winter bird species richness responded positively to moderate redcedar cover (23%-76%); however, redcedar cover negatively affected breeding bird richness, with understory and midstory nesting species showing negative responses to dense redcedar. Integration with river management authorities is crucial for effective redcedar management, considering its impacts on growth, survival, and spread, necessitating a holistic approach to address ecological dynamics and support bird communities.
Keywords
Breeding Birds, Cottonwood Mortality, Redcedar Invasion, Wintering Birds
Number of Pages
186
Publisher
University of South Dakota
Recommended Citation
Illeperuma Arachchige Done, Nadeesha Dilrukshi, "REDCEDAR EXPANSION, COTTONWOOD DIEBACK, AND BIRDS ALONG THE MISSOURI NATIONAL RECREATIONAL RIVER" (2024). Dissertations and Theses. 294.
https://red.library.usd.edu/diss-thesis/294
