Presentation Type

Poster

Abstract

Reservoir drawdown following the removal of two hydroelectric dams on the Elwha River, Washington, exposed ~800 acres of sediments and left a barren landscape in the former reservoirs. The establishment of native vegetation within these areas is critical to meeting restoration objectives. Large woody debris (LWD) can play an important role in riparian ecosystems and may assist in the development of early plant communities. LWD helps create favorable microsites for seedlings by creating shade, which decreases temperatures and increases moisture levels in sediments. In sparsely-vegetated landscapes such as those present in the former Mills reservoir, wildlife such as birds can be effective seed dispersers. Logs provide perch structures upon which birds defecate and deposit seed-rich scat from vegetated areas into seed-limited habitats.

The goal of my research is to examine the synergistic relationships between avian seed dispersal and LWD and to understand how LWD and birds interact to assist in plant establishment in the former Lake Mills reservoir. My research questions include: (1) is plant establishment greater at sites with LWD? Because LWD provides improved growing conditions due to the effects of shading and shelter from wind, which causes a decrease in sediment temperatures and evaporation rates, I hypothesize that there will be an increase in plant establishment as you approach LWD. (2) How are birds contributing to plant establishment in Mills? More specifically, what is the abundance and distribution of bird-dispersed seeds (scats), and what are the patterns in plant establishment from bird-dispersed seeds? Birds in the former Mills reservoir disperse seeds on woody perches. I hypothesize that scat abundance will be greater closer to seed sources on the vegetated valley walls and nearby forest. I also hypothesize that plant establishment from bird-dispersed seeds will be greatest around LWD.

In order to address my first question I measured plant species composition and abundance on plots with and without LWD. I examined 7 variables and will use generalized linear mixed models (GLMM) and AIC scores to determine which variable combinations best predict plant abundance. I expect that plant establishment will be affected by the location, size, orientation, and layout complexity of LWD. To address my second question I will analyze LWD characteristics (height, volume, and location) and assess their effect on the abundance and distribution of avian seeds (scat) (collected in 2015). I will use generalized linear models (GLM) to analyze my data and will use ArcGIS to create density maps of avian seed dispersal and plant establishment, as determined by LWD, across the Mills reservoir. I anticipate that the results from my study will provide important information regarding patterns in avian seed dispersal and plant establishment around LWD will help inform adaptive management decisions regarding how birds may be utilized as vectors of seed dispersal and how resources of LWD can be best implemented to increase plant establishment in former reservoirs following dam removal.

Start Date

6-5-2017 12:15 PM

End Date

6-5-2017 2:00 PM

Location

Miller Hall

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May 6th, 12:15 PM May 6th, 2:00 PM

The Role of Avian Seed Dispersers and Large Woody Debris in Plant Establishment Following Dam Removal on the Elwha River, WA

Miller Hall

Reservoir drawdown following the removal of two hydroelectric dams on the Elwha River, Washington, exposed ~800 acres of sediments and left a barren landscape in the former reservoirs. The establishment of native vegetation within these areas is critical to meeting restoration objectives. Large woody debris (LWD) can play an important role in riparian ecosystems and may assist in the development of early plant communities. LWD helps create favorable microsites for seedlings by creating shade, which decreases temperatures and increases moisture levels in sediments. In sparsely-vegetated landscapes such as those present in the former Mills reservoir, wildlife such as birds can be effective seed dispersers. Logs provide perch structures upon which birds defecate and deposit seed-rich scat from vegetated areas into seed-limited habitats.

The goal of my research is to examine the synergistic relationships between avian seed dispersal and LWD and to understand how LWD and birds interact to assist in plant establishment in the former Lake Mills reservoir. My research questions include: (1) is plant establishment greater at sites with LWD? Because LWD provides improved growing conditions due to the effects of shading and shelter from wind, which causes a decrease in sediment temperatures and evaporation rates, I hypothesize that there will be an increase in plant establishment as you approach LWD. (2) How are birds contributing to plant establishment in Mills? More specifically, what is the abundance and distribution of bird-dispersed seeds (scats), and what are the patterns in plant establishment from bird-dispersed seeds? Birds in the former Mills reservoir disperse seeds on woody perches. I hypothesize that scat abundance will be greater closer to seed sources on the vegetated valley walls and nearby forest. I also hypothesize that plant establishment from bird-dispersed seeds will be greatest around LWD.

In order to address my first question I measured plant species composition and abundance on plots with and without LWD. I examined 7 variables and will use generalized linear mixed models (GLMM) and AIC scores to determine which variable combinations best predict plant abundance. I expect that plant establishment will be affected by the location, size, orientation, and layout complexity of LWD. To address my second question I will analyze LWD characteristics (height, volume, and location) and assess their effect on the abundance and distribution of avian seeds (scat) (collected in 2015). I will use generalized linear models (GLM) to analyze my data and will use ArcGIS to create density maps of avian seed dispersal and plant establishment, as determined by LWD, across the Mills reservoir. I anticipate that the results from my study will provide important information regarding patterns in avian seed dispersal and plant establishment around LWD will help inform adaptive management decisions regarding how birds may be utilized as vectors of seed dispersal and how resources of LWD can be best implemented to increase plant establishment in former reservoirs following dam removal.