Year of Award

2017

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Systems Ecology

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

H. Maurice Valett

Commitee Members

LLoyd Queen, Anna Klene, Marc Peipoch

Keywords

Ecology, Remote Sensing, GIS, Stream Ecology, Floodplain, LiDAR

Subject Categories

Terrestrial and Aquatic Ecology

Abstract

Floodplains are biophysically complex systems that are considered among the most productive and biodiverse ecosystems on Earth. Until recently, quantitative assessment of the relationship between complexity and terrestrial production has been constrained by technological limitation. To address how floodplain biophysical complexity and ecosystem function are related, I employed remote sensing, GIS, and spatial analyses to quantify and couple metrics of complexity and terrestrial production, as well as explore the relationship among complexity, vegetation structural diversity, and terrestrial primary productivity. The study site is a 6.75-km by 1.75-km portion of the Bitterroot River floodplain near Carlton, MT upon which 551 sample plots were delimited via segmentation classification. Biophysical complexity, characterized by topographic heterogeneity, structural heterogeneity, and hydrologic connectivity was represented in each sample plot by mean standard deviation ground height, vegetative structural diversity index, mean flow length, mean flow accumulation, mean percent inundation, and gamma index metrics computed from Light Detection and Ranging (LiDAR) data, HEC-RAS inundation modeling, and ArcGIS Arc Hydro derived metrics. Potential primary production was represented by Normalized Difference Vegetation Index (NDVI) values generated from aerial 4-band multispectral imagery. Two questions were addressed in the analyses: 1) What is the causal relationship among floodplain physical complexity, vegetation structural diversity, and terrestrial productivity, and 2) How does floodplain biophysical complexity influence terrestrial primary production. Through these efforts, my goal was to explain how the dynamic nature of riverscapes translates to fundamental measures of ecological form and function. NDVI values ranged from -0.27 to 0.43, and were robustly related to biophysical complexity in which the explanatory variables together accounted for 58% of variation in NDVI (p < 0.001). In investigating the relationship between biophysical complexity, vegetation structural diversity, and NDVI, biophysical complexity was positively correlated to NDVI (r2= 0.25, p < 0.001), and structural diversity was positively related to NDVI (r2= 0.51, p < 0.001). These results suggest a causal relationship and support the complexity diversity hypothesis, and the diversity- productivity hypothesis. Structural diversity and connectivity variables accounted for the most explanatory power in all analyses, and overall results indicate that areas of the floodplain with greater biophysical complexity exhibited greater productivity.

Davis, Peter, M.S., Summer 2017 Systems Ecology

Coupling Biophysical Complexity and Forest Metabolism in Floodplain Landscapes

Chairperson: H. Maurice Valett

Floodplains are biophysically complex systems that are considered among the most productive and biodiverse ecosystems on Earth. Until recently, quantitative assessment of the relationship between complexity and terrestrial production has been constrained by technological limitation. To address how floodplain biophysical complexity and ecosystem function are related, I employed remote sensing, GIS, and spatial analyses to quantify and couple metrics of complexity and terrestrial production, as well as explore the relationship among complexity, vegetation structural diversity, and terrestrial primary productivity. The study site is a 6.75-km by 1.75-km portion of the Bitterroot River floodplain near Carlton, MT upon which 551 sample plots were delimited via segmentation classification. Biophysical complexity, characterized by topographic heterogeneity, structural heterogeneity, and hydrologic connectivity was represented in each sample plot by mean standard deviation ground height, vegetative structural diversity index, mean flow length, mean flow accumulation, mean percent inundation, and gamma index metrics computed from Light Detection and Ranging (LiDAR) data, HEC-RAS inundation modeling, and ArcGIS Arc Hydro derived metrics. Potential primary production was represented by Normalized Difference Vegetation Index (NDVI) values generated from aerial 4-band multispectral imagery. Two questions were addressed in the analyses: 1) What is the causal relationship among floodplain physical complexity, vegetation structural diversity, and terrestrial productivity, and 2) How does floodplain biophysical complexity influence terrestrial primary production. Through these efforts, my goal was to explain how the dynamic nature of riverscapes translates to fundamental measures of ecological form and function. NDVI values ranged from -0.27 to 0.43, and were robustly related to biophysical complexity in which the explanatory variables together accounted for 58% of variation in NDVI (p < 0.001). In investigating the relationship between biophysical complexity, vegetation structural diversity, and NDVI, biophysical complexity was positively correlated to NDVI (r2= 0.25, p < 0.001), and structural diversity was positively related to NDVI (r2= 0.51, p < 0.001). These results suggest a causal relationship and support the complexity diversity hypothesis, and the diversity- productivity hypothesis. Structural diversity and connectivity variables accounted for the most explanatory power in all analyses, and overall results indicate that areas of the floodplain with greater biophysical complexity exhibited greater productivity.

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