Date of Award

Summer 8-12-2020

Semester of Degree

August

Document Type

Open Access Dissertation

Degree Name

Ph.D. in Forest and Natural Resources Management

Department

Forest and Natural Resources Management

Major Professor

Rene Germain

Steering Committee Member

John Stella

Steering Committee Member

Colin Beier

Abstract

Headwater streams are disproportionately affected by forest management activities in working forests of the United States (US) due to their high densities within watersheds. Thus, assigning the right buffer distance and buffer type to represent the ecology and topography of headwater streams is an important management decision. Focusing on headwater streams, this dissertation examines different riparian delineation techniques practiced within the US and proposes alternative approaches that balance ecological and economic factors. This primary objective was addressed using two datasets. The first dataset of stand data and understory vegetation was collected from forests distributed across New York and New Hampshire. The second dataset comprised of 1-meter digital terrain models and FIA data of 33 watersheds across 17 states within the contiguous US.

On a regional scale, an ecologically significant riparian buffer was mapped using understory plants along headwater streams in Northeastern forests. A threshold distance of 6-12 m from stream edge was identified using plant species richness. Although this is not the actual extent of a functional riparian area, this distance represents an important zone for increased plant species diversity.

A functional riparian area representing topography and forest structure developed by the US Forest Service was used as a variable width riparian buffer delineation technique in this study. The functional approach was compared with state-specific riparian delineation guidelines and a 30- meter fixed width riparian buffer across a broad range of forest regions in the US. From a regional context, when using the functional approach, 16–20 % of watersheds in the West and Pacific Northwestern regions were delineated as riparian. The functional method consistently delineated more land to the riparian area than other riparian delineating methods except for sampled watersheds in the Lake States where there was little to no topography along headwater streams.

Delineating valuable timber land as riparian areas is an opportunity cost for landowners given the density of headwater streams in working forests. Alternative riparian management options such as increasing carbon stocks within riparian management zones for carbon markets can not only offset riparian allocation costs but also serve as an investment opportunity for large- scale forest landowners.

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