Date of Award

2023

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Department

Natural Resources Science

First Advisor

Mark H. Stolt

Abstract

Tidal marshes in Southern New England represent critical blue carbon ecosystems and support some of the richest carbon stocks of any ecosystem on Earth. This thesis addresses the challenge of accurately quantifying carbon stocks in these ecosystems and explores spatial strategies for carbon accounting at both a landscape and pedon level. In particular, the study investigates the effectiveness of partitioning tidal marshes into landscape or pedogeomorphic units (PGUs) based on their geomorphic characteristics and using soil morphological characteristics to estimate soil carbon stocks. Soils from 32 separate marshes were described and sampled along transects, representing four different PGUs (back barrier, cove, tidal creek, tidal river). The findings revealed significant differences (p-2) and 200 cm (83 kg m-2) depths and back barriers holding the least amount of carbon at both 100 cm (20 kg m-2) and 200 cm (27 kg m-2). Plant community and linear distance from open water were not accurate predictors of carbon stocks (p=0.859 and p=0.449, respectively). The study emphasized the need to measure carbon stocks to at least 200 cm depth for more precise blue carbon accounting, as there was a large amount of carbon stored below 100 cm. All PGUs, with the exception of back barriers, held more carbon than when applying a previously suggested single value for the contiguous United States (27.0 kg m-3), suggesting that a regional-based pedogeomorphic approach to carbon accounting in tidal marshes is more effective than a broad carbon density value. In order to model soil carbon stocks at the pedon level, we utilized soil morphological properties (including texture and color) and PGUs to develop soil material groups (SMGs) for modeling carbon density of previously described and characterized soils (285 total samples analyzed for carbon content, texture, Munsell color, and fluidity). The final grouping of SMGs includes 2 organic material SMGs (SMG A: organic soil materials from back barriers and tidal creeks; and SMG B: organic soil materials from coves and tidal rivers), and 3 mineral SMGs (dark loamy -- loamy materials with a color value of ≥3; light loamy -- loamy materials with a color value of >3; and sands -- sands and loamy sands). Significant pairwise differences (p

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