| Carex stricta is a dominant, native species in wetlands throughout eastern North America. This sedge forms tussock structures that enhance microtopography and support biodiversity, but little is known about how tussocks form, persist, or their capacity to store carbon. The overall objective of our research was to understand tussock development and maintenance in C. stricta-dominated wetlands and how these processes influence carbon storage. A combination of field surveys, mesocosm experiments, and laboratory assays were employed to quantify the composition of C. stricta tussocks, test how environmental factors affect tussock development, and investigate mechanisms regulating organic matter supply to tussocks and their decay.;Carex stricta grown in mesocosms rapidly accumulated fine roots and leaf bases above the soil surface when inundated, attaining heights that were ∼80% as tall as field tussocks (mean height of 7 sites: 15.1) in two growing seasons. Despite compositional differences between mesocosm-grown and field tussocks (the former being less dense, with finer roots and fewer shoot bases), continuous inundation and nutrient addition promoted rapid C sequestration in young tussocks (up to 400 g C/m² after three growing seasons). In the field, C. stricta tussocks were a large C pool in reference sedge meadows, comprising up to 62% total biomass C and storing up to 1700 g C/m². This C likely accumulated slowly, as radiocarbon age estimates suggested that tall tussocks (20 cm) were ∼50 years old. Compared with the underlying soil, C stored in tussocks had high mineralization rates during incubation experiments due to their high macro-organic content; when inundated, methane accounted for up to half of C mineralized, but flux in the field might be limited by oxidation in aerobic surface horizons. High root production (281--899 g m-2 yr-1 ) and root turnover (0.19--1.25 yr-1), especially in tussock tops, might promote tussock persistence above where biomass is protected by cooler, wetter conditions. Together, this work will help managers evaluate strategies to restore wetland structure and function using C. stricta, and it provides a baseline for comparison of C dynamics with other species and ecosystems. |
