Research

Management and land use change effects on soil carbon dynamics

Soil carbon content correlates with its water and nutrient holding capacities, biodiversity, and ultimately what is called “soil health”. In both forests and rangelands, progressive management techniques are considered those that preserve or build soil carbon stock.

Soil CO2 efflux and leaf area index measurements at the Alligator River site in NC	Loblolly pine plantation in coastal North Carolina after mid-rotation thinning	Vegetation survey at Davy Crockett National Forest (Photo: Dohee Kim)
Natural bottomland hardwood forest in NC	Loblolly pine plantation after thinning in NC	Fire-managed shortleaf pine in Davy Crockett National Forest, TX

The effect of prescribed burning frequency on soil carbon stock and annual carbon balance

Many pine forests in the Southern USA are burned regularly for managing the fuel load and reducing the risk of wildfires, as well as for managing the habitat for some wildlife species, like the endangered red-cockaded woodpecker.

Loblolly and shortleaf pine stand that has not been burned for over 20 years

Shortleaf and loblolly pine stand that has been burned every 3-5 years, and most recently about 3 months prior

Shortleaf and loblolly pine stand that has been burned annually for over 20 years

Belowground carbon allocation

We developed a conceptual model that allows the estimation of belowground carbon allocation at high temporal resolution (monthly to seasonal), and are currently testing its performance in different ecosystems.

Eddy covariance instruments at Alligator River flux site

Collecting air samples for isotopic partitioning of soil CO2 production (Photo: G. Miao)

Coarse root decomposition

The relative importance of coarse roots to long-lived soil carbon remains unclear. Anecdotal evidence of intact old roots in the soil does not fit with published decomposition constants and the chemical evidence suggesting that the majority of “old” soil carbon consisting of fungal

Coarse root and stem samples for burying in the “deep” pits (50 cm)

Soil pits for burying coarse root and stem sections

Closed soil pits, with collars installed above select samples for soil CO2 efflux measurements

The interactions of water and nutrient availability with ecosystem carbon dynamics

Droughts represent the biggest, most widespread and immediate disturbance to terrestrial ecosystems. Drought not only slows plant growth, but also renders them more vulnerable to subsequent pest and pathogen attacks, and alters plant resource allocation patterns. Nutrient availability, too, alters carbon allocation in plants, and appears to supersede the controls by water availability. To fully understand the controls of plant physiological processes by these two essential resources, we work with the PINEMAP Tier 3 experimental dataset on productivity and soil carbon dynamics.

Throughfall exclusion troughs at the PINEMAP Virginia study site (Photo: A. Laviner)

alpha-cellulose extraction manifold (Photo: Wen Lin)

Seasonality or phenology of ecosystem processes

Net ecosystem fluxes of carbon and water are sums of multiple individual processes, each with potentially different environmental responses. We quantify the seasonality of a number of sub-processes to better validate the seasonality of ecosystem models.

Cover image of the book “Phenology of Ecosystem Processes“

Flux seasonality metrics (Yang & Noormets 2021)

Valuation of soil carbon and other ecosystem services

Soil carbon content is an integral measure of soil health, yet generally undervalued in land use decisions. We use a few well characterized sites to quantify soil carbon cost of different management choices, and derive the value of existing soil carbon pools for these ecosystems in terms of merchantable products.

External project web pages

Ameriflux North Carolina Core Sites

Texas Water Observatory

PINEMAP