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DIRT: Detritus Input and Removal Treatments

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Organic matter is a key component of soils, providing a food source for soil organisms and influencing soil properties such as water-holding capacity, aeration, pH, and nutrient availability. Decomposition of soil organic matter by soil microorganisms is a critical source of plant nutrients, and organic matter is also an important storehouse of carbon, with soils globally holding two-thirds as much carbon in soil organic matter as the atmosphere and vegetation combined. Sequestration of carbon in soils is one way to mediate atmospheric concentrations of greenhouse gases. How aboveground and belowground plant carbon inputs (e.g., litter and root exudates) are incorporated into soil organic matter on timescales over decades to centuries is poorly understood.

The Harvard Forest DIRT experiment, part of a global network of DIRT sites, was designed to investigate how rates and sources of plant carbon inputs control the long-term stability, accumulation, and chemical nature of soil organic matter in forested ecosystems, by manipulating above- and belowground litter inputs in a mixed hardwood forest.

Treatments include: control; double litter; no litter; no roots; no roots or litter; and OA-less (a one-time replacement of organic and A horizons with B horizon soil).

This project began in 1990 and is supported by the Harvard Forest Long-Term Ecological Research program.