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DIRT: Detritus Input and Removal Treatments

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Although organic matter is a critical constituent of soils that provides structure and influences many properties and biogeochemical processes, the fundamental processes controlling organic matter incorporation and dynamics in soils are poorly understood. In the DIRT experiment we are investigating biological and physical controls on soil organic matter storage. Since 1990 we have manipulated above- and belowground litter inputs to soils in a mixed hardwood stand.

 

Treatments include:

  • 2x litter
  • no litter
  • no roots (trenched)
  • no roots-no litter
  • OA-less (one time replacement of organic and A horizons with B horizon soil)

The OA-less treatment was implemented to track soil recovery after impoverishment.

We have routinely measured key processes (soil respiration and nutrient leaching), surveyed site resources, and characterized baseline soil properties. Potentially mineralizable C and N (long-term laboratory incubations) and depth profiles for 13C and 15N contents were determined for all soils collected at the start of the study. We are collaborating with other LTER sites to establish similar experiments along climatic and edaphic gradients in North America.

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