The detrital input and removal treatment (DIRT) network: Insights into soil carbon stabilization

Kate Lajtha; Richard D Bowden; Susan Crow; István Fekete; Zsolt Kotroczó; Alain Plante; Myrna J Simpson; Knute J Nadelhoffer

doi:10.1016/j.scitotenv.2018.05.388

The detrital input and removal treatment (DIRT) network: Insights into soil carbon stabilization

Sci Total Environ. 2018 Nov 1:640-641:1112-1120. doi: 10.1016/j.scitotenv.2018.05.388. Epub 2018 Jun 6.

Authors

Kate Lajtha¹, Richard D Bowden², Susan Crow³, István Fekete⁴, Zsolt Kotroczó⁵, Alain Plante⁶, Myrna J Simpson⁷, Knute J Nadelhoffer⁸

Affiliations

¹ Oregon State University, Department of Crop and Soil Sciences, USA. Electronic address: kate.lajtha@oregonstate.edu.
² Allegheny College, Department of Environmental Science, USA. Electronic address: richard.bowden@allegheny.edu.
³ University of Hawaii, Honolulu Department of Natural Resources and Environmental Management, USA. Electronic address: crows@hawaii.edu.
⁴ College of Nyíregyháza, Institute of Environmental Sciences, Hungary. Electronic address: feketeistani@gmail.com.
⁵ Corvinus University of Budapest, Department of Soil Science and Water Management, Hungary. Electronic address: kotroczo.zsolt@gmail.com.
⁶ University of Pennsylvania, Department of Earth and Environmental Science, USA. Electronic address: aplante@sas.upenn.edu.
⁷ University of Toronto - Scarborough, Department of Chemistry, Canada. Electronic address: myrna.simpson@utoronto.ca.
⁸ University of Michigan, Department of Ecology and Evolutionary Biology, USA. Electronic address: knute@umich.edu.

PMID: 30021276
DOI: 10.1016/j.scitotenv.2018.05.388

Abstract

Ecological research networks functioning across climatic and edaphic gradients are critical for improving predictive understanding of biogeochemical cycles at local through global scales. One international network, the Detrital Input and Removal Treatment (DIRT) Project, was established to assess how rates and sources of plant litter inputs influence accumulations or losses of organic matter in forest soils. DIRT employs chronic additions and exclusions of aboveground litter inputs and exclusion of root ingrowth to permanent plots at eight forested and two shrub/grass sites to investigate how soil organic matter (SOM) dynamics are influenced by plant detrital inputs across ecosystem and soil types. Across the DIRT network described here, SOM pools responded only slightly, or not at all, to chronic doubling of aboveground litter inputs. Explanations for the slow or even negative response of SOM to litter additions include increased decomposition of new inputs and priming of old SOM. Evidence of priming includes increased soil respiration in litter addition plots, decreased dissolved organic carbon (DOC) output from increased microbial activity, and biochemical markers in soil indicating enhanced SOM degradation. SOM pools decreased in response to chronic exclusion of aboveground litter, which had a greater effect on soil C than did excluding roots, providing evidence that root-derived C is not more critical than aboveground litter C to soil C sequestration. Partitioning of belowground contributions to total soil respiration were predictable based on site-level soil C and N as estimates of site fertility; contributions to soil respiration from root respiration were negatively related to soil fertility and inversely, contributions from decomposing aboveground litter in soil were positively related to site fertility. The commonality of approaches and manipulations across the DIRT network has provided greater insights into soil C cycling than could have been revealed at a single site.

Keywords: DIRT; Density fractionation; Detritus; Litter; Priming; Respiration; SOM; Soil carbon; Soil organic matter.