Greater soil carbon stocks and faster turnover rates with increasing agricultural productivity
Date
2017-01-04
Authors
Sanderman, Jon
Creamer, Courtney
Baisden, W. Troy
Farrell, Mark
Fallon, Stewart
Journal Title
Journal ISSN
Volume Title
Publisher
European Geosciences Union (EGU) and Copernicus GmbH
Abstract
Devising agricultural management schemes that enhance food security and soil carbon levels is a high priority for many nations. However, the coupling between agricultural productivity, soil carbon stocks and organic matter turnover rates is still unclear. Archived soil samples from four decades of a long-term crop rotation trial were analyzed for soil organic matter (SOM) cycling-relevant properties: C and N content, bulk composition by nuclear magnetic resonance (NMR) spectroscopy, amino sugar content, short-term C bioavailability assays, and long-term C turnover rates by modeling the incorporation of the bomb spike in atmospheric 14C into the soil. After > 40 years under consistent management, topsoil carbon stocks ranged from 14 to 33MgCha-1 and were linearly related to the mean productivity of each treatment. Measurements of SOM composition demonstrated increasing amounts of plant- and microbially derived SOM along the productivity gradient. Under two modeling scenarios, radiocarbon data indicated overall SOM turnover time decreased from 40 to 13 years with increasing productivity - twice the rate of decline predicted from simple steady-state models or static three-pool decay rates of measured C pool distributions. Similarly, the half-life of synthetic root exudates decreased from 30.4 to 21.5 h with increasing productivity, indicating accelerated microbial activity. These findings suggest that there is a direct feedback between accelerated biological activity, carbon cycling rates and rates of carbon stabilization with important implications for how SOM dynamics are represented in models.
Description
Keywords
soil, carbon, soil organic matter (SOM), modeling
Citation
Collections
Source
SOIL
Type
Journal article
Book Title
Entity type
Access Statement
Open Access