Soil organic matter turnover rates increase to match increased inputs in grazed grasslands
Hoyt, Alison M.
Trumbore, Susan
Sierra, Carlos A.
Schrumpf, Marion
Doetterl, Sebastian
Baisden, W. Troy
Schipper, Louis A.
DOI: https://doi.org/10.1007/s10533-021-00838-z
Persistent URL: http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11203
Hoyt, Alison M.; Lawrence Berkeley National Laboratory, Berkeley, USA
Trumbore, Susan; Max Planck Institute for Biogeochemistry, Jena, Germany
Sierra, Carlos A.; Max Planck Institute for Biogeochemistry, Jena, Germany
Schrumpf, Marion; Max Planck Institute for Biogeochemistry, Jena, Germany
Doetterl, Sebastian; Department of Environmental Systems Science, ETH Zürich, Zurich, Switzerland
Baisden, W. Troy; Te Pūnaha Matatini Centre of Research Excellence, Auckland, New Zealand
Schipper, Louis A.; Environmental Research Institute, University of Waikato, Hamilton, New Zealand
Abstract
Managed grasslands have the potential to store carbon (C) and partially mitigate climate change. However, it remains difficult to predict potential C storage under a given soil or management practice. To study C storage dynamics due to long-term (1952–2009) phosphorus (P) fertilizer and irrigation treatments in New Zealand grasslands, we measured radiocarbon (14C) in archived soil along with observed changes in C stocks to constrain a compartmental soil model. Productivity increases from P application and irrigation in these trials resulted in very similar C accumulation rates between 1959 and 2009. The ∆14C changes over the same time period were similar in plots that were both irrigated and fertilized, and only differed in a non-irrigated fertilized plot. Model results indicated that decomposition rates of fast cycling C (0.1 to 0.2 year−1) increased to nearly offset increases in inputs. With increasing P fertilization, decomposition rates also increased in the slow pool (0.005 to 0.008 year−1). Our findings show sustained, significant (i.e. greater than 4 per mille) increases in C stocks regardless of treatment or inputs. As the majority of fresh inputs remain in the soil for less than 10 years, these long term increases reflect dynamics of the slow pool. Additionally, frequent irrigation was associated with reduced stocks and increased decomposition of fresh plant material. Rates of C gain and decay highlight trade-offs between productivity, nutrient availability, and soil C sequestration as a climate change mitigation strategy.