The effect of C decomposition environment on plant detritus in soil organic matter
EMSL Project ID
50044
Abstract
While it is established that increasing temperature and moisture increases the rate of soil C mineralization, we do not know whether these factors change the chemical quality or physical protection of the non-mineralized C remaining in the soil. After incubating 13C-depleted plant biomass and soil under conditions of varying temperature and moisture, we will track plant 13C in soil aggregates as well as microbial activity over the course of decomposition. Our objective is to understand whether chemical and physical stabilization of soil C is affected by temperature and moisture levels. At destructive sampling early, mid, and late in the decomposition process, we will fractionate soils into size-based aggregate classes, estimate microbial biomass C, assay extracellular enzyme activity, and examine microbial community composition via 16s sequencing. Monitoring the CO2 flux from incubations, tracking the 13C signature of microbial biomass and assaying extracellular enzyme activity will allow us to characterize microbial activity over time and calculate C use efficiency (CUE). In addition, we will fractionate soils into macroaggregate, microaggregate, and silt and clay fractions, as well as occluded microaggregates, occluded silt and clay, and coarse particulate organic matter within macroaggregates. The 13C of various aggregate fractions will illuminate whether varying temperature and moisture conditions affect how recent plant additions are incorporated into aggregates, which provide physical protection and increase the residence time of soil C. By comparing FTIR spectra of biomass and control (no biomass added) samples, we can investigate how recent plant additions alter soil aggregate C chemistry. Beyond showing that aggregates contain recent plant biomass, we will be able to evaluate whether rapid C mineralization under warm conditions affects the type of C stabilized in various locations of the soil matrix. In addition, we can probe the microbial transformation of plant C into molecules that are preferentially retained in soils by comparing the signal of plant-derived compounds, such as lignin, at varying levels of microbial biomass and CUE. This area of inquiry is critical to our understanding of soil C cycling. Current theoretical and computational models assume that if C is mineralized rapidly, less C remains and overall levels of soil C will decline over time. However, if the chemical quality or physical protection of the C remaining is changed by temperature and moisture levels during the decomposition process, the mean residence time of soil C should be adjusted accordingly. These adjustments will help us to better predict how changing environmental factors affects the quality and long-term stabilization of soil C, a key aspect of climate stabilization.
Project Details
Project type
Exploratory Research
Start Date
2017-11-03
End Date
2018-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members