Effect of Root Carbon on Microbial Abundance and Carbon Cycling in the Topsoil and Subsoil
Date
2024-04-25
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0009-0009-0002-7530
Type
Thesis
Degree Level
Masters
Abstract
Understanding the interaction between root carbon (C), microbial C cycling and soil organic matter (SOM) dynamics is crucial for C sequestration. This study aimed to look at the interaction between root C, soil microorganisms and their microhabitat on microbial C cycling and the potential for more SOM storage on a cropland. We investigated the turnover of root exudate proxies (glucose, alanine, and citric acid) and their effect on short term apparent soil organic carbon (SOC) priming and microbial abundance in cropland soils obtained from different depths (10-15 cm, 30-35 cm, 50-55 cm). We added exudates to 30 g soil at rate of 28.3 mg C g-1 SOC and measured CO2 fluxes over 408 hrs under controlled conditions and their effect on apparent priming within 22 hrs. The normalized CO2 efflux to the concentration of substrate C added was lowest at the 50-55 cm depth, indicating greater substrate C retention in the 50-55 cm soil. CO2 efflux from citric acid addition was higher than from glucose and alanine at the 10-15 cm and 30-35 cm depths and resulted in the greatest SOC priming. Alanine addition resulted in a notable increase in microbial abundance after a 22-hour period in comparison to both the control soil and other added substrates. We further conducted a field study, mixing canola root with soil from the topsoil (10-15 cm) and with the subsoil (50-55 cm) at different rates (high root biomass vs low root biomass), to test the effect of root biomass rate on C storage in different SOM fractions (mineral associated organic matter and particulate organic matter) and microbial abundance. Using reciprocal transplant, the litterbag mixture was placed at the same depth of soil collection (non-translocated) or flipped (translocated) to evaluate the effect of microhabitat on microbial abundance and C storage. We found that microhabitat but not the root biomass quantity affected microbial abundance and community structure. This finding suggests the potential for more C storage at depth due to the ability of deeper soil layers to retain more C, because of the lower mineralization rates and microbial abundance observed in the subsoil.
Description
Keywords
Carbon sequestration, Root Exudates, Soil organic matter, Soil depth Effects.
Citation
Degree
Master of Science (M.Sc.)
Department
Soil Science
Program
Soil Science