Soil microbial activity varies between aggregate size classes in a long-term tillage experiment
Abstract
Soil microbial communities are heavily influenced by the matrix in which they live. Therefore, it is crucial to consider how agricultural management strategies shape the soil physical environment and the concurrent effects on microbial community composition and physiology. It is well documented that tillage affects aggregate size class distribution with reductions in tillage increasing the proportion of macroaggregates. However, less is known about the impact this has on microbial communities. Aggregates of different sizes harbor environments with distinct physical and chemical characteristics such as available carbon. This may give rise to microbial communities with compositions and physiologies suited to the constraints of the aggregate. We hypothesize that aggregates of varying size classes house microbial communities that exhibit physiologies and compositions representative of different life history strategies. To explore this hypothesis, we sampled soils from a 6-year agricultural experiment managed under two tillage regimes (no-till and conventional till). Soils were separated into four aggregate size classes (>2mm, 1-2 mm, 250 μm-1mm, and <250 μm) using an optimal moisture sieving technique. Microbial community composition (via 16S and ITS amplicon sequencing) and physiology (carbon cycling, enzyme potential) were assessed for each aggregate size class. Microbial carbon cycling functions were assessed through measurements of carbon use efficiency and substrate induced respiration. Enzyme assays were performed to examine nutrient acquisition potential within aggregates. We found that substrate induced respiration of eight substrates differed significantly between aggregate size classes (p = 0.022). These results suggest that microbial activity varies between aggregate size classes which highlights the importance of looking at aggregate scale controls on microbial communities. Analysis of aggregates via 16S and ITS amplicon sequencing will help us to further understand the underlying causes of these physiological differences. Exploring how the soil physical environment shapes microbial physiology in agricultural systems will allow us to choose management strategies that better promote soil structure conducive to healthy microbial communities and overall soil health.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B21F2395B
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCES;
- 0486 Soils/pedology;
- BIOGEOSCIENCES