Variation in soil redox conditions with land use across the Kansas precipitation gradient.
Abstract
Anaerobic microsites are important controls on soil carbon stabilization. Environmental factors that control the abundance of anaerobic microsites in upland soils are not well known. To help fill this knowledge gap, this study examines variation in soil redox state in Kansas upland soils. We collected samples from three land use types (native prairie, restored prairie, and agricultural) at four location across the Kansas precipitation gradient. We collected soil samples during 2018 and 2019 from 0-5, 5-15, 15-30, and 30-45 cm depth intervals using a Gidding's probe and immediate placed the samples in anaerobic pouches. To provide a measure of the abundance of anaerobic microsites, we evaluated the ferrous and ferric iron content of the samples using 0.5 N HCl extractions. We also measured soil pH and bulk density and assessed statistical significance using Spearman's rank correlation tests and ANOVA. When analyzed collectively, the mass ratio of ferrous to ferric iron (Fe(II)/Fe(III)) varies significantly with soil pH, bulk density, longitude, and land use. Samples with higher Fe(II)/Fe(III) ratios tend to have higher pH (P=0.0010, r=0.28) and lower bulk density (P<0.0001, r=-0.34). Variation in Fe(II)/Fe(III) ratios with longitude is consistent with decreasing Fe(II)/Fe(III) ratios with increasing average annual precipitation (eastward) (P=0.0008, r=-0.25). However, the absolute abundance of Fe(II) and Fe(III) both increase significantly with precipitation. Two-way ANOVA calculations indicate that site location (27.9%), land use (4.4%), and interactions of both (61.3%) all share a significant relationship with Fe(II)/Fe(III) ratios (P<0.0001). Work is ongoing to collect additional samples and further characterizations, including Mössbauer spectroscopy, soil carbon analysis, and microbial community analysis. We expect that these results will further advance our understanding of controls on soil redox and carbon storage.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B21K2376K
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0486 Soils/pedology;
- BIOGEOSCIENCES;
- 1622 Earth system modeling;
- GLOBAL CHANGE