<p>Disturbance regimes like freezing and thawing (FT) can have
potentially significant impacts on nutrient release from soil and are predicted
to increase with climate change. This is particularly important in
biogeochemical hotspots like floodplains that can both remove and release
nutrients to surface waters during flooding. Connection between the river and
floodplain can improve water quality by reducing nutrient loads through
microbial processes and sedimentation. However, conditions during flooding can
also lead to phosphorus (P) release from pools that are not normally
bioavailable. Disturbance events like FT can also lead to changes in
bioavailable P due to microbial cell lysis. This study investigates differences
in P chemistry and flux during flooding from intact soil cores that have
undergone a FT cycle compared to soils that have not undergone freezing.
Floodplain soils were collected from four sites along the Wabash and Tippecanoe
Rivers in Indiana. We hypothesized that (i) the primary pools of P within the
soil would change with freezing (ii) and flooding; (iii) frozen treatment cores
would release more P during flood incubations than unfrozen control cores; and
(iv) processes controlling P release during flood incubations would change
after FT due to changes in the primary pools of P in the soil cores. </p>
<p> </p>
<p>On average, soil cores that underwent FT released greater
amounts of P than unfrozen cores over the course of the 3-week experimental
flood incubation. Phosphorus release in both unfrozen control and FT treatment
cores during flooding was explained in part by soil extractable Al and Fe and redox
status; however, P release was influenced by soil Ca-P in the FT cores to a
greater extent than unfrozen cores. Phosphorus release in FT cores occurred
faster than in control cores with overlying water concentrations peaking 2
weeks after onset of flooding, followed by lower concentrations at 3 weeks.
Whereas control cores had some release and uptake early on but then released P
throughout the 3-week incubation—supporting the hypothesis that drivers of P
release were different after FT. Interactive effects of FT and flooding suggest
that concentration gradients between soil pore water and overlying surface
water could have enhanced dissolution of the Ca-P pool, highlighting the
importance of floodwater chemistry to P dynamics following FT. This study provides
an important link between observed winter floodplain P loss and potential
drivers of release and retention, which is critical to informing floodplain
restoration design and management through all seasons.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/14524056 |
| Date | 03 May 2021 |
| Creators | Shannon K Donohue (10732299) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Phosphorus_Chemistry_and_Release_in_Restored_and_Agricultural_Floodplains_Following_Freezing_and_Thawing/14524056 |
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