PARENT SESSION
Contributed Oral Session 164: Wetland Chemistry
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal
Can wetland restoration improve water quality?
Aldous, Allison*,1, Craft, Chris2, Stevens, Carla1, Bach, Leslie1, 1 The Nature Conservancy, Portland, Oregon2 Indiana University, Bloomington, Indiana
ABSTRACT- Wetland restoration is proceeding at a rapid pace around the world, often on land that previously had been converted to agriculture. Improved water quality is an often-stated objective for restoration efforts, because these ecosystems historically were sinks for limiting nutrients such as phosphorus. Yet on land where the soil profile has been disrupted from farming, it is not known if wetland restoration can achieve nutrient retention objectives. Furthermore, the quantity of labile phosphorus in some agricultural landscapes has the potential to overwhelm historically nutrient-poor wetland ecosystems. We tested the hypothesis that flooding agricultural soils to restore wetland ecosystems would sequester phosphorus and thus contribute to improved water quality. We isolated the soils component (with accompanying roots) to focus our research on the primary sink for phosphorus. Soils from a wetland restoration project in southern Oregon were flooded continuously for four months and phosphorus uptake or release was estimated on a weekly basis. We measured an initial pulse release of phosphorus from the soils to the water column in the first month of the experiment, with maximum rates of 0.03-0.60 gTP/m2/day. For the remaining three months, we measured no significant net flux between the soils and water column. These results indicate that the soils component will not initially achieve nutrient reduction objectives. To better understand the soil pools from which the phosphorus was released, we analyzed the soil cores before and after the experiment. Contrary to our expectations, the phosphorus released did not come from the labile inorganic phosphorus fraction, but rather from the organic phosphorus fraction. Given the large size of the organic phosphorus pool, these results indicate that it is hard to predict how much phosphorus will be released upon inundation from soil phosphorus fractionation alone.
Key words: wetland restoration, phosphorus, soil, water quality