Changes in Soil and Hyporheic Nitrogen Fertility with Riparian Succession on the Nyack Floodplain, MT: Implications for Riparian Vegetation
Brouwer B and Caves J. 2007. Changes in Soil and Hyporheic Nitrogen Fertility with Riparian Succession on the Nyack Floodplain, MT: Implications for Riparian Vegetation. 2007 REU Internship. Colorado College, Colorado Springs, CO
In order to determine how N availability changes with succession, and the relative importance of soil and hyporheic zone we described vegetation patterns and measured several indices of N availability in the soil and hyporheic zone at three stages of riparian succession on the Nyack floodplain, MT. In addition we developed a hydroponics bioassay using cottonwood cuttings to test the relative fertility of soil and hyporheic water. Soil total N and Potentially Mineralizable N (PMN) both increased significantly from gravel bar sites to mature cottonwood sites. Soil mineralization, nitrification, and ion exchangeable N did not change significantly with succession. Hyporheic ion exchangeable N did not change significantly with succession. Mean soil total N and PMN were significantly higher than hyporheic sediment. Mean hyporheic ion exchangeable N was significantly higher than soil. There was no significant difference in the foliar C:N ratios of cottonwood cuttings grown with access to soil, hyporheic water, or river water. Cuttings with access to soil grew significantly more leaves and longer roots. Wild cottonwood foliar C:N ratios correlated significantly with measurements of soil total N and PMN indicating that these may be the best measurements of N availability for plants. However, the significantly higher levels of ion exchangeable N in the hyporheic zone may prove to be a substantial source of N to riparian vegetation.
- Type
- Unpublished Report
- Authors
- Brouwer, Brook; Caves, Jeremy
- Date of Issue
- 2007
- Publisher
- 2007 REU Internship
- Units
- GLAC
- Keywords
- Flathead Lake Biological Station, nitrogen availability, Nyack Creek, REU, Riparian Vegetation, Soil fertility