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Hydrologic alterations associated with urbanization can weaken connections between riparian zones, streams, and uplands, leading to negative effects on the ability of riparian zones to intercept pollutants carried by surface water runoff and groundwater flow such as nitrate and phosphate. We analyzed the monthly water table as an indicator of riparian connectivity, along with groundwater NO3 and PO4concentrations, at four riparian sites within and near the Gwynns Falls Watershed in Baltimore, MD, from 1998 to 2018. The sites included one forested reference site (Oregon Ridge), two suburban riparian sites (Glyndon and Gwynnbrook), and one urban riparian site (Cahill) with at least two locations and four monitoring wells, located 5 m from the center of the stream, at each site. Results show an increase in connectivity as indicated by shallower water tables at two of the four sites studied: Glyndon and Cahill. This change in connectivity was associated with decreases in NO3 at Glyndon and increases in PO4 at Glyndon, Gwynnbrook, and Cahill. These changes are consistent with previous studies showing that shallower water table depths increase anaerobic conditions, which increase NO3 consumption by denitrification and decrease PO4 retention. The absence of change in the forested reference site, where climate would be expected to be the key driver, suggests that other drivers, including best management practices and stream restoration projects, could be affecting riparian water tables at the two suburban sites and the one urban site. Further research into the mechanisms behind these changes and site‐specific dynamics is needed.
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Differences in the Hydration State of Riparian Pecan Trees Between Rural and Urban Settings
Urbanization causes changes in near-surface meteorology and rainfall-runoff relationships that threaten to place hydraulic stress on vegetation. The goal of this study was to investigate the differences in riparian zone tree hydration state, as indicated by leaf water potential, between an urban and a rural stream site, and to understand how the trees respond differently to precipitation events. At the rural stream site, the streambed was dry due to persistent drought conditions, whereas the urban stream site had established flow due to urban water inputs. The trees at the urban site were found to suffer less hydraulic stress than the trees at the rural site, as indicated by predawn leaf water potential measurements. Additionally, trees at the rural site were found to regulate stomatal openness to reduce transpiration on the day before rain, but not after, due to the presence of near-surface moisture introduced by the rain event. Trees at the urban site did not have to regulate stomatal openness before or after the rain, as the established flow in the stream provided consistent water access. These findings support the viability of protecting and preserving riparian ecosystems in urban settings.
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- Award ID(s):
- 2046768
- PAR ID:
- 10568107
- Publisher / Repository:
- Texas Water Journal
- Date Published:
- Journal Name:
- Texas Water Journal
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2160-5319
- Page Range / eLocation ID:
- 86 to 103
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.21423/twj.v15i1.7174
