Christopher T. Hammersmark

Vegetation and water-table relationships in a hydrologically restored riparian meadow

We examined the relationship between water-table elevations and plant community distributions in a hydrologically restored riparian meadow. The meadow, adjacent to Bear Creek in northeastern California, experienced hydrologic modification due to “pond and plug” stream restoration. Plant species composition and cover were sampled within 128 plots, and a hydrologic model was used to simulate a three-year time series of water-table for each plot. TWINSPAN was used to classify the vegetation into four community types:Eleocharis macrostachya / Eleocharis acicularis, Downingia bacigalupii / Psilocarphus brevissimus, Carex nebrascensis / Juncus balticus, andPoa pratensis / Bromus japonicus. Nonmetric multidimensional scaling was utilized to investigate the relationships between community types and hydrologic variables. Community types were distributed along the hydrologic gradient at reasonably similar positions to those found in previous studies; howeverCarex nebrascensis, a species frequently used as an indicator of shallow water tables, occurred at greater water-table depths than reported in other studies. The range of water-table depths in this meadow was greater than previously observed, presumably due to the higher temporal resolution of water-table measurements, in addition to the intermittent nature of stream flow in Bear Creek. This study provides an increased understanding of the ecology of meadow communities, and can be utilized for improved design and objective setting in future restoration projects.