Establishment patterns of water-elm at Catahoula Lake, LouisianaThis article is part of a larger document. View the larger document here.
At Catahoula Lake in central Louisiana, an internationally important lake for water fowl, hydrologic alterations to the surrounding rivers and the lake itself have led to an expansion of water-elm (Planera aquatic J.F. Gmel.) into the lake bed. In this study, we used dendrochronology and aerial photography to quantify the expansion of water-elm in the lake and identify patterns of expansion. Our data suggest woody vegetation encroached into Catahoula Lake by about 10.4 km2 (30 percent of the lake area) between 1940 and 2007. Encroachment has been concentrated in the northeast near the connection to Dry River, in the southwest at the input of Little River, and to a lesser extent south of the Diversion Canal on the eastern side of the lake. Woody vegetation is encroaching on the lake in three patterns. The first is a pattern of continuous encroachment, which occurred in 50 percent of our transects. The second pattern is a long-term stable pattern (no encroachment; younger and older trees intermingling), which occurred in 25 percent of our transects. The third pattern is complex with no discernable trend and is complicated by attempts to manage the woody expansion. The reasons for expansion are not well understood, and recently, increased rates have been manifest in multiple modes of establishment.