Restoration Response of Relict Broadleaf Marshes to Increased Water Depths

Abstract

Broadleaf marsh once covered much of the wetland landscape along the Kissimmee River in central Florida, USA, but is currently restricted to remnant portions of the channelized floodplain that have been subjected to much shallower depths. The initial phase of Kissimmee River restoration, which began in 1999, and a prior (1984–1990) demonstration project increased water depths in several relict broadleaf marshes on the floodplain. Effects of restored water depth regimes on characteristics of these altered broadleaf marsh communities were evaluated. As expected, plant species richness consistently declined in marshes with increased water depth, but cover of signature broadleaf species, Sagittaria lancifolia and Pontederia cordata, exhibited variable responses to restored hydrology. In one marsh mean cover of Sagittaria and Pontederia increased from 32 to 62% following a 37 cm increase in mean annual depths; however, in another relict marsh that underwent a similar increase in hydroperiods and depths, mean cover of these species remained below 30% and Panicum hemitomon persisted as a dominant species. Moreover, invasion of the exotic wetland shrub, Ludwigia peruviana, appears to pose a threat to successful restoration of broadleaf marshes on the Kissimmee floodplain.