Saturday, 15 July 2006

Spatial and Temporal Variability of Soil Characteristics and their Impacts on Macrophyte Diversity in Restored Wetlands in the Everglades National Park.

Angelique M. Keppler, Univ of Florida, 106 Newell Hall, Gainesville, FL 32611 and K. R. Reddy, Wetland Biogeochemistry Laboratory, Soil and Water Science Dept, Univ of Florida/IFAS, 106 Newell Hall, Gainesville, FL 32611.

The Hole-in-the-Donut (HID) region of the Everglades National Park (ENP) offers a unique opportunity to investigate the successional development of vegetation and the impact of macrophyte diversity on ecosystem functions, including biomass production, nutrient availability and storages. Historically, the HID was dominated by short hydroperiod prairies and pinelands. After 1916, farming practices were employed that altered approximately 4000 ha of natural vegetation. In 1975, farming ended and the HID was aggressively colonized by a non-native pest plant Schinus terebinthifolius (Brazilian pepper). Attempts to control Schinus through use of prescribed fire and chemical treatment proved unsuccessful. The dense canopy and lack of understory litter material made prescribed fire difficult and the high germination rate, high survival rate of seedlings, and rapid growth made chemical control difficult and costly (Doren and Whiteaker 1990, Dalrymple et al. 2003). These failures led to the use of mitigation funds from Miami-Dade County to employ a “scraping” method to restore wetlands in the HID. This method involves the mechanical removal of existing Schinus and underlying rock-plowed rubble and substrate leaving behind bedrock with pockets of captured substrate material. These pockets provide enough substrate for vegetation to develop on the scraped sites. A pilot project of 18 ha in 1989 proved successful in the natural recolonization of indigenous wetland vegetation (Dalrymple et al. 2003). This success led to the long-term wetland restoration project to restore the entire HID by use of the “scraping” method. Yearly restoration sites began in 1997 and will continue to completion in 2010. The desired dominant species within the HID is Cladium jamaicense (sawgrass). Sawgrass is the dominant species within natural, undisturbed portions of the ENP. It is present within restored sites of the HID but it is not a dominant species. It is more abundant in the earliest restored site (1989) than it is in sites that are only a few years old. In the first few years after restoration, sites are dominated by weedy generalists who can tolerate harsh conditions. In the most recent survey of the restored sites, the dominate vegetation are Typha domingenis, Andropogon glomeratus and Sagittaria lancifolia and very little Cladium jamaicense is found (Everglades Research Group 2003). Two important questions in the successional development of the HID are ‘what are colonization patterns for Cladium jamaicense and why is it not dominating the restored sites and how is species diversity impacted by changes in environmental characteristics throughout time?' In an attempt to answer these questions the project goal was to relate the diversity indices of macrophytes as well as the abundance of the dominant macrophytes and Cladium jamaicense to environmental characteristics by use of multivariate statistical analysis and to determine biomass production for above- and below-ground macrophytes and storages of carbon, nitrogen, and phosphorus of both the vegetation and the soil. Initial, dry season results of selected sites indicate biomass changes from 64.33 g m-2 in 2004 to 284.46 g m-2 in 1997 and to 428.29 g m-2 in 1989 as compared to the reference site of 476.11 g m-2. Extractable NH4 values are observed at 13.33 (2004), 24.03 (1997), 28.13 (1989), and 20.33 (reference) mg g-1 and extractable NO3 values are 7.35 (2004), 47.99 (1997), 25.55 (1989) and 20.26 (reference) µg g-1. Multivariate statistical analysis will be performed on all data to determine whether these environmental characteristics are influencing macrophyte diversity and the dominant vegetation found at each restored site.

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