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Site Sampling Design - Essay Example

he Miami-Dade County Park and Recreation Department s Natural Areas Management Section is submitting this report as required by the DEP Contract No SP 444. This document presents data collected during the monitoring sessions conducted in September 1998, October 1999 and May 2001. The objectives of the project are to enhance and restore the pine rocklands areas at Owaissa Bauer Park through the application of prescribed fire and manual hardwood removal. The objectives of the monitoring are to determine whether hardwood reduction and burn treatment affect the physical and biological characteristic of the pineland structure.

Urban development and agriculture has led to the destruction and fragmentation of almost every natural habitat, disrupting the natural cycles of fire in Florida’s wildlands. The absence of fire diminishes the diversity of plants and animals and allows the overgrowth of fuels, which leaves the pinelands more prone to a destructive wild fire. During the first month of this grant agreement NAM established photo-points, monitoring transects, and sampling methods. Initial habitat evaluation before the burn was recorded in September 1998. Physical and biological properties before and after the fire have been gathered and analyzed.

As part of the project Miami-Dade County Parks NAM coordinated the application of a prescribed fire with Florida Division of Forestry in the year 1999 to re-introduce fire to the pineland and attempt to help to control exotic vegetation and reduce canopy at Owaissa Bauer Park. Miami-Dade County Parks was responsible for all operational aspects of this project. The results of the monitoring will be used to develop a better understanding of fire as a management tool for pineland restoration. Information gained from this project will enable us to be more effective in our future management of natural areas in Miami-Dade County. The goal of improved management practices is to increase the habitat diversity, especially the threatened and endangered species in fire adapted habitat.

INTRODUCTION

Habitat In South Florida several ecosystems have developed in response to the subtropical climate and the seasonal wet and dry cycle. Along the relatively higher ground of the Coastal Ridge, distinctive pineland and hammock communities developed based principally upon abundant rainfall and high water table, well drained limerock substrate, and the presence or absence of fire. Today, only relatively small pockets and fragments of native upland habitat remain in Miami-Dade County. The two most common remaining native upland cover types are pine rocklands and hardwood hammocks.

Pine Rocklands

Pine rocklands occur only in southern Miami-Dade County, the Florida Keys, and several islands of the Bahamas. The pine rocklands is characterized by a monospecific canopy of South Florida slash pine (Pinus elliottii var. densa) trees and a diverse understory of woody plants, graminoids and herbaceous plants. The plant composition of pine rocklands can be attributed to the limestone substrate, proximity to the tropics, and peninsular connection to the Temperate Zone (Myers 1992). This unique condition has allowed for over fifty endemic plant taxa to occur in this rare habitat (Herndon 1993). Florida Natural Area Inventory (FNAI 1998) designates pine rocklands as globally and State imperiled (G1, S1). The habitat is characterized by FNAI as “critically imperiled globally because of extreme vulnerability to extinction due to some natural or man-made factor” (FNAI 1998).

The habitat is characterized as a fire-maintained successional forest (Snyder et al 1990). It is widely thought that historical fires burned through pine rocklands every 3 to 7 years, or that areas burned on the order of once to twice per decade (Snyder et al 1990). In Miami-Dade County, the absence of fire invasion in pine rocklands would result in the formation of tropical hardwood hammocks within 15 to 25 years (Robertson 1953, Alexander 1967). Periodic fires act to reduce competition from invading hardwoods. Fire also benefits the pines by reducing dangerous accumulations of litter or dry fuels, by restoring nutrients to the soil, and exposing mineral soils for pine seed germination.

MATERIALS AND METHODS

Study location Owaissa Bauer Park, located at 264 Street and 168 Avenue, contains 60 acres of pine rocklands and 30 acres of hammock forests that provide a diverse habitat for at least 261 native plant species and numerous animal species. Owaissa Bauer’s upland forest provides habitat for 52 rare plants species and 19 animal species of special concern, including deltoid spurge (Chamaesyce deltoidea spp deltoidea) and Blodgett’s wild mercury (Argythamnia blodgetti) both federally listed endangered plant species.

The 60 acre pine rockland was divided into 10 units of irregular shape. All units had been fire suppressed for several decades, and were adjacent to each other (Fig 1). Pinelands had a relatively sparse herbaceous understory and a thick litter of hardwood interspersed with bare ground. The prescribed burn was done in units 1a, 8, 6 and 5. Hardwood reduction plus the burn was carried out in unit 6, 5 and 8. Hardwood removal was conducted in units 1b, part of 7, 9 and 3. The control units were part of unit 7, and 3 (Fig 1, 2). NAM assigned numbers to identify the units in no specific order. Site Sampling Design The locations of transects and photo-points were randomly chosen within the project area and their locations fixed with rebar driven in the ground and mapped with a Global Positioning System (GPS) unit for mapping purposes (Fig 2).