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Historical Ecology of the Split Oak Forest in East Central Florida
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Restoration and management of ecologically important sites depend on an understanding of reference conditions and the ability of people to return the site to those historic conditions. Historical ecology research sifts through the data about a site to be able to offer restoration options to land managers. This project demonstrates transitions in natural communities of a protected area in East Central Florida: Split Oak Forest. Natural communities are defined based on the General Land Office (GLO) survey maps and notes and applied to historical black and white aerial photos, modern digital orthophotos, and high resolution satellite imagery. Because of the channelization of the Kissimmee River and the subsequent draining of the Everglades from 1883 onward, Split Oak, like other areas whose surroundings have been drained, cannot be returned to the conditions at the time of the GLO survey. Thus, a detailed time series of eight snapshots over 171 years will be valuable to land managers and restoration ecologists working in sites that share the hydrologically-modified Northern Everglades watershed with Split Oak. Natural community descriptions gleaned from the surveyors maps and notes and their application to current land cover are a potential backbone to future historical ecology in the southeast. Seasonally re-hydrating drained wetlands is a priority in this watershed, and is supported by cost-share funding from the State of Florida. This research affirms that most grassy wetlands on the site have transitioned to upland communities. Most of the remaining marshes have been invaded by woody plants and swamps extended their boundaries. Sandhill was used for orange (Citrus x sinensis) culture and, along with scrub and flat pine, transitioned to hammock.
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Historical aerial images are important to retain past ground surface information. The land-use land-cover change in the past can be identified using historical aerial images. Automatic historical image registration and stitching is essential because the historical image pose information was usually lost. In this study, the Scale Invariant Feature Transform (SIFT) algorithm was used for feature extraction. Subsequently, the present study used the automatic affine transformation algorithm for historical image registration, based on SIFT features and control points. This study automatically determined image affine parameters and simultaneously transformed from an image coordinate system to a ground coordinate system. After historical aerial image registration, the land-use land-cover change was analyzed between two different years (1947 and 1975) at the Tseng Wen River estuary. Results show that sandbars and water zones were transformed into a large number of fish ponds between 1947 and 1975.
The Los Angeles coastal prairie was an herbaceous plant community with high concentrations of annual forbs, similar to coastal prairie described for northern California, interspersed with a network of vernal pools with their associated specialized flora. Unfortunately, the unique community was lost before it could be studied in detail. The prairie covered about 95 km2 of coastal Los Angeles County, extending north-south from the crest of the Ballona Bluffs to the Palos Verdes peninsula and inland for 3–7 km from the lee of the El Segundo sand dunes. We present (1) historical accounts and photographs of the prairie, (2) a description of the vegetation, including a list of plants native to the prairie assembled from herbarium accessions, botanical literature, and recent surveys of a highly degraded 12-ha fragment, and (3) a review of the mammals, birds, reptiles and amphibians that were once found on the prairie. The description of the Los Angeles coastal prairie and its vernal pools should inform restoration efforts in the area, and aid in the potential identification of previously overlooked fragments of these habitats in the urban mosaic.
We investigated the dynamics of woody, characteristic bayhead species (Gordonia lasianthus, Ilex cassine, Magnolia virginiana, Myrica cerifera, and Persea palustris) invasion into 50 seasonal ponds at three sites in south central Florida. Individuals of Gordonia lasianthus and Persea palustris were concentrated in the shallow Panicum abscissum zone, while Ilex cassine, Magnolia virginiana, and Myrica cerifera were concentrated in the fringing Serenoa repens zone. Trees of all species had the largest diameters in the cutthroat zone. Deeper pond zones were less often invaded. The natural log of bayhead invasion density was negatively correlated with distance from nearest bayhead. Both large and small trees followed this pattern, suggesting that the invasion process is ongoing and has a long history. The likelihood of finding at least one bayhead invader is positively related to the area of the pond. Woody bayhead invasion of seasonal ponds depends upon the distribution of vegetation at the landscape level. Habitat destruction and fragmentation are likely to reduce the occurrence of this invasion by isolating both seasonal ponds and bayheads.
The preceding chapter concentrated on physical factors, especially geology, soils, landform, and hydrology, which create or maintain grassland within the South. In this chapter I consider a range of abiotic and biotic processes and their interactions. These processes include two major positive feedbacks—fire and large herbivores—identified in the general model as reinforcing and accelerating grassland development following a shift to a drier or more seasonal climate. Large grazing and browsing herbivores abounded within North American grasslands, including southern grasslands, for millions of years. That southern grasslands contain a mix of grazing-adapted rhizomatous (sod-forming) grasses and bunchgrasses suggests that megaherbivores influenced the development of these communities. At times the influence of herbivores may have surpassed the role of fire. Megaherbivores had natural predators, which probably exerted top-down control over their populations and affected their evolution of antipredator morphologies and behaviors over long spans of time.