Disturbance Gives Rise to Biodiversity Along the River Margins of the Mobile-Tensaw Delta
My research is focused on the community response to natural and anthropogenic disturbance. My overarching goal is to better understand how habitat degradation and disturbance influence competitive outcomes, long-term survival of native species, and the maintenance of ecosystem integrity. In addition to being disturbance-prone, the Mobile-Tensaw Delta MTD resides in the East Gulf Coastal Plain and is an excellent model for testing the Intermediate Disturbance Hypothesis, which implies that disturbance increases biodiversity. Specifically, my thesis research is focused on the effects of rainfall and flooding events that vary in duration, periodicity, and intensity, on plant community composition and diversity, and the prevalence of invasive species in flood zones along north-south and east-west gradients in the MTD to answer: Q1 How does community structure change along geographical gradients in the MTD? Q2 Do invasive species show any accelerated growth rates compared with native vegetation in respect to disturbance? I am utilizing protocols from North Carolina Vegetation Survey (NCVS) while sampling twelve 20 m x 50 m plots set along latitudinal and longitudinal gradients within the MTD. Percent cover per species is recorded for canopy, sub-canopy, and herbaceous layers for the entire plots and more intensive multi-scaled modules. Thus far, this project has identified 208 plant species including: 1) one county record and the first observation of Justicia americana (L.) Vahl in Baldwin County, AL. 2) the first record of occurrence for the non-native invasive plant, Colocasia esculenta, and 3) twelve additional plant species that have achieved invasive status in the MTD.
University of South Alabama Dept of Biology
P89 • Jane K. Marlow1, John B. Nelson2
Under the Radar and on the Move: Ficaria verna A Threat to the Southeast’s Riparian Areas
Ficaria verna, formerly known as Ranunculus ficaria and commonly called fig buttercup or lesser celandine, is reported to be invasive in the Northeast and Northwest. It is a plant that is relatively new to southeastern flora and unknown to most of us; nevertheless, it is quietly naturalizing in the Southeast and poses a serious ecological threat to riparian areas. It emerges early before most natives and is gone by June. This short growth cycle offers limited opportunity to spot it and a short window in which it is vulnerable to treatment. It thrives in mesic environments, typically on the banks of rivers, streams, lakes and ponds, as well as in wetlands. Once established it creates extensive, continuous, dense vegetative mats too thick for natives to penetrate. It has multiple reproductive strategies: Four of the five subspecies produce viable seed; two can reproduce via their numerous axillary bulbils; all have sturdy underground tubers that can make new plants if separated from the parent. Bulbils and tubers are easily spread by water events (and well-meaning weed-pullers). It is a landscape plant that is still available commercially and is often confused with marsh marigold, Caltha palustris. Many of the sites where it has naturalized are downstream from landscape plantings, and evidence indicates that these sites are more extensive and widespread than might be surmised from available range maps.
1 SC Native Plant Society and www.NameThatPlant.net; 2 A.C. Moore Herbarium, Dept of Biological Sciences, University of South Carolina, Columbia, SC
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P90 • Charles A. T. Jackson, Justin L. Hart
Potential Impact of Emerald Ash Borer on Forest Composition in Alabama
Emerald ash borer (Agrillus planipennis; EAB) is beetle native to Asia and eastern Russia. EAB was first discovered in the US in 2002 in Michigan and it has since spread to 21 states and killed tens of millions of ash (Fraxinus spp.) trees. EAB-induced mortality of ash will result in localized canopy disturbances that will in turn impact forest composition, structure, and function. To examine the potential effects of widespread and sudden ash mortality in Alabama forests, we used USDA Forest Inventory and Analysis (FIA) data in a geographic information system environment. We hypothesize the loss of ash in Alabama to be minor at the state-level, but to be locally important for stands that have relatively high ash density. We used the most recently completed FIA survey for Alabama to identify and spatially reference ash trees (F. americana, F. pennsylvanica, and F. quadrangulata) in the dataset. Field studies have indicated ash mortality in untreated, infested stands to be > 99%. Therefore, in our analysis we assumed death of all ash trees. We used tree diameter to estimate the size of canopy gaps created by the loss of canopy ash and classified all gaps as small or large. We then calculated the relative importance values (RIV) separately for overstory and understory taxonomic groups. On a per plot basis, we assumed the overstory species group with the highest RIV would capture small canopy gaps and the understory species group with the highest RIV would capture large canopy gaps created by ash mortality.
Dept of Geography, University of Alabama, Tuscaloosa, AL
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P91 • Lauren E. Cox, Justin L. Hart, Michael K. Steinberg
Pre-European Settlement Forest Composition and Structure of the Alabama Fall Line Hills
General Land Office (GLO) surveys are archives that contain quantitative and qualitative descriptions of pre-European settlement forests, and were used to map lands in the United States beginning in 1812. Data obtained from original GLO surveys provide information necessary to construct models of pre-settlement forests, which are useful for establishing place-based targets for land management. We used GLO surveys from 1820 and 1842 to reconstruct the pre-settlement forest in the Fall Line Hills of west-central Alabama. Using witness tree species and location, we analyzed relative frequencies and densities to determine the compositional characteristics of the forest at various topographic positions. Pine (Pinus spp.) composed 55% of the total forest composition, and accounted for 30% of the forest composition at lower slopes, 54% at North and East facing slopes, 72% at South and West facing slopes, and 73% at upper slope positions. Altogether, oak (Quercus spp.), hickory (Carya spp.), and chestnut (Castanea denata) comprised 27% of total forest trees. We estimated total density of pre-settlement forest to be 370 stems/ha. Results from this analysis provide a basis for the quantitative comparison between current management regimes used for longleaf pine (Pinus palustris) and the pre-European settlement forest conditions and can be used to set desired future conditions for restoration on public lands.
Dept of Geography, University of Alabama, Tuscaloosa, AL
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P92 • Stephen D. White1, Justin L. Hart1, Callie J. Schweitzer2, Daniel C. Dey3
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