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In the eastern United States, the practice of salvage logging is common to reclaim economic losses and/or reduce fuel loading following a natural disturbance. A current hypothesis states that two disturbances in rapid succession (i.e., compounded disturbance) have a cumulative severity of impact and may displace the successional trajectory further than either disturbance occurring separately. On 20 April 2011, Bankhead National Forest in Alabama was affected by an EF1 tornado with accompanying straight-line winds. Much of the damage was salvaged, however adjacent disturbance in a Wilderness Area was not harvested. A unique set of conditions allowed for comparisons of woody regeneration within a single stand, reducing uncontrolled variables to test the compounded disturbance hypothesis at a fine spatial scale. After two growing seasons, species richness, species evenness, and Shannon diversity of seedlings and saplings did not significantly differ by disturbance class. We found seedling density significantly differed between functional groups and we noted a significant interaction between functional groups and disturbance classes. In the sapling layer, density was significantly different among functional groups and among disturbance classes, but our results did not reveal a significant interaction between these factors. The wind disturbance accelerated succession in the Quercus stand toward dominance by shade-tolerant species, notably A. rubrum, and the salvage operation amplified the Quercus-to-Acer transition. However, even in wind-disturbed areas that were not salvaged, the regeneration model predicted A. rubrum to have more than twice the density of all combined Quercus species in the future stand.
Plant nutrient stoichiometry, which regulates carbon fixation and plant growth, is often strongly affected by soil nutrient availability. Disturbances such as fire can affect the absolute and relative availability of soil nitrogen (N) and phosphorus (P), as well as biotic constraints on plant nutrient uptake and allocation. In these ways, disturbances can have strong legacy effects on plant growth by altering nutrient stoichiometry. Florida scrubby flatwoods are pyrogenic ecosystems where fires are frequent and intense, and the dominant species resprout after fire. We measured foliar N and P concentrations, nutrient ratios, and δ15N of ten species in scrubby flatwoods 1 yr, 3 yr, and 12 yr after fire to determine how fire affects nutrient stoichiometry. Across all species, foliar %N and %P decreased then increased with time after fire, and were positively correlated with each other. In contrast, foliar N:P ratios increased then decreased with time after fire. The effects of time after fire on nutrient concentrations and ratios, however, were not consistent among species. For example, %P of palmettos was highest 1 yr after fire, while %P of ericaceous shrubs was highest 12 yr after fire. Our study suggests that scrubby flatwoods may be colimited by N and P, species may be differentially limited by N and P, and species may experience greater N or P limitation depending on time after fire.
Xeric limestone prairies occur in southwestern and southern Illinois. These small grassland communities are present on thin soil and commonly have relatively extensive areas of exposed rock. Warm-season clump grasses, primarily Schizachyrium scoparium and Bouteloua curtipendula, are dominant along with a mixture of prairie and open-forest species. The vascular flora of two xeric limestone prairies, located near the bluff line of the Mississippi River on the property of Mr. and Mrs. Ralph Buettner in Monroe County, Illinois, were surveyed in 2011. A total of 174 vascular plant species were recorded from the two prairies, with 60 species present in survey plots. Bouteloua curtipendula dominated the East prairie followed by Schizachyrium scoparium, Andropogon gerardii, and Ruellia humilis. Andropogon gerardii dominated the West prairie followed by Bouteloua curtipendula, Solidago ulmifolia, Aster oblongifolius, Tridens flavus, and Schizachyrium scoparium. Vegetation covers 38.0% and 33.5% of the surface in these two prairies, while exposed rock was between 17% and 19%, and bare ground and litter was from 40% to 44%.
Patterns of tree species distributions in bottomlands are a result of various environmental and biological factors, including flood tolerance, seed dispersal, and species interactions. We evaluated the patterns of distribution and seed dispersal of tree species in a naturally regenerating bottomland hardwood forest in northeast Louisiana. We used nearest neighbor analysis to determine distribution patterns of the following canopy-dominant tree species: Carya aquatica, Celtis laevigata, Diospyros virginiana, Fraxinus pennsylvanica, Gleditsia triacanthos, and Quercus nigra. Results indicated an aggregated distribution pattern for Q. nigra, G. triacanthos, D. virginiana, and Ce. laevigata, while Ca. aquatica and F. pennsylvanica had random distributions in the study area. Additionally, we designed and used three types of seed traps to assess the seed dispersal of tree species. Modeled patterns of seed dispersal for F. pennsylvanica, Ca. aquatica, and Crataegus viridis indicated aggregated seed dispersal for these species. Low seed captures for all other species prevented modeling of their seed dispersal patterns. These results indicate that many of the tree species characteristic of bottomlands have nonrandom distributions. These distributions could be due to a variety of biotic or abiotic factors. Seed dispersal was similarly aggregated, at least for species where seed capture totals were high enough for modeling. Characterizing patterns in plant distribution and seed dispersal is important for understanding how plant communities develop during succession. Bottomland reforestation efforts should focus on planting species to match their natural distributions in an attempt to restore these communities to a more natural state.
Lindera melissifolia is a federally endangered endemic shrub of the southeastern United States. Numerous populations are gender-biased. The goal of this study was to determine environmental conditions most appropriate for establishment and growth of seedlings and adult females. Seedlings were grown under varied moisture and light to compare growth rates and morphological ratios. Seedlings were clipped to simulate two levels of disturbance, and their shoot sprouting ability was assessed. Densities of adult flowering stems, co-occurring species, and solar transmittance were analyzed within two North Carolina populations. The lowest levels of light resulted in decreased growth, but light and moisture did not interact to affect seedling growth rate significantly. Morphological ratios and growth responses followed patterns expected for plants exhibiting plasticity in response to varied light levels, but not to moisture. Clipping immature plants below root collars decreased survivorship to 31%. Growth rates of new shoots when clipped below and above the root collar were 40% and 58% percent lower, respectively (p < 0.001). Percent cover of Lindera melissifolia explained 52% of the variation in the number of male flowering stems per plot and 14% of the variation in female stems per plot. No relation of stem density to percent transmittance was found. Indicator species analysis revealed association of males with facultative wetland species and a weak association of females with wetland obligates, but overall difference in vegetation composition between plots with or without females present was slight (MRPP: A = 0.02, p = 0.016). We concluded hydrology should be a primary concern for future studies.
A vascular plant reconnaissance was conducted at the Berea College Forest (BCF) during 2010–2013. A previous vascular plant report of the BCF, a 3,380 ha managed forest in portions of Madison, Jackson, and Rockcastle counties in east-central Kentucky, documented 1,017 specific and infraspecific taxa, 513 genera, and 139 families. An additional 25 taxa (13 native, 12 nonnative) were documented for the Berea College Forest including 14 new county distribution records. The known native and exotic flora for the Berea College Forest now comprises 1,042 taxa and 520 genera.
Noss, Reed. 2013. Forgotten Grasslands of the South: Natural History and Conservation. Island Press, Washington DC. 320 p. Softcover, $35.00. ISBN 978-1-5972-6489-1. Hardcover, $70.00. ISBN 978-1-5972-6488-4.