Intermediate-Scale Wind Disturbance Affecting the Development and Succession of Southern Appalachian Quercus Stands
Natural disturbances play important roles in shaping the structure and composition of all forest ecosystems and can be used to guide silvicultural practices. Disturbance intensity is measured along a gradient ranging from highly localized, gap-scale events to stand-replacing events. High wind storms such as downbursts, derechos, and low intensity tornadoes typically fall in the center of this gradient and result in intermediate-scale disturbances, removing 30-60% of basal area. Despite their frequency and widespread occurrence, little is known about how intermediate-scale disturbances drive stand development. Here I evaluated the effects of intermediate-scale wind disturbance on the development of Quercus stands in regard to structure and recruitment. My specific objectives were to: 1) quantify damage severity in basal area reduction and percent canopy loss of this particular disturbance along a gradient of wind disturbance, 2) detect structural acceleration or retrogression of stand development caused by an intermediate-scale wind disturbance, and 3) elucidate compositional acceleration or retrogression for an intermediate-scale wind disturbance. Basal area was significantly reduced from 25.5 m2ha-1 to 15.5 m2ha-1 (p < 0.001) and PAR was significantly increased within the damaged areas (p < 0.001). Larger trees (> 45 cm DBH) were removed disproportionate to their pre-disturbance density. In undamaged areas, large trees comprised 4% of total density, whereas 16% of trees killed by the storm were in this size class. Based on our findings, this intermediate-scale disturbance increased intra-stand heterogeneity and accelerated succession, favoring shade-tolerant taxa established in the understory.
1 Dept of Geography, University of Alabama, Tuscaloosa, AL; 2 Southern Research Station, USDA Forest Service, Normal, AL; 3 Northern Research Station, USDA Forest Service, Columbia, MO
P93 • Rachel L. Craven, Paradise I. Flowers, J. Christopher Havran
Leaf Anatomy of Planchonella sandwicensis on the Islands of Hawai`I
Planchonella sandwicensis is a Hawaiian endemic tree distributed in mesic to dry forests on all main Hawaiian Islands. Previous studies of this highly variable species have suggested an east-west variation in leaf morphology. Our previous research showed that specific leaf area and stomatal density exhibited a significant positive correlation with rainfall. This encouraged us to conduct further studies to see if similar findings would be evident in the internal leaf anatomy. Collections of this plant were made from Kaua`i, O`ahu, Moloka`i, Maui and Hawai`i in 2012. Leaves were fixed and sectioned to 20 μm with a cryostat microtome. Leaf sections were photographed and attributes of the leaf were quantified. We investigated geographical and ecological correlates to features of internal leaf anatomy in the species. Some components of the leaf anatomy were significantly correlated to elevation and rainfall; however, there does not seem to be a clear pattern with these correlations. Some islands possessed some unique leaf attributes. Many of the leaves exhibited multiple lower and upper epidermis layers. This may be evident of the tree’s desiccation avoidance mechanism. Specimens from O`ahu possessed smaller ranges of variation in multiple epidermis thickness than other islands. There did not appear to be a geographic pattern in leaf anatomy variation.
Dept of Biological Sciences, Campbell University, Buies Creek, NC
P94 • Haley Hegedus1, Joshua W. Campbell1, James Martin2
Pollinator and Beneficial Insect Abundance and Diversity in Four Different Biofuel Treatments
Despite the current prevalence of corn as a biofuel crop, pollinating insects rarely utilize corn fields. However, several types of grasses show potential as surrogates to corn and may also encourage greater diversity of pollinators. To investigate the effects on pollinator abundance and diversity, four different treatments of potential biofuel crops were examined. Treatments included: (1) monoculture of switchgrass (Panicum virgatum)with single harvest, (2) monoculture of switchgrass with multiple harvest, (3) native warm season grass and forb mixture with single harvest (4) native warm season grass and forb mixture with multiple harvest. Insects were collected twice a month for 3 days at a time from each of the different plots using colored bowl traps. Overall, 37,050 potential pollinators and other beneficial insects were captured. Dolochopodidae was the most common beneficial Family captured (70% of total captures). Nineteen different genera of bees were captured within our treatments. Lasioglossum was the most common genera of bees captured (21% of total captures). Overall, neither the native grass/forb mixtures nor the switchgrass treatments exhibited significant differences in pollinator abundances. We suspect the lack of significant differences among treatments is due to bees using native grass/forb mixtures as foraging habitat while switchgrass treatments may have been used as suitable nesting structure.
