|
Past Research 1996-2002 P-IIID. Effects of Natural Disturbances in the Coweeta Basin Summary: Hurricanes and sawfly outbreaks are two examples of natural disturbances that occur in the Coweeta Basin. Hurricane Opal struck the Coweeta basin on 05 October 1995. Wind gusts exceeded 130 km/h and 23 cm of rain fell. In rapidly assessing the hurricane damage we discovered that microbursts had generated replicated gaps across the site. We leveraged LTER infrastructure and long-term data to obtain additional funding (NSF DEB-9615661) and explored the effects of gap creation on insect herbivores and the foliage quality of surviving trees. Our results revealed that increased insolation, not nutrient availability, was the major factor influencing post-hurricane foliar quality (Hunter and Forkner 1999). We also compared a hurricane-disturbed hillslope to one where rhododendron (a species that has increased in cover since 1976) was experimentally removed. Between 1995-2000, soil water nutrient concentrations from soil lysimeters did not vary significantly on the experimental removal hillslope, but on the hurricane-disturbed hillslope NO3-N concentrations increased at least two orders of magnitude (Wright and Coleman 2002). There were also marked and persistent changes in SO4 (decrease), Ca (increase), and Mg (increase), with the greatest variance occurring in summer and early autumn (Yeakley et al. in revision). In May 1998 we had a study linking canopy herbivores to soil processes in progress when a sawfly (Hymenoptera: Symphyta) outbreak took place in a high-elevation hardwood forest in the Coweeta Basin (Hunter 2001). Using the instrumentation in place at defoliated and undefoliated sites we were able to measure the effects of the outbreak on soil nutrient dynamics, soil respiration, and litter decomposition. Within one month of the sawfly outbreak, elevated levels of nitrate were measured in throughfall, soil resin bag samples, and stream water draining the affected watershed. Furthermore, insect frass generated “blooms” of collembola and nematodes in forest litter (Reynolds et al. 2000, Reynolds and Hunter 2001, Hunter et al. in review).
Investigators and Collaborators: |