Short-Term Climatic Events—Synthesis
Short-term climatic events produce some of the most dramatic ecosystem responses. Sometimes the responses may last for a long time into the future. Three themes will be emphasized in this synthesis. The first is that shortterm climatic events have both short- and long-term responses in the ecosystem. Second, the timing of short-term events is important in partially determining the kind and degree of ecosystem response that might occur. A third theme is the importance of putting short-term variability into a long-term context. The chapters about hurricanes and droughts in this section demonstrate that shortterm climatic events may have short- and long-term responses in the ecosystem. Both the short- and long-term responses are important. The short-term responses have noteworthy economic influences in the agricultural ecosystem. One could argue that the ecosystems containing species with short life spans such as grasslands are able to respond and recover from a short-term climatic disturbance more quickly than those ecosystems with longer lived species such as trees. Corn responds quickly to variability in precipitation during important parts of the growing season. Gage believes the long-term effects of a short-term drought on annual rotational agronomic systems are generally minimal. Other LTER studies have documented strong relationships between annual precipitation and grassland aboveground net primary productivity (Knapp et al. 1998). Conversely, the Coweeta study brings to our attention the insidious, long-term effects of drought that quietly kills trees and leaves their dead necromass on the landscape for decades into the future. However, each ecosystem is responding at its own characteristic timescale. Boose notes that the mixed hardwood forests of central New England and the Tabonuco forests of Puerto Rico both exhibit remarkable resiliency to wind damage. In both cases, despite major structural reorganization after a hurricane, there was rapid regeneration of canopy cover through releafing, sprouting, or recruitment, which helped to reduce impacts on soil moisture, temperature, and nutrient cycling processes. Nevertheless, some signs of the hurricane impact are present for decades, although less so in Puerto Rico where decomposition and regeneration rates are much faster than in New England.