INFLUENCES OF FOREST HARVEST AND ENVIRONMENTAL GRADIENTS ON AQUATIC INVERTEBRATE COMMUNITIES OF SEASONAL PONDS

During 1999-2005, we studied aquatic invertebrate communities in 24 small, seasonally flooded wetlands (seasonal ponds) in aspen (Populus spp.)-dominated landscapes in north central Minnesota, USA. Sites were chosen from 2 different landforms, with 6, 6, and 12 wetlands selected from stands estimated to have been harvested 10-34 (young age), 35-58 (mid-age), and 59+ (old age) years before onset of the study, respectively. Of 12 ponds in the old age group, six were clear-cut during the winter of 2000-2001. Direct gradient analysis indicated that invertebrate communities were influenced by canopy openness, total phosphorus, total alkalinity, maximum depth, and hydroperiod, although relationships were complex, with no single environmental variable explaining >9.3% of invertebrate variance. Invertebrate taxon richness was negatively correlated with stand age and was also lower during the period following tree removal. However, taxon richness declined to a lesser extent in harvested old age stands relative to unharvested controls during the post-harvest time period. Our results indicated the presence of weak relationships between invertebrate communities and environmental characteristics of seasonal ponds and adjacent uplands. Innovative research strategies are needed because adaptations of aquatic invertebrates may limit interpretation of responses to natural and anthropogenic gradients in these habitats.