Patterns of macroinvertebrate production, trophic structure, and energy flow along a tallgrass prairie stream continuum
Limnol. Oceanogr., 56(3), 2011, 887-898 | DOI: 10.4319/lo.2011.56.3.0887
ABSTRACT: We estimated benthic organic matter standing stocks, macroinvertebrate production, food-web structure, and stream metabolism along a longitudinal continuum of Kings Creek at Konza Prairie Biological Station in Kansas. Benthic macroinvertebrates were sampled for 1 yr from three stream reaches (grass, shrub, gallery forest). Total habitat-weighted production ranged from 9.1 g to 31.9 g ash-free dry weight m−2 yr−1 with the grass headwaters accounting for the highest production. Functional group contributions to production were similar along the continuum, with collector–gatherers (40–56% of total) and predators (23–38%) dominating all reaches. Detrital pathways appeared to account for most energy flow in all reaches, and all reaches were net heterotrophic on all dates when metabolism was measured, except for the grass headwater reach in spring. Predators were well-represented and consumed 65–107% of total macroinvertebrate production, whereas scrapers (11–15%), shredders (2–4%), and filterers (< 1%) consumed relatively small percentages of available resources. Dominance of predators suggested top-down controls are important in this system. However, changes in energy flow through other groups reflected longitudinal variation in resource availability. This prairie stream continuum conforms to some predictions of conceptual stream continua models, but biotic interactions, which are often not considered, may override some predicted responses to changes in the physical template.