Macroinvertebrate secondary production was estimated for 2 reaches in each of 3 adjacent forested headwater streams. We had 3 objectives: 1) to compare macroinvertebrate secondary production and community structure both within and among streams to examine the spatial extent of variability, 2) to explore important habitat variables related to secondary production, and 3) to compare our secondary production values to values from other headwater streams in deciduous forests. Principal components analysis separated study streams on the basis of small differences in substrate composition, organic-matter standing crops, and instream wood, but geology, riparian tree species composition, and fine benthic organic-matter standing crops were similar among streams. Secondary production varied among streams (range ∼1.2 to 3.3 g ash-free dry mass m−2 y−1) and was low compared to estimates from other streams draining deciduous forest. Macroinvertebrate communities had relatively higher production of scrapers, predators, and collector-filterers and lower production of shredders and collector-gatherers as compared to other perennial eastern deciduous headwater streams. We expected differences in secondary production among streams to be related to leaf-litter standing crops; however, differences among streams were positively related to % cover of gravel and cobble and chlorophyll a concentrations on gravel (R2 = 0.87, p = 0.01). Total secondary production was negatively related to the number of large pieces of wood, leaf-litter standing crop, and % cover of sand. A similar, positive relationship between % cover of gravel and cobble and chlorophyll a concentrations was found for primary consumers (R2 = 0.89, p = 0.03), collector-filterers (R2 = 0.76, p = 0.02), and scrapers (R2 = 0.67, p = 0.04). Low amounts and patchy distributions of coarse benthic organic matter, leaf litter, and large wood probably resulted in more variable secondary production of predators and shredders within these streams than among all streams. Inorganic substrate composition, primary production, and water temperature probably were key factors regulating secondary production of the other functional feeding groups and total secondary production among streams.
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Vol. 26 • No. 3