Stream restoration in a post-agricultural system: Indirect effects on density and secondary production of aquatic insects.

摘要

Restoration of stream habitats, with the goal of increasing biodiversity through increasing habitat heterogeneity, has been an ongoing trend in recent decades. Current investigations suggest most of those projects fail to significantly influence ecological structure and function when evaluated in light of their affect on species richness. In order to assess the "success" of restoration on a prairie stream in northern Illinois traditional metrics such as community composition and density were examined in addition to macroinvertebrate secondary production. Restoration of Nippersink Creek, McHenry County, Illinois was completed in 2000 and this study was conducted 8 years post-restoration. Benthic samples were collected from two replicate riffle sites in each reach type (restored and natural) during each season (Autumn, Winter, Spring, and Summer). Macroinvertebrate community composition was found to be similar in both reach types, with the exception of Leucotrichia (Trichoptera: Hydroptilidae), which occurred only in restored reaches. Insect abundance (mean (+/- SE)) was greater in restored reaches (R-1: 3197 (1169) individuals m-2; R-2: 3380 (1248) individuals m-2) compared with natural sites (N-1: 793 (247) individuals m-2; N-2: 685 (320) individuals m-2). Total annual secondary production of all species across restored sites was 56.5 g m-2 yr -1 and was significantly higher than in natural reaches (t test: t(2) = 11.9, p < 0.05) where annual production was 9.0 g m-2 yr-1. These results demonstrate that restoration of stream habitat heterogeneity had minimal effect on species richness, yet higher insect abundance and annual secondary production in restored reaches relative to natural reaches may be attributable to restoration efforts. These data suggest secondary production estimates may be a valuable post-restoration assessment tool, as invertebrate density and turnover rate are important to bottom-up trophic cascades, as is invertebrate diversity.