An Examination of the Effects of Land Use and land Cover on Macroinvertebrate Communities at Two Landscape Scales

Macroinvertebrate community composition and differing patterns of land use/ land cover (LULC) were assessed in three watersheds of northern New Jersey. A total of six 40-m reaches were sampled in the agriculturally dominated Wallkill, the urbanized Rockaway and the forested Flat Brook. Qualitative observations and scorings of ten habitat factors commonly associated with stream health and water quality were made at each site. These Habitat Assessments resulted in the two Flat Brook sites being rated as “optimal” and the remaining four sites being rated as “suboptimal”. The 2007 NJDEP Land Use/Land Cover (LULC) dataset was used to determine percent urban, forested, agricultural, barren land, water and watershed cover types. LULC was analyzed for each site at two spatial scales: 1) within a 100m riparian zone upstream from the sample point and 2) the entire drainage area of the watershed upstream of the sampling point. LULC in the riparian area was not found to be highly correlated with watershed area LULC. Eleven types of single value and multimetric indices and percentages of the six types of functional feeding groups were computed from 3,908 individual benthic macroinvertebrate samples. Similarities in results from the single metric and multi-metric indices suggest that they were equally useful for most sites in determining habitat conditions based on the biota. The metrics supported the notion that as forest cover increases, the quality and biodiversity of macroinvertebrate communities improves. The strongest correlations were between macroinvertebrate multimetric indices and forest cover at both the riparian and the watershed scales. R-values at the watershed scale were highest when forest cover was correlated to the High Gradient Macroinvertebrate Index (HGMI), the Hilsenhoff Biotic Index (HBI) and the Shannon Weiner Index of Biodiversity. Poisson regression model results indicated that urban and water LULC significantly impacted the number of EPT species. Urban negatively affected the number of EPT species and water positively affected the number of EPT species. A better understanding of how to analyze biological communities at different landscape scales can improve management approaches for the physical habitat of streams and improve basin-wide water quality conditions and stream biological integrity