A preliminary assessment of the impact of forest conversion from natural to pine plantation on macroinvertebrate communities in two mountain streams in Zimbabwe

Abstract

This study presents preliminary data on the influence of forest conversion from natural to pine plantation on benthic macroinvertebrates in streams in the Chimanimani Mountains in the Eastern Highlands of Zimbabwe, a region that has received little attention with respect to human impacts on stream ecology. Benthic macroinvertebrate assemblages from the Haruni River, draining native deciduous forest, were compared with those of the Nyahode River draining commercial pine plantations. Functional feeding groups composition was not significantly different between the two rivers. Only small differences in macroinvertebrate assemblages were detected, with Shannon-Weiner diversity = 3.80 and Evenness = 0.89 in both cases and Sørensen similarity index = 0.79. Cluster analysis and multidimensional scaling ordination also demonstrated little spatial variation in the community composition of the two streams. In contrast, the clearfelling index indicated that taxonomic richness and Ephemeroptera/Plecoptera/Trichoptera (EPT) taxa richness were negatively affected by forest conversion. Taxonomic richness and EPT richness were negatively correlated with embeddedness, the single tangible evidence of forestry impact. Development of a multimetric index may enhance detection of subtle changes in macroinvertebrate communities resulting from modest alteration of the riparian vegetation.

Keywords: benthic macroinvertebrates; bioassessment; forestry impacts; mountain streams

African Journal of Aquatic Science 2008, 33(2): 115–124