Development of a plant based riparian index of biotic integrity (RIBI) for assessing the ecological condition of highland streams in East Africa

Abstract

The study of riparian plant communities along running streams offers information on the state of habitat and can help increase our knowledge on the use of bioindicators. We developed a riparian index of biotic integrity (RIBI) to evaluate the conditions of highland streams in response to anthropogenic disturbances in the southwest Ethiopian highland. To construct RIBI, we evaluated 22 potential plant metrics. Disturbance was quantified for each site using information on canopy openness, ground area without vegetation and exposed mineral soil. Five core metrics (floristic quality indexes, average C, native tree/shrub species, riparian status species and Shannon diversity index) were found to respond to anthropogenic disturbances. These metrics were significantly differentiated among sample sites categorized as low and high disturbance sites (p < .001). The core metrics and RIBI scores for this data set were also significantly correlated with environmental variables including riparian buffer width, dissolved oxygen, water temperature, turbidity, total suspended sediment, nitrate and orthophosphate. These findings provide support for the continued use of plants as indicators of highland stream condition in the East Africa, providing that the responses of plant based metrics to disturbances. Thus, the RIBI could be useful tool for the assessment and monitoring of stream ecosystems and evaluating the effect of stream restoration in the East African highland in the future.