Appraisal of Multiple-Scale Land Cover and Site-Level Physical Factors on the Contribution of Terrestrial Invertebrates to Stream Ecosystems

There is a growing body of literature emphasizing the importance of terrestrial invertebrates to the structure and function of stream ecosystems, mainly as an energy subsidy for stream fish. The input of terrestrial invertebrates from the riparian area of streams may be linked to the vegetation type and land use of the riparian area. To test this, terrestrial invertebrates falling into streams were collected with floating pan traps. These data were combined with a GIS model of surrounding land use composition, assessed at multiple spatial scales in 12 northeast Ohio streams. A site-level index of habitat quality was used to evaluate local stream characteristics to determine the scale at which factors influencing terrestrial invertebrate input are most prominent. Correlation analysis showed the strongest relationships between the amount of shrub/scrub vegetation near the stream and invertebrate diversity and the ratio of terrestrial-derived to aquatic-derived invertebrates caught in the pan traps. These relationships were significant at multiple spatial scales up to 5000 m. Site-level physical features that correlated with terrestrial invertebrate input included stream gradient and substrate quality. The results show that the contribution of terrestrial invertebrates to streams is related to land use beyond the immediate riparian area.