Impacts of Land-Use on Leaf Breakdown and Macroinvertebrate Assemblages in Southern Appalachian Streams

Abstract

Land-use practices have long been associated with alterations in stream ecosystem structure and function, however, 'exurbanization' and its impact on streams is poorly understood. This study compares the ecosystem structure and function of 9 southern Appalachian streams of differing land-use (forested, exurban, agricultural).

Impacts of land-use on leaf breakdown are examined in Chapter 1. Leaf breakdown rates were significantly related to land-use. Forested streams exhibited the slowest breakdown rates, followed by exurban streams, with agricultural streams having the fastest rates. Leaf breakdown was most strongly related to discharge (white oak) and some fine sediment metrics (red maple). Our results suggest that the altered hydrological regimes in agricultural streams, as well as the influx of fine sediments into streams from exurban development, can play a role in altering in-stream organic matter processing. The taxa and number of shredders present may play a role to a lesser extent.

Impacts of land-use on macroinvertebrate assemblages are examined in Chapter 2. Shannon diversity, %EPT, and NCBI were significantly related to land-use regime. There were significant negative relationships between macroinvertebrate diversity and conductivity and temperature. In addition, biotic integrity had a significant negative relationship with conductivity. Canonical Correspondence Analysis (CCA) showed that agricultural streams were characterized by temperature and flow, forested streams by MPS and standing stock course particulate organic matter (SSCPOM), and two of three exurban streams by conductivity and temperature. Principal Coordinates Analysis (PCoA) revealed that while macroinvertebrate communities overlapped, some differences in community assemblage could be seen between land-use types.