Effects of leaf removal and leaf addition on leaf and wood breakdown in streams.

Wood and leaves are the primary source of organic material in many small streams. Previous studies have suggested that availability of leaf litter influences the rates of decomposition of leaves and wood (Webster and Waide 1982). In this study, we are investigating the relationship between leaf litter availability and leaf and wood breakdown. We hypothesize wood substrates decompose faster in an area of stream without leaves compared to one with normal leaf litter amount. We also speculate that wood and leaves decompose slower in an area of stream with increased leaf litter compared to one with normal leaf litter amount.1.We selected three 10-m sections of the stream for our study. Each section was divided from each other by about 20-m. We used this separation length in order to minimize the effects of one site on another site. We removed all of the leaves from one 10-m section (exclusion site) and placed them in another 10-m section (inclusion site). The remaining 10-m section is used as a reference site. The sequence of sites on the stream is exclusion (most upstream), reference, and inclusion (most downstream). At each site, 20 white oak leaf substrates (hereafter referred to as leaf packs--10- g each) and 15 white oak veneer substrates (hereafter referred to as wood strips--2.5- cm by 10-cm; attached in groups of three to a section of gutter screen) were placed near the middle of each site. We are collecting samples at the following dates after initial placement: 30-d, 60-d, 90-d, 120-d, and 150-d. We take subsamples from each wood strip and leaf pack in order to find decomposition rates of each substrate. Respiration of wood strip and leaf pack biofilms are measured using a Gilson Respirometer. In addition, ash free dry mass (AFDM) is measured from each of these subsamples. With inter-site data comparisons, we will look at breakdown of wood and leaves in relation to leaf litter availability in a stream environment. Also, macroinvertebrates will be collected from each leaf pack. Diversity and density from each sample will be analyzed. We will use these data to look at macroinvertebrate colonization behavior of leaf substrates in relation to leaf litter availability in a stream environment