Leaf litter entering streams and ponds provides an important source of allochthonous organic matter and nutrients. After a period of conditioning in the water where leaves are leached of organic and inorganic components, they begin to break down and are colonized (conditioned) by bacteria and fungi. Once the leaves have been conditioned, macroinvertebrates begin feeding on them. Bacteria and fungi provide an important source of nutrients to macroinvertebrates. Macroinvertebrate species serving as shredders (species that shred leaves) assist in breaking down leaves from coarse particulate organic matter (CPOM) to fine particulate organic matter (FPOM). In turn, FPOM is consumed by collector-gatherers (species that gather FPOM) and collector-filterers (species that filter FPOM), which are themselves consumed by macroinvertebrate predators (Allan, 1995).

The rate of leaf decomposition varies depending on leaf structural content and the presence of macroinvertebrates. Stream studies have found that leaves with higher carbon content tied up in cellulose and lignin and less nitrogen content take longer to break down. Leaves higher in carbon and lower in nitrogen are also less palatable to many macroinvertebrates (Allan, 1995; Royer and Minshall, 2001).

The purpose of this lab is to 1) quantify the difference in leaf decomposition between two leaf species that differ in “toughness” (as a crude index of cellulose and lignin), and 2) determine if the presence of macroinvertebrates affects leaf decomposition.

All requirements are in attached files.

I will also give you my partner's lab report, you can refer to his experimental report, but do not copy his word!!

You should make your own table, graph and use your own word to write this lab report.