Considerable research has focused on the importance of large conifers in riparian communities, with an emphasis on large wood as key structural elements within streams. Deciduous species have received less attention for their role in riparian community dynamics; however, preliminary research suggests that these species are important contributors to the riparian community because of the nutrients they provide through leaf litter.

Rapidly decomposing red alder (Alnus rubra) leaves contain greater concentrations of nitrogen than do slower decomposing needles of Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla). Quantity, nutritional quality, and phenology of leaf litter inputs can affect populations of shredders, which are the functional group of invertebrates that feed on leaf litter in streams. These shredders in turn affect the entire community of collectors and other invertebrates that feed upon fine particulate organic material they produce. Leaf litter from riparian vegetation is a key nutritional resource for aquatic invertebrate communities, and these communities are in turn important prey for trout and salmon.

In this study we will examine terrestrial inputs to stream systems and their relationship with riparian vegetation in the Oregon Coast Range. Specifically, this study is designed to compare leaf litter and invertebrate inputs between hardwood (mostly red alder) and conifer dominated riparian areas. We hypothesize that

	•	riparian communities dominated by hardwoods contribute more nutrients and terrestrially-derived invertebrates than do communities dominated by conifers
	•	vegetation composition and density will affect terrestrial and aquatic invertebrates that fall into the stream
	•	leaf biomass inputs to these streams will be greater in hardwood dominated reaches

For additional information about this research study see the 2002 CFER Annual Report. (2.2 MB)