The overall goal of this research on riparian zones is to understand how these habitats function and what factors control their functions. The water quality factors of greatest interest are nutrients and toxic materials. The original publications which reported on these buffering functions of riparian forest were Gilliam et al. (1974), and Gambrell et al (1975). These were followed by a series of more focused reports (Lowrance et al, 1984a, 1984b; Peterjohn & Correll, 1984; 1986; Labroue & Pinay, 1986; Pinay & Labroue 1986; Schnabel, 1986; Pinay & Decamps, 1988; Correll & Weller, 1989; Sanchez-Perez et al, 1991, 1993).

Comparative data are needed to understand the role of plant communities in different riparian systems and interaction processes between compartments (Fig. 1). Such questions need to be addressed to ascertain the relative effectiveness of grass, herbs and trees; the width of vegetation needed for effectiveness; the importance of primary production, plant diversity, age structure, depth of root/rhizosphere zones; and how the surface plant community interacts with below-ground microbial communities. These systems should be characterized in respect to their hydrology, geomorphology, biogeochemistry, below-ground conditions, and hyporheic zones. More similarity needs to be developed in approaches and methods in order to produce more comparable data in the future.

GENERAL QUESTIONS FOR FUTURE RESEARCH

1. a) What are the capacities of these systems for processing nutrients and toxins?

2. b) Are these systems self-sustaining? For how long?

3. c) What are the principal mechanisms of water quality affects and what controls their rates?

4. d) What is the importance of biodiversity in controlling the efficiency of riparian zone processing of man-made chemicals?