HR: 10:30h
AN: NB42E-01 [Abstracts]
TI: The Land Cover Cascade: Cause-Effect Couples Between Watersheds and Stream Biota
AU: * Burcher, C
EM: cburcher@vt.edu
AF: Virginia Tech Department of Biology, Derring Hall, Blacksburg, VA 24061 United States
AU: Benfield, E F
EM: benfield@vt.edu
AF: Virginia Tech Department of Biology, Derring Hall, Blacksburg, VA 24061 United States
AU: Valett, H M
EM: mvalett@vt.edu
AF: Virginia Tech Department of Biology, Derring Hall, Blacksburg, VA 24061 United States
AB:
A cascade may be defined as the propagation of a stimulus through a series of interdependent cause - effect relationships
that generate an ultimate response. The cascade concept has been applied to biotic systems ranging in scope from molecules
to ecosystems. The approach has been useful in organizing complex, multivariate, biotic relationships, and in identifying
mechanisms associated with the transformation of stimuli in biotic systems. We propose the Land Cover Cascade (LCC) to
summarize the translation of anthropogenic disturbance through physical ecosystem elements to ultimate influences on stream
biota. Much is known about how individual or groups of stream elements respond to disturbance, but how element responses are coupled, and how these couples translate disturbance implications, are largely unknown. To quantify the LCC, we estimated
land-cover and physical ecosystem elements in streams influenced by agricultural land-uses. Path analysis identified
cascades that organized direct and indirect effects of elements on biotic responses, and assessed the predictive ability of
each cascade. Cascade models of 3-4 links explained 50-94 percent of variation observed in thirteen fish and
macroinvertebrate assemblage responses. This approach moves us beyond traditional bivariate relationships, and brings us
closer to identifying the mechanisms and pathways involved in ecosystem responses to disturbance.
DE: 9810 New fields (not classifiable under other headings)
DE: 9901 NABS Student Award - Basic Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly