Assessing linkages among landscape characteristics, stream habitat, and macroinvertebrate communities in the Idaho Batholith Ecoregion

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Understanding the composition of lotic communities and the landscape processes and habitat characteristics that shape them is one of the main challenges confronting stream ecologists. In order to better understand the linkages among landscape processes, stream habitat, and biological communities and to understand how accurately our measurements represent important factors influencing biological communities, it is important to test explicit hypotheses regarding these linkages. Increasing our understanding of aquatic communities in a hierarchical context and recognizing how well our measurements represent factors structuring aquatic communities will help managers better evaluate the influence of land management practices on aquatic ecosystems, direct conservation strategies, and lead to better assessments of ecological condition. In Chapter 2, spatial data, field-based habitat measurements, and macroinvertebrate community data were used to 1) examine the influence of landscape processes on two factors of stream habitat— maximum stream temperatures and fine sediment and 2) examine how well these landscape and habitat characteristics represent factors influencing gradients in macroinvertebrate community structure. The results of this study showed that spatially derived measurements may be effectively used to test hypotheses regarding landscape influences on stream habitat and that spatial data, used in conjunction with field measurements, can provide important information regarding factors influencing gradients in biological communities. In addition, spatially derived measurements may provide the same or additional information regarding influences on community structure as field-based measurements do, suggesting that further research should be done to assess how well our field measurements represent factors that are important in shaping stream communities. The objective of Chapter 3 was to compare how well single field measurements and a combination of indicator variables hypothesized to be components of a single ecological processes or concept, known as a latent variable, represent thermal stress and fine sediment influences on macroinvertebrate communities. Results from this study showed that both single and latent variables explained relatively the same amount of variation in macroinvertebrate community structure. This finding suggests that while latent variables may have a potential to better refine how we represent ecological factors, a better basis for defining a priori hypotheses is needed before these variables can provide any additional information compared to single habitat measurements.

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ELECTRONIC FILE - Zoology: Invertebrates