Communities as bio-indicators: pairing aquatic macroinvertebrates with riparian flora to assess the biotic integrity of headwater streams disturbed by cattle in the Warner Mountains

Graduation Date

2015

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Biology, 2015

Committee Chair Name

Michael A. Camann

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Benthic macroinvertebrates, Warner Mountains, Bioassessment, Humboldt State University -- Theses -- Biology, Cattle, Intermediate disturbance hypothesis, Disturbance, Iindex of biotic integrity, Riparian vegetation

Abstract

Bioassessment utilizes biological assemblages to assess ecological condition in disturbed areas. The most popular quantitative evaluation of biological health in streams involves an Index of Biotic Integrity (IBI) for benthic macroinvertebrates (BMIs), which incorporates an assessment of species' trophic status, abundance, and disturbance sensitivity. Tools similar to the IBI have been developed for riparian vegetation and are used to assess impacts of cattle grazing. The US Forest Service (USFS) Region 5 Range Monitoring Protocol uses proportional dominance of seral groups within riparian plant communities to make assertions regarding habitat quality. The objective of this study was to determine whether the IBI for BMIs and the USFS Range Monitoring Protocol would assess habitat quality in a comparable way when applied to the same sites. Twenty riparian field sites exposed to cattle disturbance were randomly selected to implement each assessment method. IBI metrics and composite IBI scores were calculated and compared to vegetative condition scores. Results indicate that the Range Monitoring Protocol and the IBI for BMIs are not comparable techniques. Each protocol ranked sites contrarily and identified different sites as most and least impaired. NMDS ordination was utilized to assess similarities in community composition between sites and to identify variables correlated with assemblage patterns. Results revealed grazing intensity drives community assemblage patterns for vegetation (R2 = 0.2953, p = 0.0162*) but not for invertebrates (R2 = 0.0027, p = 0.8273). Composition of plant communities under low grazing intensity was strongly correlated with stream bank slope and upland vegetation, which indicates grazing is not the only variable influencing composition. NMDS ordination for vegetative communities depicts an association between high grazing and community diversity and richness, which may provide support for the intermediate disturbance hypothesis. Further study should address the utility of the Range Monitoring Protocol and the extent to which it can be applied to sites with varying abiotic characteristics.

https://scholarworks.calstate.edu/concern/theses/dr26z0429

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