Identifier

etd-04262011-151723

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

Macroinvertebrates are reflective of their nearby environment and are popularly used to detect changes in water quality. In this thesis research, macroinvertebrates were collected to investigate aquatic effects of timber harvesting operations with and without the use of best management practices (BMPs) in a forested, low-gradient, subtropical watershed in central Louisiana. Habitat assessments, physicochemical and hydrologic measurements, and macroinvertebrate sampling were conducted nine times from 2006 to 2010 during the spring and late summer, at 13 site locations ranging from plot level to watershed outlet. Timber harvesting occurred in September of 2007. A total of 86,183 macroinvertebrates were identified from 634 samples and grouped into 31 metrics describing taxonomic and functional feeding groups (FFGs). Timber harvesting, regardless of BMP implementation, negatively affected 14% of the collected macroinvertebrates. Additionally, bivalve taxa and FFG scraper densities increased at all of the sites downstream of harvesting activities in the spring sampling events post-harvest. Macroinvertebrates were further explored with principal component (PC) analysis (PCA), generalized linear mixed models and zero-inflated models to discern their relationships with physical instream and riparian characteristics, and water chemistry parameters representative of the low-gradient, seasonal intermittent headwater streams. PCA composed 19 PCs that explained 81% of the variation within the physical and riparian parameters. Two PCs interpreted as describing stream intermittency helped explain densities in 5 of 19 interpretable metrics that made up over 83% of collected macroinvertebrates. Bivalve, scraper, and collector-filterer metrics were positively associated with PCs describing open canopy and immature or thinned riparian zones. Ephemeroptera, Plecoptera, and Trichoptera (EPT) densities were positively associated with dissolved oxygen (DO), and undercut banks, and negatively associated with higher levels of woody-debris, and nitrite concentrations. Intensively collected DO data suggested that the densities of amphipods, chaoborids, and isopods showed significantly positive relationships with increasing DO. This adds critical knowledge to spatiotemporal dynamics of macroinvertebrate communities in Louisiana’s low-gradient headwaters and the effectiveness of timber-harvest BMP implementation on stream health protection. The information can be utilized for the development of biological indices to help manage morphologically similar streams in subtropical climates.

Date

2011

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Xu, Yi-jun

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