Effects of Timber Harvesting with Best Management Practices on Ecosystem Metabolism of a Low Gradient Stream on the United States Gulf Coastal Plain

Abram Dasilva,Y Xu,John Beebe,Richard Stich,George Ice

doi:10.3390/w5020747

Abstract

Stream metabolism can be used as a measure of freshwater ecosystem health because of its responsiveness to natural and anthropogenic changes. In this study, we used stream metabolic rates to test for the effects of a timber harvest with Louisiana’s current best management practices (BMPs). The study was conducted from 2006 to 2010 in a loblolly pine (Pinus taeda) stand in north-central Louisiana, USA, 45 ha of which was clear cut harvested in the summer of 2007. Dissolved oxygen (DO), water temperature, and stream depth were recorded at a site upstream (serving as a reference) and a site downstream of the harvested area. Using diurnal DO change and an open-system, single-station method at each site, we quantified rates of net ecosystem productivity (NEP), gross primary productivity (GPP), community respiration (CR), and the GPP/CR ratio. The system was predominately heterotrophic, with a GPP/CR ratio of less than one for 82% of the time at the upstream site. No calculated metabolic rate was significantly changed by the timber harvest (two-way ANOVA with interaction; p < 0.001). Overall, the results suggest that timber harvests of similar intensity with Louisiana’s current BMPs may not significantly impact stream biological conditions.

Highlights

Headwater streams constitute over two-thirds of the cumulative drainage length of river basins [1,2,3,4], and most of the headwater areas in the United States are covered by forests [5]
We considered calculating the reaeration coefficient using the delta method described by Chapra and Di Toro [14], and McBride and Chapra [47]
The results from this study indicate that logging using current best management practices (BMPs) had modest, if any, impact on the metabolism of Turkey Creek

Summary

Introduction

Headwater streams constitute over two-thirds of the cumulative drainage length of river basins [1,2,3,4], and most of the headwater areas in the United States are covered by forests [5]. Stream metabolism has been measured in situ for over 50 years [12,13,14], and there has been a recent increase in the frequency of research focused on using functional methods, such as measuring stream metabolism, to answer various questions about ecosystem status [6,15]. Even with this rise in the number of stream metabolism studies, many have not been specific to low-gradient headwater streams [16,17], headwater streams being those broadly classified by Vannote et al, as those of the 1st, 2nd, or 3rd order. The majority of the research has been conducted outside of the US Gulf coastal plain, with few studies, such as that conducted by Mulholland et al [8], situated in this geographically unique ecoregion

Objectives

Methods

Results

Discussion

Conclusion