Stream Temperature Response to 50% Strip-Thinning in a Temperate Forested Headwater Catchment

Dinh Quynh Oanh,R Dan Moore,Chen-Wei Chiu,Bui Xuan Dung,Marino Hiraoka,Yuichi Onda,Takashi Gomi

doi:10.3390/w13081022

Abstract

Stream temperature is a critical parameter for understanding hydrological and biological processes in stream ecosystems. Although a large body of research has addressed the effects of forest harvesting on stream temperature, less is known about the responses of stream temperature to the practice of strip-thinning, which produces more coherent patches of shade and sunlight areas. In this study, we examined stream temperature response to 50% strip-thinning in a 17 ha headwater catchment. The thinning lines extended through the riparian zone. Paired-catchment analysis was applied to estimate changes in daily maximum, mean, and minimum stream temperatures for the first year following treatment. Significant effects on daily maximum stream temperature were found for April to August, ranging from 0.6 °C to 3.9 °C, similar to the magnitude of effect found in previous studies involving 50% random thinning. We conducted further analysis to identify the thermal response variability in relation to hydrometeorological drivers. Multiple regression analysis revealed that treatment effects for maximum daily stream temperature were positively related to solar radiation and negatively related to discharge. Frequent precipitation during the summer monsoon season produced moderate increases in discharge (from 1 to 5 mm day−1), mitigating stream temperature increases associated with solar radiation. Catchment hydrologic response to rain events can play an important role in controlling stream thermal response to forest management practices.

Highlights

IntroductionStream temperature is an important indicator for understanding hydrological processes such as groundwater inflows [1] and groundwater–surface exchange in hyporheic zones [2]
The first objective of this study was to quantify the impacts of strip-thinning on stream temperature in a forested headwater catchment
Maximum daily stream temperature increased up to 3.9 ◦ C, which was similar to increases following 50% random thinning and variable retention harvesting in previous studies, but was greater than the effect of clear-cutting with retention of riparian buffers

Summary

Introduction

Stream temperature is an important indicator for understanding hydrological processes such as groundwater inflows [1] and groundwater–surface exchange in hyporheic zones [2]. Because of tight linkages between hillslopes, riparian zones, and stream channels in headwater streams [3], stream temperature dynamics can be sensitive to hydrological processes in adjacent hillslopes and riparian zones. Changes in flow conditions (i.e., subsurface flow and groundwater inflow), as well as shading patterns along streams, alter stream heating processes [4,5]. Studies over the last five decades have revealed that changes in riparian forest condition influence stream temperature in headwater streams around the world (e.g., [8]), primarily due to the increase in solar radiation reaching the stream [9]. Harris [10] showed that increases in daily maximum stream temperature in summer increased up to 11.6 ◦ C in the first year after harvest in the coastal Pacific Northwest of North America

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