Spatial and seasonal variability of forested headwater stream temperatures in western Oregon, USA

Abstract

Thermal regimes of forested headwater streams control the growth and distribution of various aquatic organisms. In a western Oregon, USA, case study we examined: (1) forested headwater stream temperature variability in space and time; (2) relationships between stream temperature patterns and weather, above-stream canopy cover, and geomorphic attributes; and (3) the predictive ability of a regional stream temperature model to account for headwater stream temperature heterogeneity. Stream temperature observations were collected at 48 sites within a 128-ha managed forest in western Oregon during 2012 and 2013. Headwater stream temperatures showed the greatest spatial variability during summer (range up to 10 °C) and during cold and dry winter periods (range up to 7.5 °C), but showed less spatial variability during spring, fall and wet winter periods (range between 2 and 5 °C). Distinct thermal regimes among sites were identified; however, geomorphic attributes typically used in regional stream temperature models were not good predictors of thermal variability at headwater scales. A regional stream temperature model captured the mode of mean August temperatures observed across the study area, but overpredicted temperatures for a quarter of the sites by up to 2.8 °C. This study indicates considerable spatial thermal variability may occur at scales not resolved by regional stream temperature models. Recognizing this sub-landscape variability may be important when predicting distributions of aquatic organisms and their habitat under climate and environment change scenarios.

Citation

Leach, J. A.; Olson, D. H.; Anderson, P. D.; Eskelson, B. N. I. 2017. Spatial and seasonal variability of forested headwater stream temperatures in western Oregon, USA. Aquatic Sciences. 79(2): 291-307. https://doi.org/10.1007/s00027-016-0497-9.