Fig 1.
Map of study watersheds in northern California second-growth redwood forests. Data were collected in upstream reference, thinned, and downstream reaches, which were replicated at 10 total sites distributed across these three watersheds. Temperature sensors were deployed at the top and bottom of each reach indicated by blue points in illustration of study reaches. See Table 1 for characteristics of study sites. Map by David A. Roon in ArcGIS Pro (ESRI, Redlands, CA USA) using data collected by the authors and publicly-available GIS shapefiles from the California State Geoportal: https://gis.data.ca.gov/ [41, 42].
Table 1.
Study site characteristics.
Fig 2.
Riparian shade and light responses to riparian thinning.
Riparian shade and light responses to riparian thinning in northern California second-growth redwood forests. Riparian shade summarized as a) canopy closure (%), b) effective shade (%), and solar radiation summarized as c) below-canopy light (%) for Tectah and Lost Man sites. Data collected in upstream reference (US), thinned (TH), and downstream (DS) reaches during pre-treatment (2016) and post-treatment years (2017 and 2018) for each site. Points indicate mean estimates with error bars indicating 95% confidence intervals. Vertical hashed line indicates the timing of experimental thinning treatments.
Fig 3.
Stream thermal regime responses to riparian thinning.
Seasonal patterns in stream temperature in upstream reference (US), thinned (TH), and downstream (DS) reaches during pre-treatment (2016) and post-treatment (2018) water years in northern California second-growth redwood forests. Boxplots show the distribution of responses across all sites (n = 10) for selected stream thermal regime descriptors including: magnitude (a-d), variability (e-f), frequency (g), and duration (h). Stream temperature responses were summarized for each seasonal window: Fall (October-December), Winter (January-March), Spring (April-June), and Summer (July–September).
Table 2.
Stream thermal regime responses in thinned reaches.
Table 3.
Stream thermal regime responses in downstream reaches.
Fig 4.
Reach-scale longitudinal profiles of stream temperature responses.
Seasonal variation in reach-scale longitudinal profiles of stream temperature responses (pre-treatment—post-treatment) in upstream reference (US), thinned (TH), and downstream (DS) reaches for individual sites (n = 10) in northern California second-growth redwood forests. The position of thinned reaches is indicated by the yellow polygons. Black dots on blue line depict temperature sensor locations along upstream, thinned, and downstream reaches.
Fig 5.
NMS ordinations of stream thermal regimes.
Non-metric multidimensional scaling ordinations of the structure of stream thermal regimes in response to riparian thinning in northern California second-growth redwood forests. Each point represents the structure of a stream thermal regime at a site with colors indicating reach type and shapes indicating pre-treatment or post-treatment years for each watershed. The proximity of points provides an indication of how similar thermal regimes are between reaches (upstream reference, thinned, downstream), years (pre-treatment, post-treatment), and seasons (fall, winter, spring, summer) for the Tectah and Lost Man watersheds. Ellipses indicate 95% confidence intervals around the grouping variable of reach. PerMANOVA tests indicated whether the structure of stream thermal regimes differed significantly by the BACI effect of Reach*Year (α = 0.05).
Fig 6.
Relationships between shade, light, and stream temperature.
Relationships between the responses of riparian shade (a) and light (b) and stream temperature (summer MWMT) associated with riparian thinning treatments in Tectah and Lost Man watersheds in northern California second-growth redwood forests. Responses are calculated as BACI differences. Gray shading indicates 95% confidence intervals.