Weyerhaeuser Company () is an American timberland company which owns nearly 12,400,000 acres (19,400 sq mi; 50,000 km2) of timberlands in the U.S. and manages an additional 14,000,000 acres (22,000 sq mi; 57,000 km2) timberlands under long-term licenses in Canada. The company also manufactures wood products. Weyerhaeuser is a real estate investment trust.
An increase in the occurrence of large, high severity wildfires in the western Pacific Northwest (PNW), USA, has created an urgent need for science to better inform forest management and policy decisions to maintain source water quality in the region. The western PNW faces similar challenges to other regions with shifting wildfire regimes and large population centers reliant on surface water from forested catchments. However, the uniquely wet and highly seasonal climate of the western PNW suggests that findings from other, more frequently burned regions may not be directly applicable. To identify science, monitoring, and management gaps and opportunities in the western PNW, this review was collaboratively undertaken by academics, non-government and industry representatives, and local, state, and federal government entities who have been working together since the 2020 Labor Day fires in Oregon. Focusing on Oregon and Washington, we found that monitoring networks for continuous water quantity and quality cover much of the state with greater representation in western U.S. ecoregions, but few studies have analyzed and published these data to capture and communicate the post-wildfire response. Approximately half of the streamgages in Oregon and Washington record major water quality parameters, and hundreds of sites in the area have discrete sampling for a wide range of water quality constituents. Still, numerous gaps exist in understanding the short- and long-term impacts of wildfire on hydrology, water chemistry, including pH and dissolved oxygen, mobilization of metals, aquatic ecosystems, and downstream drinking water treatment. Collective action to further collect, analyze, interpret, and publish the key data could help improve our understanding of post-wildfire water quality impacts in this and other increasingly wildfire-affected regions.
The Western Washington Intensively Monitored Watersheds (IMW) study was designed to assess the cumulative effects of extensive stream habitat restoration over long durations at ‘watershed’ geographic extents. We conducted annual surveys from 2004 through 2024 at hundreds of randomly selected reaches (“sites”) throughout 10 independent watersheds (“streams”) clustered into 3 regional complexes. Our objectives were to describe cumulative change in habitat measures that are common aims of fish habitat restoration and to test for differences between watersheds with different restoration efforts. In most cases, we did not observe the expected directional changes in habitat measures summarized to whole-watershed extents nor did we observe the expected differences relative to the level of restoration effort. However, we did observe high interannual variation in fish habitat measures. The magnitude of these year-to-year fluctuations was frequently much greater than observed long-term trends. Despite physiographic differences among study watersheds, all watersheds exhibited substantial spatial variation among sites in the degree of interannual variation, indicating a widely shared pattern of within-watershed heterogeneity in habitat stability. Our results underscore the importance of anticipating and accounting for year-to-year changes in stream habitat when assessing habitat conditions and planning and implementing fish habitat restoration.
Wildfire can dramatically influence terrestrial landscapes, but effects on biodiversity can be hidden beneath the water’s surface. Following the 2020 Labor Day wildfires in Oregon’s western Cascade Mountain Range, we sampled 25 Oregon streams and 6 Washington streams representing a gradient of fire severity and pre-fire forest stand age to determine the effects of megafires on watershed biodiversity. In each watershed we used environmental DNA (eDNA) metabarcoding and traditional field surveys (Surber or electrofishing) to assess biodiversity. Our results suggest aquatic taxonomic richness for macroinvertebrates and vertebrates in the first-year post-fire was unaffected by wildfire. Diversity responses to wildfire severity and pre-fire forest stand age were inconsistent across methods indicating decreasing diversity with increasing burn severity from electrofishing and decreasing diversity with increasing stand age from eDNA, but no reciprocal method changes were observed. eDNA aquatic insect detections revealed greater species richness in older forests (> 90 years). eDNA detected 158 organisms, 48 of which were found in all fire severity categories, but each category revealed unique species compositions. We demonstrate the utility of eDNA metabarcoding for a broader taxonomic assessment of post-wildfire disturbance facilitating an improved understanding of the effects of wildfire and forest management on watershed biodiversity.
Headwater streams play a critical role in the physical, chemical, and biological functions of downstream waters. However, predicting their specific downstream impact remains a challenge. The river corridor concept provides a framework for exploring hydrologic fluxes across hillslopes, riparian zones, hyporheic zones, and stream channels. To discretize the river corridor into quantifiable and repeatable compartments, the intermediate hydrogeomorphic feature (HGF) scale has been recently defined. In this study, we used process-based modeling within and across HGFs to evaluate patterns of hydrologic connectivity and storage, and impacts on streamflow and drying. We used the Advanced Terrestrial Simulator to model hydrologic fluxes in an experimental watershed in the coastal plain of the southeastern United States, where we delineated incised, intact riparian, and wetland HGFs across watersheds. Among HGFs, incised channels gained the most water from the subsurface, wetland HGFs maintained the highest water tables, and intact riparian HGFs frequently went dry. Incised and wetland HGFs generated the majority of discharge throughout the year, but dry season discharge was dominated by streamflow gains in the incised HGFs. Together, these results suggest that stream incision increases downstream connectivity and export while wetland HGFs increase watershed capacity for storage. Our findings highlight the role of geomorphic structure in driving spatial patterns of drying, storage, and connectivity. Given the pervasiveness of stream incision across anthropogenically impacted systems, our results provide a framework for identifying locations significant to watershed-scale hydrologic export or retention. ** This is a Preprint and has not been peer reviewed. The manuscript has been submitted to Water Resources Research for review **
In short-rotation, pine (Pinus spp.) forest landscapes of the southern United States, vegetation retained in streamside management zones (SMZs) provides semi-permanent, mature forest cover within an otherwise dynamic landscape. SMZs are established as part of forestry best management practices for water quality, but have demonstrated co-benefits for wildlife, including disturbance-sensitive bird species. We examined Wood Thrush (Hylocichla mustelina), a regional species of conservation concern, use of SMZs, and adjacent forest stands in privately owned short-rotation loblolly pine (P. taeda) forests in north-central Mississippi, USA. We captured and tagged 16 individual males with GPS data loggers within SMZs during the breeding seasons (May - July) of 2023 and 2024. We recaptured nine individuals, derived use range sizes (ha) using autocorrelated kernel density estimates, quantified resource use, and examined associations with local composition (100 m) and landscape patterns (1500 m) using resource selection functions. We found that Wood Thrush with larger use range sizes occurred in smaller, narrower SMZs, suggesting wider SMZs may provide greater opportunities for food and cover resources in short-rotation pine landscapes. We also found strong positive associations with local composition of SMZs and late-rotation pine cover and negative associations with local composition of earlyestablishment forest stands. SMZ shape and low land cover diversity in the surrounding 1500 m landscape were also important factors in resource use. SMZs in southern, working pine forest landscapes may be instrumental for recovering declining Wood Thrush populations, especially when managed for wider areas of retained vegetation and proximity to other late-rotation forest.
