Treesearch

Precommercial thinning and tree pruning are frequently used together to improve timber quality and wildlife habitat in even-aged Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) stands. Thinning enhances crop tree growth and understory plant production; however, the benefits and drawbacks of tree pruning have received less attention. Tree pruning was investigated in two long-term experiments on the Tongass National Forest, Alaska, USA. Experiment 1 tracked four uniformly thinned sites for ~30 years that received 2.4, 3.6, and 5.2 m lift, and no pruning treatments....

The frequency of dissolved oxygen depletion events (hypoxia) in coastal aquatic ecosystems has risen dramatically since the late 20th century, yet the causes and consequences of hypoxia for some culturally and economically important species remain poorly understood. In rivers, oxygen depletion can be caused by high densities of spawning Pacific salmon (Oncorhynchus spp.) consuming oxygen faster than can be replaced by reaeration. This process may be exacerbated when salmon densities are artificially inflated, such as when hatchery-origin salmon stray into rivers instead of returning to...

Invasive annual grasses have long been known to increase wildfire danger in shrublands and woodlands of the American West. Ventenata (Ventenata dubia) is one such grass. First reported in North America in 1952 in Washington state, it is now expanding into previously invasion- resistant forest landscapes. Unlike cheatgrass, another invasive grass, ventenata can grow in sparsely vegetated rocky meadows. These forest scablands, often embedded within a forested landscape, have historically served as natural fire breaks. Lacking sufficient fuels, the scablands usually stopped fire from spreading...

Many models are designed to generate future predictions under climate-change scenarios. Such models are typically calibrated for a study area with climate data that represent historical conditions. However, future projections of the model may include outputs for which the model has not been calibrated. Ideally, a climate-change-impacts model would be calibrated for recent conditions and also for possible future climate conditions. We demonstrate an approach, where a vegetation model is subjected to two calibrations: conventionally to the study area and separately to the study area plus...

Understanding prey consumption patterns is critical to understanding the ways in which seabirds cope with a changing ocean. However, characterizing the dietary habitats of seabirds can be challenging. In this study, we investigated the diet of the Marbled Murrelet Brachyramphus marmoratus population that lives in waters off California, Oregon, and Washington, USA, using fecal DNA, custom metabarcoding, and high-throughput sequencing. Murrelets were captured at sea by dip-netting at night. Across this region, murrelets consumed highly diverse prey types including 17 fish species and 10...

Fledgling encounter rates at sea were used as measures of annual reproductive performance for Common Murres Uria aalge and Marbled Murrelets Brachyramphus marmoratus over 29 years in two marine biogeographic regions off the coast of Oregon, USA, north and south of Cape Blanco. In both bioregions, the adult murre population was much larger and the encounter rate of murre fledglings was much higher than for murrelets overall, but the apparent decline in productivity during El Niño events and years of poor foraging was significantly greater in murres than in murrelets. We conclude that...

Fire-exclusion has acted as a major perturbation on dry conifer forests in the western United States, increasing tree density and, in mixed-conifer forests, the dominance of shade-tolerant species. Restoration efforts aim to reverse these effects by reducing stand density, restoring relative proportions of tree species, and reintroducing recurrent fire, but there are limited long-term data on the effects of repeated burning on tree regeneration. We analyzed two decades of seedling and overstory data from the Teakettle Experimental Forest in the southern Sierra Nevada, California, United...

A forester set up a large-scale, 1600-m fire-break trial with red alder (Alnus rubraBong.) inter-planted between Douglas-fir (Pseudotsuga menziesiiMirb Franco), after the extensive 1927 Yacolt Burn in the Columbia Gorge. This now 90-year-old trial demonstrates dramatic effects of alder on soils and growth of Douglas-fir; it also provides a timely lesson for foresters deciding what to do after recent similar fires in western Oregon and Washington. We used 2015 airborne lidar to re-examine the trial effects. Douglas-fir trees in stands mixed with alder (Strip) continue to grow taller than...

We present PNW-Cnet v4, a deep neural net with an associated Shiny-based application designed to facilitate efficient data processing to detect terrestrial wildlife species through passive acoustic monitoring. PNW-Cnet v4 is a deep convolutional neural network that detects audio signatures of 37 focal species of birds and mammals that inhabit forests of the Pacific Northwest, USA, along with other commonly occurring forest sounds. The primary objective of developing PNW-Cnet v4 was to support a long-term northern spotted owl (Strix occidentalis caurina) monitoring program. By incorporating...

Past experiences influence choices, and people’s preferences for more similar (habit-forming) or different (variety-seeking) experiences are reflected in these choices. We develop a structural estimation framework to capture whether people are habit forming or variety seeking and apply it to the choice of recreation site. This research contributes to the revealed preference literature by demonstrating how to account for habit or variety-seeking behavior in recreation site choice models in a two-stage framework. Using this framework, we estimate similarity weights that reflect the birders...