Treesearch

Growth rhythm that is well synchronized with seasonal changes in local climatic conditions is understood to enhance fitness; however, rapid ongoing climate change threatens to disrupt this synchrony. To evaluate phenotypic selection on growth rhythm under expected warmer and drier future climate, seedlings from 49 populations of whitebark pine (Pinus albicaulis Engelm.) were grown and measured over more than 10 years in two common garden field experiments on sites that approximate the projected future climate of the seed origins. Selection on growth rhythm was assessed by relating individua...

Recently, Stewart et al. (2017) investigated the origins of contemporary fisher populations in the Cooking Lake Moraine (CLM) of east-central Alberta, Canada, where fishers (Pekania pennanti) from Ontario and Manitoba, Canada were reintroduced in the early 1990s. To address this objective, Stewart et al. (2017) compared microsatellite alleles from extant fisher populations in the CLM to those from Ontario, Manitoba, and other Alberta populations. They reported that the CLM population clustered with adjacent native Alberta populations, consistent with recolonization, but also that 2 of 109...

Subsistence harvesters in high latitudes rely on frozen rivers for winter access to local resources. During recent decades, interior Alaskan residents have observed changes in river ice regimes that are significant hindrances to travel and subsistence practices. We used remote sensing in combination with local observations to examine changes in seasonality of river breakup and freeze-up and to assess the implications on travel for subsistence harvesters. Spring and autumn air temperatures, respectively, were found to impact timing of breakup (-2.0 days °C-1) and freeze-up (+2.0 days °C-1)....

Geolocator technology has recently demonstrated that many songbird species exhibit prolonged stopovers during migration that may be analogous to the staging behavior typically attributed to shorebirds. Although staging areas can act as ecological bottlenecks, there is little information on how or why songbirds engage in prolonged stopover and whether this behavior differs among individuals. We used automated radio telemetry along the eastern coastline of North America to compare stopover and migration behavior of Blackpoll Warblers (Setophaga striata) and Red-eyed Vireos (Vireo olivaceus),...

In forested landscapes, creation of habitat for early-successional shrubland birds is controversial because of perceived conflicts with the conservation of mature-forest birds. Nonetheless, many mature-forest birds, especially fledglings, readily use early-successional stands during the post-breeding period. This suggests that for mature-forest birds, creating habitat for early-successional birds could involve a tradeoff: reduced abundance and nest survival due to the loss of nesting habitat versus enhanced fledgling survival in early-successional stands. Our research addressed the effects...

A growing body of research shows affluent White neighborhoods have more acres of parks and more park facilities than low-income ethnic minority communities in many Global North cities. Most of these investigations focused on neighborhood-level differences and did not analyze broader inequities across cities. This is a particularly significant limitation in the U.S., where changes in the political economy of parks due to a reduced local tax base have led cities to compete against each other to secure park funding from national nonprofits and public agencies. To address this gap, we examined...

Wound closure is an important component of tree recovery from bole damage. Damage to young Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) stands in the precommercial and commercial stages is common, yet few studies have looked at how trees at these stages of stand development respond to common forms of damage. Using data from a 10-year study of artificially damaged Douglas-fir trees, we found reduced potential for relative wound closure with increasing initial tree bole diameter, and increasing initial relative bole area damaged. Wound-closure rates increased for longer periods of time...

Fire plays an important role in wildland ecosystems, critical to sustaining biodiversity, wildlife habitat and ecosystem health. By area, 70% of US prescribed burns take place in the Southeast, where treatment objectives range widely and accomplishing them depends on finding specific weather conditions for the effective and controlled application of fire. The climatological variation of the preferred weather window is examined here using two weather model reanalyses, with focus on conditions critical to smoke dispersion and erratic fire behaviour. Large spatial gradients were evident in...

The Blue Mountains Adaptation Partnership (BMAP) was established to increase climate change awareness, assess vulnerability to climate change, and develop science-based adaptation strategies for national forest lands in the Blue Mountains region of northeast Oregon and southeast Washington (USA). The BMAP process included (1) development of a science-management partnership, (2) a vulnerability assessment of the effects of climate change on natural resources and infrastructure, (3) development of adaptation options that will help reduce negative effects of climate change and assist the...

We computed four stand-level canopy stratum variables important for crown fire modelling – canopy cover, stand height, canopy base height and canopy bulk density – from forest inventory data. We modelled the relationship between the canopy variables and a set of common inventory parameters – site index, stem density, basal area, stand age or stand height – and number of prescribed burns. We used a logistic model to estimate canopy cover, a linear model to estimate the other canopy variables, and the information theoretic approach for model selection. Coefficients of determination across...