Treesearch

Historically, oak woodlands in western North America were maintained by frequent fire that killed competing conifers. Today, these woodlands are often in decline as competition from conifers intensifies. Among oak species affected is the ecologically important California black oak (Quercus kelloggii Newberry). Within its range, large high-severity wildfires have become more common. We examined responses of black oak to two mixed-severity wildfires 12 years apart (2000 Storrie Fire and 2012 Chips Fire reburn). Regeneration was examined in relation to fire severity as measured by the...

Climate change is anticipated to affect freshwater resources, but baseline data on the functioning of tropical watersheds is lacking, limiting efforts that seek to predict how watershed processes, water supply, and streamflow respond to anticipated changes in climate and vegetation change, and to management. To address this data gap, we applied the distributed hydrology soil vegetation model (DHSVM) across 88 watersheds spanning a highly constrained, 4500 mm mean annual rainfall (MAR) gradient on Hawai‘i Island to quantify stream flow at 3-h time-steps for eight years in response to the...

Trees in more competitive environments appear to respond to climate differently than trees in less competitive environments. In turn, climate patterns may affect inter- or intra-specific competition, favoring certain individuals over others. Using dendrochronological methods, we sampled cores from dominant pine trees and their nearby competitors in 40 stands in the northern Sierra Nevada. Our dendroclimatological analyses showed complex responses to climate for the dominant pine and their competitors. Pinus lambertiana Dougl. and Pinus ponderosa Dougl. Ex P. & C. Laws benefited from cooler...

The physical properties and dimensions of foliage are necessary inputs for some fire spread models. Currently, almost no data exist on these plant characteristics to fill this need. In this report, we measured the physical properties and dimensions of the foliage from 10 live shrub and conifer fuels throughout a 1-year period. We developed models to predict relative moisture content, apparent density, length, width, needle length, thickness, stem diameter, and surface area. Seasonal variability of the response variables was found to be adequately explained with a single model, so season-spe...

Although the American pika (Ochotona princeps) continues to receive attention due to documented declines and range retractions, particularly in the Great Basin, thorough range inventories have yet to be completed in many parts of the region. Here we report on recently discovered populations in northwestern Nevada in areas not suspected to support pika activity under current climate regimes. We describe 238 new locations (“sites”) with evidence of past or current occupancy by pikas that cluster into 31 locales, which we interpret as metapopulations or “demes”, in 15 distinct mountain ranges...

We review the mechanisms of deleterious nitrogen (N) deposition impacts on temperate forests, with a particular focus on trees and lichens. Elevated anthropogenic N deposition to forests has varied effects on individual organisms depending on characteristics both of the N inputs (form, timing, amount) and of the organisms (ecology, physiology) involved. Improved mechanistic knowledge of these effects can aid in developing robust predictions of how organisms respond to either increases or decreases in N deposition. Rising N levels affect forests in micro- and macroscopic ways from physiologi...

Large numbers of migratory bats are killed every year at wind energy facilities. However, population-level impacts are unknown as we lack basic demographic information about these species. We investigated whether fatalities at wind turbines could impact population viability of migratory bats, focusing on the hoary bat (Lasiurus cinereus), the species most frequently killed by turbines in North America. Using expert elicitation and population projection models, we show that mortality from wind turbines may drastically reduce population size and increase the risk of extinction. For example,...

Past and current forest management affects wildland fire smoke impacts on downwind human populations. However, mismatches between the scale of benefits and risks make it difficult to proactively manage wildland fires to promote both ecological and public health. Building on recent literature and advances in modeling smoke and health effects, we outline a framework to more directly quantify and compare smoke impacts based on emissions, dispersion, and the size and vulnerability of downwind populations across time and space. We apply the framework in a case study to demonstrate how different...

Animals often increase their fitness by moving across space in response to temporal variation in habitat quality and resource availability, and as a result of intra and inter-specific interactions. The long-term persistence of populations and even whole species depends on the collective patterns of individual movements, yet animal movements have been poorly studied at the landscape level. We quantified movement behavior within four native species of Hawaiian forest birds in a complex lava-fragmented landscape: Hawai‘i ‘amakihi (Chlorodrepanis virens), ‘oma‘o (Myadestes obscurus), ‘apapane...

Cronartium ribicola Fisch. has not been found infecting any of the five-needle white pines (Pinus subgenus Strobus) in Utah, despite being established on both white pine and Ribes hosts in the other 10 western states, defined as those west of the 102° meridian. Krebill (1964) reported C. ribicola infecting limber pine 53 km north of the Utah border in the Wasatch Mountains of southern Idaho. Apparently, this is the closest to the northern border of Utah the pathogen had spread to that date. Thirty-six years after Krebill’s report, Smith and Hoffman (2000) reported finding no evidence of C....