Treesearch

Sport hunting of ungulates is a predominant recreational pursuit and the primary tool for managing their populations in North America and beyond, given its influence on ungulate distributions, social organization, and population performance. Similarly, land management, such as motorized vehicle access, influences ungulate distributions during and outside hunting seasons. Although research on ungulate responses to hunting and land use is widespread, knowledge gaps persist about space use of hunters and what landscape features discriminate among hunt types and between successful and unsuccess...

Changes in the distribution and abundance of invasive species can have far-reaching ecological consequences. Programs to control invaders are common but gauging the effectiveness of such programs using carefully controlled, large-scale field experiments is rare, especially at higher trophic levels. Experimental manipulations coupled with long-term demographic monitoring can reveal the mechanistic underpinnings of interspecific competition among apex predators and suggest mitigation options for invasive species. We used a large-scale before–after control–impact removal experiment to...

Homelessness is often associated with urban areas, yet since the Great Depression, national forests have served as a refuge for individuals and families. In recent years, more people are living on the national forests and grasslands, whether by choice or because of economic circumstances. Unfortunately, the presence of nonrecreational campers affects the experience of other users and results in increased levels of trash and resource degradation that can be costly to remediate.In 2015, Lee Cerveny, a research social scientist with the USDA Forest Service, Pacific Northwest Research Station,...

Propensity score matching (PSM) and distance-adjusted PSM enable estimation of causal effects from observational data by selecting controls that are similar to treated observations in terms of environmental covariates and spatial locations. Quantifying effects of natural disturbances such as wildfires often encounters limited availability of observational data due to the scarcity of ecological events or cost of data collection over large areas. Using empirical data of national forest inventory plot measurements, we conducted a sensitivity analysis of distance-adjusted PSM on data availabili...

As the frequency and size of wildfires increase, accurate assessment of burn severity is essential for understanding fire effects and evaluating post-fire vegetation impacts. Remotely-sensed imagery allows for rapid assessment of burn severity, but it also needs to be field validated. Permanent forest inventory plots can provide burn severity information for the field validation of remotely-sensed burn severity metrics, although there is often a mismatch between the size and shape of the inventory plot and the resolution of the rasterized images. For this study, we used two distinct...

Empirical evidence of the vulnerability of dryland ecosystems to suffer abrupt changes in response to global change is highly needed to assess the applicability of threshold models, understand the underlying mechanisms and anticipate the onset of abrupt shifts.We study the onset of abrupt changes in Mediterranean holm oak (Quercus ilex) woodlands, by analyzing the combined effect of past human disturbance (mainly deforestation) and aridity on the functional state of these ecosystems. We determine ecosystem state in terms of herbaceous/woody species ratio, species richness and soil propertie...

We show that aerial tips are self-similar fractals of whole shrubs and present a field method that applies this fact to improves accuracy and precision of biomass estimates of tall-shrubs, defined here as those with diameter at root collar (DRC) ≥ 2.5 cm. Power function allometry of biomass to stem diameter generates a disproportionate prediction error that increases rapidly with diameter. Thus, biomass should be modeled as a single measure of stem diameter only if stem diameter is less than a threshold Dmax. When stem diameter exceeds Dmax, then the stem internode should be treated as a...

Temporal series of lidar, properly field-validated, can provide critical information allowing in-ferences about the dynamics of biomass and carbon in forest canopies. Forest canopies gain carbon through net primary production (NPP) and lose carbon through canopy component damage and death, such as fine and coarse woody debris and litterfall (collectively, debris-fall). We describe a statistical method to extract gamma distributions of NPP and debris-fall rates in forest canopies from lidar missions repeated through time and we show that the means of these distributions covary with ecologica...

A major challenge in predicting species’ distributional responses to climate change involves resolving interactions between abiotic and biotic factors in structuring ecological communities. This challenge reflects the classical conceptualization of species’ regional distributions as simultaneously constrained by climatic conditions, while by necessity emerging from local biotic interactions. A ubiquitous pattern in nature illustrates this dichotomy: potentially competing species covary positively at large scales but negatively at local scales. Recent theory poses a resolution to this...

We review science-based adaptation strategies for western North American (wNA) forests that include restoring active fire regimes and fostering resilient structure and composition of forested landscapes. As part of the review, we address common questions associated with climate adaptation and realignment treatments that run counter to a broad consensus in the literature. These include the following: (1) Are the effects of fire exclusion overstated? If so, are treatments unwarranted and even counterproductive? (2) Is forest thinning alone sufficient to mitigate wildfire hazard? (3) Can...