Treesearch

The summer of 2018 saw intense smoke impacts on the eastern side of the Sierra Nevada in California, which have been anecdotally ascribed to the closest wildfire, the Lions Fire. We examined the role of the Lions Fire and four other, simultaneous large wildfires on smoke impacts across the Eastern Sierra. Our approach combined GOES-16 satellite data with fire activity, fuel loading, and fuel type, to allocate emissions diurnally per hour for each fire. To apportion smoke impacts at key monitoring sites, dispersion was modeled via the BlueSky framework, and daily averaged PM2.5 concentration...

Cross-validation using randomized subsets of data—known as k-fold cross-validation— is a powerful means of testing the success rate of models used for classification. However, few if any studies have explored how values of k (number of subsets) affect validation results in models tested with data of known statistical properties. Here, we explore conditions of sample size, model structure, and variable dependence affecting validation outcomes in discrete Bayesian networks (BNs). We created 6 variants of a BN model with known properties of variance and collinearity, along with data sets of n...

There are about 303 million hectares (ha) of forest lands in the U.S. (Oswalt and Smith 2014). National forests comprise 58 million ha (or roughly 145 million acres). Conducting silvicultural maintenance and restoration on these lands is important in correcting the current degraded state of overstocking or excess downed woody debris (Reinhardt et al. 2008). Overstocked trees and understory competition can induce physiological stress, and trees may become more susceptible to wildfire, insect pests, and disease (Weatherspoon and Skinner 2002). These conditions ultimately increase the...

Trees are known to provide various ecosystem services and disservices to urban communities, which can be quantified using models based on field and environmental data. It is often uncertain how tree structure and environmental variables impact model output. Here we perform a sensitivity analysis (SA) of i-Tree Eco, a common urban forest model, to analyze the relative impact of different model inputs on three module outputs: biogenic volatile organic compound (BVOC)(isoprene and monoterpenes) emissions, carbon storage and sequestration, and dry deposition of nitrogen dioxide, sulfur...

Mixed-stand management (MSM) involves growing of pine and hardwood trees in the same stand (Figure 1). You may be familiar with pine plantations, which have been successful across the southeastern United States due to logistical simplicity, silvicultural advancements, pine genetic improvements, and the past existence of a vibrant pulp industry region wide. While plantation management continues to be an attractive management strategy to many landowners, changing social, biological, and economic conditions may make MSM a viable alternative for landowners looking to accomplish a broader set...

This study was conducted to improve estimation of concomitant variables for implementation of a stand density management diagram (SDMD) for ponderosa pine (Pinus ponderosaLaws.) in northern California and Oregon. In traditional SDMD, isolines for variables such as stand volume are presented in such a way that uncertainty with estimation is not available. We developed the new top height and stand volume equations, as well as aboveground biomass and percent canopy cover, for building isolines in the SDMD using high-quality data collected from well-managed even-aged stands. The data were...

When alien species make incursions into novel environments, early detection through surveillance is critical to minimizing their impacts and preserving the possibility of timely eradication. However, incipient populations can be difficult to detect, and usually, there are limited resources for surveillance or other response activities. Modern optimization techniques enable surveillance planning that accounts for the biology and expected behavior of an invasive species while exploring multiple scenarios to identify the most cost-effective options. Nevertheless, most optimization models omit...

The Sudden Oak Death (SOD) Blitzes consist of yearly surveys led by citizen scientists designed to map the distribution of Phytophthora ramorum, cause of the forest disease called SOD, across northern California. During the 2017 Santa Cruz County SOD Blitz, six rare or endangered Arctostaphylos(manzanita) species were found to be possibly symptomatic for the first time. Symptoms included branch cankers and associated canopy mortality, and affected multiple individuals per species. Isolates of P. ramorumwere obtained from each of the six species and, through a 30-day-long inoculation...

The objective of this study was to understand how genetic variation in a riparian species, Populus angustifolia, affects mass and energy exchange between the land and atmosphere across ~1,700 km of latitude of the western United States. To examine the potential for large‐scale land–atmosphere feedbacks in hydrologic processes driven by geographic differences in plant population traits, we use a physical hydrology model, paired field, and greenhouse observations of plant traits, and stable isotope compositions of soil, stem, and leaf water of P. angustifoliapopulations. Populations show...

Sustaining the structure, function, and services provided by forest ecosystems in the face of changing climate and disturbance regimes represents a grand challenge for forest managers and policy makers. To address this challenge, a range of adaptation approaches have been proposed centered on conferring ecosystem resilience and adaptive capacity; however, considerable uncertainty exists regarding how to translate these broad and often theoretical adaptation frameworks to on-the-ground practice. Complicating this issue has been movement away, in some cases, from other recent advances in...