Treesearch

The foothill yellow-legged frog (Rana boylii) is a stream-breeding amphibian that has experienced significant population declines over a large portion of its historical range. This frog is nearing extirpation in much of the Sierra Nevada region where existing populations are sparse. Water development and diversions are likely to be the primary cause of population declines and are currently a prominent risk factor because they result in hydrological changes that chronically affect several aspects of the species’ life history. Other primary risk factors include climate change, mining and...

Wood properties and microbial community characteristics were compared between loblolly pine (Pinus taeda L.) logs protected or unprotected from termites (Blattodea: Rhinotermitidae: Reticulitermes spp.) and other arthropods for two years in seasonally flooded and unflooded forests in the southeastern United States. Significant compositional differences were observed between treatments and between flood patterns for both bacterial and fungal communities. Bacteria were 8e9-fold more abundant in unprotected logs compared to protected logs in both flooded and unflooded forests, with the...

We present a new methodology for fitting nonparametric shape-restricted regression splines to time series of Landsat imagery for the purpose of modeling, mapping, and monitoring annual forest disturbance dynamics over nearly three decades. For each pixel and spectral band or index of choice in temporal Landsat data, our method delivers a smoothed rendition of the trajectory constrained to behave in an ecologically sensible manner, reflecting one of seven possible ‘shapes’. It also provides parameters summarizing the patterns of each change including year of onset, duration, magnitude, and...

Wildfire is a global phenomenon that plays a vital role in regulating and maintaining many natural and human-influenced ecosystems but that also poses considerable risks to human populations and infrastructure. Fire managers are charged with balancing the short-term protection of human assets sensitive to fire exposure against the potential long-term benefits that wildfires can provide to natural systems and wildlife populations. The compressed decision timeframes imposed on fire managers during an incident are often insufficient to fully assess a range of fire management options and their...

Humans affect fire regimes by providing ignition sources in some cases, suppressing wildfires in others, and altering natural vegetation in ways that may either promote or limit fire. InNorthAmerica, several studies have evaluated the effects of society on fire activity; however, most studies have been regional or subcontinental in scope and used different data and methods, thereby making continent-wide comparisons difficult.We circumvent these challenges by investigating the broad-scale impact of humans on fire activity using parallel statistical models of fire probability from1984 to...

Forested catchments throughout the world are known for producing high quality water for human use. In the 20th Century, experimental forest catchment studies played a key role in studying the processes contributing to high water quality. The hydrologic processes investigated on these paired catchments have provided the science base for examining water quality responses to natural disturbances such as wildfire, insect outbreaks, and extreme hydrologic events, and human-induced disturbances such as timber harvesting, site preparation, prescribed fires, fertilizer applications, pesticide...

In forests, total belowground carbon (C) flux (TBCF) is a large component of the C budget and represents a critical pathway for delivery of plant C to soil. Reducing uncertainty around regional estimates of forest C cycling may be aided by incorporating knowledge of controls over soil respiration and TBCF. Photosynthesis, and presumably TBCF, declines with advancing tree size and age, and photosynthesis increases yet C partitioning to TBCF decreases in response to high soil fertility. We hypothesized that these causal relationships would result in predictable patterns of TBCF, and partition...

The southern pine beetle Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is attracted to an aggregation pheromone that includes the multifunctional pheromone component endobrevicomin. The effect of endo-brevicomin on attractive lures varies from strong enhancement to reduction of beetle attraction depending upon release rate, lure component spacing, and proximity of beetle infestations. Anecdotal observations have further suggested that the effects of endo-brevicomin vary during the year. We investigated this possibility under nonoutbreak conditions in southwestern...

The southern pine beetle, Dendroctonus frontalis Zimmermann is generally considered to be one of the most significant biotic mortality agents of pines within North America, with a range stretching from New England to eastern Texas and from Arizona south to Nicaragua. As with other aggressive pine beetles, it relies on semiochemicals for coordinating the mass attacks necessary for colonization of healthy pines. Over the past 50 years its chemical ecology has received extensive study aimed at development of effective and practical semiochemical-based management strategies which might replace...

Rates of terrestrial wood decomposition are known to vary widely depending on regional and local climatic conditions, substrate characteristics and the organisms involved but the influence of many factors remain poorly quantified. We sought to determine how bark and insects contribute to decomposition in a southeastern U.S. forest. Open-topped stainless steel pans with screened bottoms were used to prevent subterranean termite (Rhinotermitidae: Reticulitermes spp.) colonization from “protected” logs. After a 20-month study period, we compared mass loss and lignin content between these and...