Treesearch

Southern California's South Coast Air Basin includes the heavily urbanized Los Angeles and Orange counties, the inland urban and suburban areas, and the surrounding mountain ranges. Historically high air pollution makes the region a natural laboratory for investigating human impacts on natural systems. Regional lichen distribution records from the early 1900s compared to more extensive montane data collected in the 1970s demonstrated declining species distribution ranges, attributed to increasingly heavy air pollution conditions. In 2008, we surveyed 21 sites in the mountains surrounding...

Urban green space is purported to offset greenhouse-gas (GHG) emissions, remove air and water pollutants, cool local climate, and improve public health. To use these services, municipalities have focused efforts on designing and implementing ecosystem-services-based "green infrastructure" in urban environments. In some cases the environmental benefits of this infrastructure have been well documented, but they are often unclear, unquantified, and/or outweighed by potential costs. Quantifying biogeochemical processes in urban green infrastructure can improve our understanding of urban...

Trees do not just die; there is always a primary cause, and often contributing factors. Trees need adequate quantities of water, heat, light, nutrients, carbon dioxide, oxygen, and other abiotic resources to sustain life, growth, and reproduction. When these factors are deficient or excessive, they cause mortality. According to the concept of baseline mortality (Chapters 1, 2, and 3), a certain number of trees must die as a forest ages to maintain a healthy condition. Abiotic factors kill trees in different ways, e.g., starvation, desiccation, uprooting, or stem breakage. The patterns of...

We review the ecological consequences of N deposition on the five Mediterranean regions of the world. Seasonality of precipitation and fires regulate the N cycle in these water-limited ecosystems, where dry N deposition dominates. Nitrogen accumulation in soils and on plant surfaces results in peaks of availability with the first winter rains. Decoupling between N flushes and plant demand promotes losses via leaching and gas emissions. Differences in P availability may control the response to N inputs and susceptibility to exotic plant invasion. Invasive grasses accumulate as fuel during...

The redhaired pine bark beetle Hylurgus ligniperda (F.) is native to Europe but was discovered in Los Angeles, California, in 2003. This root- and stump-feeding beetle is a common vector of Ophiostomatales, which are potential tree pathogens or causes of blue stain of conifer sapwood. In this study Ophiostomatales were isolated on a cycloheximideamended medium from 118 adult H. ligniperda collected from infested logs of Pinus halepensis and P. pinea at two sites in California. In total eight species of Ophiostomatales were identified and seven species that occasionally were isolated were...

An invasive population of the goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), is colonizing and killing three species of oaks in San Diego Co., California. However, the interactions of A. auroguttatus with oaks in its native range in southeastern Arizona have not been recorded. We present a complete inventory of the North and Central American collection records of A. auroguttatus and Agrilus coxalis Waterhouse from the literature and from a survey of the holdings of 27 museum and personal collections. We also discuss the relationship between this collection...

The banded elm bark beetle, Scolytus schevyrewi Semenov (Coleoptera: Scolytidae), native to Asia, was detected in the United States in 2003, and as of 2011 it is known to occur in 28 states and four Canadian provinces. S. schevyrewi infests the same elm (Ulmus spp.) hosts as the longestablished invasive, the European elm bark beetle, Scolytus multistriatus (Marsham). Information on the basic biology of S. schevyrewi in its native range is sparse; thus, we conducted laboratory studies and field studies in Colorado and Nevada. Comparisons of flight and behavioral responses were made with...

We investigated how multiple fuel treatment types, organized in varying spatial arrangements, and at increasing proportions of a mixed-conifer forest in the Klamath Mountains of northern California (~20,000 ha) variably affect carbon sequestration and emissions over a 50 year time period. Preliminary analysis of three fuel treatment scenarios (fire only, mechanical only, and fire + mechanical) and an untreated landscape indicates that treating large areas with prescribed fire may increase carbon emissions in the short term but may be off-set by an increase in long term carbon storage.

Airborne remote sensing at infrared wavelengths has the potential to quantify large-fire properties related to energy release or intensity, residence time, fuel-consumption rate, rate of spread, and soil heating. Remote sensing at a high temporal rate can track fire-line outbreaks and acceleration and spotting ahead of a fire front. Yet infrared imagers and imaging spectrometers typically used for earth remote sensing are saturated by—and incapable of measuring—the very bright infrared light that radiates from wildland fires. The Forest Service, Pacific Southwest Research Station, and its...