Treesearch

Chaparral is the dominant vegetation type on dry steep slopes of the national forests in southern California. Chaparral ecosystems are dominated by evergreen fire-adapted shrubs with the ability to recover after fire through fire-stimulated seed germination from a large dormant seed bank or resprouting from unburned root crowns. Despite the resilience of chaparral ecosystems to periodic fire, their integrity is challenged by high frequencies of human-ignited fires, which can occur before resprouting species renew their carbohydrate reserves or regenerating individuals (from seed) reach...

Widespread yet vulnerable, sagebrush (Artemisia spp.) steppe ecosystems provide a variety of biological, hydrological, and recreational ecosystem services throughout the Interior West (Homer et al. 2015). One particular service is the provision of essential habitat for the greater sage-grouse (Centrocercus urophasianus), which was considered for listing under the Endangered Species Act. That listing was avoided in 2015 by an unprecedented conservation partnership across organizations and state boundaries (Chambers et al. 2017). The once widespread sagebrush steppe ecosystem has been...

This report originated from a workshop on long-term postfire ecological restoration held in late 2015 at Yosemite National Park, and a second workshop held at the Natural Areas Conference at the University of California-Davis in late 2016. Workshop attendees included ecologists from the U.S. Forest Service Pacific Southwest Region Ecology Program; scientists from the U.S. Forest Service Pacific Southwest Research Station; and national forest specialists from a variety of fields, including silviculture, soils, and hydrology. In this concluding section, the editors highlight some of the key...

Over the past century, a variety of environmental stressors, combined with effects from past and current management activities (e.g., fire exclusion, past timber harvest practices, livestock grazing, water diversion), have substantially altered the status of most California ecosystems. These changes include major shifts in ecological disturbance regimes, such as flooding, insect and disease outbreaks, and fire (Barbour et al. 2007, Mooney and Zavaleta 2016). For terrestrial ecosystems, the most profound ecological disturbances are those that substantially increase plant mortality, and in...

Land managers grapple with a variety of questions concerning the management of burned landscapes. All fires more than 500 ac (200 ha), and smaller fires if critical values are involved, trigger a Burned Area Emergency Response (BAER) program assessment that addresses emergency stabilization in the first year, with possible maintenance treatments for up to 3 years. After assessments for BAER and postfire reforestation have been completed, years of rehabilitation and restoration may be conducted, including planting trees, reestablishing native species, restoring habitats, and treating...

A significant increase in treatment pace and scale is needed to restore dry western US forest resilience owing to increasingly frequent and severe wildfire and drought. We propose a pyrosilviculture approach to directly increase large-scale fire use and modify current thinning treatments to optimize future fire incorporation. Recommendations include leveraging wildfire’s “treatment” in areas burned at low and moderate severity with subsequent pyrosilviculture management, identifying managed wildfire zones, and facilitating and financing prescribed fire with “anchor,” “ecosystem asset,” and...

Fire severity patterns are driven by interactions between fire, vegetation, and terrain, and they generate legacy effects that influence future fire severity. A century of fire exclusion and fuel buildup has eroded legacy effects, and contemporary fire severity patterns may diverge from historical patterns. In recent decades, area burned and area burned at high severity have increased and landscapes are transitioning back to an active fire regime where disturbance legacies will again play a strong role in determining fire severity. Understanding the drivers of fire severity is crucial for...

Many old-growth pine forests across the western United States have encountered widespread and concerning increases in tree mortality attributed to increased competition and reduced vigor associated with prolonged fire exclusion that can make trees more vulnerable to bark beetles. We investigated the importance of growth and resin duct defense on recent mortality of large sugar pine (Pinus lambertiana) in a fire-excluded, mixed-conifer forest of the Sierra Nevada, in California, USA. Growth and defense were measured from tree rings for 33 pairs of live and dead sugar pine. The 10-year trend...

Forest disturbances are events that disrupt the structure and composition of forest ecosystems as well as their protective, productive, and social functions (Führer 2000, Holmes et al. 2008). The increasing severity and frequency of environmental and anthropogenic forest disturbances challenge the sustainable management and protection of forests in the United States and the benefits that they provide to individuals and communities. About 1.42 percent (3.6 million ha) of U.S. forest land was disturbed annually between 1985 and 2015 (Masek et al. 2013). Tree mortality stemming from disturbanc...

Forests not only provide forest products to meet people’s demands, but also sequester enough carbon to offset more than 11% of anthropogenic CO2release in the United States. An accurate estimate of forest carbon sequestration over different forest and forest product combinations requires the species-specific and site-specific allometric biomass equations for trees and understory vegetation at particular forest developmental stages. Here, we constructed the above- and below-ground allometric equations by harvesting 108 20-year-old ponderosa pine (Pinus ponderosa) trees grown under four...