Treesearch

Air pollution, principally in the form of photochemical ozone and deposition of nitrogen compounds, has significantly affected mixed conifer forests in the mountains of southern California. Foliar injury, premature needle abscission, crown thinning, and reduced growth and vigor have been well documented, particularly for ponderosa (Pinus ponderosa Laws.) and Jeffrey (P. jeffreyi Grev. and Balf.) pines on the western side of the pollution deposition gradient in the San Bernardino Mountains. Tree mortality of the more ozone-susceptible ponderosa and Jeffrey pines has led to alterations in...

The coastal sage scrub (CSS) vegetation of southern California is rapidly converting to annual grasslands, perhaps in part because of air pollution. By contrast, chaparral and coniferous forest are subject to equally high levels of air pollution but are relatively stable. A comparative analysis of ozone and nitrogen deposition on plants of CSS, exotic annual grassland, chaparral, and coniferous forest shows these vegetation types have different susceptibilities to each pollutant. Historically high concentrations of ozone in the local mountains weakened pines, contributing to tree mortality....

In southern California, most estuarine wetlands are gone, and what little habitat remains is degraded. For this reason, it is often of interest to assess the condition of estuaries over time, such as when determining the success of a restoration project. To identify impacts or opportunities for restoration, we also may want to know how a particular estuary, or area within an estuary, compares with neighboring areas. Comparisons among wetlands require knowledge of different estuary types. The seven types of estuaries described in this paper can be easily grouped into two functional types,...

This paper describes the establishment of an interdisciplinary, large-scale ecological research project on the Goosenest Adaptive Management Area of the Klamath National Forest in northeastern California. This project is a companion to the Blacks Mountain Ecological Research Project described by Oliver (2000). The genesis for this project was the Northwest Forest Plan (USDA and USDI 1994a). As a part of the Northwest Forest Plan, a network of Adaptive Management Areas was created in Oregon, Washington, and northern California. One of the primary goals of the Goosenest Adaptive Management...

Over 60,000 acres of ponderosa pine (Pinus ponderosa P. and C. Lawson) forest on the Warm Springs Indian Reservation (WSIR) in Oregon are managed using an uneven-age system. Three on-going studies on WSIR address current issues in the management of pine forests: determining levels of growing stock for uneven-age management, fire effects on wood suitability for engineered wood products, and mechanical forest fuel reduction alternatives. To evaluate various levels of growing stock, WSIR installed twelve 1.01-hectare plots in four areas of the ponderosa pine forest to test three basal area...

Many lessons have been learned during reforestation of large wildfires and clearcuts in interior Northern California, a region of low rainfall and summer drought typical of a Mediterranean climate. Challenges appeared from time of establishment right up to commercial thinning. Establishment issues included procurement of improved seed, site preparation, soil mitigation, seedling performance, season of planting, and timing of vegetation management. Important decisions also had to be made with regard to mechanical vs. hand pre-commercial thinning (PCT), achieving a proper balance between...

Ponderosa pine ecosystems provide important foraging habitats for both wild and domestic ungulates. Livestock typically graze ponderosa pine ecosystems from May through October. Mule deer and elk may utilize these habitats on a yearlong basis in some areas. Stand density has a significant effect on understory production. Competition for soil moisture and nitrogen limit understory production. Since these systems typically exist at lower elevations, south aspects and on rather shallow soils, soil moisture is usually unavailable to understory species by mid summer. Optimal forage quality,...

Standing dead trees (snags) with cavities are a critical ecological component of western coniferous forests. These structures provide foraging, roosting, and nesting habitat for numerous species of invertebrates, amphibians, reptiles, birds, and mammals. Snags may be created through a variety of interrelated processes including wildfire, drought, insects and disease. However, dead trees containing excavated cavities are primarily the result of nest excavation by woodpeckers. While the specific factors leading to cavity generation in certain snags is not well understood, the manner in which...

The ponderosa pine ecosystems of the West have change dramatically since Euro-American settlement 140 years ago due to past land uses and the curtailment of natural fire. Today, ponderosa pine forests contain over abundance of fuel, and stand densities have increased from a range of 49-124 trees ha-1 (20-50 trees acre-1) to a range of 1235-2470 trees ha-1 (500 to 1000 stems acre-1q). As a result, long-term tree, stand, and landscape health has been compromised and stand and landscape conditions now promote large, uncharacteristic wildfires. Reversing this trend is paramount. Improving the...

Several diseases affect the growth and survival of ponderosa pine in the Pacific Northwest and serve as agents of disturbance. Probably the most widespread and damaging class of disease agents is dwarf mistletoe, which causes serious growth loss and mortality of ponderosa pine. Dwarf mistletoes (Arceuthobium spp.) are seed plants that can parasitize all age classes of pine. Decades of research and observation have shown that although dwarf mistletoes spread slowly within and among trees, their localized effects can be quite spectacular. Root diseases caused by the fungi Armillaria ostoyae...