Treesearch

The goldspotted oak borer (GSOB), Agrilus auroguttatus (Coleoptera: Buprestidae), is a flatheaded borer introduced to San Diego County, California, in the late 1990s or early 2000s and also detected at one site in Riverside County in 2012. It was likely brought into the state on oak firewood collected and transported from the insect's native range in southeastern Arizona or northern Mexico. Although currently confined to San Diego and Riverside counties, this pest will likely invade other areas of California.

Thousand cankers disease (TCD) of walnut is a result of feeding in the phloem by the walnut twig beetle (WTB), Pityophthorus juglandis, and subsequent canker formation caused by Geosmithia morbida around galleries. TCD has caused extensive morbidity and mortality to Juglans nigra in the western United States and, in 2010, was discovered in the eastern United States, where the tree is a highly valuable timber resource. WTB and G. morbida also have been found in J. regia orchards throughout major production areas in California, and the numbers of damaged trees are increasing. We tested the...

Instar determination of field-collected insect larvae has generally been based on the analysis of head capsule width frequency distributions or bivariate plotting, but few studies have tested the validity of such methods. We used head capsules from exuviae of known instars of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), to determine the larval instars with the frequency distribution method and Dyar's rule. Head capsule widths of S. exigua ranged from 0.313 to 1.446 mm. The number of instars from the analytical method matched that from the observed data. Based on...

In 1926, the California Forest Experiment Station, which later became the Pacific Southwest (PSW) Research Station, was established at the University of California, Berkeley. Today, the PSW Research Station represents the research and development branch of the USDA Forest Service in California and Hawaii and the U.S.-affiliated Pacific Islands. The PSW Research Station develops and delivers science-based information, technologies, and applications to help people make informed decisions about natural resource management, conservation, and environmental protection. This comprensive history...

We periodically measured overstory ponderosa pine (Pinus ponderosa) growth and understory cover and abundance in a long-term study on the west slope of the Sierra Nevada, California, USA. The study was established in 1969 in a 20-year-old plantation, thinned to basal areas of 9, 16, 23, 30, and 37 m2 ha-1 and re-thinned three times. The objective was to determine the effect of stand density regimes on productivity, understory vegetation, aboveground carbon storage, and mortality mainly caused by Dendroctonus infestations. Results showed that without mortality, basal area or volume increment...

We analyzed 45-yr data collected from three ponderosa pine (Pinus ponderosa Lawson & C. Lawson) levels-of-growing-stock installations in Oregon (OR) and northern California (CA), USA, to determine the effect of stand density regimes on stand productivity and mortality. We found that periodic annual increment (PAI) of diameter, basal area (BA), volume, and aboveground dry weight were significantly related to Stand Density Index (SDI) and stand age at start of period; the quadratic trends varied among sites. Precipitation departure from the normal for each period explained a significant...

Forests mitigate climate change by sequestering CO2 from the atmosphere and accumulating it in biomass storage pools. However, in dry conifer forests, fire occasionally returns large quantities of CO2 to the atmosphere. Both the total amount of carbon stored and its susceptibility to loss may be altered by post-fire land management strategies. Forest managers face a great challenge when asked to manage these lands for C sequestration and simultaneously reduce fire hazard. The objective of our study was to understand how differing post-fire management strategies affect C sequestration and...

In California, River Otters (Lontra canadensis) are most commonly associated with food-rich lowland aquatic habitats where they forage primarily on fish and crustaceans. Their distribution in high-elevation montane regions of the state, areas in which fish and crayfish were absent historically, is largely unknown.We compiled occurrence records of River Otters in California from elevations.1100 m, and evaluated them using evidentiary standards. Based on 126 records, we report the widespread presence of River Otters in the Klamath, southern Cascades, and Sierra Nevada mountain ranges,...

Forest managers need accurate biomass equations to plan thinning for fuel reduction or energy production. Estimates of carbon sequestration also rely upon such equations. The current allometric equations for ponderosa pine (Pinus ponderosa) commonly employed for California forests were developed elsewhere, and are often applied without consideration potential for spatial or temporal variability. Individual-tree aboveground biomass allometric equations are presented from an analysis of 79 felled trees from four separate management units at Blacks Mountain Experimental Forest: one unthinned...

Forest fires affect millions of people worldwide, and cause major ecosystem and economic impacts at different scales. The management policies implemented to minimize the negative impacts of forest fires require substantial investment of financial, human and organizational resources, which must be justifiable and efficient. Decision support systems based on economic models can help to optimize the allocation of limited resources. This paper exposes the development of the economic theory for the efficiency analysis of fire management measures. Then, it provides a review of four fire managemen...