Treesearch

California has 18+ million acres of land owned by the USDA Forest Service. This is almost 20 percent of the area of the state. From 1994-2000 the Region 5 Remote Sensing Lab collected forest, vegetation and fuels inventory data from thousands of permanent monitoring plots established on diverse sites on Forest Service lands throughout the region. The plots are stratified among 165 vegetation types, or strata. Collectively, these data are known as the Regional Forest Inventory and Analysis (FIA) database. An analysis of the plot data for California’s oak, including species, distribution and...

The objective of this project was to develop a technique for rapidly determining the extent of wildfire damage to blue oaks (Quercus douglasii) that would be usable by landowners without requiring extensive training. In late winter 2000, 100 oaks of various sizes and degrees of damage were selected from 10 plots located where wildfires had burned in the previous year. Measures of individual tree parameters, stand structure and scorch characteristics were taken and tested for their adequacy in predicting mortality. These same oaks were re-evaluated in August 2000. Sixteen percent of the...

California valley oak is threatened by landscape alteration and failing recruitment in remnant stands. Its reproductive ecology is a key element of the seedling recruitment process. We first examine the mating system, to determine the extent of inbreeding in a population at Sedgwick Reserve, in Santa Barbara County. We then quantify variation in germination success and acorn size, evaluating their spatial patterns across the site. We collected acorns from 21 mapped focal trees in fall 1999, measured their average seed weight and germination success, and identified their multilocus genotypes...

We studied the survival and regrowth of naturally-occurring blue oak saplings burned in a September 1996 arson fire in Vacaville, California. The saplings (pre-fire height 33-353 cm) were burned in a rapid, low-moderate intensity fire. Of 67 blue oak saplings surveyed, 4 failed to resprout after the fire and 2 more died within the following 5 years (9 percent mortality overall); all mortality was among saplings less than 100 cm tall. Saplings which were completely topkilled (51/67) were significantly smaller on average than those which were only partially topkilled (12/67). Saplings taller...

This study characterized the distribution of geographic variation in water relations traits for six populations of California blue oak along a precipitation gradient (two each from high, medium and low precipitation environments). Acorns were collected from each population, germinated and the resulting seedlings were experimentally treated with three different watering regimes in a greenhouse experiment. There were significant among-population differences in growth and biomass production characteristics in the seedlings. Significant among-treatment differences indicated at least low levels...

We examined population trends and factors related to the abundance and presence of European starlings (Sturnus vulgaris) at the San Joaquin Experimental Range in the foothills of the western Sierra Nevada, 31 km east of Madera, California. Starlings first appeared there in low numbers in the late 1960s and are now abundant breeders. Simple models examining trends in starling numbers and presence/absence using point-counting data from 210 counting stations from 1985 through 2000 showed significantly increasing yearly trends in starling abundance and distribution. The yearly trend in...

In a number of deciduous tree crops a reliable pressure chamber measurement of water stress (midday stem water potential or SWP) has been recently developed and found to be closely related to both irrigation regime and tree physiological responses to stress. A standard pressure chamber is used for the measurement of SWP, but prior to sampling, the leaf is enclosed in a reflective plastic bag and allowed to equilibrate with the water potential in the stem at the point of leaf attachment. In this study, measurements were made on valley oak trees under a variety of landscape conditions in...

This study examines the effect of rural residential development and landscape composition on breeding birds in Placer County’s foothill oak woodlands. Point count survey data were used to construct generalized linear models for individual species' abundance or probability of occurrence, based on two sets of variables: GIS-derived landscape characteristics, including development density, oak woodland proportion, and habitat diversity; and field-collected local habitat parameters. We found that many species examined were sensitive to either development density or landscape composition at...

The intensity of the 1993 Old Topanga Fire raised many concerns about the recovery and response of the coast live oak trees (Quercus agrifolia) and their understory vegetation. Preliminary information on the status of the trees 6 months post-fire has been previously reported. This report provides follow up assessment of the condition of the 90 trees in the original study and assesses the recovery of their understory vegetation over the 8 years since the burn. This long-term study documenting the recovery of coast live oak communities in three different locations (open riparian, ridgeline...

We determined the impact of insects on both acorns and seedlings of coast live oak (Quercus agrifolia Nee) and Engelmann oak (Quercus engelmannii E. Greene). Our goals were to (1) identify insects feeding on acorns and levels of insect damage, and (2) measure performance and preference of a generalist leaf-feeding insect herbivore, the migratory grasshopper (Melanoplus sanguinipes [Fabricus] Orthoptera: Acrididae), on both species of oak seedlings. Acorn collections and insect emergence traps under mature Q. agrifolia and Q. engelmannii revealed that 62 percent of all ground-collected...