Treesearch

After a century of fire suppression, prescribed fire and mechanical thinning are widely used to restore mixed-conifer forests in California’s Sierra Nevada, yet after these treatments, trees sometimes fail to regenerate on many sites, for several possible reasons. Notably, competition between shrubs and tree seedlings for scarce water during prolonged summer dry seasons is suspected to influence seedling survival, yet this hypothesis has been tested in few manipulated field experiments. We investigated the effects of vegetation patch types, root competition, putative mycorrhizal connections...

Past riparian microclimate studies have measured changes horizontally from streams, but not vertically through the forest canopy. We recorded temperature and relative humidity for a year along a two-dimensional grid of 24 data-loggers arrayed up to 40 m height in four trees 2 - 30 m slope distance from a perennial second order stream in the Sierra Nevada. Our objective was to quantify diurnal and seasonal changes in vertical and horizontal microclimate gradients. Our data suggest a dynamic zone of riparian influence on microclimate that fluctuates diurnally and seasonally. Stream influence...

Due to high fire hazard and perceived reductions in forest health, thinning of small diameter trees has become a prevalent management activity particularly in dense stands. Creation of large amounts of logging slash, however, has created large quantities of habitat for bark beetles primarily in the Ips genus (Coleoptera: Curculionidae, Scolytinae). Evidence indicates that prior to Euro-American settlement fire played a major role in maintaining ponderosa pine stands in a condition that was much more open in structure than today (Cooper 1960, Covington and Moore 1994, Kolb et al. 1994). In...

In forests, high-severity burn patches—wherein most or all of the trees are killed by fire—often occur within a mosaic of low- and moderate-severity effects. Although there have been several studies of postfire salvage-logging effects on bird species, there have been few studies of effects on bird species associated with high-severity patches in forests that have otherwise burned at lower severities. From 2004 to 2006, we investigated the foraging presence or absence of three woodpecker species, the Black-backed (Picoides arcticus), Hairy (P. villosus), and White-headed (P. albolarvatus)...

Fire and thinning restoration treatments in fire-suppressed forests often damage or stress leave trees, altering pathogen and insect affects. We compared types of insect- and pathogen-mediated mortality on mixed-conifer trees 3years after treatment. The number of bark beetle attacked trees was greater in burn treatments compared with no-burn treatments, and in some cases, larger pine trees were preferentially attacked. Restoration treatments are not expected to change the trajectory of spread and intensification of dwarf mistletoe. Thinning treatments may have provided a sanitation effect...

Truffles are an important food resource for wildlife in North American forests, but decades of fire exclusion have altered the availability of this resource. In Yosemite National Park, resource management policies seek to restore essential forest processes such as fire while minimizing adverse ecological impacts that may result from burning decades of accumulated fuels. Burning can impact truffles through heat stress, elimination of soil organic layers, and damage to tree hosts, but these effects may be dependent on time lags between fires and fire frequency. We examined truffle abundance,...

Currently, oak woodlands of Northern California and their associated mycorrhizal fungi are receiving more attention. In order to address the impact mycorrhizal fungal associations have on survival of various tree species in oak woodlands, we investigated the extramatrical fungal hyphae associated with several mature oak woodland tree species. Specifically our objective was to quantify the fungal hyphal biomass in soils near blue oak (Quercus douglasii), interior live oak (Quercus wislizeni), foothill pine (Pinus sabiniana), and Ponderosa pine (Pinus ponderosa). We developed methods to...

Isozyme analysis of the rare Oenothera wolfii (Wolf's evening primrose) and the garden escape, O. glazioviana, indicates that hybridization between these species may be more widespread than morphological evidence indicates. Although both species contained low amounts of genetic variation, unique alleles were identified in both taxa. Analysis of 22 populations, including pure populations of each species, identified eight populations as containing putative hybrid individuals. Four of these putative hybrid populations were considered pure O. wolfii based on morphological analysis. This study...

Even as the magnitude of wildfire problems increases globally, United Nations agencies are acting to mitigate the risk of wildfire disasters to members. Fire management organizations worldwide may vary considerably in operational scope, depending on the number and type of resources an organization manages. In any case, good fire weather information is vital. This paper describes an approach for introducing fire weather/fire danger-rating technology into fire agrometeorology operations, based on the collective experience of the United States, Canada, and Australia. A prototype fire weather...

Between-year variation in snowpack (from 20 to 200% of average) and summer rainfall cause large fluctuations in volume of small lakes in the higher elevation (> 3000 m) Sierra Nevada, which are important habitat for the imperiled Sierra Nevada Yellow-legged Frog, Rana sierrae. Climate change (global warming) is predicted to increase these fluctuations, potentially leading to more frequent summer lake drying of shallow, fishless ponds where most R. sierrae breeding and larval development (requiring ≥ 3 years) occurs today. This study explored the interaction between water availability and...