Understanding the role of fire in forested landscapes is fundamental to fire reintroduction efforts, yet few studies have examined how fire dynamics vary in response to interactions between local conditions, such as soil productivity, and more broadscale changes in climate. In this study, we examined historical fire frequency, seasonality, and spatial patterning in mixed conifer forests across a distinct gradient of soil productivity in the northern Sierra Nevada. We cross-dated 46 different wood samples containing 377 fire scars from 6 paired sites, located on and off of ultramafic serpentine soils. Forests on serpentine-derived soils have slower growth rates, lower biomass accumulation, and patchier vegetation than adjacent, non-serpentine sites. Due to these differences, we hypothesized that historical fire frequency and spatial extent would be reduced in mixed conifer forests growing on serpentine soils. Fire scars revealed a history of frequent fire at all of our sites (median composite interval: 6–22.5 years) despite clear differences in soil productivity. Fire frequency was slightly shorter in more productive non-serpentine sites, but this difference was not consistently significant within our sample pairs. While fires were frequent, both on and off of serpentine, they were also highly asynchronous, and this was largely driven by differing climate–fire relationships. Fires in more productive sites were strongly associated with drought conditions in the year of the fire, while fires in less productive serpentine sites appeared to be more dependent on a cycle of wet and dry conditions in the years preceding the fire. Widespread fires that crossed the boundary between serpentine and non-serpentine were associated with drier than normal years. In our study, fine-scale variation in historical fire regime attributes was linked to both bottom-up and top-down controls. Understanding how these factors interact to create variation in fire frequency, timing, and spatial extent can help managers more effectively define desired conditions, develop management objectives, and identify management strategies for fire reintroduction and forest restoration projects.

Outside of the immediate coastal environments, little is known of fire history in the North Coast Range of California. Fire scar specimens were collected from ponderosa pine (Pinus ponderosa C. Lawson), sugar pine (Pinus lambertiana Douglas), incense cedar (Calocedrus decurrens [Torr] Florin), and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) for seven plots in mixed-conifer forests from the Mendocino National Forest, California, USA. Five plots were on high ridges immediately adjacent to the Sacramento Valley (DRY plots). The other two plots were on mesic north facing slopes interior in the range (MESIC plots), and were separated from the Sacramento Valley by at least one to several ridge systems. These two plots were selected because they supported populations of rare lady's slipper orchids (Cypripedium fasciculatum [Kellogg ex S. Watson] and C. montanum [Douglas ex Lindl.]). We found that DRY plots had unusually short fire return intervals (FRI) compared to other areas in northwestern California. The median FRI for these plots ranged from 4.5 yr to 6 yr in comparison with a tenth percentile of 11 yr, grand median of 24 yr, and ninetieth percentile of 66 yr for FRIs from other mixed conifer plots (n = 109) in the region. In northwestern California, most fire scars have been found primarily at ring boundary (68%) and secondarily in latewood (23%) with few in earlywood (9%). In contrast, in the DRY plots 35% (88) of the fire scars were in earlywood with only 15% (39) at the ring boundary. Fire occurrence was associated with drought conditions in the year of fire, and with wet conditions three years before the fire year. Before ∼1850, fires that scarred at least two trees on a site were quite frequent for the DRY plots while being less frequent and more variable on the MESIC plots. However, the MESIC orchid habitats burned with frequency and seasonality similar to mixed conifer forests in the Klamath Mountains of northern California. Fires were less frequent after ∼1850, with fires ceasing on most plots shortly after 1900. We suggest that these unusually low FRIs and high incidence of fire scars in earlywood were due to the adjacency of the DRY plots to the hot, relatively dry Sacramento Valley grasslands that were likely influenced by the burning practices of Native Americans.

Philip M McDonald, Celeste S Abbott and Gary O Fiddler

Logging disturbance on 5 study areas (forest plantations) in northern California favored development of bracken fern (Pteridium aquilinum [L.] Kuhn var. pubescens L. Underw.), which can be an impediment to successful reforestation. Velpar herbicide (hexazinone) offered short-term control of vegetation, including bracken fern, sufficient to establish ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa) seedlings and ensure vigorous growth. Our examination of site preparation techniques, including burning residual logging debris followed by chemical and mechanical control of vegetation, indicated that bracken fern density, foliar cover, and height were highly variable both within and among study areas. After 5 growing seasons, bracken density in the control (site preparation only) ranged from 5800 to 40850 fronds/ha (2345 to 16 530 fronds/ac), foliar cover from 1% to 24%, and height from 0.5 to 0.6 m (1.8 to 1.9 ft). Among conifer release treatments (control of unwanted vegetation), Velpar effectively controlled bracken, but Garlon herbicide aided bracken by killing competing shrubs. After 10 growing seasons, more than 22000 bracken fronds/ha (8910/ac) were present in all treatments. Bracken fern demonstrated remarkable ecological amplitude, was virtually independent of other species, and was only moderately influenced by a wide range of environments. Growers and planters should be aware of these findings and use herbicides that show demonstrated effectiveness.

Abstract Vegetation management can direct trends in early plant development and species succession and through various treatments achieve specific combinations of species desired by the ecosystem manager. Density and development of several plant species were studied in an area in northern California that was planted with 1-yr-oldponderosa pine (Pinus ponderosa var. ponderosa) seedlings in 1986 and treated with three herbicides (Velpar L, Garlon 4, Escort) in fall 1986 and spring 1987. Abundant species in the new plantation were bush chinquapin (Chrysolepis sempervirens) that regenerated from root crowns, greenleaf manzanita (Arctostaphylos patula)from seed, and bracken fern (Pteridium aquilinum var. pubescens )from rhizomes. After 11 growing seasons, chinquapin sprouts in the control averaged more than 15,900/ac, manzanita seedlings over 16,400/ac, and bracken fronds 11,400/ac. Mean ponderosa pine diameter (5.1 in.), height (12.9 ft), and crown diameter (7.6 ft) were significantly greater in the Velpar treatment than in the control. Additional information is presented on plant diversity, the onset of statistically significant differences among treatments for pine, and the makeup of the plant community in the near future. West. J. Appl. For. 14(4):194-199.

On a poor site in northern California, a brushfield community was treated in various ways which left initial densities of no shrubs, light, medium, and heavy shrubs. Density and development (height, foliar cover, crown volume) for three shrub species (alone and combined), one grass, and planted ponderosa pine in these categories were quantified from 1966 to 1992. Successional trends (ascendance and decline) are presented for these species and for forbs from 1962 (the date pines were planted) through 1992. Regression equations that model density and development are presented for the shrubs and pine. In general, greenleaf manzanita prospered during the study; snowbrush initially developed well, but then declined; Sierra plum endured, but was relegated to the understory; needlegrass invaded rapdily, peaked early, and was mostly gone by the end of the study. Only a trace of forb species remained by study end. Needlegrass displayed strong environmental preference, becoming dense and developing well in shrub-free areas, but was scarcely present in heavy shrubs. Ponderosa pine grew well in no-shrub plots, farily well in light-shrub plots, and poorly in medium- and heavy-shrub plots. Extensive testing showed that shrub foliar cover and crown volume per acre explained more variation in several pine parametersmore » than shrub height or density.« less

The effects of small openings in forest stands has interested silviculturists and ecologists for years. Interest generally has centered on the vegetation in the openings, not on that immediately outside of them. Quantitative information on the growth of trees adjacent to group-selection openings, although often mentioned in forestry textbooks as contributing to cost effectiveness, is scant. Five conifer and three hardwood species bordering 9-, 18-, and 27-m diameter openings in the northern Sierra Nevada of California were examined for diameter growth 10 years before and 10 years after an initial group selection cutting. Ten-year diameter growth at breast height of various combinations of species and diameter classes did not differ significantly (P > 0.05) among opening sizes 10 years after cutting. But mean basal area growth of pines (ponderosa and sugar) 10 years after cutting was significantly greater (P < 0.05) than that before cutting in 18- and 27-m openings. This difference also was found for shade-tolerant conifers (Douglas-fir, incense-cedar, and California white iir) bordering all opening sizes. Mean basal area growth of hardwoods (California black oak, tanoak, Pacific madrone) did not differ before and after cutting for any opening size.

Abstract One-year-old Sierra chinkapin (Castanopsis sempervirens) sprouts, greenleaf manzanita (Arctostaphylos patula var. platyphylla) seedlings, and new fronds of bracken fern (Pteridium aquilinum var. pubescens), present in a 1-yr-old ponderosa pine (Pinus ponderosa var. ponderosa) plantation in northern California, were treated once with one of three herbicides (Velpar L, Escort, and Garlon 4) in fall 1986 and spring 1987 and their density and development compared among treatments and to a control. After 6 growing seasons, chinkapin sprouts in the control averaged more than 16,000 per acre, manzanita seedlings over 19,000, and bracken ferns more than 13,000 per acre. After 6 growing seasons, mean ponderosa pine diameter ranged from 2.03 in. in the Velpar treatment to 1.28 in. in the control. Cover of combined shrubs, also after six seasons, was about 3% with Velpar, 7% with Garlon, 20% with Escort, and 51% in the control. Bracken fern cover was greatest (13%) where foliage-active Garlon reduced competing shrubs, and least in the soil-active Velpar treatment (2%) and the control (3%), where heavy competition from shrubs precluded establishment. West. J. Appl. For. 9(1):24-28.

Forty-eight openings of 30, 60, and 90 feet in diameter were created in previously unmanaged mixed conifer-hardwood stands on a high-quality site in northern California in 1963.They were an attempt to convert an essentially even-aged forest to an uneven-aged arrangement and comprised the initial cut in the group-selection system.Five conifers and three hardwoods produced 36 seed crops that ranged from very light to heavy during the 10-year study period (1964)(1965)(1966)(1967)(1968)(1969)(1970)(1971)(1972)(1973).Sound seed for four conifer species combined (not sugar pine) for 10 years amounted to the equivalent of more than 302,900 seeds per acre and, in general, did not differ significantly among opening sizes.Shade and roots from bordering trees were major influences on seedling survival and development in the openings.Density of established conifer and hardwood seedlings (at least 4 years old) ranged from 12 per acre for incense-cedar in 90-foot openings to about 9,600 ponderosa pines per acre in 60-foot openings after 10 years, and did not differ significantly among opening sizes.Conifer seedling heights ranged from 0.8 to 1.7 feet after 9 years.Average height of ponderosa pines and hardwoods differed significantly between the largest and smallest opening size with height being best in the largest.Normally multi-stemmed and wide-crowned shrubs were conspicuous by their single spindly stems.Parry) and deerbrush (Ceanothus integerrimus H. & A.) are abundant in the soil almost everywhere on the Experimental Forest.Apparently, these species were abundant in the past in many areas where not a trace above ground remains today.Herbivores, chiefly deer (Odocoileus spp.), woodrats (Neotoma spp.), and deer mice (Peromyscus maniculatus), are plentiful throughout the Experimental Forest.Summers on the Experimental Forest are hot and dry; winters cool and moist.The average midsummer maximum United States

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