Quercus Kelloggii Newb Research Articles

DOZER LINES INFLUENCE POST-FIRE PLANT COMMUNITY RECOVERY

As wildfires increase in extent and intensity and threaten local communities, active suppression tactics are becoming more common, including the creation of fire lines. Post-fire, these sites can become populated with non-native species and risk type conversion if native species recovery is lacking. Minimal research exists on the plant community trajectory of these mechanically disturbed sites. We studied the 32-Fire located east of Chico, CA. A fire line approximately 0.5 km long ranging in width from 6–12.2 m was created by a bulldozer. To assess plant recovery, we established plots in three pre-fire vegetation types: California Black Oak (Quercus kelloggii Newb.), Manzanita (Arctostaphylos manzanita Parry), and Wedgeleaf Ceanothus (Ceanothus cuneatus [Hook.] Nutt.) within three disturbance levels: burned, unburned (reference), and disturbed dozer line. Sites were sampled in 2018 (six-months post-fire) and in 2019 (18-months post-fire). In 2019, dozer line sites in the Manzanita and Wedgeleaf Ceanothus vegetation types did not have the dominant species found in similar unburned or burned sites. Across all vegetation types, dozer line sites had significantly higher average percent non-native species cover, compared with respective burned (P < 0.001, 95% C.I. = 33.2, 64.8) and unburned areas (P < 0.001, 95% C.I. = -77.2, -45.5). While unburned Wedgeleaf sites average non-native cover was 11% (SD = 9) in 2018 and 20% (SD = 5) in 2019, Wedgeleaf dozer line sites average non-native cover remained high between survey years at approximately 85%. Manzanita dozer line sites had average nonnative cover of 76% (SD = 16) and 57% (SD = 25) in 2018 and 2019, respectively, while unburned Manzanita had 9% (SD = 9) and 16% (SD = 16). Manzanita and Wedgeleaf Ceanothus species present on the study site are obligate seeders. Since neither species survived the implementation of the dozer line and no new recruitment of these species was observed, future recruitment of obligate seeders in these areas is unlikely. This suggests that dozer line sites with obligate seeders as dominant or co-dominant species are at risk of type conversion from native chaparral to annual grasslands dominated by non-native species.

THE ROLE OF WINTER PRECIPITATION AS A CLIMATIC DRIVER OF THE SPRING PHENOLOGY OF FIVE CALIFORNIA QUERCUS SPECIES (FAGACEAE)

Understanding the phenological sensitivity of keystone plant species, such as oaks, to climate variables provides a foundation for assessing the impacts of changing climate on ecosystem resilience, biodiversity, and carbon sequestration. This study assessed the responsiveness of bud burst, flowering, and fruiting phenophases of five native California oaks to climate variables using 2012–2019 USA National Phenology Network data, which are contributed by scientists and trained volunteers. Climate data included seasonal measurements of precipitation and maximum and minimum temperatures. Phenophase data for five oak species: Quercus agrifolia Née and Quercus kelloggii Newb. from Quercus section Lobatae (red oaks), Quercus douglasii Hook. & Arn., Quercus garryana Douglas ex Hook., and Quercus lobata Née from Quercus section Quercus (white oaks) were analyzed. The majority of the trees in the study were located in California, although a small number of sites were beyond their normal distribution ranges. No significant differences were found among species for bud burst and fruiting onsets using ANOVA and Tukey HSD tests. However, significant differences were identified between the flowering onsets of the white oaks Quercus lobata and Quercus douglasii and between Quercus lobata and the red oak Quercus agrifolia. Multiple regression models identified the strongest climate predictors of oak phenophase onset as: (1) winter precipitation, (2) mean accumulated precipitation, and (3) maximum winter temperature, so that winter precipitation and temperature have been found to be the main climate drivers of vegetative growth and reproductive potential for these native California oaks.

Modeling the forest dynamics of the Sierra Nevada under climate change using SORTIE-ND

Key messageModel simulation results suggest that forests in the Sierra Nevada mountains of California will tend to increase in density and basal area in the absence of fire over the next century, and that climate change will favor increases in drought-tolerant species.ContextClimate change is projected to intensify the natural summer drought period for Mediterranean-climate forests. Such changes may increase tree mortality, change species interactions and composition, and impact ecosystem services.AimsTo parameterize SORTIE-ND, an individual-based, spatially explicit forest model, for forests in the Sierra Nevada, and to model forest responses to climate change.MethodsWe use 3 downscaled GCM projections (RCP 8.5) to project forest dynamics for 7 sites at different elevations.ResultsBasal area and stem density tended to increase in the absence of fire. Climate change effects differed by species, with more drought-tolerant species such as Jeffrey pine (Pinus jeffreyi A.Murray bis) and black oak (Quercus kelloggii Newb.) exhibiting increases in basal area and/or density.ConclusionIncreasing forest density may favor carbon sequestration but could increase the risk of high-severity fires. Future analyses should include improved parameterization of reproduction and interactions of disturbance with climate effects.

Do repeated wildfires promote restoration of oak woodlands in mixed-conifer landscapes?

Oak woodlands are dependent on frequent fire to maintain the low stem density and diverse understories that typify these ecosystems. Without this recurrent disturbance, fire-sensitive conifer competitors encroach on oaks, reducing their vigor, and diminishing habitat quality. In fire-excluded oak woodlands, stand-replacing wildfire can trigger shifts in canopy dominance from seed-generated conifers to oaks, which are capable of vigorous sprouting following topkill. We examined the occurrence and sprouting dynamics of California black oak (Quercus kelloggii Newb.) following repeated wildfires in the Lassen National Forest, California. We found that following reburn, changes in oak relative stand dominance, as well as oak sprout basal area and height, were each positively related to fire severity (P < 0.0001 for each analysis). While conifer regeneration suffered complete mortality at moderate and high reburn severities, 97% of topkilled oaks resprouted from surviving rootstocks, reinforcing oak dominance. Black oak resprouts that originated following topkill in the first wildfire were frequently topkilled in the second fire, including at lower burn severities survived by advance conifer regeneration. The results of this study indicate that while as individuals, black oaks are resilient to recurring wildfire, restoration of historic woodland structure and function is an unlikely outcome of these repeated disturbances. Management of post-wildfire regenerating oak stands in this region will require supplemental fuel reduction treatments, including prescribed burning.

Eutrophic lichens respond to multiple forms of N: implications for critical levels and critical loads research

Epiphytic lichen communities are highly sensitive to excess nitrogen (N), which causes the replacement of native floras by N-tolerant, "weedy" eutrophic species. This shift is commonly used as the indicator of ecosystem "harm" in studies developing empirical critical levels (CLE) for ammonia (NH3) and critical loads (CLO) for N. To be most effective, empirical CLE and/or CLO must firmly link lichen response to causal pollutant(s), which is difficult to accomplish in field studies in part because the high cost of N measurements limits their use. For this case study we synthesized an unprecedented array of atmospheric N measurements across 22 long-term monitoring sites in the Los Angeles Basin, California, USA: gas concentrations of NH3, nitric acid (HNO3), nitrogen dioxide, and ozone (n = 10 sites); N deposition in throughfall (n = 8 sites); modeled estimates of eight different forms of N (n = 22 sites); and nitrate deposition accumulated on oak twigs (n = 22 sites). We sampled lichens on black oak (Quercus kelloggii Newb.), and scored plots using two indices of eutroph (N tolerant species) abundance to characterize the community-level response to N. Our results contradict two common assertions about the lichen-N response: (1) that eutrophs respond specifically to NH3 and (2) that the response necessarily depends upon the increased pH of lichen substrates. Eutroph abundance related significantly but weakly to NH3 (r2 = 0.48). Total N deposition as measured in canopy throughfall was by far the best predictor of eutroph abundance (r2 = 0.94), indicating that eutrophs respond to multiple forms of N. Most N variables had significant correlations to eutroph abundance (r2 = 0.36-0.62) as well as to each other (r2 = 0.61-0.98), demonstrating the risk of mistaken causality in CLE/CLO field studies that lack sufficient calibration data. Our data furthermore suggest that eutroph abundance is primarily driven by N inputs, not substrate pH, at least at the high-pH values found in the basin (4.8-6.1). Eutroph abundance correlated negatively with trunk bark pH (r2 = 0.43), exactly the opposite of virtually all previous studies of eutroph behavior. This correlation probably results because HNO3 dominates N deposition in our study region.

Interactive effects of O3 exposure on California black oak (Quercus kelloggii Newb.) seedlings with and without N amendment

We examined the short-term separate and combined effects of simulated nitrogen (N) deposition (fertilization) and ozone (O(3)) exposure on California black oak seedlings (Quercus kelloggii Newb.), an ecologically important tree of the San Bernardino Mountains downwind of Los Angeles. Realistic concentrations of O(3) were found to cause statistically and biologically significant negative effects on plant health, including lowered photosynthetic ability, lowered water use efficiency, and increased leaf chlorosis and necrosis. When subjected to abrupt changes in light levels, O(3)-exposed plants showed both a slower and smaller response than O(3)-free plants. Fertilized plants exhibited a significantly greater pre- to post-treatment decline in A at saturated [CO(2)] and a significantly lower level of post-treatment chlorosis than unfertilized plants. Fertilization tended to reduce plant sensitivity to O(3).

Antennal responses of the western pine beetle, Dendroctonus brevicomis (Coleoptera: Curculionidae), to stem volatiles of its primary host, Pinus ponderosa, and nine sympatric nonhost angiosperms and conifers

Summary. Stem volatile extracts from ten trees that are sympatric with the western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae) were assayed by gas chromatographic-electroantennographic detection analysis (GC-EAD). The extracts were from the primary host, ponderosa pine, Pinus ponderosa Dougl. ex Laws. (Pinaceae); two nonhost angiosperms, California black oak, Quercus kelloggii Newb. (Fagaceae), and quaking aspen, Populus tremuloides Michx. (Salicaceae); and seven nonhost conifers, white fir, Abies concolor (Gord. & Glend.) Lindl. ex Hildebr. (Pinaceae), incense cedar, Calocedrus decurrens (Torr.) Florin (Cupressaceae), Sierra lodgepole pine, P. contorta murrayana Grev. & Balf. (Pinaceae), Jeffrey pine, P. jeffreyi Grev. & Balf. (Pinaceae), sugar pine, P. lambertiana Dougl. (Pinaceae), Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco (Pinaceae), and mountain hemlock, Tsuga mertensiana (Bong.) Carr. (Pinaceae). Sixty-four compounds were identified from the ten trees, 42 of which elicited antennal responses in D. brevicomis, usually in both sexes. In addition, several synthetic compounds, including a number of the antennally-active compounds from the extracted trees and some bark beetle pheromone components, elicited antennal responses in a manner similar to that observed with the extracts. Of the antennally-active compounds known to be present in trees sympatric with D. brevicomis, only geraniol was unique to its host. Four antennally-active compounds were found in the host and in other conifers; five compounds were found only in nonhost conifers; eight compounds were found in either or both of the nonhost angiosperms; eight compounds were found in either or both of the angiosperms and in nonhost conifers, but not in the host; and 19 were found in both the host and in angiosperms and/or nonhost conifers. Several bark beetle pheromone components were found in the stem volatile extracts. Conophthorin was identified from both nonhost angiosperms; exo-brevicomin was identified in A. concolor; verbenone was identified from a number of nonhost conifers; and chalcogran was identified from P. tremuloides. The number of nonhost volatile chemicals that D. brevicomis encounters and is capable of detecting, and the diversity of sources from which they emanate, highlight the complexity of the olfactory environment in which D. brevicomis forages. This provides a basis for further work related to chemically-mediated aspects of foraging in this insect and perhaps other coniferophagous bark beetles, and highlights the need to consider foraging context in the design and implementation of semiochemical-based management tactics for tree protection.

Nitrogen mineralization and nitrification in a mixed-conifer forest in southern California: controlling factors, fluxes, and nitrogen fertilization response at a high and low nitrogen deposition site

Net fluxes of nitrogen (N) mineralization and nitrification were measured in situ on a monthly basis for 3 years at a high (HN) and low (LN) N deposition site in the San Bernardino Mountains, California. Mean N mineralization fluxes in the forest floor and top 10 cm of mineral soil were 19.0 and 59.8 kg N·ha–1·year–1 at LN and HN, respectively. Mean net nitrification fluxes were 11.2 and 55.9 kg N·ha–1·year–1 at LN and HN, respectively. Relative nitrification (the percent N mineralized that was nitrified) was generally lower under Pinus ponderosa Dougl. ex P. &amp; C. Laws. (or Pinus jeffreyi Grev. &amp; Balf.) canopies than under Quercus kelloggii Newb. or open canopies. The rate of net N mineralization was the key factor for predicting the rate of net nitrification. Fertilization with 50 and 150 kg N·ha–1 at LN significantly increased the rates of net mineralization and net nitrification. At HN fertilization had no significant effect on net nitrification. We conclude that at low-deposition sites increased nitrification occurs in the short term in response to added N, but that sustained elevated net nitrification is driven by the accumulation of N-enriched litter and soil organic matter in conjunction with chronic throughfall N deposition inputs.

Prescribed fire mortality of Sierra Nevada mixed conifer tree species: effects of crown damage and forest floor combustion

Logistic regression equations of prescribed fire mortality were developed for white fir ( Abies concolor [Gord. and Glend.] Lindl.), sugar pine ( Pinus lambertiana Dougl.), ponderosa pine ( Pinus ponderosa Laws.), incense-cedar ( Calocedrus decurrens [Torr.] Floren.), and giant sequoia ( Sequoiadendron giganteum [Lindley] Buchholz) in the southern Sierra Nevada, California. A total of 1025 trees were analyzed in this study. Variables included in the mortality equations are diameter at breast height, percent crown volume scorched, crown scorch height, and local forest floor consumption. The likelihood ratio χ 2 was highly significant ( P<0.0001) for all models developed and the receiver operating curve statistic ranged from 0.736 to 0.997 indicating good overall model performance. None of the logistic regression models developed for California black oak ( Quercus kelloggii Newb.) produced a maximum likelihood estimate indicating that the variables measured were not significant predictors of mortality. Probability of death is lower for giant sequoia, incense-cedar, and ponderosa pine at high levels of percent crown volume scorched when compared to sugar pine and white fir. Forest floor consumption was a significant factor in the majority of the models developed indicating that mortality is not solely a function of crown damage. These models may be useful to forest managers planning prescribed fires and to ecologists interested in modeling the effects of fire on mixed conifer forests.

Nitric acid vapor effects on forest trees — deposition and cuticular changes

Nitric acid (HNO 3) vapor is an important component of photochemical smog and occurs in high concentrations in forests of the San Bernardino and San Gabriel Mountains of southern California. Ponderosa pine ( Pinus ponderosa Dougl. ex. Laws.) and California black oak ( Quercus kelloggii Newb.) seedlings were exposed to H 15NO 3 in a series of short-term experiments performed in a Teflon cuvette system. The highest H 15NO 3 deposition occurred on foliar surfaces of both species. Substantial transcuticular transport of the pollutant into the leaf interior and stems and roots of two species was determined. Exposures of pines for 12 h in light to 50 ppb H 15NO 3 caused deterioration of needle cuticle (lesions and collapsed cells). After 12 h of dark exposures to 200 ppb H 15NO 3 epicuticular wax structure of oak started to disintegrate and trichomes showed a wilting appearance. Exposures to H 15NO 3 changed chemistry of epicuticular waxes of pines — content of fatty acids decreased and alkyl esters increased. Results of this study showed a potential for HNO 3 phytotoxic effects in southern California forests in addition to the observed damage caused by ozone.

Estimating seed crops of conifer and hardwood species

Cone, acorn, and berry crops of ponderosa pine (Pinusponderosa Dougl. ex Laws. var. ponderosa), sugar pine (Pinuslambertiana Dougl.), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), California white fir (Abiesconcolor var. lowiana (Gord.) Lemm.), incense-cedar (Libocedrusdecurrens Torr.), California black oak (Quercuskelloggii Newb.), tan oak (Lithocarpusdensiflorus (Hook. &amp; Arn.) Rehd.), and Pacific madrone (Arbutusmenziesii Pursh) were evaluated over a 24-year period (1958–1981) from an area in northern California by an easy to use visual crop rating system. Seed-trap data, also for 24 years, were gathered for four conifer species. Together, these data provide the wild-land manager with knowledge on seed-crop quantity, quality, and timing. The visual rating system involves visually estimating the amount of fruit in trees and the proportion of trees with fruit, and ranking the crop by species. Regressions of sound seed and total seed on seed-crop rating are provided for the two species with the most seed crops: ponderosa pine and Douglas-fir. Regressions were significant at the 1% level, and coefficients of determination ranged from 0.58 to 0.76.

Effects of Ozone and Sulfur Dioxide on Phyllosphere Fungi from Three Tree Species

Short-term effects of ozone (O(3)) on phyllosphere fungi were studied by examining fungal populations from leaves of giant sequoia (Sequoiadendron giganteum (Lindl.) Buchholz) and California black oak (Quercus kelloggii Newb.). Chronic effects of both O(3) and sulfur dioxide (SO(2)) were studied by isolating fungi from leaves of mature Valencia orange (Citrus sinensis L.) trees. In this chronic-exposure experiment, mature orange trees were fumigated in open-top chambers at the University of California, Riverside, for 4 years with filtered air, ambient air plus filtered air (1:1), ambient air, or filtered air plus SO(2) at 9.3 parts per hundred million. Populations of Alternaria alternata (Fr.) Keissler and Cladosporium cladosporioides (Fres.) de Vries, two of the four most common fungi isolated from orange leaves, were significantly reduced by chronic exposure to ambient air. In the short-term experiments, seedlings of giant sequoia or California black oak were fumigated in open-top chambers in Sequoia National Park for 9 to 11 weeks with filtered air, ambient air, or ambient air plus O(3). These short-term fumigations did not significantly affect the numbers of phyllosphere fungi. Exposure of Valencia orange trees to SO(2) at 9.3 parts per hundred million for 4 years reduced the number of phyllosphere fungi isolated by 75% compared with the number from the filtered-air treatment and reduced the Simpson diversity index value from 3.3 to 2.5. A significant chamber effect was evident since leaves of giant sequoia and California black oak located outside of chambers had more phyllosphere fungi than did seedlings within chambers. Results suggest that chronic exposure to ambient ozone or SO(2) in polluted areas can affect phyllosphere fungal communities, while short-term exposures may not significantly disturb phyllosphere fungi.

New Copidosomopsis (Hymenoptera: Encyrtidae) from California, with Comments on the Genus

Copidosomopsis tanytmemus , sp. nov., is described. This polyembryonic encyrtid was reared out of larvae of the pyralid Anagasta kuehniella (Zeller) that were feeding on acorns of Quercus kelloggii Newb. in El Dorado County, Calif. A key to separate the females of C. tanytmemus from the other known species of Copidosomopsis is presented. The six known species can be segregated in two groups: four with female club entire, including C. arenicola (Trjapitzin) and C. bohemicus (Hoffer) from the Palearctic Region, and C. nacoleiae (Eady) and C. perminutus Girault from the Indo-Pacific Region, and two with female club three-segmented, including C. plethoricus (Caltagirone) from the Nearctic and northern Neotropical regions, and C. tanytmemus (Caltagirone) from the Nearctic Region.