San Bernardino mountains

Fig. 8-3. Relationship between Los Angeles Basin s urban sources of photochemical smog and the San Bernardino Mountains, where ozone damage has occurred to the ponderosa pines. The solid lines are the average daily 1-hr maximum dose of ozone (ppm), )uly-September 1975-1977. Source Adapted from Davidson, A., Ozone trends in the south coast air basin of California, in "Ozone/Oxidants Interaction with the Total Environment.". A ir Pollution Control Association, Pittsburgh, 1979, pp. 433-450.

How have ozone and insects interacted to damage trees in the San Bernardino Mountain National Forest of California ... 

This cascading effect may have been best demonstrated from interdisciplinary research addressing the consequences of chronic oxidant air pollution exposure to the mixed conifer forests of the San Bernardino Mountains of Southern California. Miller et al. (76) reported that chronic exposure to oxidant air pollutants resulted in decreased photosynthetic capacity, premature... 

Even that kind of information is not available for forest species. Other than chronic injury to white pine (associated with ozone, sulfur dioxide, and their mixtures), no clearly defined examples of chronic injury from ozone have been reported for eastern forests, and no information is available on PAN. It is of interest that both Virginia and jack pine appear more sensitive than white pine to acute ozone exposures, but chronic symptoms have not been observed in either species. The relationship between oxidant dose and injury in the San Bernardino Mountains area suggests that ponderosa pine is moderately to severely injured in areas that receive oxidant at above 0.08 ppm for 12-13 h each day (Chapter 12). Ponderosa pine seems to be the most sensitive western pine, but in some areas Jeffrey pine is about as sensitive. White fir, incense cedar, and sugar pine all appear more tolerant, even to the high oxidant concentrations in the San Bernardino Mountains. PAN may play some role in the chronic responses noted in the western forest species, particularly by broadleaf deciduous trees and some shrubs. 

The daytime changes in oxidant concentrations at several stations (A, B, C, and D in Figure 12-1) along the southern slope and at the crest of the San Bernardino Mountains are illustrated in Figure 12-3. In... 

FIGURE 12-2 Altitudinal sequence of ecosystems in the San Bernardino Mountains. Reprinted with permission from Miller etal. ... 

FIGURE 12-3 Daytime changes in oxidant concentrations along a west-to-east transect in the southern coastal air basin, including the slopes of the San Bernardino Mountains (see Figure 12-1). Reprinted with permission from Edinger et al. 

FIGURE 12-4 The relationship of times of occurrence of the daily oxidant peak concentration to temperatures and vapor-pressure gradients in an elevational sequence (see Figures 12-1 and 12-2) on the slopes of the San Bernardino Mountains, July-August 1969. Reprinted with permission from Miller et at. ... 

ANNUAL TRENDS OF TOTAL-OXIDANT CONCENTRATIONS AT A SAN BERNARDINO MOUNTAIN STATION AND THE NEARBY CITY OF SAN BERNARDINO... 

FIGURE 12-5 Monthly summation, June-September 1968-1974, of total-oxidant dose and total number of hours at a dose > 157Mg/m (0.08 ppm) at Rim Forest-Sky Forest, Calif., in the San Bernardino Mountains. Numbers in open bars indicate percentage of total possible hours for which data were available. Reprinted with permission ftwm Kickert et al. ... 

The recent history of the mixed-conifer forest of the San Bernardino Mountains has be n analyzed. This analysis included an initial inventory of ecosystem components and processes, as indicated in Figures 12-8 through 12-12. The inventory emphasizes ponderosa and Jeffrey pines, the most dominant species in the climax community, and is... 

FIGURE 12-13 Topographic projection. San Bernardino Mountains, with comparison of oxidant injury to black oaks at major study sites, August 31, 1974, with accumulated total-oxidant dose for June-August measured at nearby monitoring stations. Higher score means less injury. Reprinted with permission from Kickert f al. ... 

FIGURE 12-14 Topographic projection, San Bernardino Mountains, showing how ponderosa pine (PP) and Jeffrey pine (JP) in major study sites are distributed in six injury classes according to seasonal dose of total oxidant. A, dead, 0 B, very severe, 1-8 C, severe, 9-14 D, moderate, 15-21 , slight, 22-28 F, very slight, 29-35 C, no visible damage, 36 +. Reprinted with permission from Kickert et al. 

Yonkers et al, have tested the ozone susceptibility of 15 species of annuals common to the Mojave Desert just north and east of the Los Angeles basin (and San Bernardino Mountains). Compared with the susceptible pinto bean plants included in the experiment with ozone at 0.35 ppm, Plantago sp., Cercidium sp., and Prosopsis sp. were also sensitive. Further interpretation of these results is complicated by the influences of plant age and pre-exposure conditions. 

Wildfire is a very important factor in western forest ecosystems. In the San Bernardino Mountains, the fire frequencies were determined by McBride and Laven in two stand types before and after 1893, when the area was first set aside as a forest preserve and fire protection began. Before 1893, the average interval between fires in ponderosa stands was 12 yr after 1893, it was 24 yr. The comparable numbers for Jeffrey pine stands were 16 and 38 yr. The buildup of heavy fuels due to ozone-caused mortality and fire protection results in hotter fires, and the thinning of the tree canopy results in increased rates of fire spread. Hotter fires decrease tree survival. Moisture interception by condensation in living tree crowns would decrease as the stands became thinner, thus causing some sites to be drier. ... 

Qiapter 8 indicates that oxidant air pollutants may adversely affect the olfactory and sight senses, degree of activity, general health and vigor, reproductive rate, heart and kidney function, protein synthesis, respiratory function, and disease resistance in domestic vertebrates under laboratory conditions. Many of these adverse physical responses develop at or near the concentrations of ozone currently experienced daily in ambient air in parts of the San Bernardino Mountains. 

In the San Bernardino Mountains, our goals have been to describe the terrestrial vertebrate community within this mixed-conifer forest, particularly in relation to ponderosa and Jeffrey pine stands, and to determine the effects of oxidant air pollutants on this community. The possible interactions of vertebrates in this system are shown in Figures 12-8 through 12-12. 

Likewise, WoodwelPs prediction" of enhancement of the activity of insect pests and some disease agents (which has been demonstrated in the San Bernardino Mountains forest) could lead to an increase in vertebrate species that feed on invertebrates or utilize dead plants for cover. Birds would be the most likely to increase and, to a lesser extent, such small mammals as deer mice, which are partially insectivorous. 

California black oak and white fir and less often on incense cedar in the San Bernardino Mountains. No direct effects of oxidants have been noted on the mistletoe plant itself under field conditions. The true mistletoe obtains mainly water from its host and would be indirectly affected by debilitation of die host tree. The dwarf mistletoes Arceuthobium spp.) are common on ponderosa, Jeffry, and sugar pines in the San Bernardino National Forest. They depend on their host for both water and carbohydrates. Heavily infected or broomed" branches on ponderosa or Jeffrey pines severely injured by ozone often have more annual needle whorls retained than do uninfected branches on the remainder of the tree. The needles are also greener. It can be hypothesized that the infected branch is a carbohydrate sink where a pooling of carbohydrates occurs higher carbohydrate concentrations may be instrumental in either preventing or helping to repair ozone injury to needles on the broomed branches. In the long term, stresses from mistletoe and ozone are probably additive and hasten tree death. 

In the San Bernardino Mountains, studies are going on to describe the effects of oxidant injury to ponderosa and Jeffrey pines on the microarthropods and fiingi of the litter layer under trees with various degrees of injury. Initial observations suggested lower population densities of microarthropods in the classes Insecta, Arachnida, and Myriapoda under some severely injured trees. ... 

Horton, J. S. Vegetation Types of the San Bernardino Mountains, California. Pacific Southwest Forest and Range Experiment Station Technical Paper 44. Berkeley, Calif. U.S. Department of Agriculture, 1960. 29 pp. 

Kolb, J. A., and M. White. Small mammals of the San Bernardino Mountains. California. Southwest. Natural. 19 112-113, 1974. 

Taylor, O. C. (Principal Investigator). Oxidant Air Pollutant Effects on a Western Coniferous Forest Ecosystem. Task B Report Historical Background and Proposed Systems Study of the San Bernardino Mountain Area. Riverside University of California, Statewide Air Pollution Research Center, [1973]. (278 pp.]... 

Oxidant injuty to the mixed-conifer stands of the San Bernardino Mountains began in the early 1940 s and is well advanced. A similar problem is developing in the forests of the southern Sierra Nevada. Both places show both direct and indirect effects on all subsystems of the forest ecosystem—producers, consumers, and decomposers. For example ... 

A viable example of the widespread and dramatic change that pollution can initiate on a plant community is found in the conifer forest of the San Bernardino mountains. This vivid example of what photochemical oxidants can do to initiate biological change provides an instructive base for future speculations. Paul Miller covers oxidant-induced community change in a mixed conifer forest. 

Influence on Host—Parasite Relationships. Cobb and Stark (11) have directed considerable attention to the increased incidence of attack of oxidant-injured ponderosa pines by bark beetles in the San Bernardino mountains. They suggest that ponderosa pine will nearly be eliminated from the mixed conifer forest if such attacks continue. Increased activity of other insect pests of ponderosa pine or associated conifers has not been observed. 

Spotila JA, Farley KA, Sieh K (1997) The exhumation and uplift history of the San Bernardino Mountains along the San Andreas fault, California, constrained by radiogenic helium thermochronometry. Tectonics 17 360-368... 

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