SUMMARY OF IHRMP MONITORING
AND RESEARCH

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Accompanying the educational activities of the IHRMP is an aggressive research and monitoring program committed to finding answers to questions about the hardwood range ecosystem and the impacts of various management alternatives.

To help the joint CDF and UC research effort prioritize research needs, a nine member Policy Advisory Committee was formed and consulted regularly. Committee members came from a variety of different groups, including the State Board of Forestry, the Range Management Advisory Committee, universities, agencies, various resource management professionals, and representatives from several conservation groups.

Between $500,000 and $600,000 have been available annually for each of the past five years to fund research studies on hardwood range management and ecology. In general, the University of California is funding longer term, more basic research studies, and the California Department of Forestry and Fire Protection is funding shorter term, policy-oriented studies.

Over the five years of the IHRMP, 65 different research projects have been funded by UC and CDF. Table 8 shows a list of these projects. The results of the research program are evaluated below.


Monitoring Current Status of Hardwood Rangelands
CDF has assumed the lead for the monitoring effort of the IHRMP. The Forest and Rangeland Assessment Program (FRRAP) of CDF has most of the spatial monitoring stored on its geographic information system (GIS) for use by local planners, and for policy analysis.

The monitoring effort of the IHRMP has been to develop maps that display the various components of hardwood rangelands in order to assess the values of the system and the sustainability of values derived from the landscape. Since a large number of variables are required to understand the system, it is not surprising that the mapping of important variables is incomplete. Vegetation and ownership are the principal state variables currently mapped.

IHRMP has been engaged in two major hardwood vegetation mapping efforts. The first (project 63963) mapped hardwood rangelands by six major overstory species classes and four canopy cover classes from 1981 aerial photos. This classification closely corresponds to the hardwood habitats in the Wildlife Habitat Relationships database (WHR), allowing general inferences about wildlife habitat from the vegetation maps.

A second IHRMP project (project 96121) currently underway will produce new hardwood maps from remote sensing data to allow direct comparison with the earlier maps and therefore will show hardwood rangeland changes over time. This project will map site variables which correspond more closely to the WHR classification and will include other variables such as understory vegetation.

IHRMP has also funded (project 63912; Allen et al, 1991) the development of a more detailed description of hardwood rangeland cover types which corresponds at its coarsest level to the general WHR habitat descriptions but differs considerably in how it classifies vegetation at a finer grain. While WHR classifies vegetation according to structure, the hardwood rangeland cover type system classifies vegetation principally by botanical composition. The hardwood cover type descriptions are not yet tied to a response database, such as WHR. A project is underway, however, to construct a response database (project 96020).

CDF has also mapped a number of socioeconomic and land tenure variables that are important in hardwood rangelands because these affect future status of these lands. CDF’s ownership map delineates public from private ownership. Public ownership of hardwood rangelands is relatively small. The status of private hardwood rangelands will be determined by private owners who display wide variation in their management (Huntsinger and Fortmann 1990) and are themselves expressions of larger economic forces. A non-IHRMP project has determined that County Assessor rolls and US Census data provide great detail on private sector ownership of hardwood rangelands.

Oak Seedlings Given Away New Publication on Harvesting Firewood for Sustained Yield on Oak Rangelands During this past year, a new publication was released which shows how owners of hardwood rangelands can cut oak firewood for their own use or to supplement income from livestock raising, and still maintain the oak resource for the future. This leaflet can be used as a guide on how to inventory an oak stand, assess its productivity for growing wood, and then use the information to develop a firewood-harvesting strategy that optimizes economic return and sustains the wood, wildlife, and forage resources over time (Standiford and Tietje, 1990).

Land Use Change
IHRMP research has led to some conclusions about the processes that cause change in the hardwood rangeland. These changes can be classified as "permanent" changes, which convert hardwood rangelands to some other use such as urban land or crop agriculture land, or habitat modifications that occur within existing hardwood rangelands, such as thinning or planting seedlings.

Permanent Land Use Changes
Clearing oaks for forage production and firewood.—The incidence of oak clearing has been affected by a host of factors, such as financial incentives, firewood prices, and the perception of the value of intact oak trees by individual hardwood range owners. Since clearing is usually too costly to justify on the basis of increased forage production alone, the sale of firewood is linked to clearing. Doak and Stewart (project 42151) suggested that low livestock prices during the 70’s encouraged hardwood range owners to sell firewood to maintain income. They developed a conceptual model of the firewood market that might be developed into an econometric model of firewood harvesting on hardwood rangelands in future research. A multiple use model of hardwood rangeland management activities also shows this same result, that is, firewood harvest occurs during periods of low cattle prices to reduce the probability of negative cash flow (project 8614).

In addition, producer behavior may not remain consistent in the future. As new types of owners buy hardwood range, economic pressures may be less important. Many new owners are less concerned with economic return from the land and may be less influenced by firewood and livestock markets (Huntsinger and Fortmann 1990).

The incidence of clearing was important prior to 1970 but since then it has declined as other conversions have increased (Bolsinger 1988). The current incidence of harvesting is quite low with clearcutting virtually absent (see section on short-term monitoring).

Although the short-term effects of clearing on the vegetation composition are fairly well known, the long-term effects on the resource values are less certain. While clearing is often permanent, blue oaks have apparently resprouted on some cleared sites. The geography of resprouting will therefore have a pronounced effect on the longer term effects (McCreary et al, 1991).

The effect of clearing on soil erosion has been assessed, and specific "critical sites" which should be protected to maintain water quality have been identified based on erosion hazard ratings and proximity to streams (project 74546). Additional models to predict the quantitative impact of trees on sediment production and transport are still being developed (project 896).

The effect of clearing on wildlife can be estimated with the WHR model. While the WHR prediction gives an expected change in species presence, no IHRMP research has actually cleared hardwood habitats to confirm the predicted shift in species. Two new projects to conduct this type of controlled treatment effect on wildlife species have just been initiated (project 912 and 913). Projects have demonstrated both the plasticity in habitat requirements of many species (74574) and the importance of habitat diversity, rather than the importance of any one habitat (42114). Consequently the scale of clearing and its effects on local habitat diversity are probably important determinants of the effect of clearing on wildlife.

As with the previous outputs, criteria have been proposed for critical sites for wildlife. These criteria include the presence of threatened and endangered species or their habitat, migratory deer habitat, riparian habitat, and habitat diversity. Of these, only migratory deer habitats currently exist within the FRRAP GIS. The location of threatened and endangered species is currently being obtained from the Natural Heritage Division of the Department of Fish and Game. If riparian habitats and habitat diversity can be located and classified, it may be possible to map preliminary critical sites for wildlife.

The yield of wood from clearing a stand has been estimated by Standiford (8614) as a function of the site index and the canopy cover. The effect of clearing on forage production appears to differ according to precipitation but accurate prediction at the management level is more difficult. On wetter sites, naturally open or cleared areas produced more herbage than areas under canopies (42137, Jansen 1987). However in drier environments or during dry years herbaceous production under canopies is equal to or greater than that in adjacent open areas (42137, 8616). These latter studies do not show that clearing in drier environment depresses forage production, but do show that the presence of trees may increase forage production. Soils under canopies are more fertile than in open arm, presumably because of nutrient inputs from lower soils layer through leaf fall, and therefore might respond with greater production even in drier areas after clearing (project 896). However since this effect is created by the trees, any burst of higher productivity after clearing is likely to be transient. Therefore complete removal of oaks on drier sites could lead to a long term decrease in site productivity.

Research on the genetic architecture of coast live oak (project 866) indicates that clearing is unlikely to eliminate distinct local populations. Continuing research (projects 866, 893) may determine if genetic variation in blue oak is similarly uncorrelated with geography. The larger question of biodiversity as a function of vegetation pattern remains unanswered. Finally, studies on the long-term effects of clearing on site productivity are underway (project 894).

Agricultural Conversion:
Conversion of hardwoods to agricultural production was the principal factor leading to the loss of over 90 percent of valley oak stands in the state. By the 1950s the massive loss of hardwoods to agriculture had already occurred.

Doak and Stewart (project 42151) provided a conceptual model that outlined the major factors currently governing conversion to agriculture. The availability of both appropriate land and irrigation water currently constrain agricultural conversion, although this project cites San Diego County, North Coast counties, and the Sierra foothills as areas where agricultural conversion to high value horticultural crops is continuing.

Like clearing for firewood harvesting, conversion to agriculture involves many separate 10 to 40 acre clearings which may nonetheless be important locally. The Farmland Mapping Program and improvement values from County Assessor rolls provide the best data from which to assess the extent of agricultural conversion.

Like clearing, the direct effect of agricultural conversion is severe. In general, all trees are removed (though a few large heritage oaks may be left) and the entire area converted to cropped land. Agricultural conversion may alter the local forage supply and grazing patterns. Doak and Stewart's case study of clearing in Monterey County showed that conversion of oaks to horticultural crops on steeper lands may greatly increase soil erosion. Furthermore, it may fragment the landscape with significant impacts on fire risk and biodiversity.

Urbanization and Subdivision Pressure:
Population growth in coastal and foothill counties of California has led to an unprecedented conversion of hardwood rangelands to human habitat, Residential and commercial development with the associated highways are now the most prevalent form of conversion (Bolsinger 1988).

Both demand (population growth, interest rates) and supply (zoning, use restrictions, availability of water) jointly influence the pace of development. While IHRMP has located or developed means of measuring these variables (Farmland Mapping, projects 42151, 63967) we cannot yet map settlement on the county level, nor construct a spatial model that will predict where settlement will occur within the hardwood range. However, IHRMP has drafted a document (project 85304) that suggests how county planners can incorporate resource concerns in their plans for settlement.

The effect of settlement on wildlife merits particular consideration. It is not clear that the WHR model can simulate the results of settlement, since in all but the densest development patterns, the vegetation type remains relatively unchanged. This situation does not invalidate the model but suggests that it is not yet the appropriate tool to model the effects of this most important type of conversion. Two research projects (891, 892) are currently quantifying the change in species fists and abundances in response to residential development.

Settlement has been presumed to constrain how ranchers and farmers manage their resources and has also been assumed to increase the risk of fire and decrease the efficiency of resource protection. These factors have riot been rigorously studied within IHRMP research.

Blue Oak Canopy Effect on Forage Production and Quality A study at he San Joaquin Experimental Range has shown that in areas of scattered blue oaks (7% blue oak canopy cover), forage production and quality are enhanced beneath the canopy of trees. The increased forage production began in March and continued through the end of the forage growing season. The forage beneath blue oaks was generally of better quality, higher in crude protein and lower in fiber and lignin. To estimate the integrated effect of forage abundance and quality on grazing animals, crude protein intake of a nursing cow was calculated in both the open grassland and beneath blue oak canopy situations and related to her daily requirements. In the open grassland there was only 1 brief period (March) when daily dietary crude protein intake was in excess of the requirement, while beneath blue oak canopies an excess of crude protein was provided from mid-December through May. This research suggests that retention of existing blue oak trees in this region can benefit livestock operations. 1986-90 Average Forage Production (pounds/acre) Open grassland Blue oak canopy September 0 9 November 89 131 January 272 310 March 712 1140 Peak standing crop 1303 2392 1987-89 Crude Protein Content of Forage (percent) Open grassland Blue oak canopy November 8.19 12.94 January 16.69 24.93 March 13.25 17.31 May 5.06 8.75 July 3.94 6.44

Habitat Modification
Habitat modification involves all natural and management-related processes that occur within intact hardwood rangelands. The growth, reproduction and mortality of the herbaceous, shrub and tree layers determine habitat structure. Diseases of hardwoods merit special attention since, in the absence of cutting, they are a major source of mortality in mature hardwoods. Similarly, herbaceous growth establishes a competitive situation which may account for most oak seedling mortality. Wildfires can have major impacts on the system. Grazing, prescribed fire, thinning and artificial regeneration interact with natural processes to affect the hardwood rangeland ecosystem.

Sustainability of Oak Stands:
The net effect of growth, recruitment and mortality on the oak overstory influences the sustainability of oaks on hardwood rangelands. IHRMP research has identified how these factors interrelate (project 63669), although the spatial extent of each process remains unclear. Standiford (8614) derived site indices for hardwood rangelands and presents associated growth rates. A map of the site indices, comparable to the hardwood cover type map (63963), would permit stand growth rates to be applied across the hardwood range. Similarly, several researchers have proposed both measures of regeneration success (42136, 85301) and suspected correlates of regeneration failure (63669, 84965, 862, 865). If a statistically valid relationship exists between regeneration data from plots and vegetation attributes of map polygons, it may be possible to map regeneration failure.

The identity, mechanisms and environmental correlates of insect- and disease-related hardwood mortality have been incorporated in a database by IHRMP research (74545). However, the lack of information on mortality incidence limits assessment of its role in regulating hardwood populations. Nevertheless, it may be possible to assess the probability of insect and disease mortality on the basis of stand structure and environmental variables. The effects of wood rot fungi, the principal agents of mortality in mature trees, appear to be inversely related to the growth rate of the host. Thus stands consisting of large, slow-growing individuals in droughty conditions have a high probability of disappearing due to a single disease outbreak. If regeneration is insufficient to replace them, these stands constitute another type of critical site.

Oak Regeneration Workshops This past spring, two workshops on oak regeneration were held at the Sierra Foothill Range Field Station. They were attended by over 250 people. The IHRMP has been a leader in developing nursery and field planting technologies to ensure survival and growth of oaks planted on hardwood rangelands. These workshops highlighted the latest results from research studies on a variety of propagation, planting, and protection methods. The increasing importance of restoration as a part of mitigation required following conversion or development, as well as the demand by both public and private landowners to reestablish oaks on areas they once occupied, makes this an important topic for a variety of resource management professionals. Techniques on acorn collection, tree and acorn planting, and site preparation were presented, as well as a comparison of the different types of oak planting stock now widely available in both state and private nurseries.

The presence of mycorrhizal fungi may be critical to regeneration success. IHRMP research has shown that mycorrhizal fungi are not present in grassland soils, but are located beneath oak canopies (865). The potential for mycorrhizal infection on the edge of the canopy zone between canopies may be very important, since many researchers have noted that successful recruitment to the sapling class usually occurs on the periphery of the canopy zone. Thinning may therefore have an effect on the maintenance of mycorrhizal inocula, and resulting regeneration success.

The naturalized annual grasses and forbs of hardwood rangelands may out-compete hardwood seedlings for available soil moisture. Competition for soil moisture was detected by comparing seedling growth beneath and away from tree canopies under both grazed and ungrazed conditions (52754). Seedlings under tree canopies within grazed pastures experienced greater moisture stress than did seedlings in the open or within ungrazed pastures. Naturalized annual grasses were shown to more rapidly deplete soil moisture availability to oak seedlings than native perennial grasses (project 861). The conversion of range to naturalized annuals may at least partially explain the apparent poor recruitment in some areas. If competition can be shown to be a major factor regulating oak recruitment in hardwood populations, an assessment of its incidence over the whole of the hardwood range is needed. Canopy closure and grazing pressure may also be useful indicators.

Herbaceous biomass is obviously important for assessing the value of land for livestock production. The growth of herbaceous layer has been modeled by Standiford (project 8614) with respect to site and precipitation. This approach could be applied to other sites to generate a map of forage production. Another project (74755) summarizes herbage productivity under favorable and unfavorable weather conditions across a range of soil units that include some of the hardwood range. While these soil units have been mapped, the current scale and form of mapping make its incorporation in a GIS very expensive.

The population biology of shrubs (their reproduction, growth, mortality over space) and their influence on the hardwood overstory have not been well studied in IHRMP research. Hardwood range reference areas (85641) may indicate areas in which the absence of grazing and prescribed bums have allowed these processes to manifest their importance and should therefore illuminate the role of shrubs in oak woodland ecology.

Effects of Fire:
Fire can change the stand structure by top-killing saplings. However, its long-term effects may be minimal since most of these saplings resprout and grow rapidly for several years until they are indistinguishable from unburned ones (project 85301). Repeated fires diminish the ability of saplings to resprout, while intense summer/fall fires damage saplings far more than cooler spring/summer fires (project 862). Therefore, periodic prescribed fires to reduce fuels do not appear inimical to oak regeneration, while hotter summer fires, either wild or prescribed, may imperil regeneration. The long-term fire effects on herbaceous productivity, shrub response, nutrient mobilization and biodiversity are not well-understood to date.

Effects of Grazing:
Grazing may interact with numerous other processes to determine stand structure. Grazing tends to increase herbaceous growth and may thereby establish a competitive relationship between hardwood seedlings and grasses (projects 52754, 861). Grazing of hardwood seedlings themselves could after stand structure (projects 85301, 84964). Finally grazing may compact soils and increase runoff from mature stands sufficiently to shift the competition between trees and wood rot fungi toward the fungi (project 74545). The importance of these mechanisms is still subject to debate. The best dataset on grazing impacts on regeneration shows only one species, valley oak, to decline in the presence of grazing (project 42136). In the absence of a clear link, the utility of grazing incidence data for predicting hardwood stand dynamics is minimal. It does seem apparent that the simple removal of grazing does not ensure the regeneration of perennial grass stands. The opportunities and constraints in this area are unknown.

Grazing may have deleterious effects on biodiversity through degradation of riparian areas and through encouragement of exotic annuals over native species. A study of the response of the vegetation of hardwood riparian areas to grazing exclusion has just been started (project 911).

Effects of Thinning:
Thinning has obvious initial effects on stand structure but the long-term effects have not been studied by IHRMP. Hardwood species have different resprouting capacities (project 42136, McCreary et al, 1991). Thinning effects on sod and water quality can be analyzed using the methods developed for clearing. Its effects on wildlife can be simulated with WHR since thinning generally reduces canopy density by at least one class. However, research has shown that simple changes in canopy closure are less important to birds than the pattern of structure within a stand and the diversity of stands across space (project 42114). In a different approach Standiford (project 8614) did not calculate the direct effect of thinning on deer populations but used canopy cover as one variable in the production function for hunting income. Revenue from deer hunting may provide an economic incentive for maintaining oak canopy levels.

The relationships between hardwood canopy cover and the subsequent production of forage and firewood form the core of the hardwood range management model (project 8614). Reductions in wood volume due to thinning increases growth rate of the stand, and increases forage production depending on the moisture regime of the site.

ABOVE: The grasshopper above is devouring a grape leaf. Grasshoppers also pose a threat to the survival of oak seedlings. (Click on image for larger view.)

Artificial regeneration:
IHRMP research has tested a number of silvicultural techniques appropriate for the artificial regeneration of valley, blue and Engelmann oak and has developed a set of technical packages. A project to assess the effects of both ecological conditions and different management practices on regeneration statewide will be completed in 1993. Two projects (84965, 85381), however, relate artificial regeneration efforts to sites, in one case for valley oak, by the use of a key that leads to different packages, and in the other for Engelmann oak, by determining more precisely the natural site requirements of the species. To date, few of the projects have reported the costs of artificial regeneration, which is necessary for an assessment of economic feasibility and reasonable subsidy rates.

Once survival of the planted trees is ensured, the final effect of artificial regeneration on outputs and values can be considered the reverse of those of thinning, though clearly on a different time scale. The maximum utility of hardwoods for soil and water quality concerns may be in stabilizing riparian areas. Artificial regeneration could be a very powerful means of improving wildlife habitat and increasing biodiversity if we knew optimal patterns of vegetation for each of these. While retention guidelines may be sufficient for guiding thinning, much more detailed guidelines on die scales of variation in density and botanical species composition will be required to guide implementation of the much more expensive option of artificial regeneration. Artificial regeneration appears to have little relevance for forage or firewood production. In these cases, more palatable shrubs or exotic firewood species may make more sense and could reduce harvesting pressures on native hardwoods.


Table 8. Hardwood Related Research Projects by Theme and Agency

Theme Areas/Agency/FY/Title P.I. No. I. Improving oak regeneration CDF 1983-84 Survey of natural regeneration of oaks 1984-85 Analysis of oak regeneration 1985-86 Effect of fire on oak regeneration Forage and sapling response to canopy removal and defoliation 1986-87 Oak regeneration assessment- a problem analysis 1987-88 Disease and insect impacts on oaks impacts on oaks Restocking native oaks 1988-89 Restoring valley oaks Restoring Engelmann oak Engelmann oak stand age structure Grazing and blue oak Effects of fire/grazing Organize oak regeneration Bartolome (UCB) Bartolome (UCB) Bartolome (UCB) Menke (UCD) Lang (Jones & Stokes) Swiecki & Arnold (Plant Science) McCreary (UCB) Swiecki (Plant Science) St. John (UCR) Scott (UCB) George (UCD) Bartolome (UCB) McBride (UCB) 30767 42136 52961 52754 63669 74545 74639 84965 85381 85385 84964 85301 84822 UC 1986-87 Ecophysiological responses of oak seedlings during establishment— the influence of mycorrhiza Effect of fire on seedlings and saplings of Engelmann oak and coast live oak Natural regeneration in Engelmann oak Genetic variability of California oak species Oak woodland regeneration Ecology and regeneration of hardwood rangelands 1991-92 Planting blue and valley oak acorns and nursery stock Individual and site factors critical to reproductive strategies in central CA Effect of two livestock grazing strategies on survival & growth of blue oak saplings Evaluation of site and mgmt. factors important for natural regeneration Parker & Seidl (SFSU) Zedler & Lawson (SDSU) Lathrop & Griggs (Loma Linda Univ.) Riggs & Millar (Genentech) Plumb (Cal Poly) Rice, Welker & Menke (UCD) Adams (UCD) Koenig and Griffin (UCB) Jansen (CSU-Chico) Phillips (UCCE) 865 864 862 866 863 861 915 916 917 918 II. Maintenance of hardwood rangeland wildlife habitat CDF 1994-85 Silvicultural options in managed oak woodlands to benefit breeding birds. 1987-88 Habitat relationships in oak woodland Regionalizing WHR 1988-89 Wildlife habitat characteristics on hardwood rangeland riparian areas Noon (HSU) Morrison (UCB) Fitzhugh (UCD) Barrett, Weitkamp & Tietje (UCB) 42114 74574 4573 84963 UC 1986-87 Wildlife-habitat relationships in oak woodlands Breeding habitat of cavity nesting birds in hardwood range habitat 1989-90 Effect of urbanization on wildlife Effect of urbanization on wildlife in a large subdivision in Madera County 1991-92 Responses of wildlife to stand mgmt. Responses of wildlife to stand mgmt. Develop methodologies to evaluate the impacts of subdivisions on wildlife Morrison & Block (UCB) Noon & Waters (HSU) Scott (UCB) Duncan Morrison (UCB) Tietje (UCB) Sanders (Baersky and Assoc.) 868 869 891 892 912 913 914 III. Investigating the causes and impacts of land use change CDF 1985-86 Urban attitudes toward oak trees 1986-87 Inventory and analysis of the federal and state statutory environment for hardwood rangeland ownerships Analysis of local control of hardwood use protection Land utilization factors 1987-88 (none) 1988-89 Hardwood conservation incentives Hardwood resources guidelines Mitigation markets for hardwood rangeland Polaris R&D Green, Fairfax & Johnson (Pacific Meridian) Green, Doak, Fairfax & Johnson (Pacific Meridian) Doak (Pacific Meridian) Doak (Pacific Meridian) Tietje (UCB) Johnston (UCD) 53053 63762 63763 63967 84966 85304 85456 IV. Developing management strategies that contribute to the conservation of hardwood rangeland resources CDF 1984-85 Herbage production on hardwood range Bartolome, (UCB) 42137 UC 1986-87 Alternative management strategies for hardwood range Overstory canopy effects on forage production and utilization, and on soil characteristics Development of ranch model of California hardwood rangelands Price structures at big game hunt clubs 1991-92 Management of riparian uplands on hardwood rangelands to protect and enhance water quality Dennis (Jones & Stokes) Frost & Duncan (FSU) Standiford (UCB) & Howitt (UCD) Fitzhugh & Loomis (UCD) Allen-Diu (UCB) 8612 8616 8614 8613 911 V. Monitoring condition, status and use of hardwood lands CDF 1984-85 Monitoring system for oak removal California rangeland economy study Oak inventory 1986-87 Ecological type classification for hardwood rangelands California livestock industry economic model Assessment of California hardwood lands 1987-88 Hardwood rangeland soil and water quality 1988-89 Remote sensing for hardwood monitoring Grazing use information Hardwood rangeland reference mew Migratory deer mapping 1989-90 Monitoring hardwood resources Management response database Doak (Pacific Meridian) Gardner (UCD) Pillsbury (Cal Poly SLO) Allen (UCB) CH2M Hill Pillsbury (Cal Poly SLO) Harper (Jones & Stokes) Congalton (UCB) Tosta (real) Millar (PSW) Pillsbury (Cal Poly SLO) Pacific Meridian George (UCD) 42151 42134 42113 63912 63817 63963 74546 85458 85460 85461 85465 96121 96060 UC 1989-90 Long-term changes in structure and extent of oak vegetation types Genetic architecture and ecotypic variation in oaks Ecotypic, variation in blue oak Nutrient cycling in managed oak woodland grass ecosystems 1990-91 Ecological genetics of oak resistance to drought and herbivory Byrne, Edlund & Mewing (UCB) Riggs (Genentech) McBride (UCB) Dahlgren, Singer (UCD) & Firestone (UCB) Rice (UCD) 893 894 895 896 901\