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DEBORAH L. ROGERS Institute of Forest Genetics Pacific Southwest Research Station U.S. Forest Service Berkeley, California 28 CONSTANCE I. MILLAR Institute of Forest Genetics Pacific Southwest Research Station U.S. Forest Service Berkeley, California ROBERT D. WESTFALL Institute of Forest Genetics Genetic Diversity Pacific Southwest Research Station U.S. Forest Service Berkeley, California within Species ABSTRACT cies. Fortunately, tree improvement programs in the Sierra Ne- vada (both public and private cooperatives) have long used Based on our review of literature and survey of geneticists working sophisticated and ecologically appropriate genetic diversity and on California taxa, we find genetic information lacking for most spe- genetic conservation guidelines. Similarly, in operational forest cies in the Sierra Nevada. This situation is likely to remain in the regeneration, federal, state, and local regulations regarding future, with specific groups of taxa or occasional rare or high-interest genetic diversity in planting mostly have high standards and species receiving specific study. Where we do have empirical infor- are backed by a fair amount of research. Seed banks exist for mation, we find few generalities emerging, except occasionally within public and private reforestation that maintain high standards of closely related or ecologically similar taxa. Despite these difficulties seed origin and genetic diversity, although exigencies presented in assessing genetic diversity, we direct attention to situations esti- by potentially large, severe wildfire may not be adequately met. mated to be most deserving of attention from a genetic standpoint. The focus for seed banking is the commercial conifers, and only slowly has seed banking emphasized other species with Severe wildfire: With the significantly increased risk of severe storable seeds. These programs, which have histories of sev- fires currently facing the Sierra Nevada, large, stand-replacing eral decades in the Sierra Nevada, serve as models for other fires present significant risks to gene pools of most middle- and taxa where similar activities occur (e.g., fish stocking). low-elevation Sierran forests, with direct and indirect conse- Research is inconclusive about the long-term genetic con- quences to the genetic diversity of plants and animals that live sequences of timber harvest on commercial tree species. Nev- in them. ertheless, traditional silvicultural practices, which were designed primarily to maximize growth of the target species, tended to Habitat alteration: For most taxonomic groups evaluated in the result in spatial patterns of harvest and live-tree retention that Sierra Nevada, the major threat to genetic diversity is habitat acted in concert with genetic conservation guidelines. By con- destruction, degradation, or fragmentation. Estimated effects trast, some new forestry practices, which combine fiber pro- involve not only direct losses of population-level genetic struc- duction with ecological stewardship for wildlife and nontimber tural diversity but also changes in genetic processes (gene flow, species, may have potential for minor dysgenic effects on na- selection), effective population sizes, and genetically based fit- tive timber species. For instance, leaving clumps of trees, es- ness traits. High-priority areas would be the foothill zone on the pecially suppressed individuals (e.g., for wildlife protection) may west slope, several of the trans-Sierran corridors (especially in promote inbreeding or lowered fitness if the members of the the central Sierra Nevada), and scattered locations of concen- clumps are related, as they appear to be. trated development elsewhere. Ecological restoration: Practitioners of ecological restoration Silviculture: Management actions that are extensive across the have only recently become aware of genetic concerns in plant- landscape yet intensive in manipulating individuals and popu- ing. Although many programs focus on restoring correct native lations have the greatest theoretical potential (but limited if no species, an understanding of the appropriate genetic material empirical evidence) for direct and significant genetic effects. within species, its origin, diversity, and collection, remains miss- As such, silvicultural activities, including tree improvement pro- ing or rudimentary in many programs. Thus, genetic contami- grams, operational forest regeneration (artificial and natural), nation problems may be more severe than if exotic species and timber harvest, potentially affect gene pools of target spe- Sierra Nevada Ecosystem Project: Final report to Congress, vol. II, Assessments and scientific basis for management options. Davis: University of California, Centers for Water and Wildland Resources, 1996. 759 760 VOLUME II, CHAPTER 28 had been planted. The significance of this genetic threat in the the harvesting of special forest products (especially mushrooms Sierra Nevada is lowest in projects of ecological community and other fungi, ladybird beetles, lichens, etc.), the use of bio- restoration and highest in postfire erosion control projects. Fre- cides with wide action against native insects, and forest-health quently these involve grass species and occasionally forb mixes. practices whose goals are to reduce or eliminate populations Although exotic grasses (especially rye grass) previously were of native insects and pathogens. used routinely, native grasses are increasingly becoming fa- Land management: Most human-mediated (as well as natural) vored. There is often little understanding of the potential ge- activities have some genetic consequences. The question is netic consequences of planting seeds of native species but not whether we create genetic change, but which effects are unknown (often commercial nursery) origins. significant enough to warrant altering our behavior. In general, Fish management: Management of fish species and genetic there has been a pervasive lack of awareness of the potential diversity within species in the Sierra Nevada is done in a way genetic consequences of land management, from local prac- that potentially disrupts many native gene pools. The introduc- tices to regional landscape plans. Genetic awareness, evalua- tion of hatchery, nonlocal, and genetically altered genetic stocks tion, prescription, mitigation, monitoring, and restoration have of native fish species has had the direct effect of creating con- generally been very low in public and private management and ditions for intraspecific hybridization, gene contamination, and have been concentrated in a few land-use programs (e.g., tree gene pool degradation. Indirectly, the introduction of exotic regeneration). Although it is broadly recognized that most man- fishes has large effects on biodiversity through displacement agement actions have effects on wildlife, there are few instances of native fish species and impacts on aquatic invertebrates and where environmental analyses—for instance in National Envi- amphibia, which affects gene pools through loss of populations. ronmental Policy Act (NEPA) contexts—have considered ge- netic effects. Land-management agencies do not place Range improvement: Similar to fish management, although geneticists broadly throughout the Sierra Nevada, and genetic lesser in effect in the Sierra Nevada, is the direction and intent knowledge usually resides centralized (e.g., with tree improve- of range improvement projects. In past decades, range shrubs, ment headquarters) or within silviculture staffs, where it is fo- particularly bitterbrush, were widely planted in Great Basin ar- cused mostly on the already established genetic management eas (on the border of the Sierra Nevada) to improve range- programs of commercial timber species. lands for cattle. Very little of the shrub germ plasm planted in the past derived from local seed zones or followed genetic di- What is needed is a general awareness that genetic consequences versity guidelines that maintain native genetic structure. More must be considered and evaluated for land-management activities in recently, shrubs have been planted for wildlife habitat enhance- general, and a framework and strategy for doing so. It is not enough ment. These are increasingly falling under seed transfer and to lump these concerns under general biodiversity evaluation, since genetic diversity guidelines, with the result that native local this often takes into account only immediate effects on the popula- seeds are being collected and planted. tion or species viability of a few indicator species. This chapter pro- Exotic pathogens: Exotic pathogens create direct and indirect poses some management guidelines and standards for preserving genetic threats in the Sierra Nevada. For example, white pine and enhancing genetic diversity in the Sierra Nevada. blister rust is fatal to sugar pines that carry the susceptible gene. The resistant gene exists naturally in very low frequencies in sugar pine. Although a well-funded and genetically sophisticated program exists for developing and outplanting sugar pine that is resistant to white pine blister rust, there has been limited INTRODUCTION recognition of the genetic consequences of the current federal harvest practices for the species. At present, known resistant Genetic diversity is not a front-page, public issue. Whereas old-growth sugar pines are not cut, but susceptible trees may species extinctions, loss of old-growth forests, and degrada- be harvested, and in areas where resistance is unknown,

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