 SCOPE AND BACKGROUND OVERVIEW OF SIERRA NEVADA ECOSYSTEMS AND ASSESSMENT STATUS MANAGEMENT STRATEGIES FOR ECOSYSTEM SUSTAINABILITY INSTITUTIONAL INTEGRATION OF ASSESSMENTS AND SOLUTIONS
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rev. Jun. 17, 1996 |
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* Institutions Institutional Incapacities Many Sierran ecosystem declines are due to institutional incapacities to capture and use resources from Sierran beneficiaries for investment that sustains the health and productivity of the ecosystems from which benefits derive. The costs of achieving desired objectives for conservation and ecosystem restoration in the Sierra are greater than available resources. Public funding sources (federal, state, and local governments) have not met the need or demand. Current economies are such that money obtained from using Sierran resources (water, timber, recreation, grazing) is inadequate for restoration, conservation, and ecosystem management. Institutions and communities have not effectively informed the public about real costs or responded with creative approaches for funding conservation. Sources of Institutional Incapacities Institutional incapacities arise from four primary sources: (1) fragmented control of ecosystems among different jurisdictions, authorities, and ownerships, (2) absence of exchange mechanisms among these entities to sustain rates of investment and cooperative actions that reflect ecosystem values, (3) detachment between those who control ecosystems and communities that depend upon and care for them, and (4) inflexibility in response to rapid changes in population, economy, and public interests. Existing institutional capacities and arrangements do not adequately support planning and management at the Sierra-wide scale for issues whose natural scales are at that level. Interwoven patterns of private and public land ownership in portions of the Sierra Nevada create conditions that impede the attainment of management objectives because of the difficulty of merging divergent goals across a landscape. Regionalism The sources of institutional capacity and of potentials to improve upon capacity differ among the regions of the Sierra, which vary greatly in their institutional as well as ecological, demographic, and economic characteristics. The pattern of regions in the Sierra (i.e., delineation of number of regions, size, boundaries, and characteristics) also varies by issue, although enough commonalities exist to generally define five or six distinct regions that reflect most issues. * Fire and Fuels Ecological Functions of Fire Fire is a natural evolutionary force that has influenced Sierran ecosystems for millennia, influencing biodiversity, plant reproduction, vegetation development, insect outbreak and disease cycles, wildlife habitat relationships, soil functions and nutrient cycling, gene flow, selection, and, ultimately, sustainability. Most vegetation types below the subalpine zone have been highly influenced by and are adapted to regular fire. Effects of Climate Climatic variation plays an important role in influencing fire patterns and severity; fires have been most extensive in periods of dry years. During cool-climate periods of the past centuries, fires were less numerous but larger than during warm-climate periods. Presettlement Fire Regimes In most low-elevation oak woodland and conifer forest types of the Sierra Nevada, presettlement fires were frequent, collectively covered large areas, burned for months at a time, and, although primarily low to moderate in intensity, exhibited complex patterns of severity. Locally severe fires occurred and played an important role in forest dynamics. It is unclear what spectrum and frequency of patch sizes (a few acres to thousands of acres) were created by severe fire; however, contiguous areas of predominately high-intensity fire larger than a few thousand acres almost certainly were much less common than today. Effects of Suppression Fire suppression in concert with changing land-use practices has dramatically changed the fire regimes of the Sierra Nevada and thereby altered ecological structures and functions in Sierran plant communities. Alterations have occurred especially in plant communities historically influenced by frequent low- to moderate-intensity fire. Fuel Conditions Live and dead fuels in todays conifer forests are more abundant and continuous than in the past. Many factors have affected fuel quantities and distribution in Sierran forests, including variation in climate, timber harvest, mining, grazing, human settlement patterns and land-use practices, and nearly a century of fire suppression. Effects of Logging Timber harvest, through its effects on forest structure, local microclimate, and fuel accumulation, has increased fire severity more than any other recent human activity. If not accompanied by adequate reduction of fuels, logging (including salvage of dead and dying trees) increases fire hazard by increasing surface dead fuels and changing the local microclimate. Fire intensity and expected fire spread rates thus increase locally and in areas adjacent to harvest. However, logging can serve as a tool to help reduce fire hazard when slash is adequately treated and treatments are maintained. Fire Size Trends The commonly expected consequence of decades of fire suppressionthat large, infrequent fires are becoming larger and small, frequent fires smalleris generally not confirmed by records for twentieth-century Sierran forests. The central western Sierra Nevada is the only region where evidence exists that this pattern has occurred. This region has experienced the greatest increase in human population, which has affected both the incidence of fire ignitions and the suppression strategies once fires have begun. By contrast, the Plumas National Forest has had no change in the observed size and frequency of fires during this century, and in SequoiaKings Canyon National Parks small, frequent fires are larger and large, infrequent fires are smaller than before 1950, that is, the opposite pattern to that in the central western Sierra Nevada. The latter observations are complicated by the active prescribed fire-management program in the parks, the results of which are included in these data. Fire Surrogates Although silvicultural treatments can mimic the effects of fire on structural patterns of woody vegetation, virtually no data exist on the ability to mimic ecological functions of natural fire. Silvicultural treatments can create patterns of woody vegetation that appear similar to those that fire would create, but the consequences for nutrient cycling, hydrology, seed scarification, nonwoody vegetation response, plant diversity, disease and insect infestation, and genetic diversity are mostly unknown. Similarly, although combining managed fire with silvicultural treatments adds the critical effects of combustion, the ecological effects and fire hazard reduction of this approach are largely unknown. Urban-Wildlands Intermix Projected trends in urban settlementhomes intermixed with flammable wildlandsplace an increasing number of homes and people at high risk of loss from wildfire unless hazards are mitigated. Current fuel levels and projected future uses, especially in the west-central Sierra Nevada foothills and lower mixed conifer zones, are incompatible without active fuel management. The presence of homes can force changes in suppression strategies and increase suppression costs. 
 
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