ABLA/VASC Meters2 Biophysical
Total Page:16
File Type:pdf, Size:1020Kb
Table 2.1—Hierarchical relations between assessment scales and various types of ecosystem delineation. Biophysical Environments Existing Conditions Assessment Terrestrial Aquatic Vegetation Social Scale Units1 Units2 Units3 Assessment Units Global Domain Zoogeographic Region Class Continent Continental Division Zoogeographic Subregion Subclass Nation Regional Province River Basin Group State Subregion Section Subsection Subbasin Formation County Landscape Landtype Association Watershed/Subwatershed Series Community Land Unit Landtype Phase Valley Section/Stream Reach Association Neighborhood Site Ecological Site Channel Unit Species Individual 'ECO Map 1993 2USDA Forest Service 1994a 3Driscoll and others 1984 Example: ABLA/VASC 107 106 105 Fire Group 7 (0 ABLA Rocky Forests Mountain Subalpine 102 Forest ABLA Seecf\Snowbank Germination 104 106 108 1010 1012 Meters2 Plot/Stand Landscape i Ecoregion Continent ABLA=Subalpine Fir PICO=Lodgepole Pine VASC=Grouse Whortleberry Figure 2.2—An ecosystem characterization example of subalpine fir forests in the Northern Rocky Mountains. Biophysical 113 Ecological units (Bailey and others 1994a; Cleland » Geologic Environments and others, in press; McNab and Avers 1994), • Geoclimatic Ecological Units \,land units (Zonneveld 1989), ecoregions ^(Omernick 1987), biogeoclimatic ecosystems » Potential Vegetation Settings (Meidinger and Pojar 1991), and land systems * Hydrologic Environments (Christian and Stewart 1968) are examples of biophysical environment mapping systems that » Integrated Ecological Reporting Units delineate ecologically homogeneous environments Ecological pattern and process relations, successional at different spatial scales based primarily on climatic, pathway dynamics, and management potential/ geomorphic, and biotic criteria. Hierarchical hazard ratings were developed for these biophysical watershed/geoclimatic maps are additional examples environment maps to assist various SIT and Envi- of biophysical environment maps that are increas- ronmental Impact Statement (EIS) team efforts. ingly being used in aquatic system assessment Descriptions of these biophysical environments and efforts (Jensen and others 1996, Maxwell and suggestions concerning rJieir use and limitations in others 1995). ecological assessment activities are provided in The ecosystem components used in developing the following discussion. biophysical environment maps (for example, climate, landforms, geology, or soils) do not Geologic Settings change following most management activities; consequently, such maps provide a useful template Despite the fact that the geologic components of a for interpretation of data such as existing vegeta- biophysical environment do not change as a result tion that commonly display change following of management activity, geologic process rates may management treatments. These types of data change dramatically as a result of management. describe the "existing condition" of the landscape Geologic components and processes profoundly and are commonly associated with appropriate influence other ecosystem components and pro- biophysical environment settings in determining cesses, including current and potential vegetation the condition or "health" of an area. The effects of patterns and successional processes, as well as management practices on the landscape are most terrestrial and aquatic habitat and productivity, efficiently described by contrasting the "existing and human settlement patterns. Changes in condition" of an area with other managed or geologic process rates due to human activity may unmanaged areas of similar biophysical environ- also profoundly affect ecosystems through increased ment settings. This process minimizes the natural erosion, sedimentation, and toxic element release. variability among sites, facilitating more direct Human activity can also improve ecological condi- descriptions of the relations between observed tions through management activities diat preserve or landscape conditions and management treatments. mimic natural processes. From a human perspective, some important geologic processes are catastrophic; Biophysical environment maps may be delineated these include volcanic eruptions and dieir associated at different spatial scales (table 2.1) dependent effects, earthquakes, earth movements such as on assessment needs and the types of ecological landslides and rockfalls, and large floods. The patterns and processes to be predicted. Regional, influence of, and interactions between, geologic subregional, and landscape scales of biophysical processes and other ecosystem processes are environment maps were developed by the Land- described later in this chapter. The geologic scape Ecology Staff for use in the assessment of the environments that constrain such processes are Basin. These maps included: described below. 114 Biophysical General Description of the Geologic » Rocks that formed as oceanic crust and have Environments of the Basin since been transported onto continents by plate tectonics. The geologic components of any ecosystem can be subdivided into bedrock and surficial geologic * Flood basalts that cooled from giant lakes of lava. units. Bedrock geologic units are those that are » Volcanic rock formed by the present-day solid and underlie any unconsolidated surficial Cascade volcanos. materials. These two types of units affect and interact with other ecosystem processes at many * Sandstones, shales, and conglomerates that spatial and temporal scales. For example, erosion formed through erosion and deposition of rates for most bedrock types with associated "natural" older rocks. vegetative cover are generally low. Physical erosion * Carbonate rocks formed from animal remains. rates for unconsolidated surficial deposits (such as alluvium, loess, or glacial till) are commonly « Chemically deposited sedimentary rocks. higher than those found on bedrock units. Chemical Additionally, unique physical or chemical properties weathering rates determine the release of rock of lithologies such as serpentinite, some tuffs, and components, such as nutrients and toxic elements, carbonate rocks provide unique habitat for selected into the ecosystem. Disturbance of vegetative species that contributes to the landscape and cover, road building, mining, agriculture, urban- species diversity of the Basin. ization, dam building, and other human activities may profoundly increase the physical and chemical Different geologic processes have affected the weadiering rates of geologic materials. In a similar rocks of the Basin in numerous ways during the manner, such disturbances may also affect water course of geologic history. These processes (for retention or other characteristics of the rocks and example, erosion, deposition, consolidation, uplift, soils of an area in such a way that they no longer metamorphism, volcanism, and geochemical support predisturbance vegetation cover types. changes) have all occurred at different times Increased fluxes of sediment, toxic elements, and throughout the history of the Basin, resulting in nutrients, or decreased water flows caused by the different physiography, erosion characteristics, human activities may irrevocably alter ecosystem nutrient availability, and other landscape parameters processes and must be considered in land manage- present today. It is impossible, for example, to ment planning. An understanding of both the classify granite into a single erosion group or geologic environments and geologic processes of a characteristic. Although much of the granitic planning area are essential components of any rock of the Idaho batholith is crumbly and erodes ecological assessment effort. relatively easily, other granitic units (for example, rocks in the Bighorn Crags or the Sawtooth The lithologic characteristics of rocks within Mountain Range) display wide ranges in natural the Basin are diverse, which in many cases defies erosion rates. simple classification of rock types by ERU. Bed- rock geologic units within the Basin range in age Surficial geologic units may develop directly from Precambrian rocks older than 2.7 billion through physical and chemical weathering of years, to volcanic rocks formed during the Mt. bedrock geologic units, or they may be transported St. Helens eruption of 1980. Rocks include: from elsewhere as glacial till and alluvium, or as wind-blown dust, sand, or volcanic ash. Discus- » Those that crystallized deep within the earth's sion of the surficial geologic units of the Basin and crust from liquids or by metamorphism, and their related soil properties is presented later in which were subsequently exposed at the earth's this chapter. surface by erosion. Biophysical 115 Approach Used in Geologic Setting ment over the Basin within the next 10 years. The Description longer term metallic mineral resource potential of the Basin was displayed in maps of permissive or Geologic, hydrologic, and mineral resource data favorable rankings for the occurrence of 29 distinct were compiled, interpreted, and synthesized from mineral deposit types (Box and others, in press). published and unpublished sources and databases. The economic feasibility of development of as yet The earth science themes for the Basin assessment undiscovered mineral deposits in permissive areas were delineated and developed through collabora- was also described (U.S. Bureau of Mines 1995). tion with scientists from all SIT staff disciplines. In addition to their economic applications, such Individual digitized state geologic