ECOSYSTEM MAPPING METHODS FOR BRITISH COLUMBIA A. B A N N E R and D.V. M E I D I N G E R British Columbia Ministry of Forests, Research Branch, 31 Bastion Square, Victoria, British Columbia, V8W 3E7, Canada and E.C. L E A , R.E. M A X W E L L and B.C. V O N S A C K E N British Columbia Ministry of Environment, Lands, and Parks, Wildlife Branch, 780 Blanshard Street, Victoria, British Columbia, VSV 1X4, Canada
Abstract. Most resource professionals in British Columbia recognize the value of ecosystem classification in providing a conceptual framework and common language for organizing ecological information and management experience about ecosystems. Ecosystem mapping utilizes principles of ecosystem classification in order to provide a permanent record of the location and distribution of ecosystems. This spatial framework is often required for developing, applying, and monitoring landscape level and site-specific management prescriptions for many potential resource values. Over the past 20 years, several approaches to ecosystem mapping have been applied throughout the province. Standard procedures for provincial resource inventories and standards for medium and large scale ecosystem mapping (1:10 000 to 1:100 000 scales) have recently been proposed for the province. The proposed mapping approach combines dements of two classification systems currently in use in the province: ecoregion classification and biogeoclimatic ecosystem classification (BEC). Ecoregion and biogeoclimatic units stratify the landscape into broad physiographically and climatically uniform units. Within this broad framework, permanent landscape units are then delineated based on terrain features. Ecosystem units represent the lowest-level mapping individuals and are derived from the site series classification within BEC. Ecosystem units thus reflect moisture and nutrient regime and the climax vegetation potential of the site. Additional site modifiers are included to recognize variation in topography and soils within the site series. Structural stage and seral association modifiers are included to describe existing vegetation characteristics. The mapping methods present a core list of attributes required for basic resource interpretations, as well as additional attributes required for more specific interpretations.
1. Introduction
In British Columbia, ecological land classification has become a standard tool in resource management and planning (MacKinnon et al., 1992). It is used both for broad-level planning, as in the development of a protected areas strategy for the entire province (95 million ha), and for site-specific planning, as in the development of a silvicultural prescription for individual cutblocks (Mah et al., this volume). Ecological classification is applied province-wide using a combination of descriptive and interpretive field guides (e.g., Braumandl and Curran, 1992; Banner et al., 1993; Green and Klinka, 1994) and maps (e.g., Pojar et al., 1988; B.C. Ministry of Forests, 1992; Demarchi, 1993). To date, however, province-wide mapping has been restricted to delineation of broad ecological units (biogeoclimatic units and Environmental Monitoring and Assessment 39:97-117, 1996. (~) 1996 Kluwer Academic Publishers. Printed in the Netherlands.
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ecoregion units) at relatively small scales (1:2 000 000 to 1:250 000). Detailed site- or ecosystem-level mapping, at scales of 1:5 000 to 1:10 000, is carded out as part of the legislated silviculture prescription process for individual harvest blocks. Some large scale (1:10 000 to 1:50 000) ecosystem (or "habitat") maps have also been produced for several study areas throughout the province, either as base line information for research projects (Klinka, 1976; Klinka and Skoda, 1977; Banner et aL, 1986) or for operational planning purposes (Klinka et al., 1980; Inselberg et al., 1982; Lindeburgh and Trowbridge, 1985; Mitchell and Eremko, 1987; Courtin et al., 1989; Lea et al., 1990; Cichowski and Banner, 1993). While an ecosystem classification provides the taxonomic framework for describing the nature and pattern of ecological units within a landscape, an ecosystem map depicts the actual spatial distribution of these ecological units. More and more, ecosystem mapping is considered to be a necessary tool in the development of management plans for medium to large sized landscape planning units. With the increased demand for ecosystem mapping throughout the province has come the need for standard mapping methods. The provincial Ministry of Forests and Ministry of Environment, Lands, and Parks have cooperated on documenting such methods based on their pooled expertise and experience in ecosystem classification and mapping over the past 20 years. This paper summarizes these methods. A more detailed account has also been recently produced (Resources Inventory Committee, 1995).
2.
Rationale, History, and Background
Ecosystem mapping can be defined as the stratification of a landscape into map units based on ecological criteria, primarily climate, physiography, surficial material, soil, and vegetation. Why do we need an ecosystem map? Here are five practical reasons: - It provides a biological and ecological framework for land management. - It integrates abiotic and biotic ecosystem components on one map. - It provides basic information on the distribution of ecosystems from which management interpretations can be developed, from broad-scale landscape planning to site-specific interpretations. - It provides an historic record of ecological site conditions that can be used as a framework for monitoring ecosystem response to management. - It is an excellent demonstration tool for portraying ecosystem and landscape diversity. Although ecosystem classification and mapping are closely related activities, the linkage between these two procedures is not necessarily direct and straightforward. A classification describes synthetic conceptual units that are used as a basis for delineating and labelling discrete polygons, possessing a certain set of attributes, on a map. Depending on the specific objectives of a survey, the level of detail
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required, and the approach of the mapper, a single classification system can give rise to many different types of map products. Ecosystem mapping is especially challenging because of its multi-disciplinary nature. An ecosystem map attempts to integrate five disciplines or types of information (see above) on one map; it describes ecological site potential, physical site characteristics, and present stand condition. Although an ecosystem classification forms the basis for the map units, other classifications (such as terrain and soils) are utilized as well, either directly in polygon labels or indirectly in map legends or polygon attribute (data) files. These factors, in addition to the historical development of two distinct ecosystem classification approaches (biogeoclimatic ecosystem classification and biophysical habitat classification) in B.C., have given rise, over the past 15 to 20 years, to the development of several ecosystem mapping approaches within government agencies, universities, and by private consultants. Two recent government initiatives in B.C. have emphasized the need to produce one standard methodology for mapping terrestrial ecosystems in the province: the Resources Inventory Committee (RIC) and the Forest Practices Code (FPC). The Resources Inventory Committee was formed in 1991 to address the concerns outlined in the report of the Forest Resources Commission (1991), regarding the inadequacies and narrow scope of the existing natural resources inventory of the province (Anonymous, 1993). Through RIC, standard inventory methods are being produced for many disciplines, including terrestrial, aquatic, and marine ecosystems, earth and atmospheric sciences, and cultural resources, with the view toward increasing the scope and integration of the provincial inventory. The ecosystem mapping methods presented here are one of many standardized methodologies resulting from the RIC initiative. The recently implemented Forest Practices Code sets out legal requirements for environmentally sound forest practices in British Columbia, from the landscape planning stage through to the preparation and implementation of site specific management prescriptions (B.C. Ministry of Forests, 1994). The standardized inventory and mapping methods developed through RIC will play an important part in the implementation of the code.
3. Approach and Concepts 3.1. OVERVIEW OF MAPPING APPROACH
The approach to ecosystem mapping presented here represents a refinement and amalgamation of two previous mapping methods documented for B.C. (Mitchell et al., 1989; Demarchi et al., 1990a). Our goal was to build on the collective experience with mapping and field methods that have been tested and proven effective in different parts of the province.
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TABLE I Hierarchy of ecoregion classification levels used in British Columbia. Ecodomain
Ecodivision
Ecoprovince
Ecoregion
Ecosection
4 units
7 units
10 units
43 units
110 units
Humid Continental Highlands
Central Interior
Fraser Plateau
Bulkley Basin
Example: Humid Temperate
While the Ministry of Forests' mapping methods (Mitchell et al., 1989) have emphasized forestry (especially silvicultural) interpretations, the Ministry of Environment, Lands, and Parks' methods (Demarchi and Lea, 1987; Demarchi et al., 1990a) have emphasized wildlife habitat interpretations. The provincial methods outlined in this paper provide guidelines and standards for compiling map information necessary for interpretations related to five broad subject areas: forest management, range management, wildlife management, soil management and biodiversity management. The specific objectives of any mapping project will determine the survey intensity level chosen and the actual field data collected. These standards are designed to be applied at scales between 1:5 000 and 1:100 000, though they are best suited to scales larger than 1:50 000. Ecosystem unit polygons (site level map units), representing areas from less than one hectare to several hundred hectares, depending on scale, are displayed within larger ecoregion and biogeoclimatic polygons (landscape level map units), that typically encompass several thousand to several hundred thousand hectares. 3.2. CLASSIFICATION CONCEPTS 3.2.1. Ecoregion classification Ecoregion classification provides a hierarchical, systematic description of the geography of British Columbia (Demarchi et al., 1990b; Demarchi, 1993). The classification is based on the interaction of macroclimatic processes (Marsh, 1988) and physiography (Holland, 1976; Mathews, 1986). Ecoregion classification stratifies the province at five levels of generalization (Table I). The geographic units defined within each of the levels circumscribe all elevations. The classification defines geographic areas in general climatic and physiographic terms, from the very broad, global context (ecodomains and ecodivisions) to the more detailed, local levels (ecoprovinces, ecoregions, and ecosections). The ecosection level, comprising 100 terrestrial units in B.C., is the level generally applicable to medium to large scale
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TABLE II Hierarchy of biogeoclimatic classification levels used in British Columbia. CLIMATE (ZONAL) LEVEL Zone Subzone
Variant
Phase
0--5variants per subzone; +/-160 subzone/vafiants currently recognized
used as needed to describe very localized climatic variation within subzoneJvariants; currently only 6 phases recognized
Example (see Figures 1 and 2): Sub-boreal Moist Cold Subzone Spruce Zone (SBS) (SBSmc)
Babine Variant (SBSmc2)
cold air drainage phase (hypothetical)
SITE LEVEL Site association
Site series
Site type and phase
about 1100 site series currently recognized
used as needed to describe variation in environmental properties within site series (relatively few described to date)
14 zones in B.C.
about 500 site associations currently recognized
1-30 subzones per zone: +/-90 subzones currently recognized
Example (see Figure 2): Spruce - Huckleberry SBSmc2/01 SpruceHuckleberry
SBSmc2/01(a) fine-textured phase
ecosystem mapping. Figures 1 and 2 illustrate the relationship between ecoregion and biogeoclimatic classification and mapping within a portion of the Prince Rupert Forest Region, northwestern B.C. Three ecosections are highlighted on the map. The Bulkley Ranges (BUR) represents a small mountain range leeward of the coast mountains; the Bulkley Basin (BUB) represents a broad continental lowland area; and the Nass Ranges (NAR) represents a mountainous coast/interior transitional area. Each of these ecosections can be further divided on the basis of climate and zonal vegetation into biogeoclimatic units (see below). 3.2.2. Biogeoclimatic ecosystem classification (BEC) Biogeoclimatic ecosystem classification (BEC) describes variation in climate, vegetation, and site conditions in British Columbia. BEC is also hierarchical with separate climate and site levels (Table II). Pojar et al. (1987) and Meidinger and Pojar (1991) describe the system in detail.
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Fig. 1. An example of ecoregion and biogeoclimatic classification from the Prince Rupert Forest Region, northwestern British Columbia (adapted from Pojar etal., 1988). See Figure 2 for explanation of symbology.
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a) Variation in climate and broad vegetation patterns within ecosections is described by biogeoclimatic zonation
Ecosection
Biogeoclimatic Zone
9 Bulkley Ranges ( B U R ) Z
lnterior(icH)Cedar-Hemlock Zone
* Bulkley Basin (BUB) ~
Sub-boreal Spruce Zone (SBS) Engelmann Spruce - Subalpine Fir Zone (ESSF)
* Nass R a n g e s ( N A R )
x~,
b) Biogeoclimatic subzones describe further variation in climate and broad vegetatiou patterns within zones Biogeoclimatic Zone 9 Interior Cedar - Hemlock Zone ~ (ICH) / 9 Sub-boreal Spruce Zone (SBS) ~ 9 Engelmann Spruce - Subalpine Fir Zone (ESSF)
Biogeoclimatic Subzone Sub boreal Spruce dry cool subzone (SBSdk) Sub-boreal Spruce moist cold subzone (SBSmc)
c) Tile site series describes the major variation in ecological site potential within biogeoclimatic subzones and variants 9 Sub-boreal Spruce dry cool subzone (SBSdk) 9 Sub-boreal Spruce moist cold subzone (SBSmc)
Site-level classification (site potential)
Site Series 01 Spruce - Huckleberry
(SH) 0~2Pine - ttuckleberry - Cladonia (PH) {]6 Spruce - Oak fern '~ (OF) 09 Spruce - Devil's club
T
{DC)
I 0 Spruce - Horsetail
{HT} Fig. 2. An example of ecosystem classification levels within the Bulkley Basin ecosection in northwestern British Columbia. See also the map illustration in Figure 1.
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3.2.2.1. Climate level of BEC At the climate level, 14 biogeoclimatic zones are recognized within B.C. Zones represent large geographic areas with a broadly homogeneous macroclimate. Subzones, variants, and phases are recognized within zones and these represent finer subdivisions, based on regional and local climatic variation that is reflected in zonal vegetation patterns. To date there are about 90 subzones recognized within B.C. and many of these have two or more variants occurring within them. Only a few phases are recognized. Biogeoclimatic zonation within ecosections is illustrated in Figures 1 and 2. Each of the highlighted ecoregions incorporates valley bottom to mountain top environments as well as north-south and east-west gradients. The resulting climatic variation is captured by the biogeoclimatic stratification within ecosections. For example, the Bulkley Basin (BUB) ecoregion includes areas predominantly within the valley bottom to montane Sub-boreal Spruce (SBS) zone but also includes subalpine areas of the Engelmann Spruce - Subalpine Fir (ESSF) zone and very minor areas of the Interior Cedar - Hemlock (ICH) and Alpine Tundra (AT) zones. Still further climatic differentiation within the SBS zone is described at the subzone level; the SBSdk or dry cool subzone occupies the valley bottoms and lower slopes, and the SBSmc, or moist cold subzone occurs at higher elevations between the SBSdk and the ESSF zones. The SBSmc is widespread elsewhere in the northern half of the province, but is here represented by the Babine variant (SBSmc2). 3.2.2.2. Site level of BEC Variation in site conditions encountered within a biogeoclimatic unit is accommodated within the site level of BEC. The site series describes all land areas capable of supporting a specific climax plant association and reflecting a specified range of soil moisture and nutrient regimes within a subzone or variant. Figure 2c illustrates the site series classification for the SBSmc2. Ecologically equivalent site series occurring under more than one climatic regime (i.e., in more than one subzone or variant) are grouped together to form a site association. For example the Spruce-Huckleberry site series within the SBSmc2 belongs to a widespread site association that spans many subzones of the SBS (see Meidinger and Pojar, 1991 for more details). The concept of the zonal site is central to BEC. Zonal sites exhibit intermediate soil moisture and nutrient conditions and thus best reflect the regional climate. Subzones and variants are identified and differentiated on the basis of the zonal site series. Classification at the site series level emphasizes climax site potential and forms the basis for defining the ecosystem units used in ecosystem mapping; additional components such as the site modifier, structural stage, and seral association are added to the site series designation to better describe existing stand conditions within map polygons.
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3.3. MAPPING CONCEPTS 3.3.1. Terminology Some definitions of terms are required to avoid confusion in the following discussion of mapping concepts. Further details on mapping terminology can be found in Valentine (1986) and Mitchell et al. (1989). MAP POLYGON: Map delineations that represent discrete areas on a map bounded by a continuous line. Map polygons are labelled according to the map units they contain. On an ecosystem map, polygons depicting ecosystem map units are nested within larger polygons containing the biogeoclimatic and ecosection map units. Polygons depicting ecosystem map units represent areas from less than one hectare to several hundred hectares, depending on scale. Polygons depicting ecoregion and biogeoclimatic map units typically encompass several thousand to several hundred thousand hectares. MAP UNITS: Map units are established as a result of applying a classification to map polygons. Ecosystem maps contain three kinds of map units: ecoregion map units, biogeoclimatic map units, and ecosystem map units. These are derived from the three levels of classification used in ecosystem mapping. Ecoregion and biogeoclimatic units are always mapped as "pure" map units. Ecosystem map units are either "pure" (composed of one ecosystem unit) or "complex" (composed of up to three ecosystem units). All ecosystem map units may have minor inclusions that are too small to map at the scale of the survey. These inclusions should generally comprise less than 20% of the polygon. 3.3.2. Bioterrain mapping approach Terrain classification and mapping is integral to ecosystem mapping. Our methods utilize a "bioterrain" approach to ecological mapping whereby ecosystem or bioterrain unit polygons are developed from an initial stratification of air photos based on permanent terrain features, utilizing the Terrain Classification System for British Columbia (Howes and Kenk, 1988). Terrain units are then further refined or "enhanced" by recognizing the biologically significant attributes within them that control ecosystem development. Factors such as inferred moisture, nutrient, and temperature/solar radiation regimes (as indicated by vegetation characteristics, slope position, aspect, soil depth and texture) and disturbance history are used to further subdivide the initial terrain polygons according to the ecosystem units they contain. The finalized polygons that result can then be displayed either as bioterrain map units or as ecosystem map units or both, depending on the requirements of the user. Resources Inventory Committee (1995) presents a more detailed description of bioterrain mapping. 3.3.3. Components of ecosystem units Ecosystem units incorporate the site series of BEC in addition to site modifiers, structural stages, and in some cases seral associations. Symbology for ecosystem
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Symbology for Ecosystem Units Spruce - Huckleberry (site series)J.
Tall shrub (structural stage)
S H kc 3b wa cool aspect, coarse-textured (site modifiers)
Willow-Aider Woodland (seral association)
Fig. 3. Standardized mapping symbology for ecosystem units.
units is portrayed in Figures 3 and 4. Each of the separate components will be briefly outlined here: SITE SERIES: (see definition above) The site series forms the basis of ecosystem units and indicates climax site potential. All currently defined site series for the province have been given two-letter connotative codes (Resources Inventory Committee 1995). Examples for the SBSmc2 are presented in Figure 2. Additional codes for previously unclassified units as well as anthropogenic and other special sites (clearings, cultivated fields, rock outcrops etc.) are also being compiled. SITE MODIFIERS: Site modifiers are used to more specifically characterize site conditions where they differ significantly from the modal conditions expected (i.e,, described in the legend) for a site series. A list of standard site modifiers has been developed (Resources Inventory Committee, 1995) and others may be added on a project-specific basis. Some examples are: topography (gullying -g, ridgetop -r, terrace -t); moisture (drier than average -x, moister than average -y); and soil (coarse-textured -c, peaty -p). STRUCTURAL STAGE: While the site series describes site potential, actual stand conditions will vary considerably, depending on disturbance history, stand age, species composition, and chance. The structural stage describes the dominant stand appearance or physiognomy at the time of mapping. Structural stage categories (modified from Hamilton, 1988) are listed in Table III. SERAL ASSOCIATION: The seral association may be used to describe present vegetation where the site series is not in climax or near-climax state. The seral association is defined as a non-climax plant association, differentiated using a diagnostic combination of species, and belonging to the successional sequence of ecosystems within one or more site series. The seral classification within BEC has only been developed for very localized areas in the province and will only be applied on a project-specific basis where study objectives warrant this degree of
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Fig. 4. Example of ecosystem mapping from the Sub-boreal Spruce, moist cold subzone (Bulkey Basin ecosection), northwestern British Columbia (adapted from Mackenzie and Banner, 1991; approx, scale is 1:10 000). Ecosystem unit symbology is described in Figure 3. Abbreviations for the map unit components are explained in Figure 2 and Tables III and IV.
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TABLE III Structural stage categories used in ecosystem mapping. 1a
lb 2 3a 3b 4 5 6 7
Non-vegetated Sparse Herb Low Shrub Tall Shrub Pole/Sapling Young Forest Mature Forest Old Forest
TABLE IV Some examples of seral associations used in the Sub-boreal Spruce, moist cold subzone (SBSmc) in northwestern British Columbia. Site series
Seral associations
Spruce - Huckleberry (SH)
Pine - H u c k l e b e r r y - M o s s ( p m ) Mixed Wood (mw) Willow - Alder Woodland (wa)
Pine - Huckleberry - Cladonia (PH)
Mixed Wood (mw) Aspen - Willow Woodland (aw)
Spruce - Oak fern (OF)
Mixed Wood (mw) Willow - Alder Woodland (wa) Thimbleberry - Alder Mixed Shrub (ta)
detailed vegetation description. S o m e e x a m p l e s o f seral associations occurring in the S B S m c 2 are described in Table IV. Each o f the a b o v e c o m p o n e n t s collectively m a k e up individual e c o s y s t e m units. although s o m e o f these c o m p o n e n t s will not always be used (i.e., site modifiers and seral associations). E c o s y s t e m units m a y be m a p p e d as simple m a p units, containing only one e c o s y s t e m unit or as c o m p o u n d m a p units, containing 2 to 3 distinct e c o s y s t e m units in an estimated (decile) proportion (see Figure 4). 3.3.4. Components of ecoregionlbiogeoclimatic units E c o s y s t e m p o l y g o n s are nested within larger ecoregion/biogeoclimatic polygons. T h e s e larger p o l y g o n s will be labelled according to the ecosection and biogeocli-
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matic units they represent, using standard abbreviations (Meidinger and Pojar, 1991; Demarchi, 1993) (Figure 4). Ecosections and biogeoclimatic units will always be mapped as simple map units because they depict relatively broad, physiographically and climatically controlled concepts rather than discrete ecosystem or bioterrain units on the ground. Because ecosection and biogeoclimatic map unit boundaries are relatively "fuzzy", for simplicity, their polygon boundaries are generally made to coincide with ecosystem map unit boundaries.
4. Polygon Attributes and Interpretations Our methods assume that a digital map with an associated polygon database will be produced for each mapping project, using one of the many geographic information system (GIS) software packages currently available. The number of individual data attributes that could potentially be recorded for each map polygon in such an ecosystem map database is very large, in comparison to the information actually portrayed in a map unit label. The interpretive power of the map is indeed dependant on the scope of information stored in the map database. Through discussions with a wide range of potential users of ecosystem maps, we have grouped potential interpretations into five broad subject areas. Table V lists a few example interpretation topics under each of these subject areas. It was then possible to look at which information requirements are common to many or all topics and which are specific to only a few. From this, we have developed minimum standards for the core polygon data required for "baseline" ecosystem maps and then outlined additional data attributes that are required to make more specific interpretations. Table VI lists the core attributes and provides some examples of additional attributes required to make some specific forest management interpretations. This approach provides some guidelines on establishing data requirements when designing a mapping project. The final decision on which attributes (over and above the core attributes) are estimated for each polygon will be determined by the survey objectives, financial constraints, as well as time and other logistical constraints. A complete list of interpretation-specific attributes is provided in Resources Inventory Committee (1995). This list will require modification as more experience is gained in developing site interpretations. Also, many mapping projects will have some unique data requirements that will have to be added on a project by project basis.
5. Overview of Mapping and Field Survey Procedures Survey and mapping procedures for ecosystem mapping are outlined in detail in Resources Inventory Committee (1995). Only a brief summary of mapping
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A. BANNERET AL. TABLE V Examples of interpretations supported by ecosystemmapping under five general interpretation subject areas. Interpretation subject area Exampleinterpretations Forest management
Site index/productivity Vegetation potential Tree species selection
Range management
Livestock capability rating Noxious weed potential Season of use
Soils management
Site sensitivity/hazard assessment Agricultural capability Waste management
Wildlife management
Wildlife capability/suitability Forage potential Habitat description
Biodiversity management
Landscape-level biodiversityplanning Gap analysis - ecosystemconservation Riparian/wetland management
procedures and standards for survey intensity levels, and field sampling methods is provided here. 5.1. PROJECTPLANNING Proper and thorough planning is critical to the successful completion of an ecosystem mapping project. The objectives of the project should be clearly defined in a working plan so that the correct balance between survey intensity level and desired map product is decided on and achieved within the available budget. Table VII provides some guidance on choosing survey intensity levels appropriate to project objectives. Once the study area is defined and objectives established, all available data, reports, and maps relating to the natural resources of the area should be collected to aid in ecosystem mapping. Available aerial photography, both current and historical, of a scale equal to or larger than the desired final map scale must be obtained. Colour photography is preferable but not essential. A good quality, up-to-date base map
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TABLE VI Polygon attribute requirements for ecosystem mapping. Core attributes for base- Examples of interpretation-specific line ecosystem mapping attributes (derived and mapped) Project ID Mapsheet number Polygon number Ecoregion Ecosection Biogeoclimatic subzone/variant Site series Structural stage Moisture regime Nutrient regime Terrain texture Surficial material Qualifying descriptor Surface expression Geologic process Soil drainage Slope Aspect Disturbance history Data source Reliability qualifier
Site modifier
Seral association
Forest floor classification and depth Coarse woody debris estimates
Soil texture Forage species
- required to highlight specific site characteristics relevant to project-specific interpretations - required for habitat assessment, vegetation potential - required for more detailed productivity and site sensitivity assessment - required for site productivity and habitat assessments - required for detailed site sensitivity assessments - required for detailed habitat assessments
o f the appropriate scale and available in digital format is essential for transferring the polygon lines and production o f the final map. An initial reconnaissance o f the study area is valuable to test the applicability o f the existing ecosystem classification to the specific study area and to establish tentative relationships between air photo characteristics and ecosystem attributes. An initial working legend can then be established for ecoregion, biogeoclimatic, terrain and ecosystem units prior to beginning the photo-typing phase. It is critical that the entire mapping team - terrain specialist, pedologist, and ecologist - take part in the initial reconnaissance so that they can correlate their observations o f ecological and geological processes in the study area.
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A. BANNERETAL. TABLE VII Survey intensity levels for ecosystem mapping. Survey Polygon Suggested Area Covered Range of Intensity Inspections Scales by 0.5 cm2 Study Area Level (%) (ha) Size (ha)
Interpretation Examples
1
76--100
20-500
Site-specific silvicultural prescriptions; site sensitivity to erosion, compaction, etc.
2
50-75
100-10 000
Silviculture planning; tree species selection; habitat enhancement prescriptions
1:50 000
5 000500 000
Forestry, wildlife, and range capability Local resource planning;landscape management
1:5 000 to 1:20 000
0.25-2
1:10 000 to 0.5-12.5 1:50 000
3
26-49
1:10 000 to 0.5-12.5
4
10-25
1:20 000 to 2-12.5 1:50 000
10 0001 000 000
5
< 10
1:50 000 to 12.5-306 1:250 000
500 000Local and 1 000 000 + regional planning; landscape management planning
5.2. PRE-TYPING OF AIR PHOTOS Pre-typing begins with delineation o f alpine and subalpine parkland boundaries if applicable within the study area. This initial stratification o f lowland to subalpine closed forests, open subalpine parkland forest, and open alpine areas is done prior to the delineation o f terrain units in order to capture the most obvious elevationally controlled climatic breaks within the study area. Breaks between low elevation grassland and forest areas can also be delineated at this stage. Delineation o f initial terrain units according to standard methods (Howes and Kenk, 1988) follows. Further differentiation within terrain units based on ecological factors (i.e., bioterrain mapping; see above) results in the delineation o f map unit polygons used as a basis for field sampling (see Figure 4). This initial phototyping may be carried out in two phases by separate individuals or in a more integrated fashion by one individual competent in both terrain and ecosystem mapping.
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FIELD SAMPLING
5.3.1. Sampling objectives Sampling is required to develop or refine the classification of ecosystem units, to provide descriptions (either statistical or qualitative) of ecosystem units, and to confirm map unit designations and boundaries based on initial photo interpretation. The resulting classification can be extrapolated and applied to map areas that are not sampled. Several sampling designs are possible, including both authoritative (purposive) and probability (random) sampling schemes (see Forbes et al., 1982; Valentine, 1986; Mitchell et al., 1989). The use of authoritative transects, chosen subjectively to cover the greatest environmental variation, with plots established to sample typical or modal site characteristics, is generally considered to be the most efficient and cost-effective approach. Plots are established on uniform sites within strata (polygons), thus avoiding transitional areas (Daubenmire, 1968). In some cases, the objectives of a mapping project may require that summary statistics and confidence limits be generated for certain ecological properties. In these instances, some type of probability sampling is necessary (e.g., simple random sampling, grid sampling, or stratified random sampling). These methods all require considerably more field time, especially in mapping projects covering large areas or in terrain where access is difficult. 5.3.2. Field inspection and plot sampling The intensity of polygon sampling required in preparing an ecosystem map is usually determined by the projected use of the map together with logistical constraints (funding, manpower, and size and accessibility of study area). If the map is to be used for making specific management decisions about portions of land (e.g., soil sensitivity to harvesting equipment, site preparation options, tree species selection, etc.), then the map needs to be very reliable. Increased reliability is usually achieved through a higher sampling intensity and selection of a larger map scale. Both these factors increase the cost of the mapping project. If funds are limited and the map is to be used only for more general landscape planning, then a product that has a lower reliability and a smaller scale may be acceptable. Polygon inspection percentages for the five survey intensity levels are outlined in Table VII. Field inspections can be of three forms: detailed plots, reconnaissance plots, and visual checks. Regardless of the survey intensity level (% of total polygons sampled), these inspections should be carried out in a 20:40:40 proportion. DETAILED PLOTS: Detailed plots are done at specific locations (point samples) within polygons according to the sampling scheme chosen (see above) and form the basis for ecosystem unit descriptions and any summary statistics for ecosystem units. Regardless of the sampling scheme utilized, the boundaries of the actual sample plot should encompass a homogeneous ecosystem in terms of soil and vegetation properties (Daubenmire, 1968; Mueller-Dombois and Ellenberg,
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1974). Plot size may vary from 200 to 400 m 2 in forested communities; smaller plot sizes (25 to 100 m z) may be used in non-forested habitats such as wetlands and grasslands. Plot shape and size may vary to ensure that the plot encompasses a homogeneous unit. Data collection procedures for detailed plots involve a complete site, soil, and vegetation description following Luttmerding et al. (1990), as well as any project-specific data requirements (e.g., wildlife, range). RECONNAISSANCE PLOTS: Reconnaissance plots represent "abbreviated plots" where data are recorded for a core set of attributes considered to be the minimum required to confirm (rather than completely describe) the ecosystem unit. Data should be recorded for elevation, slope, aspect, mesoslope position, moisture and nutrient regimes, disturbance history, soil and humus form classification (to the subgroup level), terrain classification, seepage water and root restricting depth, rooting zone soil texture, and major vegetation components. In addition, the site series, structural stage, and (if applicable) the seral association and site modifier are confirmed and recorded. VISUAL CHECKS: Visual checks represent the least detailed form of polygon inspection and are done to confirm the map unit designation that was assigned through aerial photo interpretation. Visual checks may be done while walking the sampling transects between ground inspection plots or detailed plots, or they may consist of observations of road cuts or polygon observations from low flying (or hovering) aircraft. Visual checks are generally recorded on project-specific polygon inspection forms. These forms should ideally allow for recording data and percentiles for up to three ecosystem units per polygon. 5.4. DATA SYNTHESIS AND ANALYSIS
Vegetation and environment data from detailed plots are computer coded for analysis and ultimate presentation in vegetation and environment summary tables for each ecosystem unit using the computer program VTAB (Kayahara, 1992; Britton et al., this volume). This will ensure data compatibility with existing B.C. Ministry of Forests databases. VTAB vegetation/environment tables will be the standard back-up documentation for substantiating site series designation as well as for proposing previously undescribed units (new site series, seral associations, site modifiers, etc.). Other vegetation analysis programs such as ORDIFLEX (Gauch, 1977), DECORANA (Hill, 1979a), TWlNSPAN (Hill, 1979b), and CERO (Ceska and Roemer, 1971) can also be used to analyze and summarize plot data. 5.5.
FINAL MAPPING
Final photo typing, labelling, and data entry for each polygon is done after field work is complete, the vegetation/environment data are tabulated and analyzed, and ecosystem units are finalized for the study area. Type lines are finalized on air photographs, and data recorded for each polygon according to a standard format.
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Polygon linework must then be transferred to a base map of an appropriate scale and then digitized for production of the final map (see Figure 4). The resulting digital map must then be edited and polygon data checked against the original air photo polygons. At this stage, producing a plotted map of ecoregion, biogeoclimatic, and ecosystem unit lines, together with topographic lines, will facilitate the validation of elevational breaks used in ecosystem mapping. A final legend is produced to accompany the map. Details of the mapping project, including objectives, methods, descriptions of map units, and interpretations are generally outlined in a separate report. A standard legend format is described in Resources Inventory Committee (1995).
6. Summary and Conclusions The ecosystem mapping methods proposed here represent a cooperative approach developed by the two natural resource ministries in B.C. responsible for inventorying and managing terrestrial ecosystems. By establishing one province-wide approach, which links permanent terrain features and ecological site attributes, it is hoped that the use of ecosystem mapping as a standard tool in resource planning and management will be greatly facilitated.
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