With increasing human pressures on the natural environment, resource management plans must be based on an understanding of the ecosystems of the province. Through an ecologically based classification system planners have the ability to develop effective land use plans which incorporate an understanding of the cumulative effects of multiple resource use. The broad ecosystem classification is an ecologically based framework which provides an ecosystem perspective for resource management.
A Broad Ecosystem Unit (BEU) is a permanent area of the landscape that supports a distinct type of dominant vegetative cover, or distinct non-vegetated cover (such as lakes or rock out-crops). Each unit is defined as including potential (climax) vegetation and any associated successional stages (for forests and grasslands). Ecosystem units are based on the integration of vegetation, terrain (surficial material), topography, and soil characteristics. This approach emphasizes those site characteristics that determine the function and distribution of plant communities in the landscape. Broad ecosystem units are developed from the site classification level of the biogeoclimatic ecosystem classification of British Columbia. Mapping of BEUs ties together the Ministry of Environment, Lands, and Parks (MoELP) Ecoregion classification and mapping, and the Ministry of Forests (MoF) climate level biogeoclimatic ecosystem classification (BEC).
The Ecoregion classification was developed and mapped for British Columbia to provide a systematic view of the broad geographic and climatic relationships of the province (Demarchi, 1996; Demarchi, 1995). There are five levels in the Ecoregion classification including, Ecodomain, Ecodivision, Ecoprovince, Ecoregion and Ecosection. The highest two levels of this classification, Ecodomains and Ecodivisions, are very broad and place British Columbia in a global context. The three lowest levels, Ecoprovinces, Ecoregions, and Ecosections, are progressively more detailed and narrow in scope. They relate different segments of the province to one another based on areas of similar climate, physiography, oceanography, hydrology, vegetation, and wildlife potential (Demarchi, 1996).
The Ecosection is the classification unit depicted in broad ecosystem mapping. Presently British Columbia is mapped to the ecosection level at two scales of presentation: 1:2,000,000 (Demarchi, 1993) and 1:250,000 (MoF, Research Branch, unpubl.). All ecoregion units are always mapped as simple map units.
Within the terrestrial environment each Ecoregion and Ecosection can be further subdivided into biogoclimatic units based on the interaction of the climate, soil, topography, and vegetation. The biogeoclimatic ecosystem classification system has been revised and adopted by the B.C. Forest Service since 1975 (Meidinger and Pojar, 1991). Biogeoclimatic Units, as mapped by MoF, provide a hierarchical framework for mapping plant community distribution with separate climate and site levels (Pojar et al., 1987, Meidinger and Pojar, 1991). At the climatic level biogeoclimatic ecosystem classification can be broken down into the zone, subzone, variant, and phase. The subzone is the basic unit which can be grouped in zones or divided into variants and phases based on the characteristics of the regional climates. Each subzone is based on a distinct climax (or near-climax) plant association on a zonal site. A zonal site exhibits intermediate soil moisture and nutrient conditions and thus best reflects the regional climate. Subzones with similar climatic characteristics and zonal ecosystems are grouped into broad, macroclimatically homogeneous biogeoclimatic zones. Biogeoclimatic variants are created to account for the variation of the regional climates at the subzone level (eg; areas which are slightly wetter or warmer than other areas in the subzone). This climatic variation results in differences in the vegetation, with the presence of distinct climax plant subassociations on zonal sites. In some subzones and variants local relief has resulted in further regional climatic variation. Biogeoclimatic phases account for these areas of local relief, where topographic or topoedaphic variation has resulted in ecosystems which are atypical for the given regional climate (Meidinger and Pojar, 1991).
The biogeoclimatic zones are mapped for the province at 1:2,000,000 while the subzone/variant level is mapped at a scale between 1:100,000 and 1:500,000 for each of the forest regions. Subzones and variants are the main biogeoclimatic units mapped for the Broad Ecosystem Unit Classification (phases are included when present). They are always mapped as simple units.
The site level of this classification groups ecosystems or sites which have similar environmental properties and potential (climax) vegetation. Groups of sites are first divided into site associations based on potential vegetation of each site. Further divisions into site series, utilizing subzones and variants, create climatically and edaphically uniform site units (Meidinger and Pojar, 1991).
As described earlier, it is the site series which exhibits intermediate soil moisture and nutrient conditions, the zonal site series, that best reflects the regional climate. These zonal site units define each of the various subzones and variants throughout the province. In order to truly understand each of these regional climates, a number of azonal site units have been defined. Each of these site units depicts extreme soil, moisture and nutrient conditions as compared to the zonal site unit in a given regional climate. For example, an azonal site unit may be drier or wetter, or have a much higher or lower nutrient content than is typical for a zonal site.
Broad ecosystem units are amalgamations of all of these site series units. Thus each BEU may have many distinct climax plant associations. BEUs were correlated to all site series which have been described to date in the regional MoF field guides [for example; the ESSFmc 01 site series unit was correlated to the BEU, Engelmann Spruce - Subalpine Fir Dry Forested(EF)]. Non-forested units (including alpine, parkland, grassland and wetland units) are poorly defined in these field guides and as they become better defined, these correlation tables will have to be updated.
The current broad ecosystem unit classification originated in the late 1980's, as A First Approximation of Wildlife Habitats of British Columbia, developed by Andrew Harcombe and Ted Lea. These wildlife habitats had been initially created for the Wildlife Habitat Handbook for the Southern Interior Ecoprovince but eventually, expanded to cover the Province for the Regional Wildlife Plans (Harcombe and Lea, 1990, unpubl.). This first draft was ordered by administrative rather than ecological regions.
The Broad ecosystem units are a further development or expansion of these broad habitat classes. Basically, the classification was changed to broad ecosystem units in order to characterize individual ecosystems rather than just habitats best suited for wildlife. Each BEU provides wildlife biologists with broad ecological information that can be used for a wide spectrum of species assessments. For example the detail needed to assess bear and ungulate foraging habitat is unecessary to assess the canopy structure important to bird habitat. The broad ecosystem unit provides a framework which is applicable to a greater number of species, both plant and animal.
BEU maps provide an interpretative base map for the development of landscape level plans including timber supply areas, land and resource management plans, and regional wildlife plans (Lacelle, 1994; Demarchi, 1996).
The ultimate goal of broad ecosystem unit classification is to provide an ecologically based provincial framework for MoELP and MoF resource management. The objectives of this report are to describe Broad Ecosystem Unit Classification, providing detailed descriptions of major ecosystem types mapped at a scale sufficient for broad planning initiatives.
This classification was designed to provide the information required for the development of effective land and resource management plans. This guide together with broad ecosystem maps and the accompanying databases provide sufficient material to produce effective broad scale management plans. The ecosystem units have been grouped according to vegetative dominance or other unique characteristics which set them apart from each of the other units. Ten major ecosystem groupings have been created: (1) coastal forest ecosystems, (2) southern interior forest ecosystems, (3) central and northern interior forest ecosystems, (4) forested wetland and riparian ecosystems, (5) subalpine parkland and krummholz ecosystems, (6) shrub and herb dominated ecosystems, (7) nonforested wetland and aquatic ecosystems, (8) nonforested subalpine and alpine ecosystems, (9) sparsely vegetated ecosystems and (10) urban and agricultural ecosystems.