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6.3 Field Sampling

6.3.1 Establishing survey intensity

Table 6.3

Survey intensity levels for ecosystem mapping

Survey IntensityLevel	Percentage of Polygon Inspections	Ratio of Full Plots: Ground Insp.: Visual Checks1	Suggested Scales (K =1000)	Area Covered by 0.5 cm2	Range of Study Area (ha)	Interpretation Examples
1	76-100%	2 : 15 : 83	1:5 K to 1:10 K	0.25-0.5 ha	20-500		Site specific silviculture prescription; soil sensitivity to erosion, soil compaction, etc
2	51-75%	3 : 17 : 80	1:10 K to 1:20 K	0.5-2 ha	100-10 000		Silviculture planning; tree species selection
3	26-50%	5 : 20 : 75	1:10 K to 1:50 K	0.5-12.5 ha	5 000-50 000		Vegetation potential; forest productivity; habitat enhancement prescriptions
42	15 - 25%	5 : 20 : 75	1:20 K to 1:50 K	2-12.5 ha	10 000-500 000		Forestry, wildlife capability; ecosystem representation; general forest productivity; local resource planning; landscape management planning
53	5-14%	5 : 20 : 75	1:20 K to 1:50 K	2-12.5 ha	10 000-1 000 000		Forestry, wildlife capability; ecosystem representation; general forest productivity; local resource planning; landscape management planning
R3,4	0-4%	0 : 25 : 75	1:20 K to 1:50 K	12.5-306 ha	50 000-1 000 000+		Regional planning; broad landscape management planning

1	Inspection ratios are guidelines; actual project ratio should be set by project ecologists responsible for administering project
2	Survey intensity level recommended for most mapping. This provides a reasonable balance of cost and reliability
3	Survey intensity level recommended when Level 4 is too costly and lower reliability is acceptable
4	Level R (reconnaissance) ecosystem mapping should only be conducted by ecologists who have considerable field experience in the ecosystems of the study area

Table 6.4

Field inspection density for selected survey intensity/map scale combinations

1	Values are guidelines only and are based on an average polygon size of 3-4 cm2. Mapsheet areas and hectares per field inspection are based on an average map size; actual values will vary somewhat, depending on latitude
2	Based on new 1:50 000 mapsheets (blocks of four 1:20 000 maps)

The survey intensity used in the preparation of an ecosystem map should be determined by project objectives and the proposed use of the map. 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), then the map needs to be very reliable. Increased reliability is usually achieved through a higher survey intensity and selection of a larger map scale. However, both of these factors increase the cost of the mapping project. If the map is to be used only for general land planning, then a lower survey intensity is appropriate and mapping can be done at a smaller scale. A low survey intensity does not necessarily mean that a map will be less reliable, although this is generally the case. Other factors influencing reliability are ecosystem complexity, relationship of ecological variation to readily identifiable aerial photo attributes, and surveyor knowledge and experience.

For example, in balancing cost and reliability of ecosystem mapping for landscape planning and wildlife capability/suitability, it is recommended that most mapping be conducted at level 4. The appropriate scale would be 1:20 000 or 1:50 000, depending on the complexity of ecosystems and the requirement for accuracy. At 1:20 000, this translates into a minimum of one inspection per 100 ha. If a lower cost and reliability is acceptable to the user, ecosystem mapping at level 5 or level R could be conducted.

Survey intensity level is not always related to scale; any intensity level can be conducted at any scale. However, smaller scale maps are generally used for land management planning and the higher costs of a more intense survey level are not usually warranted for broad management planning. Table 6.3 includes scale as a guide only to determine intensity level.

Another consideration in selecting mapping scale is the scale of the aerial photographs and other imagery to be used. The final map scale should not be significantly larger than the photo scale, as it will be difficult (maybe even impossible) to recognize and delineate small ecosystems on the photos that should be delineated at the map scale.

6.3.2 Designing a sampling plan

• Size of study area
• Topography
• Previous ecological sampling (number, type, and location)
• Existing information (e.g., biogeoclimatic units, site series classification, adjacent ecosystem mapping, geology, terrain, and soils)
• Additional data collection requirements for samples (e.g., wildlife, coarse woody debris, mensuration, range) and polygon database attributes
• Interpretations to be produced from the mapping
• Survey intensity level
• Sampling ratio of full plots, ground inspections, and visual checks
• Possibility for "new" site units
• Access (using topographic, forest recreation, forest cover, and forest development maps, recent aerial photos, latest access information from Ministry of Forests District Office)
• Questions from pre-typing or development of working legend
• Knowledge level and experience of field crews and mappers in the ecosystems of the area.

Clear objectives for all field inspections should be articulated in the sampling plan. Some inspections may be to sample homogeneous areas for descriptive purposes, others to assess polygon boundaries, or assess ecosystem unit proportions within polygons. Because of their cost, detailed plots and ground inspections should focus on uniform sites within polygons and avoid transitional areas. Sampling at slope, moisture, or soil boundaries makes it very difficult to ascertain ecological determining factors, unless numerous plots are established systematically across the gradient. Visual checks can be planned to assess boundaries, confirm questionable areas from photo interpretation, or do whatever is necessary to confirm ecosystem designations and to meet project objectives. Again, it is best to have some focus for all plot inspections so that field crews are clear about their sampling objectives.

Sampling is required to characterize common and widespread ecosystem units, as well as those units that occur infrequently, such as wetlands and riparian ecosystems. Sampling intensity may consider the relative confidence in local biogeoclimatic mapping or focus on site series that are difficult to identify at the pre-typing phase. Intensive sampling may be done in ecosystems that are considered more valuable or more sensitive than others. For example, in a range mapping project, more sampling may have to be done in productive grassland communities and in forests with open canopies and higher forage values. Similarly, for wildlife studies, areas that are known winter ranges or are important for biological diversity (such as riparian ecosystems) may require more intensive sampling.

Using the set of maps with the compilation of resource information, and with the objectives of each of the sample types clearly articulated, the mapper should then plan where the transects will be located. It is important to keep in mind that the sampling plan is only a plan-improvisation in the field will be required, as some transects may not sample as planned or access may be restricted (e.g., by road washouts, bad weather). Therefore, more transects than required should be planned. Flexibility is the key. A tally sheet should be designed to keep track of what is sampled and what is still needed, and all information should be communicated to crews to ensure they know what is required.

After the sampling plan is developed, it should be reviewed by the Regional Ecologist or project ecologist to confirm that it meets the project objectives. The information (e.g., transects, required inspections) should then be transferred to the non-typed set of field photos to make it easier to use in the field. A well-thought-out sampling design will greatly increase field efficiency.

6.3.3 Conducting field inspections and plot sampling

As full plots account for only a small proportion of the inspections and are the most costly to establish, they need to be carefully selected. The sampling plan should clearly set criteria for establishment of these plots (e.g., one sample of each site series, two in each zonal site series to confirm biogeoclimatic units, three or more in a new site series).

Table 6.5

Minimum data collection requirements for Ecosystem Field Forms (FS882)

Site Form

1	Date (Y/D/M)	15	Ecosection
2	Plot number	16	Moisture regime
3	Project Identification	17	Nutrient regime
4	Surveyor(s)	18	Successional status
5	General location (should be specific enough to find plot again easily)	19	Structural stage
6	Forest region	20	Realm/class (for wetlands only)
7	Mapsheet	21	Site disturbance
8	UTM (zone, easting and northing) or latitude and longitude	22	Elevation
9	Air photo no. (incl. Flight line)	23	Slope
10	Co-ordinates (X and Y)	24	Aspect
11	Site diagram	25	Meso slope position
12	Plot representing	26	Surface topography
13	Biogeoclimatic unit	27	Exposure type (if applicable)
14	Site series	28	Surface substrates (organic matter, decaying wood, bedrock, rocks, mineral soil, water)

Soil Form

1	Plot number	15	Flooding regime (if applicable)
2	Surveyor(s)	16	Organic horizons/layers; for each:
3	Bedrock (at least to general level, where significant to site)		horizon/layer code and depth mycelial abundance
4	Coarse fragment lithology (at least to general level)		fecal abundance von Post (for organic soils)
5	Terrain texture, surficial material, surface expression, geomorphological process	17	Mineral horizons/layers; for each: horizon/layer code and depth
6	Soil classification (to subgroup)		colour (when required for diagnostic purposes)
7	Humus form (at least to group)		colour aspect (when colour entered)
8	Hydrogeomorphic unit (at least to system)		soil texture (< 2 mm fraction)
9	Rooting depth		% coarse fragments (gravel, cobbles, stones, and total)
10	Rooting zone particle size		comments (especially mottles)
11	Root restricting type and depth (if applicable)	18	Profile diagram
12	Water source (if applicable)	19	Notes
13	Seepage depth (if applicable)
14	Drainage

Vegetation Form

1.	Surveyor(s)	5.	Species by layer
2.	Plot Number	6.	Cover for each species by layer and sublayers
3.	Species list “complete” or “partial”	7.	Notes
4.	% cover by layer (A, B, C, D)

Mensuration Form

1.	Surveyor(s)
2.	Plot Number
3.	For three largest diameter trees of dominant tree species (if stands meet SIBEC standards)
	• tree number • species code • dbh • height calculations	• height to dbh • total height • Breast height age • suppression	• pathological indicators • damage • site series

The standards indicate that about 5% of sample plots should be full plots (see Table 6.3). This number is a guideline and the number required for a project depends on the survey intensity level and the assessment of a few criteria for the area. The following questions should be asked:

• Is there an existing site series classification?
• How well does the existing classification fit the project area?
• Do biogeoclimatic boundaries require extensive revision?
• How many existing full plots are there?
• What descriptive data is needed for a report?
• Is there a possibility of new site series or biogeoclimatic units being identified?

The project ecologist responsible for administering the project should assess the full sample requirements before the sampling plan is developed and/or a contract let for the project. Another criterion that is important in determining the number of full plots is the surveyor’s knowledge and experience in the study area. With contract mapping, however, this is generally not known until after the bidding.

Full plots are essential for describing new ecosystems (site series). To be added to the provincial vegetation classification, the new data must first be evaluated by the Regional Ecologist in the area, and then compared with other site series. Therefore, the full plot data need to be carefully collected according to the standards outlined in Field Manual for Describing Terrestrial Ecosystems (BC Ministry of Forests and BC Ministry of Environment, 1998a) with a complete species list, all species confirmed, and good soils and site data. An adequate number of samples is also required, preferably five or more (minimum of three) for each new site series. It is very important that the appropriate Regional Ecologist be consulted and new site series names and labels be approved before the map is finalized.

Ground inspections

Ground inspections are abbreviated plots from which data are recorded to confirm the identification of the ecosystem unit or polygon designation, or determine polygon boundaries. They also provide some data for characterizing ecosystem attributes (e.g., abbreviated species lists can be used to characterize structural stages). These plots should make up about 20% of inspections at most survey intensity levels (see Table 6.3) (about one inspection per 375 ha for level 4, 1:20 000 mapping). Data should be recorded on the Ground Inspection Form (GIF). Minimum data requirements for ground inspections are listed in Table 6.6.

Ground inspections are point samples. Although plot size and shape are the same as for full plots, for speed of recording, plot boundaries are rarely marked. The data collected should be sufficient to confirm the ecosystem unit: site series, site modifiers, and structural stage. Dominant and indicator plant species should be recorded. These are generally all species on the main substrate above approximately 3–5% cover (so-called “dominants”) and those species listed in the vegetation tables of the Ministry of Forests field guides (indicator species). Although a soil description need not be completed, data required on terrain classification, humus form, rooting zone texture, seepage water, and root-restricting depth, and so on, means that a small soil pit must be excavated.

Ground inspections are likely to be the main form of sampling for wetlands, alpine, and other non-forested ecosystems. Ground inspection forms completed on these ecosystems need to include notes on type of wetland or alpine ecosystem, so that this information can be used in mapping. In wetlands, for example, an indication as to whether the ecosystem is a marsh, swamp, fen, bog, etc., is essential. In alpine areas, an indication of site conditions like talus slope, wind-swept ridge, meadow, etc., is useful.

Table 6.6 Minimum data collection requirements for ground inspections

1.1. G (Ground) vs V (Visual) 2. Air photo number 3. Date 4. Project ID 5. Surveyor(s) 6. Mapsheet 7. Plot no. 8. Polygon no. 9. Lat./Long. or UTM 10. Aspect 11. Elevation 12. Slope 13. Soil moisture regime 14. Soil nutrient regime 15. Meso slope position 16. Drainage – mineral or organic soils 17. Mineral or organic soil texture 18. Surface organic horizon thickness

19. 19. Humus form (to order level) 20. Depth to and type of restricting layer (if applicable) 21. Coarse fragment content 22. Terrain texture, surficial material, surface expression, and geomorphological processes 23. BCG unit 24. Ecosection 25. Site series 26. Site modifiers 27. Structural stage 28. Crown closure 29. Total % cover by stratum 30. Dominant/indicator plant species 31. % cover of dominant/indicator species 32. Complete or partial 33. Notes

Visual checks

Visual checks are the least detailed and also the predominant form of field inspection. They should account for approximately 75% of inspections (about one inspection per 100 ha at level 4, 1:20 000 mapping), and can take the form of notes on photos or maps, notes in a field book, notes recorded on tape, or polygon summaries on Ground Inspection Forms. These checks are intended to be quick inspections for mapping purposes and can include one or more of the following: confirm site series, site modifiers, structural stage, terrain attributes, soil textures and soil depths, briefly describe vegetation, assess biogeoclimatic mapping, record ecosystem or terrain component percentages, evaluate polygon boundaries, or note special features. They do not have to be entered in a database, but should be summarized in spreadsheet format for ease of use and presentation to project administrators or correlators.

Visual checks can be conducted on the ground, from the air (helicopter), or from viewscapes. Emphasis should be on the ground as air calls and viewscapes are limited in the types of information which can be confirmed. Map reliability is most likely to be improved if more ground is covered during field work.

Visual checks can also be used to supplement full plot or ground inspection data. They also can be used to provide information for ecosystems adjacent to areas that were sampled with a more complete inspection. For example, they could be used to characterize the series of wetland communities around a small pond or depression.

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