Practical and Field Skills
Measurement and mapping
Map reading means scale, grid reference, contour interval and slope interpretation. A compass gives bearings; a clinometer or Abney level gives slope angle and tree height; GPS gives coordinates with a stated datum. Tree measurement: girth at breast height is taken at 1.37 m above ground; diameter equals GBH divided by π; basal area equals πd²/4. Inventory uses quadrats (nested for trees, shrubs, herbs), line transects for animals, and sampling designs - random, systematic, stratified.
Recording and identification
Keep a field notebook in pencil with date, locality, coordinates, habitat, slope and observer. Herbarium specimens need leaves, flowers and a complete label. Soil texture is judged by the feel or ribbon test, pH by indicator or meter. Rock identification uses a hand lens, hardness test, streak and dilute HCl.
Worked example
A tree has a girth of 94.2 cm. Diameter = 94.2 / 3.14 = 30 cm. Basal area = 3.14 × 0.30² / 4 = 0.0707 m². With 400 such stems per hectare, basal area is 28.3 m²/ha. Reasoning: convert girth to diameter first, then to cross-sectional area, then scale.
Traps
Measuring girth at ground level instead of 1.37 m. Forgetting slope correction on taped distances. Estimating tree height from the base without adding the observer's eye height. Recording without a datum or locality.