Description and Uses
Step-pin is a modification of the intended to reduce step-point’s potential for bias. The Step Pin Method involves making observations along a walking transect at specified intervals (e.g., number of steps). At each interval, a pin is lowered to the ground without looking at it and all vegetation intercepting the pin and the soil surface are recored. Step-pin measures cover for individual species, total cover, and species composition by cover. Like step-point, the step-pin method does not require using an actual tape measure to mark the transect line. Instead with this method the transect is selected by determining the transect bearing and using a prominent distant landmark, such as a peak, as the transect bearing point.
Advantages and Limitations
The main advantage of the step-pin method over the step-point method is that it decreases the potential for bias by moving the pin away from the observer and by having it blindly lowered to the ground. Whether intentional or not, it is very hard for observers to place their feet on the ground without any regard to the vegetation or other surfaces on the ground. This introduces bias into the method. By placing the pin in front of the observer and not looking at it while it is being lowered, it becomes less critical where the observer’s feet land; thus reducing bias in the measurements. The step-pin method, though, can still be biased in situations like dense or thick vegetation, or where large shrubs or trees (especially those with thorns) are encountered.
Because step-pin is just a modification of the step-point method, if it is described at all, it is generally described with the step-point method in manuals and technical references.
- Sampling Vegetation Attributes 1734-4. http://www.blm.gov/nstc/library/pdf/samplveg.pdf.