written by Karen Colson and Jason Karl
Description and Uses
The Step Point Method involves making observations along a walking transect at specified intervals (e.g., number of steps) and using a pin to record cover or “hits.” It measures cover for individual species, total cover, and species composition by cover.
Unlike point or line intercept methods, the step-point 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. The observer reads the hits at specified intervals by placing the heel of the boot on the ground with the sole of the boot at a 30-degree angle to the ground and placing the pin into the notch in the toe of the boot and vertically lowering the pin until it either intersects a plant or the ground. When obstructions such as juniper trees, are encountered the observer sidesteps 90° from the transect line and continues pacing parallel to the transect to avoid the obstructions, returning to the original transect line as soon as possible by sidestepping 90° in the opposite direction.
Advantages and Limitations
The step-point method is simple and easy to use. It is also a more rapid approach, for example, large areas can easily be sampled (especially in areas where the vegetative cover is reasonably uniform) and it allows for a fairly large number of samples to be collected in a relatively short time. It also requires little equipment.
However, sample size is extremely important when using this method since there can be a lot of variation between observers in the data collected when sample sizes are small. It is also difficult to pace in a straight line, particularly when obstructions occur. Having to sidestep these obstructions adds additional bias to the data collection because the observer ends up avoiding those components of the community. Traditionally, the toe of the boot is used as the point, wich can significantly overestimate cover because the boot pushes plants over, artificially increasing the measured cover data. This method can be revised to be more accurate by using a pin in place of the toe of the boot. As with point intercept, plant species with very low cover may not be hit on the transects.
- Sampling Vegetation Attributes 1734-4. http://www.blm.gov/nstc/library/pdf/samplveg.pdf.
Technical and Application References
- Evans, R. A. and R. M. Love.1957. The step-point method of sampling-a practical tool in range research. Journal of Range Management. 10(5):208-212.
line_point_intercept: Point Intercept also estimates percent cover at fixed intervals along one or more transects, but the transects are fixed and established using measuring tape, which reduces observer bias.