Natural Resource Biometrics

Herbaceous Sampling

Fixed area plots

One of the most common method to sample herbaceous vegetation is with the use of fixed area plots. These plots range in size from quite small 1/4 m square in grassland sampling to quite large 1/4 hectare in forest understory sampling.

In sampling herbaceous plants you must determine the quanity or abundance of each of the various species in the plot. This can be done in several ways.

• In forage production the plants are often clipped and weighed.
• Ocular estimates of percent coverage are common. Accurate estimates of plant coverage require the estimator to see the entire collection of plants being estimated at one time. This is why some people break up the plot in to parts or quadrats to estimate the coverage.

  Often people are less interested in coverage and focus on presents-absents of the species to gain a more complete species list by picking up more rare species. Large plots favor this focus. Small plots favor accurate estimates of coverage for common species.

Line intercept

Another method of sampling herbaceous plants is with the use of line transects. A measuring tape is used as the sample unit plants are recorded that cover a proportion of the sample tape. The length of the measuring tape covered is recorded for each plant encountered. Relative abundance and percentage canopy coverage can be estimated with this method.

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