Tuesday, January 5, 2010

Field techniques - Percent cover part 2, the microplot

Although visual estimation of percent cover is quick and inexpensive, we also make use of more accurate and intensive methods for estimating percent cover, especially during monitoring projects. Here is CNHP ecologist Renée Rondeau using a point-frame to read a microplot on the shortgrass prairie.

vegetation microplot sampling
Make sure not to count your feet!

The wooden frame is divided by wires into a grid with 50 points, each 5 cm apart. A similar grid could also contain 100 points, with each point representing a percent - the key feature is that the observer must be able to look directly down on every single point to identify what lies below. In this potential mountain plover habitat, Renée is estimating the percentage of bare ground and litter by counting the number of points with bare soil, biotic soil crusts, pebbles, cowpies, or downed dead vegetation (including stump remains of grasses) directly beneath.

With a large enough sample of microplots, we can begin to determine whether the area is suitable for the plovers. Obviously this technique can be time-consuming, so we try to rope in additional field assistants whenever we can:

horses with point-frame
clop...clop...clop...Three percent? Got it.

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