The quadrat

The quadrat is sampling shape. It is often thought of as a square or rectangular frame used in the field to sample an area. This is the way the quadrat appears in geographical, ecological, or forestry studies. But the fact is that the quadrat is not necessarily a 2-dimensional sampling shape.

Before looking into the more general definition of a quadrat lets consider the 2-dimensional quadrat. That an area. Typically, an area is a square or rectangle. There’s a simple reason for that. It’s easy to make a quadrat of that shape. A few boards and fasteners and the quadrat is done.  Early on it was realized that there existed a problem with quadrats. The problem was realized as early as probably the late 1890s when Clements and Pounds published there article on the quadrat. One of the early solutions was the proposal to use disc shaped quadrats. This meant that the quadrat minimized the edge effect. In fact, it didn’t. The problem was that the sampling rules associated with curved quadrats were too complex to use effectively.

You’d think that the square quadrat would have been the choice. It enclosed a large area for the perimeter. That didn’t happen. It was learned that the long thin quadrats such as the belt or strip quadrats were more effective sampling methods.

The shapes of quadrats was a hot topic in a number of disciplines from range management, to forestry, to ecology, to grassland studies. In all of this of course the assumption was that a quadrat was a 2-dimensional shape.

A quadrat is geometric sampling shape. It can be any dimension from 0 to 3 dimensions. These are points, lines, areas, and volumes. Even though you might think of a quadrat as a square frame, a quadrat can be any sampling geometric shape that is needed to get the work done and done efficiently.


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