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Woodland Inventory Procedures for Estimating Stocking in Riparian Areas

Woodland Inventory Procedures for Estimating Stocking in Riparian Areas

 

  1. Use a 10-factor angle gauge (the width of a penny) or prism to inventory basal area.  A minimum of one plot per 10 acres or 3 plots per field/stand, whichever is more, is recommended.

  2. Sampling plots may be located either systematically or randomly.  A systematic location of plots should be based on knowledge of the are, stand characteristics, site characteristics, field boundaries and time constraints.  On all sites, plots should be located a minimum of 100 feet apart from each other and 25 feet from field borders.

  3. Locate your plot point and mark with a flag or stick.  Using an angle gauge or prism, site on trees 4 1/2 feet above the ground that are at least 2 inches in diameter.  Distance of the tree from the plot point does not matter.

  4. If using an angle gauge (or penny): Straddle the marked point and rotate the angle gauge 360 degrees.  The angle gauge should be kept at a proper distance (25 inches) from the eye when making inventory determinations.  As you turn, record each tree that completely fills or more than fills the 10-factor opening of the gauge (see diagrams) or record each tree that is visible on both sides of the penny.  Multiply the number of trees counted by 10 to compute the basal area of the plot.  Compute the average of all tallied plots.

    If using a prism:  Maintain prism over the plot center point as the prism is being rotated 360 degrees.  Distance from the eye to the prism does not matter.  As you turn, tally all trees where the prism image overlaps the tree outline (see diagrams).  Multiply the number of trees counted by 10 to compute the basal area of the plot.  Compute the average of all tallied plots.

  5. Record tree diameter at 4 1/2 feet above the ground of the 5 closest trees to the plot center that are greater than 2 inches in diameter.  Compute the average of the five trees.

  6. Using Figure 5 in FS General Technical Report NC-98 find the point on the graph where the calculated basal area intersects with the computed average tree diameter.  This point is the estimated stocking percent.  If the point falls in or below the understocked section of the graph, the site needs additional stocking or trees to have a fully functional riparian system.  If the point falls in the fully stocked or overstocked sections of the graph, the site can be considered adequate.