Agenda - Environmental Policy Board - 07/19/2021

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Title 190-Forestry Inventory Methods Technical Note Point and fixed plot sampling methods are used to collect information for developing management plans and silvicultural prescriptions. The inventory typically includes plot -level measurements that are summarized to provide stand -level information including site index, basal area ((BA), sq.ft./acre), trees per acre (TPA), species present in each canopy class from dominants to ground vegetation, size class, wood or nontimber production potential, and other metrics needed to plan and schedule future management activities, or implement near -term activities. There are a number of considerations in choosing between point and fixed plot methods. Fixed plots may be better suited to large stands with low variability; generally, in these situations, fewer plots are needed for an adequate sample size than if point sampling is used. In many stands, especially those with open understories, point sampling usually requires less time per plot which allows more plots to be sampled. A relatively larger number of plots is needed to provide statistically reliable estimates in stands with variable density and a diversity of tree species (Oderwald 1981). Plot sampling and strip sampling methods are based on measuring a percentage of the stand. A proportion of the area is measured based on the assumption that the samples are representative of the entire stand. The percentage of the area sampled depends on how the information will be used as well as the uniformity of the stand and its size. For most planning purposes, a low intensity inventory is sufficient. Sampling percentages can range from as low as 0.2 percent using fixed -radius regeneration plots in homogeneous stands, up to 20 percent for variable -radius plots in diverse forests of a small acreage. As acreage increases, inventory intensity typically decreases. A complete discussion on statistical sampling intensity can be found in forest mensuration textbooks, such as Avery and Burkhart (1994). Strip sampling is a form of fixed plot sampling using long, narrow plots. This method may be suitable for sites with variation due to environmental gradients. Transect sampling is often used for seedling survival inventories. It is an efficient method when the number of entities is the main attribute of interest. Crop tree inventory identifies desired trees to retain for objectives that may include wildlife habitat, visual quality, water quality, timber and nontimber products, and others. A crop -tree inventory is supplemented with a demonstration plot to illustrate forest management concepts and allow landowners to determine the desired intensity of management. The zig-zag transect method was developed by NRCS, then known as the Soil Conservation Service (SCS), in the 1960s. It allowed SCS foresters to use a simplified process to quantify forest tree and stand characteristics and was useful in communicating information to landowners. Although the zig-zag transect method is no longer a common inventory technique, under certain stand conditions it is an efficient method to use and provides good estimates for stands that are dominated by one tree species, are even -aged, and have a narrow diameter range. Purpose of Inventory Forest inventories are conducted for different purposes, but in NRCS they usually support the development of a forest management plan (FMP) or a conservation plan. Inventory methods are chosen to — (Technical Note No. 190-FOR-01, Jul 2018) 2