A plot level species inventory is intended to provide a rapid appraisal of the floral biodiversity of an area. Species level inventory occurs in conjunction with other survey methods such as the line-point intercept transect survey, which quantitatively measures soil cover and plant canopy cover. The same plots developed for the line-point intercept inventory are used in the species level inventory. If the species inventory is part of a National Resources Inventory (NRI) survey, the plots should be divided into sections with an area of 1,641 m2 to ensure compatibility. The species-level inventory occurs after vegetation height, line-point, and gap intercept measurements on transects are complete. It is conducted by a single observer who systematically and uniformly searches the entire plot for 15 minutes.
Each of the these plot layouts achieve an area of 1,641 m2 as part of an NRI survey. The dashed lines represent paths walked by the observer.
This method is a compromise between the more thorough but time intensive modified Whitaker species richness approach and the more approximate estimates of biodiversity achieved through canopy level inventories, which sometimes fail to accurately account for the presence of rare or invasive species. A high level of plant identification competence is necessary to efficiently inventory a plot. Unknown species are flagged during the inventory and are later identified, which can offset the time savings achieved through a 15 minute time limit placed on inventorying each plot.
As stated earlier, a species level inventory is used in association with other inventory methods including the line-point intercept transect survey and cover measurement. A complete census enumerates the entire population eliminating sampling error, but at the expense of considerable investment in resources. Often only invasive or rare species are enumerated.
Electronic record keeping is recommended. The Database for Inventory, Monitoring & Assessment (DIMA) contains data entry forms which can be downloaded as part of an MS Access database. DIMA is compatible with PDAs and tablets. Alternatively, a paper version of the species inventory form can printed from the appendix of the Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems.
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