Habitat-based Plant Element Occurrence Delimitation Guidance, May 2020

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The “Element Occurrence” (EO) is a fundamental unit of information in the NatureServe Natural Heritage methodology. NatureServe’s Element Occurrence Data Standard (hereafter, EO Data Standard) defines an Element Occurrence (EO) as “an area of land and/or water in which a species or natural community is, or was present.” Sub-EOs can be used for tracking information on more localized areas that are part of a single EO.

While EOs are often self-evident for vascular plants, two fundamental questions regularly arise in developing botanical EO data:

• Minimum criteria for an EO –whether an observation, collection, or other report of a plant at a particular place can be considered to be sufficient basis for an EO record.
• Separation distances for nearby EOs –whether two (or more) observations in different but nearby places should be considered different EOs, or combined into a single EO.

The EO Data Standard provides for use of Element Occurrence Specifications (“EO specs”) to delineate and differentiate EOs, including both minimum criteria and separation distances. Individually written (“custom”) EO specs are of two general kinds. Element-specific EO Specs are written for a particular, generally well-known element, drawing on element-specific information on ecology, species biology, threats/vulnerabilities, management needs, etc. Group EO Specs are written for a group of related or ecologically similar elements (specified by a list or by a scoping definition), drawing on various considerations broadly applicable to the particular group. Custom EO specs may also be developed to address unusual population structures or dispersal dynamics. Note that custom EO specs may specify shorter as well as longer separation distances when considered appropriate in particular cases. Minimum EO criteria usually follow generally accepted (although not well-documented) criteria, considering such evidence as successful or potentially successful establishment, presumed naturalness (including deliberate restorations and reintroductions within the element’s historical range), and review of reliability of identification and locality information. A single well-established individual plant is often considered to meet the minimum criteria for an EO. The issue of minimum EO criteria is addressed more extensively in the EO Data Standard, and is not further considered here. When necessary, custom EO specifications can be written to identify minimum EO criteria for a particular taxon.

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Reference Code: U20NAT01IDUS <br>

Full Citation: NatureServe. 2020. Habitat-based Plant Element Occurrence Delimitation Guidance, May 2020. Version 1.0 published October 2004; Revised May 2020. NatureServe, Arlington, VA. p. 15. Available from https://www.natureserve.org/sites/default/files/eo_specs-habitat-based_p... <br>

Location: ELECTRONIC FILE - BOTANY: OTHER <br>

Keywords: NatureServe, plant, EO, Element Occurrence, delimitation, guidance, specification, decision tree <br>

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