Habitat-based Plant Element Occurrence Delimitation Guidance, 1 October 2004

Decision Tree
Decision Tree

Notes and Definitions for Habitat-based Plant EO Delimitation Guidance, 1 October 2004

EO Features – This Habitat-based Plant Element Occurrence (EO) Delimitation Guidance addresses whether two separate observations of the same element belong to the same EO, or to two different EOs, in the absence of more specific guidance (for example, element or group custom EO specifications). In the context of the Biotics EO Methodology, Basic Features should be compared, to assure consideration of locational uncertainty. (However, note that the differences between Basic and final Procedural Features are negligible here.) Each observation must independently meet the minimal EO criteria (see EO Data Standard) for that element prior to comparison.

Persistently unsuitable habitat – Surveyed or unsurveyed areas that, under natural conditions, are virtually certain to remain incapable of supporting viable individuals of an element during the next 25 years or more. Such areas are neither apparently suitable habitat nor parts of a dynamic landscape mosaic that includes the element (see definitions below). The potential for rare or highly irregular events (such as tornadoes, unusual hurricanes, earthquakes, 300-year floods, rare fires, or catastrophic volcanism) may be ignored. Similarly, incremental effects of long-term phenomena (such as slow erosion or deposition, climate change, or sea-level rise) may usually be ignored on the timescale of interest here; over longer times, almost everything changes.

Apparently suitable habitat – Surveyed or unsurveyed areas not known to be occupied by an element, but which appear capable (under natural conditions) of supporting viable individuals of that element, based on one or more observed or mapped factors (soils, geology, hydrology, vegetation, topography, aspect, elevation, etc.) known to delimit or predict other occurrences (current or historical) of the same element.

Dynamic landscape mosaics – Landscape or habitat mosaics (other than linear riparian/shore systems; see below) in which an area of potentially suitable habitat includes natural disturbance patches (or similar phenomena) which are produced and subsequently fade in various places within the area, with a natural disturbance return interval of about 5-50 years, considering both past and expected future conditions. Elements in such areas typically grow in (or are excluded from) the dynamic disturbance patches, persisting as seed (or other dormant stages) in patches not currently suitable for growth, or dispersing readily among suitable patches. Examples include many chaparral- or pine-dominated fire systems, dune blowouts, and beaverdam wetlands. Note that such habitats as intermittent wetlands, in which the conditions appropriate for growth (or exclusion) of an element may not be met every year, are still considered stable if their locations and extents remain generally constant for 25 years or more.

Linear riparian/shore systems – Systems dominated by water-current dispersal in a linear zone generally <1 km wide (riparian corridors, shores, and similar narrow systems), including those with dispersal by occasional events (major floods, storm waves, etc.) with significant potential to occur during the next 25 years. Examples include many "100-year" riparian floodplains, coastal shorelines, shorelines of big lakes with large waves, estuarine shorelines and tidal zones, and floodplains of small streams or dry drainages subject to frequent flash floods. Small, quiet ponds and lakes, as well as wide marshes or backwater swamps, generally would not be included here. EO features are assumed to share linear flow if they are aligned in a reasonable flow direction along a river, stream, shore, etc., unless contrary data exist. This is usually not the case with upstream EO features on different tributaries, or with EO features on opposite shores of rivers >1 km wide; however, such features may be indirectly connected if they each share flow with a common downstream EO feature. For an aquatic element inhabiting open water of a river, assume connection by water-current flow unless evidence suggests that this is unlikely.


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