Appendix C: Natural Disturbance Types

Natural disturbance types (NDTs) as outlined in the Forest Practices Code Biodiversity Guidelines (1995) characterize areas with different natural disturbance regimes. Natural disturbance regimes include fire, wind, insects and disease. The following five natural disturbance regimes are recognized in the Forest Practices Code Biodiversity Guidebook:

NDT	Definition
NDT1	Ecosystems with rare stand-initiating events
NDT2	Ecosystems with infrequent stand-initiating events
NDT3	Ecosystem with frequent stand-initiating events
NDT4	Ecosystem with frequent stand-maintaining events
NDT5	Alpine Tundra and Subalpine Parkland ecosystems

All of the Biogeoclimatic subzones and variants recognized provincially have been classed into one of the above natural disturbance types. These natural disturbance types have been used in the Standard for Terrestrial Ecosystem Mapping to help define structural stages for mature and old forests. This document recognizes that because of their frequent stand initiating events, ecosystems falling under NDT3 should be considered mature and old sooner than all of the other NDTs. As outlined in Table 3.3, ecosystems falling within the Biogeoclimatic subzones/variants listed under NDT3 are recognized as being mature starting at 80-120 years, and old at greater than 140 years (100 years for BWBS). Other ecosystems within NDT1, NDT2, NDT 4 and NDT5 are considered mature starting at 80-120 years, and old greater than 250 years. For simplification the table below lists all subzone/variants recognized under NDT3, and calls them Subzone Group A. All subzone/variants recognized under NDT1, NDT2, NDT 4 and NDT5 are listed under, Subzone Group B.

GROUP A & B BIOGEOCLIMATIC ZONES IN TRITISH COLUMBIA

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