Potential Natural Vegetation and Landscape simulation Review and progress to date by Jennie Pearce P

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Potential Natural Vegetation andLandscape
simulationReview and progress to dateby
Jennie PearcePearce Associates Ecological
Research
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What is PNV?

• the vegetation structure that would become
  established if all natural sequences were
  completed without interference by man under the
  present climatic and edaphic conditions
  (including those created by man)
• Definition implies only latest seral stage
  considered
• Definition does not include natural disturbance

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Mapping PNV

• Four mapping methods
• Map presettlement condition using land surveyor
  records,
• Model individual species using land surveyor
  records, and combine these individual models to
  derive maps of ecosite distribution.

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• Model individual species using current records,
  and combine these individual models to derive
  maps of ecosite distribution
• Derive expert rules to relate ecosites to mapped
  environmental variables.

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But .

• Our goal is to
• all seral stages that would be expected to occur
  in a naturally functioning ecosystem under a
  natural disturbance regime, given present
  climatic and edaphic conditions.
• Therefore, we need a temporal component to the
  definition, so that the PNV represents
• all seral stages
• under a natural disturbance regime ,
• given present climatic and edaphic conditions.

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• Therefore we need to
• Derive rules to map oldest seral stage ecosites
• Use VDDT to adjust the landscape based on
  disturbance history to assign younger seral stage
  ecosites to the landscape

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5 START
5 START
Topography Digital elevation model, slope,
topographic position, moisture index.
6.1 Project objectives
Define GIS mapping rules for each vegetation unit.
Soil properties Drainage, wetness, acidity, soil
texture, fertility.
Expert knowledge.
6.2 Planned uses of PNV model
6 Expert Panel Bounding discussion
6.3 Selected vegetation unit
3.2.4 Are there unique mapping rules for each
vegetation unit?
No
Geology Bedrock, surficial.
Yes
3.2.3 Map vegetation units in GIS.
6.4 Extent of study area
3.2.5 METHOD 1 Combine unmapped Vegetation
units into mappable Vegetation groups.
Disturbance Fire, wind, harvesting, succession,
insect
7.1 Specify linkages between vegetation units
OUTPUT Level 1 Succession pathways
7 Expert Panel define succession pathways
between vegetation units
3.2.6 METHOD 2 Identify probability of
occurrence for each unmapped vegetation unit to
identify the expected proportion of the landscape
occupied by each. Assign proportions to the
landscape.
7.2 Specify disturbance types that lead to
vegetation unit change
3.2.8 Simulate succession using VDDT and mapped
vegetation units to derive stable landscape
4.3 OUTPUT Level 3 Proportion of landscape in
each PNV vegetation unit
8 Develop draft state-transition models (VDDT
compliant)
8.1 Convert succession pathways to VDDT
state-transition models
3.2.9 Run TELSA using mapped vegetation units
to derive stable mapped landscape
8.2 Add transition probabilities obtained
through literature review
9 Expert panel Refine state-transition models
4.4 OUTPUT Level 4 Map of PNV
4.2 OUTPUT Level 2 VDDT State-transition
models for PNV vegetation units
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Next steps

• Expert workshops to define state transition
  pathways
• Expert workshop to define PNV mapping rules
• Input state-transition models into VDDT