Adapting a mortality model for southeast interior british columbia
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Adapting a Mortality Model for Southeast Interior British Columbia. By - Temesgen H., V. LeMay, and P.L. Marshall University of British Columbia Forest Resources Management Vancouver, BC, V6T 1Z4 The 2001 Western Mensurationists' Meeting Klamath Falls, Oregon June 24-26/2001.

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Adapting a Mortality Model for Southeast Interior British Columbia

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Adapting a mortality model for southeast interior british columbia

Adapting a Mortality Model for Southeast Interior British Columbia

By - Temesgen H., V. LeMay, and P.L. Marshall

University of British Columbia

Forest Resources Management

Vancouver, BC, V6T 1Z4

The 2001 Western Mensurationists' Meeting

Klamath Falls, Oregon

June 24-26/2001


Adapting a gy model

BC Biogeoclimatic

Ecosystem

Classification units

US Habitat Types

Adapting a GY model

  • The Northern Idaho prognosis variant (NI) has been adapted to the southeast interior of BC, PrognosisBC


Adapting a gy model cont d

Adapting a GY model (cont’d)

  • Different measurement units (metric), basic functions (e.g., volume and taper) and standards

  • Classification of US habitat type to BEC can be subjective

  • Sub-models coefficients and model form may not fit BC data

  • Insufficient ground data for some types of stands


Adapting a mortality model for southeast interior british columbia

Adapting a GY model

  • Sub-model components:

  • large tree diameter and height growth

  • small tree diameter and height growth

  • small and large tree crown ratio

  • mortality and regeneration

  • others


Background

BACKGROUND

  • Mortality is:

    • an essential attribute of any stand growth projection system

    • frequently expressed as a function of tree size, stand density, individual tree competition, and tree vigor

  • In PrognosisBC, periodic mortality rate is predicted using tree (Ra) and stand based (Rb) mortality functions


Background cont d

BACKGROUND (cont’d)

  • Ra is a logistic function of tree size taken in context of stand structure.

  • Rb operates as a convergence on normal basal area stocking and maximum basal area (BAMAX)

  • Rb isbased on the concept that:

    • for each stand, there is a normal stocking density

    • there is a BAMAX that a site can sustain and this maximum varies

      by site quality


Objectives

Objectives

  • to adapt a mortality model for southeast interior BC

  • to evaluate selected mortality models for conifers and hardwoods in southeast interior BC


Methods

METHODS

  • Three approaches of adapting mortality model were assessed, using BC based PSPs:

    • a multiplier function (Model 1)

    • re-fit the same model form by species/zone combination (Model 2)

    • changing variables (Models 3, 4, and 5)

  • PSPs that were re-measured at 5 to 12 years interval and that consistently included all trees > 2.0 cm were included


Methods cont d

METHODS(cont’d)

  • For each PSP, individual tree records were coded, as either live or dead at each measurement period, and variables listed in the mortality models were extracted


Methods cont d1

METHODS (cont’d)

  • Only species/zone combinations with more than 30 dead trees were selected.

  • To handle the unequal re-measurement periods in the PSP data sets, each model was weighted by the number of years between remeasurement periods.

  • The PSP data set was divided into model (70%) and test data (30%) sets  

  • Observed and predicted number of live and dead trees by species/zone were compared and then a model was selected


Results

RESULTS

  • Noticeable differences were found in the % of correctly classified trees among the five models and the species/zone combinations considered in this study

  • Model 5 had lower Akaike Information Criterion (AIC) and Schwartz Criterion (SC) for most species/zone combinations


Percent of correctly classified trees in the ich zone using test data

Percent of correctly classified trees in the ICH zone, using test data


Adapting a mortality model for southeast interior british columbia

Number of observed (N_OBS) and predicted (N_Exp) dead trees by species in the ICH zone, using Model 5 on test data


Adapting a mortality model for southeast interior british columbia

Number of observed (N_obs) and predicted (N_Exp) dead trees by diameter class in the ICH zone, using Model 5 on test data


Percent of correctly classified trees in the idf zone using test data

Percent of correctly classified trees in the IDF zone, using test data


Adapting a mortality model for southeast interior british columbia

Number of observed (N_OBS) and predicted (N_Exp) dead trees by species in the IDF zone, using Model 5 on test data


Adapting a mortality model for southeast interior british columbia

Number of observed (N_obs) and predicted (N_Exp) dead trees by diameter class in the IDF zone, using Model 5 on test data


For species zone combination with little or no data

For species/zone combination with little or no data

  • substitution by similar species or BEC zone is suggested.

    FORUSE

    • Bl in IDFICH

    • Cw in IDF ICH

    • E in MSICH

    • Fd in PP IDF


Summary

Summary

  • Model 5 predicts mortality of both conifers and hardwoods reasonably well

  • BC based BAMAX values improved the predictive ability of the model

  • Inclusion of eco-physical factors such as slope, aspect, and elevation into the mortality model might increase the predictive ability of the model.


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