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Stand and Tree Integrated Model
The growth processes included in stand growth model, the individual tree model, and in the reconciliation adjustment are described below.
Stand Growth Model
This component is the focal point model of the whole model system. It is similar to that described by Hyink et al. (1988): top height increment is first derived from height-age curves; survivor basal area is next predicted as a function of top height increment and other known variables; mortality and ingrowth are predicted subsequently. Predictions are made in annual increments as follows:
Tree Growth Model
This component serves several purposes: it provides data on the stem diameter distribution of the grown stand, it serves as an independent check of the stand model projections, and it can be used on a stand-alone basis. The model operates by making projections of class averages. Typically, these averages are input by the user. If not, they will be generated by the model, in which case they will comprise 12 classes with an equal number of trees in each class. Apart from trees that die, a tree will thus remain within a class for the duration on the projection period. Similarly, apart from ingrowth, the number of classes will remain constant. The steps of the tree model prediction are as follows:
The reconciliation process is one of adjusting the output form one model to correspond with the output from the other. Generally, the tree model output is adjusted to that of the stand model, under the assumption that the later gives more robust projections at the stand level. The adjustments consists of:
More information about STIM development can be found in the publication by Bonnor et al. (1995).
Western hemlock: most of the data used to develop STIM is a product of the Western Hemlock Cooperative Database Project, completed by the Stand Management Cooperative in 1985. It is calibrated for both natural and thinned western hemlock stands in coastal B.C., Oregon, and Washington. The database has an age range from 7 to 110 years (breast height age), top heights from 5.5 to 50 m, and site index from 21 to 42 m. The database summary by ownership is presented in Table 1.
After the validation and editing procedures the original 1662 plots were reduced to 1339 plots containing 5304 measurement sets with an average of 3.96 measurement sets per plot.
Trembling aspen: this version calibrated for both natural and thinned trembling aspen stands based on data from across Canada. The database has an age range from ? to ? years (breast height age), top heights from 12 to ? m, and site index from ? to ? m.
Model Components (Interface)
Each stand scheduled for projection is either a young (seedling) stand or an older (tree) stand. The three options of the "Stand Input" selection are:
Data can also be input through the "Command" line box. Any missing data are generated STIM to ensure that a full set of data is available for input into the predicting equations.
Growth Options: A stand can be grown using three approaches:
Silvicultural treatments: the only silvicultural treatments available is the thinning option. The user should enter amount and type of thinning to be done.
Other options: On the menu bar, the "File" option includes the capability of accessing a filed set of stand and tree data, and of deleting one or more stands. The "Options" include model control choices:
It also includes a capability of setting and changing default values, and entering batch commands to process batch data.
Model output can be in the form of tables or graphs. Link to the following examples.
STIM generates growth and yield information for even-aged stands of coastal western hemlock and trembling aspen. It is mainly used for:
Some of the limitations of STIM are:
Last Modified: 2002 OCT 25. Ministry Contact: Mario di Lucca