Using the Group Fragments Tool

As discussed in Key Concepts, we will have to group some of the polygons of the inventory into "blocks" to simplify the landbase for Patchworks. Knowing in advance how Patchworks carries out blocking directs you to what information is necessary in your inventory.


A Block is the smallest spatial unit of the model that can consist of one or more polygons from the original inventory (managed and/or unmanaged) and is relatively homogenous for silviculture since it will be the 'building block' for harvest areas.

Since the spatial coverage of your landbase will be used as an input, you must be extra sure that this key dataset is in good shape and includes the necessary fields to link to aspatial data. Once we have kneaded and manipulated the spatial inventory into shape, we refer to the cover as the "fragments" file, as it contains the original inventory polygons that will be grouped into blocks. The fragments file should contain:

Specifically, the fragments file must include fields for the following information:

  1. Unique Polygon ID

    • There must be only one polygon per id number.

  2. Area

    • This field must be present - check that it is correct!

  3. Age

    • This field must be present in years.

  4. Eligibility for blocking

    • This field will determine whether or not the polygon should be included in the analysis. Stands should not be included in the analysis if they are missing the necessary data and don't contribute to key model indicators (this can drastically reduce the size of the dataset). Some common fields used to reselect from are Forest Unit (could be an unclassified stand), Yield Curve (no growth information) or Owner (could be private land).

  5. Stratification

    • The fields used to determine which polygons can be grouped, must be also be present in the inventory. Common stratification fields are forest unit, silvicultural intensity, depletions and succession pathways, land ownership and habitat reserves.


If several analyses are going to be performed to compare differences in land base configurations, separate availability fields should be created to represent the different net downs. Separate datasets can then be created by changing a few parameters in the ForestModel XML before running through the Matrix Builder.