Updated: Aug 7
Yearly inventory I'm defining here is where a separate inventory is made and maintained over the span of a single year. At the end of the year, a copy is made for the new year and maintenance continues anew.
This has advantages like an archive of prior years and freedom to change stands as needed during the current year without fear of messing up prior year archives.
There are a few necessary features to accomplish this though and they can get a bit obscure. And like any process, there are the nice to haves that are usually works in progress.
I'm hoping to discuss and explain how Assisi accomplished these here.
The Assisi Library is "open blog space" where you are encouraged to comment and even edit the blog itself. Posts are not fixed in time so the blog itself will get updated as we go.
Cruise Data and Inventory Units
It is typical for cruise data to be stored in a single unit, separate from units made for inventory years. The cruise data unit is not an inventory: it is simply a repository of all cruises for all time. The cruise data unit is filled with stands (or strata) and the actual cruise data performed in the field. The inventory units are filled with stands that exist during a given inventory year and use the expansion process to copy cruise results from the cruise stands to the inventory stands.
Inventory units often use the year of inventory for their name. Each new inventory year a new unit is made. Over time, the database stores inventories for prior years in a convenient archive.
To give the inventory units an actual inventory (trees, volumes etc.) the cruise data are compiled and then results copied over to inventory stands. This process is called Expansion in Assisi.
Each stand in an inventory unit gets an expansion record that determines the cruise data source inventory will be copied from. A single cruise data stand can be mapped to any number of inventory stands for example in a stratified inventory. The source cruise data stand and the destination inventory stand end up having the same content: trees, species, cover, etc.
Cruise data are often many years old. Assisi's growth process estimates growth to give a more accurate up to date estimate of inventory. During growth processing, Assisi can simulate a number of actions such as stand establishment, planting, fertilization, thinning, clear-cutting and stand disposal. These historical actions are defined in Assisi's history tables. A typical stand history might be:
9/15/2000 Establish - The first date the stands polygon began to be tracked.
10/15/2000 Plant - Stand was planted. Assisi records species and density of seedlings.
2/15/2003 Fertilization - Assisi can simulate an application of nitrogen.
10/15/2015 Precommercial Thin - Simulate removal of under performing trees.
10/15/2035 Commercial Thin - Selective harvest of marketable trees.
10/15/2050 Clearcut - Final cut of stand.
10/15/2050 Disposal - Stand polygon and name are no longer being tracked.
Each of these history records allows Assisi to more accurately estimate the inventory as the years progress. The effect of some actions, such as fertilization, depends on the growth model being used.
Where to Store History
History can be stored on either the cruised stands or the inventory stands. The choice depends on what stands you are growing to obtain the current year inventory.
When history is stored on cruise data, cruise data should be grown first before expansion run. If a cruised stand was thinned or modified, you will want that history simulated during growth and the results copied over to inventory stands. Storing history on cruise data has the advantage that history occupies a single location for all inventories: on the cruised stand records.
When history is stored on inventory stands, expansion should be performed first then growth run on the expanded inventory. Growth will simulate the stand history to create a current inventory.
Storing history on the inventory stands rather than the cruised stands has the advantage of being able to process partial harvests and stand splitting. Cruise data reflects a stand as it existed at the time of cruise. If a stand has been partially harvested or split, a history record for the split can be stored on the inventory stand and the split simulated when the inventory stand is grown.
The process of Expansion in Assisi starts with adding Expansion records to stands. Expansion records are kind of like Cruise records in that both specify what the source of an inventory is. For a Cruise, the source is a cruise. For an Expansion, the source is another stand's inventory.
Define Expansions as you would Cruises using the Field Data Editor.
Note that each Expansion defines the source unit and stand as well as overrides for the stand's growth year, total and breast height age. After the expansion is processed,the destination stand will have the same inventory but different growth year and age if the overrides are set.
Expansions are processed like growth is processed: select stands (shift click) and press the Expand button:
Expansion does not compile cruise data so selected plots are ignored. Each source stand should already have an inventory. Whether cruised or grown, whatever the source stand's inventory is, it will be copied to the destination stand.