|
TASS is a very successful tool for describing and predicting the growth
of even-aged stands. We are currently expanding TASS to include uneven-aged stand
capability.
Transition from even-aged to all-aged simulations.
To achieve this goal, a number of new technologies are being developed and/or added to TASS:
 |
1) Trees of various ages must be able to coexist in the
modelled stand. This means that crowns of younger trees must be able to survive and develop
under fragmented crowns of older, taller trees. |
 |
2) Uneven-aged stands do not have a clearly defined
beginning, so TASS must be able to read in a stand description, and project that
stand into the future. |
 |
3) As the stand develops, trees will die, and new
trees will establish themselves. In order to simulate natural regeneration, TASS must contain a mechanism to generate seedlings at the appropriate times and locations. |
Assuming all trees in the stand have the same age has
allowed for a number of conveniences in TASS. These assumptions must now be removed,
and dealt with in a more general manner.
Even-aged TASS
|
All-aged TASS
|
| Every stand can be generated from age 0 |
Can start from arbitrary existing stand |
| Tree mortality can be "guided" by top height. |
Mortality guided by tree surroundings |
| Trees falling below the main canopy can be slowly ignored, as they
contribute less and less to stand statistics and harvestable products. |
Trees below canopy may be new seedlings, released to full growth following
removal of larger trees by mortality or thinning. |
| Crowns expand until they bump into neighbours |
Crowns expand until there is insufficient light |
Eliminating the even-age assumptions will require substantial
modifications to the core components of TASS.
In summary, TASS must have these new abilities:
Research Branch contact: Ken Polsson
|
