Subject: New ACORNS Event Monitor function
Name: C. Keyser
Date: March 15, 2012
Variants affected: All

Description: This function,ACORNS(a,b), returns the number or biomass of acorns 
per acre from the specified oak species as described by Rose et al. (2011). Acorns 
are assumed to come from dominant and co-dominant trees with DBH 5 inches or greater. 
A tree is considered dominant or co-dominant if it is at least as tall as the 60th 
percentile tree in the height distribution. This function is applicable to the central
and southern Appalachian mountains and possibly throughout the eastern US where these 
species occur.

Argument 1: Code indicating which value to return, as follows:
1 = number of acorns per acre
2 = pounds of acorns per acre

Argument 2: Species code (species alpha code, species sequence number, species group name, 
or species group sequence number). Only trees of the specified species or species group 
that are also in the list of recognized oak species below will be included. Any species not 
in the recognized list are ignored. Code a zero (or All) to include all of the recognized 
oak species shown below.

Recognized Oak Species
BO = black oak
CO = chestnut oak
RO = northern red oak
SO = scarlet oak
WO = white oak

Rose, Anita K.; Greenberg, Cathryn H.; Fearer, Todd M. 2011. Acorn production prediction models
for five common oak species of the eastern United States. The Journal of Wildlife management.
9999:1-9; DOI: 10.1002/jwmg.291

Impact on users: Users have the ability to calculate acorn production.

Files:
./base/evldx.f - added ACORNS instruction and execution code.
./base/algkey.f - added ACORNS to keywords and opcodes.
./base/algev.f - added branch to execute ACORNS operation.
