Number of trees that the tree object represent on the sample plot. Can be more than one if the tree object represents a group or cohort of trees.
If the value is 1 in the first period, it will usually be less than 1 in subsequent periods due to mortality, since mortlaity probablibilty is
applied as a frequency, where a tree object is considered a representative of a group of trees rather than an actual tree individual.
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2