My colleague and I were going over some numbers that he generated using rFIA and grouping by SUBP. He compared those to values that I had scripted out by aggregating from TREE table that I pulled directly from FIADB. The data from the tree tables were both identical; the issue came when summarizing at the subplot level. rFIA values of TPA and total BA were too low when grouped by the subplot level. We determined that this is because, in rFIA, the TPA_UNADJ is not being multiplied by 4 to account for the smaller area in a subplot compared to the entire plot. This is a major problem for anyone using rFIA for subplot level aggregations who is unaware that the returned values should be multiplied by 4 to be correct.

I see 2 potential solutions - it could be either preventing aggregation at the subplot level, or altering the rFIA package so that when SUBP is selected as a grouping variable, TPA_UNADJ is multiplied by 4. There may be another solution that I’m not considering.

Thanks for addressing this.

-Erin Berryman (RMRS-FIA)