A new method for capturing stem taper variation for trees of diverse morphological types

Understanding variation in tree stem form is fundamental to both ecological and economic assessments of forest ecosystem structure and function. Stem taper models (STMs) are widely used to describe tree form, but it can be challenging to apply them to trees with stems that diverge from an idealized norm, often leading to exclusion of many trees from stem taper studies. Here, new ‘whole-tree’ form type classes are advanced, as simple and useful groupings for capturing stem form variation of trees of diverse morphological types, and tested with a large tree data set without exclusion criteria. New form type classes explained much more of main stem form variation than knowledge of tree species, while ‘merchantable form types’ explained most stand-to-stand level variation. Broad-leaved species were much more likely to have complex stem forms than needle-leaved, but species ‘evergreeness’ was a very weak predictor of stem form variation, when tree and stand –level form variation was accounted for. A new, generalized framework for stem taper modeling is demonstrated, using both species and merchantable form types to capture tree-level random effects. New form types and the STM approach are relatively easy to apply and should be relatively simple to integrate into any conventional forest inventory system. Overall, the study demonstrates the importance of including and accounting for the diversity of observed stem forms in developing STMs.

The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.