Dear colleagues, I am looking for empirical tests of the accuracy and efficacy of the absolute density and basal area estimations in stands using the point- centered quarter (PCQ) sampling method (Cottam & Curtis 1956). I am an academic grandson of Curtis and used this method for my Ph.D. research, but after 35 years of increasing doubts am now involved in a project (PalEON project funded by NSF Macrosystems) where we need to determine the efficacy and confidence of these estimates. I am aware of seven published studies comparing point-quarter numbers with conjunct plot/map determinations, overall giving very unstable results. I know of the widespread use in class field exercises classes and other unpublished studies. Thus I would like to hear off-list from anyone with comparisons of the point-centered quarter sampling method with plots/tallies/mapped stand data. Simple summaries of the absolute density and basal areas from PCQ and census methods with a brief description of location, forest type, dbh cutoffs, number of points, total census method, and researcher credit are entirely sufficient. I hope that this will finally lead to a perspective on the use this widespread forest census methodology use by ecologists and educators.
Best, Charlie Cogbill Collaborator Harvard Forest 82 Walker Lane Plainfield, VT 05667 802 454-8619 [email protected]
