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Estimating Gap Origin Probabilities for Canopy Trees
Author(s) -
Lorimer Craig G.,
Frelich Lee E.,
Nordheim Erik V.
Publication year - 1988
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1941026
Subject(s) - tsuga , understory , canopy , yellow birch , range (aeronautics) , diameter at breast height , ecology , hardwood , maple , tree canopy , silviculture , biology , forestry , environmental science , geography , materials science , composite material
A method is presented for estimating the probability that existing canopy trees were growing in gaps during the sapling stage, given observed mean 5—yr radial growth rates starting at the point where the trees were 4 cm diameter at breast height (dbh). Required calibration data are frequency distributions of radial growth rate for existing saplings that are currently suppressed in the forest understory vs. those of saplings growing in gaps. Threshold growth rates for high confidence of gap origin are calculated in an iterative fashion using growth rate data and interpretation of radial increment patterns. The method is illustrated with data from sugar maple (Acer saccharum) and eastern hemlock (Tsuga canadensis) in mature and old northern hardwood forests of western Upper Michigan. The proportion of canopy trees that had been growing in gaps during the sapling stage ranged from 35—67% in different stands. This wide range suggests the adaptability of these two late—successional, shade—tolerant species to a variety of stand microenvironments.