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Has Pine Growth Declined in the Southeastern United States? *
Author(s) -
ZEIDE BORIS
Publication year - 1992
Publication title -
conservation biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.2
H-Index - 222
eISSN - 1523-1739
pISSN - 0888-8892
DOI - 10.1046/j.1523-1739.1992.620185.x
Subject(s) - forest inventory , basal area , geography , sampling (signal processing) , artifact (error) , forestry , environmental science , forest management , biology , computer science , computer vision , filter (signal processing) , neuroscience
The United States Forest Service inventory specialists discovered that since 1972 a significant decline has occurred in growth of natural pine stands in the southeastern United States. This decline was puzzling because neither internal nor external changes in stand conditions were a sufficient explanation. Nor did related observations help solve the puzzle: pine plantations in the same region showed no growth reduction; the decline was not associated with an increased level of pollution; no excessive loss of needles or change in needle coloration were found. Reexamination of the original inventory data that included the latest, third, growth period revealed that high basal area increments during 1961–72 were due to abnormally low basal areas at the 1961 inventory (third inventory). These data suggest forest decline prior to 1961, rather than after this date. A more plausible explanation is the deficiency of the data especially that collected during the third inventory when, for the first time, point sampling was used instead of fixed area plots. An analysis of increments from remeasured plots, numerous outliers, and inconsistencies in relationships between other variables raise further questions about the validity of the data. It seems that the reported forest decline is an artifact of shifting inventory protocols, the complexities of point sampling, and faulty treatment of the data. We need to know the true state of the nation's forests—both over‐estimates and under‐estimates of decline ultimately defeat sound management. My analysis concludes with the following suggestions for a revision of the Forest Service inventory system: incorporate forest inventory into the wider framework of Geographic Information Systems (GIS); make forest inventory useful to practicing foresters and not just to regional or national planners; use fixed area methods instead of point sampling; establish external quality control and quality assurance procedure, and develop procedures that take into account mutual correlation among plots by utilizing concepts of geostatistics, spatial analysis, and time series analysis.