An historical perspective on forest decline of eastern white pine : Air Pollution and Forest Decline. 14th International Meeting for Specialists in Air Pollution Effects on Forest Ecosystems

1989

1 Abb., 33 Lit. Ang.

Unselbständiges Werk

9091

200034646

A compilation and review of over 60 foliar injury surveys of eastern white pine since 1900 throughout its natural range has found that all but a few fail our criteria for scientific acceptance. Most were not based on random sampling of symptomatic and asymptomatic trees or used non-diagnostic symptoms. The few surveys that were scientifically acceptable were performed at the margins of the natural range of the species and do not convey an overall picture of foliar injury that ist consistent with air pollutants as causal agents. It appears customary to asume that a survey that detects sublethal foliar injury is equivalent to saying that the species surveyed is undergoing forest decline, an assumption we question because of uncertainly about the relationship between foliar injury and tree growth and mortality. Nevertheless, we examined injury surveys and found that current foliar injury incidence and severity levels for white pine form two patterns. One symptom (chlorotic mottle) occurs locally at high incidence but very low severity, while necrotic needle trees occur locally at very low incidence but high severity. Three lines of evidence are described that challenge lines of evidence are described that challenge the notion that eastern white pine as a species is hyper-sensitive to air pollutants. Hypersensitive individuals occur rarely in stands and, if stressed, may undergo tree decline. However, due to voids in our knowledge base, we can find no compelling evidence that the species is or is not a proven case of forest decline.