SUGAR MAPLE DECLINE DISEASE ACROSS A GRADIENT OF GEOLOGIC SUBSTRATES

Sugar maple decline disease, or multiple stress syndrome, has been reported sporadically across the range of the species during the 20th century, and with increasing severity and frequency over the last 25 years. We studied a particularly widespread and severe episode focused on the Allegheny Plateau of northwestern Pennsylvania during the 1980's to early 1990's. Forty three study stands were established to document health, nutritional status, and site characteristics across the range of soils where sugar maple is found. Declining stands were located on unglaciated plateau tops while stands on unglaciated side and lower slopes and all glaciated sites remained healthy. All declining stands had calcium and magnesium, as measured by foliar or soil chemistry, below a threshold level and a history of severe insect defoliation in the preceding decade. Stands with poor calcium and magnesium nutrition and little defoliation pressure, and stands with good calcium and magnesium nutrition, regardless of defoliation history, remained healthy. Seeps delivering deep weathering products to the rooting zone were responsible for better nutrition on lower slope, unglaciated sites. Glaciated sites had better nutrition due to replenishment of weatherable minerals in glacial soil parent materials. A retrospective soil sampling program found that unglaciated plateau top sites had soil calcium and magnesium above threshold levels in 1967, but below in 1997. These results suggest that the unglaciated plateau top has been particularly susceptible to base cation depletion, inferred to be the result of high levels of anthropogenic acid deposition.