Relationships among crown condition, growth, and stand nutrition in seven northern Vermont sugarbushes

We compared growth with soil and foliar elemental composition in seven stands of sugar maple (Acer saccharum Marsh.) in northern Vermont characterized by high or low incidence of crown dieback over the period 1989-1992. In stands with low-quality crown conditions, such as elevated crown dieback, long-term basal area growth rates were approximately half of those in stands with higher crown quality. Average annual basal area growth was 17.5 cm2 for dominant trees in these stands during the period 1953-1992 compared with 32.3 cm2 for trees in higher quality stands. The occurrence of elevated crown dieback was apparently unrelated to stand characteristics such as stand age, basal area, stem density, elevation, or aspect among the stands sampled. Stands with elevated crown dieback were found on soils characterized by low pH (< 4.0), low base cation pools (particularly Ca and Mg), and higher Al in soil surface horizons than higher quality stands. Over 4 years, sugar maple stands with elevated crown dieback exhibited significantly lower (P < 0.01) foliar Ca concentrations and somewhat lower foliar N and Mg than higher quality stands, while soil and foliar K were similar in both dieback classes. Among survey plots sampled in 1989, soil pH and Ca were strongly correlated with foliar Ca and K (P < 0.001). Soil pH, soil Ca, and foliar Ca were also strongly correlated with the level of crown dieback among plots and stands (P < 0.0001). Our results indicate that podzolic soils in northern Vermont may present marginal conditions for sugar maple growth in terms of soil pH and soil Ca availability, but that P and K pools appear to be sufficient for growth. While a lack of historical data prevents identification of long-term trends in nutrient availability in these soils, factors promoting losses base cations from acidic, base-cation-poor Podzols may also exacerbate foliar nutrient deficiencies and thus affect the crown condition of sugarbushes in northern Vermont.