Size-specific mortality, growth, and structure of a Great Smoky Mountains red spruce population

Abstract

Old-growth population dynamics of Picearubens Sarg. were studied in a montane spruce–fir forest in North Carolina and Tennessee. Size-class structure fit a semilogarithmic rotated sigmoid curve typical of a stable population. Although the population contained trees of all ages, a large proportion of the population was less than 100 years old; few trees were greater than 350 years old. Mortality rates were estimated from a 2-decade census and from population structure data. For trees above breast height, annual mortality was approximately 1% of the population. Small trees (<30 cm dbh) and large trees (>60 cm dbh) had mortality rates exceeding 0.7% per year. Intermediate-sized trees tended to have low mortality rates (<0.5% per year) and high radial growth rates. Growth in the 10-year interval preceding death tended to be slow for standing dead trees. Standing death of canopy trees was more prevalent than death by windfall. These findings emphasized the influence of stand dynamics on spruce growth and mortality.