Multivariate Analysis of Radial Growth of Black Cherry (Prunus serotina Erhr.) in Southern Wisconsin Oak Forests

Abstract

Following extensive disturbance of oak forests in southern Wisconsin in the 1930 decade, black cherry, Prunus serotina Erhr., successfully established across a wide range of habitats. The purpose of this study was to assess its ability to reach maturity on all parts of the moisture gradient. Radial growth in 122 black cherry saplings and trees was correlated with edaphic and micrometeorological parameters during 3 growth seasons. Although total basal area change and the duration of rapid growth increased consistently from suppressed through the dominant crown class, the metabolic potential was distinctly lower in the suppressed crown class. The intermediate crown class was very similar in metabolic potential to codominant and dominant classes. Correlation of growth rate to environmental parameters was complicated by marked within-season changes. Correlation between soil moisture and growth rate in 1965 showed a consistent monthly increase from May through August (r = .19*, -.27**, .34**, .38**, respectively*,** = statistical significance at .05 and .01 probability levels) but decreased in September (r = .14). Rapid soil moisture depletion in June coincided closely with the period of maximum growth acceleration. The growing seasons of 1964, 1965, and 1966 contrasted sharply in temperature and soil moisture levels. The Palmer severity index indicated that drought in 1964 was greater than in 1934. May-September air temperature and precipitation in 1965 departed only slightly, from normal while in 1966 air temperature was low. Analysis of growth response by principal components analysis and multiple regression clearly reflected these differences. Despite low metabolic potential and notable dependence on soil moisture levels, prediction of survival in suppressed strata was complicated by the marked capacity of black cherry to regenerate by means of basal sprouts and the eventuality of disturbance in the oak canopy. INTRODUCTION The purpose of this study is to determine significant factors controlling radial growth of black cherry (Prunus serotina Erhr.) in southern Wisconsin oak forests. In this area, oak forests originated with the cessation of fires which maintained prairie and oak savanna in the era predating Europ;ean settlement 125 years ago (Curtis, 1959). Black cherry is presently the most abundant species in sapling and small tree sizes but is relatively uncommon as a canopy tree (Curtis, 1959; Cottam, 1963). Its widespread establishment is the result of ubiquitous disturbances in the oak forest and its marked capacity for opportunistic behavior (Auclair and Cottam, 1971). Climax species such as Acer saccharum and Tilia americana with 1 Present address: Biology Department, McGill University, Montreal 101, Quebec, Canada.