CONTRASTING RADIAL GROWTH AND CANOPY RECRUITMENT PATTERNS IN LIRIODENDRON-TULIPIFERA AND NYSSA-SYLVATICA - GAP-OBLIGATE VERSUS GAP-FACULTATIVE TREE SPECIES

Radial growth patterns, canopy recruitment characteristics, and distur bance histories were examined in a shade-tolerant species, Nyssa sylva tica Marsh., and a shade-intolerant species, Liriodendron tulipifera L ., to determine the influence of canopy gaps in species with contrasti ng life histories. Tree cores of these co-occurring species were taken from three mixed-Quercus forests in northern Virginia. Most N. sylvat ica individuals became established prior to 1850 and experienced multi ple release and suppression periods coinciding with logging during the late 1800s and early 1900s. Many L. tulipifera became established dur ing the early 1900s following logging, and only a few individuals expe rienced prolonged suppression periods. Regardless of site, L. tulipife ra grew faster than N. sylvatica (average radial growth >1.70 mm/year for L. tulipifera vs. <0.82 mm/year for N. sylvatica.). Liriodendron t ulipifera also exhibited longer periods of mean yearly growth >2 mm (1 5-37 years for L. tulipifera vs. <5 years for N. sylvatica). Consecuti ve growth <0.5 mm/year ranged from 43 to 66 years in N. sylvatica vs. 2-11 years in L. tulipifera. Ring width patterns indicate that both sp ecies used different strategies following disturbance that enabled the m to coexist in these forests. Nyssa sylvatica persisted in subcanopy positions for extended periods of time but was capable of responding t o release even after 170 years (i.e., gap facultative). In contrast, L . tulipifera appeared to rely on a strategy of rapid height and radial growth for canopy accession following large disturbances (i.e., gap o bligate). The results of this study indicate the importance of using d endroecological techniques in the study of forest dynamics and species ' growth strategies.