In 2002, the abundance of A. altissima within the woodlot interior was determined using transects running through the woodlot beginning at the woodlot edge.
All A. altissima stems found within a plot were counted and assigned into size classes: 1 = stems < 30 cm in height were considered seedlings or small clonal sprouts, 2 = stems 30-133 cm (saplings), 3 = stems [greater than or equal to] 134 cm, but not a canopy tree (subcanopy), and 4 = any canopy tree.
Macroplots were used to examine the relationship between A. altissima population density and distance from the woodlot edge, as well as the annual understory survival rate of A.
Within each subplot, including edge plots, all A. altissima stems were counted, tagged, and assigned one of the same size classes as described for the transects.
In order to determine the annual mortality of the tagged understory A. altissima stems we resampled three of the macroplots (O1, O2, and S2) in mid July 2002.
If A. altissima was present, we visually estimated the fraction of the foliage that was A.
For the transect plots, chi-squared tests compared similarities in the frequency of occurrence of A. altissima for the old and secondary growth woodlots.
Variables included distance from the woodlot edge, number of A. altissima stems, basal area of A.
Achenes of Ageratina luciae-brauniae were sown [TABULAR DATA FOR TABLE 1 OMITTED] on 5 October 1987 on a sandstone-derived soil collected on the Allegheny Plateau in Vinton County, Ohio, and those of A. altissima were sown on 26 October 1994 on a 3:1 (v/v) mixture of limestone-derived topsoil and river sand.
Unlike freshly matured achenes of Ageratina luciae-brauniae, most of those of A. altissima were dormant when dispersed in mid-autumn (Table 2).
Dormancy loss in achenes of A. altissima is similar to that in the majority of species in the Asteraceae in temperate eastern North America (cf.
There is a possibility that achenes of Ageratina luciae-brauniae and A. altissima collected from other populations in the geographic range of each species might differ in the degree of dormancy.
In contrast, achenes of A. altissima required light to germinate at high percentages (Table 2).
Most achenes of A. altissima are not dispersed until after the middle of November (C.
On the other hand, most A. altissima achenes dispersed at the time of maturation in late autumn are unlikely to germinate because of low temperatures.