This study reports on woody plant succession patterns in experimental plots initiated in 1989 at the Hutcheson Memorial Forest Center, New Jersey Piedmont region. The random block experiment was set up 20 years ago; it was intensively sampled for five years; it was last sampled 10 years ago. The experimental design tested the importance of starting conditions to plant community succession by altering physical or biological variables after plowing the fields. The physical treatments consisted of either a control treatment, a shade tent treatment, a 70% covering of mulch, or sulfur to lower the nutrient availability. The biological conditions were native seed additions of early, middle, and late succession plants, or a control of no seed additions. Seed additions and shade tents were stopped after three growing seasons. Sulfur and mulch applications only occurred at the beginning of the study. Our sampling strategy focused on woody species. We counted the number of species, the number of individuals, took the DBH of the saplings and mature trees on each plot, and sampled seedlings using random quadrats to determine the numbers and species.
Results/Conclusions
Initial physical treatments had significant impacts on the present day vegetation. The highest species diversity and density of trees with a DBH greater than 10cm were found on plots with the shade treatment, and lowest on the plots with the sulfur treatments. Although Juniperus virginiana was the dominant species in all treatments, its relative importance was highest on the sulfur treated plots, and lowest on the control and shade treated plots. Prunus serotina and Betula populifolia had the highest relative importance of all the deciduous trees in all treatments except the sulfur treatment, where the invasive species Elaeagnus umbellata was dominant. Seed treatments had very little impact on any of the measurements except the number of trees over 10cm in diameter, where nearly half of the trees belonged to the plots treated with a mix of early succession seeds. Seedling species and number adhered to the same general patterns as mature trees. These results indicate that the differences in initial conditions in old-fields on the New Jersey Piedmont can lead to long term differences in vegetation, and that physical conditions immediately after abandonment have a greater impact on the subsequent vegetation than the composition of the seed banks.
