Gradient Analysis, Ecotones, and Forest Communities

Abstract

The analysis of changes in distributions and relative dominances of individual tree taxa emphasizes their autecological responses to environmental changes. Analyses of pollen accumulation rates (PAR) indicate that in addition to inherent life-history strategies of individual taxa, changes in dominance may be related in part to competition during times of invasion and population expansion. When the late-Quaternary vegetational record is examined in this light, the impression gained is one of ecological interactions predominantly on the population level. However, the paleovcgetation data (the array of dominance of taxa by site and by time) are also pertinent to quantitative plant community analysis. In this chapter we ask questions relevant to determining whether temperate forest communities have been stable through time, in the sense of long-term persistence as intact assemblages. We also examine changes in the position and steepness of ecotones between major forest types through the past 20,000 years.