Native American geography shaped historical fire frequency in forests of eighteenth-century Pennsylvania, USA.

Researchers have debated the relative importance of environmental versus Indigenous effects on past fire regimes in eastern North America. Tree-ring fire-scar records (FSRs) provide local-resolution physical evidence of past fire, but few studies have spatially correlated fire frequency from FSRs with environmental and anthropogenic variables. No study has compared FSR locations to Native American settlement features in the eastern United States.

A regional assessment of white-tailed deer effects on plant invasion.

Herbivores can profoundly influence plant species assembly, including plant invasion, and resulting community composition. Population increases of native herbivores, e.g.

Is climate an important driver of post-European vegetation change in the Eastern United States?

Many ecological phenomena combine to direct vegetation trends over time, with climate and disturbance playing prominent roles. To help decipher their relative importance during Euro-American times, we employed a unique approach whereby tree species/genera were partitioned into temperature, shade tolerance, and pyrogenicity classes and applied to comparative tree-census data. Our megadata analysis of 190 datasets determined the relative impacts of climate vs.

Age class, longevity and growth rate relationships: protracted growth increases in old trees in the eastern United States.

This study uses data from the International Tree-Ring Data Bank website and tree cores collected in the field to explore growth rate (basal area increment, BAI) relationships across age classes (from young to old) for eight tree species in the eastern US. These species represent a variety of ecological traits and include those in the genera Populus, Quercus, Pinus, Tsuga and Nyssa. We found that most trees in all age classes and species exhibit an increasing BAI throughout their lives.

Ecophysiological analysis of woody species in contrasting temperate communities during wet and dry years.

This study employed an intensive sampling regime in which leaf gas exchange and tissue-water relations were measured simultaneously on the same leaf at midday on 19 tree species from three distinct forest communities during wet (1990) and dry (1991) growing seasons. The study sites were located on a xeric barrens, a misic valley floor, and a wet-mesic floodplain in central Pennsylvania, United States. The xeric, mesic, and wetmesic sties had drought-related decreases in gravimetric soil moisture of 53, 34 and 27%, respectively.

Genotypic and phenotypic variation as stress adaptations in temperate tree species: a review of several case studies.

Species that occupy large geographic ranges or a variety of habitats within a limited area deal with contrasting environmental conditions by genotypic and phenotypic variation. My students and I have studied these forms of ecophysiological variation in temperate tree species in eastern North America by means of a series of field and greenhouse experiments, including controlled studies with Cercis canadensis L., Fraxinus pennsylvanica Marsh.

Adaptations and responses to drought in Quercus species of North America.

Most North American oaks (Quercus spp.) are adapted to drought-prone sites by an ability either to avoid, or to tolerate, water stress, or both. Generally, they have deep-penetrating root systems, enabling them to maintain relatively high predawn water potentials during drought.