Background: Past burning by Native Americans can be analyzed from tree-ring fire-scar records (FS... more Background: Past burning by Native Americans can be analyzed from tree-ring fire-scar records (FSRs) via dendrochronological methods. However, the degree to which FSRs have adequately captured the varied locations where Native Americans burned landscapes, at both local and regional scales, remains largely unknown. Also unassessed is whether individual studies utilizing FSRs provide adequate spatial contextualization of FSR sites alongside Native American geography (e.g. settlements, travel corridors) to facilitate understanding of spatial relationships between fire and settlement. This paper assesses (1) the representativeness of FSR sites with respect to Native American settlement (circa 1760-1820) in eastern North America, (2) whether FSR-based studies provide adequate contextualization of their study sites with respect to settlement, and (3) spatial relationships between settlement and fire frequency gleaned from available FSRs. Results: Many locations with past Native American s...
In a 2004 clearcut of a former even-aged oak (Quercus) forest, we examined the number and maximum... more In a 2004 clearcut of a former even-aged oak (Quercus) forest, we examined the number and maximum height of stump sprouts for three oak species in east-central Pennsylvania. The greatest number of sprouts was produced by black oak (Quercus velutina) and chestnut oak (Q.montana) as compared with white oak (Q. alba). Logistic regression showed that diameter of stumps was a significant factor in determining the probability of sprouting for black oak, and an inverse relationship between stump diameter and the number of sprouts per stump was foundfor all three species. The number of white oak sprouts peaked in the 10‐20-cm diameter class and declined on larger stumps. The number of black oak sprouts peaked in the 20‐50-cm classes, and trees in the 70‐80-cm class produced the fewest sprouts. The mean annual growthof the tallest sprout on each stump was greater for black oak and chestnut oak than white oak.
Background: The Ogasawara (Bonin) Islands of Micronesia lie in the western Pacific Ocean and are ... more Background: The Ogasawara (Bonin) Islands of Micronesia lie in the western Pacific Ocean and are unique in terms of their isolation, climate, soils and diversity of rare plant species. We hypothesized that the vegetation on the islands will be a robust model system to study long-term climate change impacts on vegetation dynamics. Methods: A large, long-term vegetation monitoring plot was established on Chichijima Island and measured in 1976 and 2017. It was located in an undisturbed dry forest area that contained many endemic and endangered species. Results: During the 41 year study period, total basal area of tree species increased by 24.6% and was dominated by Schima, Distylium and Pouteria, whereas tree density declined by 30%. Tree genera exhibiting the largest increases in basal area were Elaeocarpus, Ilex, Pandanus, Pouteria, Rhaphiolepis, Syzgium and Schima. During the study period, the annual average (23.2ºC), minimum and maximum temperatures increased by 0.5 to 0.8ºC, respe...
Long-term induced water stress in field-grown grapevine leads to a progressive decline of stomata... more Long-term induced water stress in field-grown grapevine leads to a progressive decline of stomatal conductance, accompanied by a decrease in CO 2 assimilation (40%). The apparent quantum yield also decreases (59%), which may reflect a relative increase in alternative processes for electron consumption. There is also a shift to non-stomatal regulation, as judged from significant depletions (37%) in maximum photosynthesis rate at saturating CO 2 related to limited ribulose biphosphate (RuBP) regeneration, whereas small, non-significant effects are observed on carboxylation efficiency. A high correlation (87%) between photosynthesis and stomatal conductance is observed for all experimental data and declines in intercellular CO 2 concentration parallel reductions in stomatal conductance. The data show that field response of grapevines to increasing soil water deficit involves stomatal and non-stomatal effects but, due to gradually induced drought, regulation mechanisms able to adjust me...
Background: Past burning by Native Americans can be analyzed from tree-ring fire-scar records (FS... more Background: Past burning by Native Americans can be analyzed from tree-ring fire-scar records (FSRs) via dendrochronological methods. However, the degree to which FSRs have adequately captured the varied locations where Native Americans burned landscapes, at both local and regional scales, remains largely unknown. Also unassessed is whether individual studies utilizing FSRs provide adequate spatial contextualization of FSR sites alongside Native American geography (e.g. settlements, travel corridors) to facilitate understanding of spatial relationships between fire and settlement. This paper assesses (1) the representativeness of FSR sites with respect to Native American settlement (circa 1760-1820) in eastern North America, (2) whether FSR-based studies provide adequate contextualization of their study sites with respect to settlement, and (3) spatial relationships between settlement and fire frequency gleaned from available FSRs. Results: Many locations with past Native American s...
In a 2004 clearcut of a former even-aged oak (Quercus) forest, we examined the number and maximum... more In a 2004 clearcut of a former even-aged oak (Quercus) forest, we examined the number and maximum height of stump sprouts for three oak species in east-central Pennsylvania. The greatest number of sprouts was produced by black oak (Quercus velutina) and chestnut oak (Q.montana) as compared with white oak (Q. alba). Logistic regression showed that diameter of stumps was a significant factor in determining the probability of sprouting for black oak, and an inverse relationship between stump diameter and the number of sprouts per stump was foundfor all three species. The number of white oak sprouts peaked in the 10‐20-cm diameter class and declined on larger stumps. The number of black oak sprouts peaked in the 20‐50-cm classes, and trees in the 70‐80-cm class produced the fewest sprouts. The mean annual growthof the tallest sprout on each stump was greater for black oak and chestnut oak than white oak.
Background: The Ogasawara (Bonin) Islands of Micronesia lie in the western Pacific Ocean and are ... more Background: The Ogasawara (Bonin) Islands of Micronesia lie in the western Pacific Ocean and are unique in terms of their isolation, climate, soils and diversity of rare plant species. We hypothesized that the vegetation on the islands will be a robust model system to study long-term climate change impacts on vegetation dynamics. Methods: A large, long-term vegetation monitoring plot was established on Chichijima Island and measured in 1976 and 2017. It was located in an undisturbed dry forest area that contained many endemic and endangered species. Results: During the 41 year study period, total basal area of tree species increased by 24.6% and was dominated by Schima, Distylium and Pouteria, whereas tree density declined by 30%. Tree genera exhibiting the largest increases in basal area were Elaeocarpus, Ilex, Pandanus, Pouteria, Rhaphiolepis, Syzgium and Schima. During the study period, the annual average (23.2ºC), minimum and maximum temperatures increased by 0.5 to 0.8ºC, respe...
Long-term induced water stress in field-grown grapevine leads to a progressive decline of stomata... more Long-term induced water stress in field-grown grapevine leads to a progressive decline of stomatal conductance, accompanied by a decrease in CO 2 assimilation (40%). The apparent quantum yield also decreases (59%), which may reflect a relative increase in alternative processes for electron consumption. There is also a shift to non-stomatal regulation, as judged from significant depletions (37%) in maximum photosynthesis rate at saturating CO 2 related to limited ribulose biphosphate (RuBP) regeneration, whereas small, non-significant effects are observed on carboxylation efficiency. A high correlation (87%) between photosynthesis and stomatal conductance is observed for all experimental data and declines in intercellular CO 2 concentration parallel reductions in stomatal conductance. The data show that field response of grapevines to increasing soil water deficit involves stomatal and non-stomatal effects but, due to gradually induced drought, regulation mechanisms able to adjust me...
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