PARENT SESSION
Oral Session #5: Plant Demography and Reproductive Ecology.
Presiding: R. Kobe
Monday, August 5. 8:00 AM to 11:30 AM. Coconino Meeting Room, TCC.

Population dynamics and demography of tree species in Brownfield Woods from 1939-2001.

LIN, YICHING^*,1, AUGSPURGER, CAROL, ¹ University of Illinois, Urbana, IL 61801

ABSTRACT- Long-term studies of demography are essential to understand factors that result in changes in relative species abundance within a community. In this comparative study we examined temporal changes in population size, size structure, recruitment, mortality, and growth rate of the eight most common species from 1939-2001 in a forest fragment in central Illinois. The major goal was to identify demographic parameter(s) accounting for the sharp rise in commonness of sugar maple (Acer saccharumMarsh.). We used four historical maps in which all individuals greather than 7.6 cm DBH were censused and mapped in 16 quadrats (48 m x 68 m) in 1939, 1951, 1988, and 2001. From 1939-2001, population size of sugar maple and Ohio buckeye (Aesculus glabraWilld.) increased 1.5 and 2.9 fold, respectively, while all other tree species decreased. During the 62-yr period, size structure of the eight species differed substantially among species and within species. Both species with increasing population size moved towards smaller individuals after 1951. Sugar maple also increased in larger size classes. The increase in number of sugar maples arose from both its relatively high per capita recruitment and low mortality. Only Ohio buckeye showed higher per capita recruitment and lower mortality than sugar maple. Among species, sugar maple and Ohio buckeye ranked seventh and eighth, respectively, in growth rate. Therefore, the faster growth rate of rare species was not sufficient to maintain their populations, while the high recruitment and low mortality of sugar maple and Ohio buckeye contributed to their increasing commonness.

KEY WORDS: Commonness and rarity, Demography , Forest dynamics, Long-term studies