Impact of spatial heterogeneity of neighborhoods on long-term population dynamics of sugar maple (Acer saccharum)

We evaluated the impact of spatial heterogeneity resulting from disturbance and neighbor density on long-term population dynamics of sugar maple (Acer saccharum) in Brownfield Woods, an old-growth forest remnant in central Illinois. All trees with diameter at breast height (DBH) ≥ 7.6 cm in eight discrete quadrats (48 m × 68 m) and one large quadrat (216 m × 260 m) were mapped in Brownfield Woods in 1951, 1988, and 2001. Two sets of neighbor-specific transition matrices were constructed for two census periods (1951-1988 and 1988-2001) based upon historical maps of trees. Different neighborhoods defined by the occurrence of disturbance and neighbor density resulted in major differences in subsequent demography and population dynamics of A. saccharum in Brownfield Woods during 1951-2001. Disturbance subpopulations with high neighbor density demonstrated greater population growth than the other subpopulations and were characterized by relatively high recruitment and mortality. Dutch elm disease subpopulation shared similar characteristics. In contrast, non-disturbance subpopulations demonstrated census-specific demography. Using matrix modeling, we demonstrated the importance of spatial heterogeneity at the scale of neighboring trees to the dynamics at the scale of tree populations.