Considerable work in population ecology is being conducted at many of the sites that constitute the LTER Network
Under its LTER renewal grant, Harvard Forest (HFR) is broadening the scope of its forest ecology studies to include spatially explicit work in the population biology of animals and plants. Harvard Forest, due to its long history of research in forest ecology, has an extraordinary spatial and temporal database. This wealth of information permits a multi-scale approach to the study of populations in the context of the LTER Program, forest disturbance, and landscape ecology. For example, deforestation and agriculture in north central Massachusetts during the 18th and 19th centuries destroyed or disrupted populations of forest plant species, but subsequent reforestation has led to a period of population expansion for these species. Work completed under HFR’s initial LTER grant showed that the current pattern of plant species distribution in the area resulted from differences in species’ abilities to respond to changes in land-use activity.
Site-based studies are being initiated that will focus on selected understory plants and their associated butterfly herbivores to determine the impact of the physical disturbance of plowing on host plant distribution, and whether or not this impact cascades across trophic levels. Landscape and regional studies will determine whether butterfly and host plant distribution are decoupled because of processes acting at different scales. The distribution of a butterfly species at a site may depend on the presence of host plants. At a landscape scale, distribution will depend on its ability to colonize and persist in available habitats.
Additional studies, to be linked with existing long- term ecosystem-level studies such as the chronic nitrogen addition experiment, will focus on the potential effects of land use on nutrient levels. Increases in soil nitrogen may increase host plant quality, affecting herbivore growth rates and fecundity. Remotely-sensed canopy nitrogen estimates and ground-based surveys of insect damage to foliage will be used to predict the location of future insect outbreaks. These studies will link population- and ecosystem-level processes.
Richard Lent / Harvard Forest and Taber Allison /NSF Division of Environmental Biology