Host Quality, Mediated by Land-Use History and Landscape Position, Shapes Distributions of Parasitic Plants in Postagricultural Forests.

Premise of research. Land-use legacies in plant communities have been attributed to dispersal limitation and the environmental impacts of past disturbance. Less is known about the role of plant-plant interactions in shaping postagricultural forest community assembly. Parasitic plants are a useful model system for understanding the relative importance of host presence, site history, and environmental gradients to second-growth forest succession. I tested the hypothesis that land-use history shapes parasitic plant distributions by altering host availability. Methodology. Field sampling took place in deciduous forests in Athens County, Ohio. I surveyed populations of two tree parasites, Conopholis americana and Epifagus virginiana , in a factorial replicated chronosequence of 40 postagricultural stands that consisted of upland and valley sites sorted into four age classes: 40–60, 61–80, 81–100, and >130 yr since canopy closure. The flowering stems of the target species, abundance, and the basal area of the host trees were recorded. Pivotal results. The presence of both species and the abundance of C. americana were linked to large individual host trees. Conopholis americana was associated with uplands and older forests, and E. virginiana was limited to stands of more than 80 yr old. However, C. americana was most abundant in sites with remnant pasture trees. The relationships of parasitic plants with land-use history are therefore complex and reflect specific effects of past disturbances on host species. Conclusions. I conclude that parasitic plant distributions are shaped by host tree availability and quality. These results support symbiont limitation, mediated through forest age and edaphic gradients, as an assembly process influencing postagricultural community dynamics. [ABSTRACT FROM AUTHOR]