Current and legacy effects of neighborhood communities on plant growth and aboveground herbivory

Abstract

Current and legacy effects can greatly affect the growth of a focal plant and its interactions with herbivores and such effects can be mediated by above- and belowground effects. However, determining the relative importance of current and legacy above- and belowground effects in natural conditions is a major challenge. In a long-term grassland experiment, we examined the relative importance of the current and legacy above- and belowground effects of plant communities on the growth and aboveground herbivore damage on a focal plant, Leucanthemum vulgare. Focal plants were planted into tubes with soil collected from different plant communities and placed back into the plant communities. Weekly, plant growth and damage were recorded and after 12 weeks plant biomass was measured. We analyzed how well aboveground and belowground characteristics of the current and legacy plots explained plant growth and herbivory. We found both current plant communities and legacy plant communities significantly affected plant growth (shoot biomass and the number of leaves) and herbivory. Root biomass of the focal plants was influenced by current plant communities only. Current and legacy above- and belowground characteristics explained 12% and 11% of the variation in shoot biomass. Root biomass was mainly explained by current above- and belowground characteristics with a total explained variation of 10%, while legacy effects explained 3%. Legacy effects explained most variation in the number of leaves during the first two weeks of measurements, and the effect remained present during the growth season. In contrast, characteristics of the current community explained most of the variation in herbivory throughout the growth period, with on average 6% explained variance aboveground vs. 5% belowground. Our grassland field study highlights that both current and legacy effects influence plant growth, but herbivory on focal plants is caused by current neighborhood effects only and not by legacy effects.