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Harvard Forest REU Symposium Abstract 2019

  • Title: How many seedlings does it take to make a tree?
  • Author: Eleanna Vasquez Cerda (Mount Holyoke College)
  • Abstract:

    Tree seedlings are under-studied in forest ecology. However, power-scaling theory states that size is inversely related to abundance, and energy use increases with size. This could mean that tree seedlings as a size class contribute as much energy as trees in larger size classes, meaning we would be underestimating the contribution seedlings have to carbon cycling. While the power-scaling theory is not species specific, it alludes to the importance of seedlings within the ecosystem. This study focuses on the population dynamics of specific species to document demographic transitions and patterns amongst seedlings, which determine tree species richness and composition over time. We assessed growth and survival for the species Acer rubrum and Pinus strobus. We predicted that the generalist species Acer rubrum would exhibit a higher growth rate than Pinus strobus, which is less resilient in high shade conditions. But we expect that Acer rubrum will have lower survival probability because of the low number of adult Acer rubrum individuals in the overstory and the high observed seedling mortality. Contrary to our expectations, linear regression models indicate that the growth rate of the two species are similar from 2017-2018 and 2018-2019. Another surprising result was that the abundance of Pinus strobus increased significantly in 2018, but declined the following year. In spite of this, the survival probability of Pinus strobus in 2018 was higher than that of Acer rubrum. Our continued analysis will shed light on how these species' life histories will determine the future of the forest.

  • Research Category: Group Projects; Large Experiments and Permanent Plot Studies; Physiological Ecology, Population Dynamics, and Species Interactions