Mode of competition for light and water amongst juvenile beech and spruce trees under ambient and elevated levels of O3 and CO2

Maria Joy Daigo Schulte, Rainer Matyssek, Sebastian Gayler, Eckart Priesack, Thorsten E.E. Grams

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Key message: Our study provides evidence that neither elevated CO2 nor elevated O3 alters the positive asymmetric competition for light and the symmetric competition for water among beech and spruce individuals grown in monoculture. We conclude that the mechanism of competition (i.e. symmetric/asymmetric) above (e.g shading or overtopping effect) and belowground (e.g. non-preemption or foraging) rather than abiotic treatments such as elevated CO2, O3 and CO2 /O3 regimes, plays a dominant role for ensuring competitive success among tree saplings. Despite numerous studies conducted on plant responses to increasing CO2 and O3 concentrations, there is still a gap in understanding on how these gasses would affect the mode of competition (e.g., the ability by which larger and smaller plants capture resources) at the individual level of intra-specific beech and spruce saplings. Using empirical data and simulations from the plant-growth model PLATHO, we analyzed underlying mechanisms of competition and extrapolated effects beyond the time span of the experiment. We hypothesized that among juvenile beech and spruce trees planted in monoculture, +CO2 would diminish the positive asymmetric competition for light. Conversely, +O3 would enhance this outcome. In addition, we hypothesized that the symmetric mode of competition belowground for water would remain unchanged, irrespective of +CO2 and/or +O3 treatments. Our results showed that +CO2 and/or +O3 treatments did not alter the mode of competition aboveground for light. Conversely, we accepted our hypothesis that the mode of competition for water would remain unchanged under both treatments. Overall, we conclude that neither +CO2 nor +O3 alters the positive asymmetric competition for light and the symmetric competition for water among beech and spruce individuals grown in monoculture. We further conclude that competitive mechanism above (e.g., shading or overtopping effect) and belowground (e.g., non-preemption or foraging) rather than abiotic treatments, such as elevated CO2, O3 and CO2/O3 regimes, plays a dominant role for ensuring competitive success among tree saplings.

Original languageEnglish
Pages (from-to)1763-1773
Number of pages11
JournalTrees - Structure and Function
Volume27
Issue number6
DOIs
StatePublished - Dec 2013

Keywords

  • Beech and spruce saplings
  • CO
  • Light
  • Mode of competition
  • O
  • Water

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