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Spatial patterns and competition of tree species in a Douglas-fir chronosequence on Vancouver Island


  • Stephan Getzin,

  • Charmaine Dean,

  • Fangliang He,

  • John A. Trofymow,

  • Kerstin Wiegand,

  • Thorsten Wiegand

S. Getzin ( and K. Wiegand, Inst. of Ecology, Univ. of Jena, Dornburger Str. 159, DE-07743 Jena, Germany. – C. Dean, Dept of Statistics and Actuarial Science, Simon Fraser Univ., Burnaby, BC V5A 1S6, Canada. – F. He, Dept of Renewable Resources, Univ. of Alberta, Edmonton, AB T6G 2H1, Canada. J. A. Trofymow, Canadian Forest Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, BC V8Z 1M5, Canada. – T. Wiegand, Dept of Ecological Modelling, UFZ-Centre for Environmental Research, PF 500136, DE-04301 Leipzig, Germany


While the successional dynamics and large-scale structure of Douglas-fir forest in the Pacific Northwest region is well studied, the fine-scale spatial characteristics at the stand level are still poorly understood. Here we investigated the fine-scale spatial structure of forest on Vancouver Island, in order to understand how the three dominant species, Douglas-fir, western hemlock, and western redcedar, coexist and partition space along a chronosequence comprised of immature, mature, and old-growth stands. We quantified the changes in spatial distribution and association of the species along the chronosequence using the scale-dependent point pattern analyses pair-correlation function g(r) and Ripley's L-function. Evidence on intra- and inter-specific competition was also inferred from correlations between nearest-neighbor distances and tree size. Our results show that 1) the aggregation of Douglas-fir in old-growth was primarily caused by variation in local site characteristics, 2) only surviving hemlock were more regular than their pre-mortality patterns, a result consistent with strong intra-specific competition, 3) inter-specific competition declined rapidly with stand age due to spatial resource partitioning, and (4) tree death was spatially randomly distributed among larger overstory trees. The study highlights the importance of spatial heterogeneity for the long-term coexistence of shade-intolerant pioneer Douglas-fir and shade-tolerant western hemlock and western redcedar.

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