1. Convergence of Development Phases in a Multi-Aged Primary European Beech Forest at Small Scales Eric K. Zenner 1, Martina L. Hobi 2, Brigitte Commarmot 2 1 Penn State University, Univ. Park, PA, USA 2 Swiss Federal Institute for Forest, Snow and Landscape Research WSL Birmensdorf, CH, 19 June 2014

2. Development Stages and Phases (DS & P)  Long history of using DS & P in European primary/old-growth forests  Generally 3 stages (i.e., initial or growing up; optimal; decay or breaking down); often 3 phases nested in each stage  Stages correspond to the idea of biomass accumulation (sensu Bormann and Likens 1979)

3. Development Stages and Phases (DS & P)  Areas within forests characterized by differences in composition & structure that enable deduction about forest dynamics  # canopy stories, dbh dist n, volume, gaps….  Multivariate differences among DS & P

4. Multi-aged Primary European Beech Forests  Small-scale disturbances (gap dynamics)  Mosaic of small-scale patches of different DS & P; intimate mixture of phases typical  Multi-aged and uneven-sized structures

5. Multi-aged Primary European Beech Forests  Despite the overall “appearance” of primary beech forests (e.g., negative exponential diameter distribution, gaps, large trees), the plenter phase (many- storied structure phase) is thought to be of limited extent and short duration  Is this due to the scales at which phases are typically distinguished?

6. Multi-aged Primeval European Beech Forest of Uholka  Located in the Ukrainian Carpathians  Part of UNESCO World Heritage site

7. Multi-aged Primeval European Beech Forest of Uholka  Largest primeval beech forest in Europe (>10,000 ha)  10 ha monitoring plot est’d in 2000 (stem-mapped); >95% Eur. beech

8. Forest Characteristics (2010) Live trees ≥ 6 cm DBH Tree density (N ha -1 )295.9 Basal area (m 2 ha -1 )37.5 Volume (m 3 ha -1 )660.9 Deadwood Tree density (N ha -1 )36.8 Volume (m 3 ha -1 )177.6

9. Development Phases (adapted from Tabaku 2000)  CPA – crown projection area live  DS – prop. dead BA  NQD – normed quartile distance 100*(75 th –25 th )/ median  PSH – prop. stand ht

10. Development phase Description / Interpretation Gap or regenerationNo regen, canopy cover <30 % EstablishmentDense stands, max DBH <20 cm, mean DBH <16 cm, low growing stock/volume Early optimalDense stands, max DBH ≥20 cm, high increment, increasing growing stock; canopy gaps closing, regen ± missing; phase divided by max DBH (20-40; 41-60; >60 cm) Mid optimal Late optimal PlenterUneven-aged; highly structured; large DBH range TerminalLess structured; high growing stock; age- related mortality; few gaps DecayLow density of large trees; high amount of deadwood; growing stock decreasing; large canopy gaps; increasing vertical structure

11. Methods  Fixed grid cells of increasing areas:

12. Results

13. 156.25 m 2 625 m 2 2500 m 2

14. Conclusions  Phase assignment appears strongly scale dependent  Proportion of the plenter-phase increased steadily with scale  At scales ≥625 m 2, only the plenter, terminal, and decay phases (i.e., structurally most complex) remained  not an unexpected result under gap dynamics!

15. Conclusions  Convergence to plenter-phase nearly complete at the scale of 1 ha  Results are in contrast to other studies that report limited spatial extent of plenter- phase  maybe too fine scaled? Context?  Does it make sense to distinguish phases of very small extent? If so, to what end?  Is a gap = phase?