Projects

Testing for non-equilibrium dynamics in old-growth dark taiga in Siberia

Scientist(s): Christian Wirth, Anja Fankhänel
Funding: Max-Planck-Society
Duration: 2005-2006

Background: The old-growth stage of the Siberian dark taiga is formed by three conifers, Abies sibirica (Siberian fir), Picea obovata (Siberian spruce) and Pinus sibirica (Siberian stone pine). An initial survey of old-growth forests in the Central Siberian mountain range (60° N, 91° E) revealed that the proportions of these three species are highly variable and that these variations in species composition are not related to site conditions in any obvious way.

Central hypotheses / questions:
(1) Mixed old-growth forests develop into pure Abies forests given long enough periods without fire.
(2) Picea and Pinus depend on post-fire conditions for regeneration and do not successfully regenerate through gap phase dynamics.
(3) Diversity is highest during the mid-successional phase and thus maintained by fire.

Methods: During an expedition in summer 2005 we investigated six old-growth stands (three upland and three floodplain sites). A full stand inventory was done in transects of 20 x 50 m and the regeneration was mapped in successively smaller transects within the large plot depending on size class (down to one-year old seedling). To develop growth-light functions hemispherical photographs were taken above sample trees which were later harvested for growth analysis. Dead saplings were inventoried and harvested to establish a relationship between growth suppression and the probability of mortality. To calculate mortality rates the time of death is reconstructed with cross-dating. The data are suitable to calibrate the individual-based succession model SORTIE, which will be used to test our hypotheses.

Collaborators: Jeremy Lichstein (Princeton University), Alexander Kirdyanov, Nastasja Knorre (Sukachev Institute of Forest SB RAS, Krasnoyarsk), Jana Wäldchen (MPI-BGC), Gernot Hardes and Martin Siry.

Publications:
Schulze E-D, Wirth C, Mollicone D, Ziegler W (2005): Succession after stand replacing disturbances by fire, windthrow and insects in the dark Taiga of Central Siberia. Oecologia 146: 77-88.<br>