Projects

Multiple successional pathways after fire in Siberian forests

Scientist(s): Susanne Tautenhahn (PhD), Christian Wirth
Funding: Max-Planck-Society
Duration: 2006-2008

Background: Fire is the main agent triggering regeneration in boreal forests. Many factors influence the abundance and performance of seedlings during the early phase of establishment after fire: Propagules need to arrive at the sites or meristems have to be present vegetative regeneration. These processes are sensitive to the size and severity of the fire, but also pre-fire conditions. Unlike vegetative sprouts seedlings require safe-sites for establishment and are highly sensitive to climate conditions (especially drought) and competition during this time. The interaction of all these factors determines the starting conditions of secondary succession. Boreal forests are among the biomes where global warming is most pronounced and there are indications that fire extent and severity has increased during the last decade. Given what was said earlier, it is very likely, that these changes have their strongest impact during the early post-fire phase. Here, they may immediately change successional pathways and may even lead to alternate stable states dominated by shrubs and grasses.

Central hypotheses / questions: (1) Drier climate and larger and more severe fires will favour non-forest vegetation of forests, (2) Because of the interaction with fire, species change is not a continuous but a threshold function of climate.

Methods: Post-fire areas of varying size and age identified by remote sensing imagery will be visited in light and dark taiga ecosystems in Central Siberia. Abundance and performance of tree saplings, pre-fire stand structure, substrate conditions and cover of non-forest vegetation will be studied along transects that reach from the intact forest into the centre of the burn. Seed rain will be measured with seed traps along selected transects. The data will be analysed to parameterize dispersal and recruitment kernels and substrate-specific mortality rates. The resulting functions will be incorporated in a landscape succession model to analyse how regeneration success depends on species traits, fire size and severity and soil moisture.

Collaborators: Jeremy Lichstein, Stephanie Bohlman (Princeton University), Anatoly Prokushkin, Sergey Verkhovets, Olga Slinkina (Sukachev Institute of Forest SB RAS, Krasnoyarsk), Hermann Heilmeier (TU BA Freiberg), Anja Fankhänel, Antje M. Moffat (MPI-BGC)

Publications:

McGuire A, Chapin II FS, Walsh J and Wirth C: Integrated regional changes in high-latitude climate feedbacks: Implications for the global climate system. Annual Review of Environment and Resources 31:61-91

Wirth C, Chapin III FS, Lichstein JW, Chen A und Pacala SW: Abundance and performance of post-fire regeneration of Black and White spruce in relation to seed source, burn severity and edaphic conditions. Ecology (in press).