Factors promoting larch dominance in central Siberia: fire versus growth performance and implications for carbon dynamics at the boundary of evergreen and deciduous conifers

The relative roles of fire and climate in determining canopy species composition and aboveground carbon stocks were investigated. Measurements were made along a transect extending from the dark taiga zone of Central Siberia, where Picea and Abies dominate the 5 canopy, into the Larix zone of Eastern Siberia. We test the hypotheses that the change in canopy species composition is based (1) on climate-driven performance only, (2) on fire only, or (3) on fire-performance interactions. We show that the evergreen conifers Picea obovata and Abies sibirica are the natural late-successional species both in Central and Eastern Siberia, provided there has been no fire for an 10 extended period of time. There are no changes in the climate-driven performance of the observed species. Fire appears to be the main factor explaining the dominance of Larix. Of lesser influence were longitude, hydrology and active-layer thickness. Stand-replacing fires decreased from 300 to 50 yr between the Yenisei Ridge and the upper Tunguska. Repeated non-stand-replacing surface fires eliminated the regenera15 tion of Abies and Picea. With every 100 yr since the last fire, the percentage of Larix decreased by 20 %. Biomass of stems of single trees did not show signs of age-related decline. Relative diameter increment was 0.41±0.20% at breast height and stem volume increased linearly over time with a rate of about 0.36 tCha−1 yr−1 independent of age class and 20 species. Stand volumes reached about 130 tCha−1 (equivalent to about 520m3 ha−1). Individual trees of Larix were older than 600 yr. The maximum age and biomass seemed to be limited by fungal rot of heart wood. 60% of old Larix and Picea and 30% of Pinus sibirica trees were affected by stem rot. Implications for the future role of fire and of plant diseases are discussed.

SCHULZE Ernest Detlef;  WIRTH Christian;  MOLLICONE Danilo;  VON LUPKE N.;  ZIEGLER Waldemar;  ACHARD Frederic;  MUND Martina;  PROKUSHKIN A;  SCHERBINA S; 

2012-04-20

COPERNICUS GESELLSCHAFT MBH

JRC68624

1726-4170,   

http://www.biogeosciences.net/9/1405/2012/bg-9-1405-2012.html,    https://publications.jrc.ec.europa.eu/repository/handle/JRC68624,   

10.5194/bg-9-1405-2012,