Poster, BIOGEOMON, Helsinki: 2009-06-29 - 2009-07-03
Soil freeze-thaw cycles (FTC) influence nutrient cycling, but their consequences for vegetation are not well investigated. Ongoing global warming will increase the recurrence of FTC in cool-temperate and other high-latitude regions. Here, we compare the above- and belowground biomass production as well as the nitrogen nutrition of two common vegetation types, grassland and heath, after intensified FTC in a controlled field experiment in Central Europe. Furthermore, we analyze the duration of the observed effects. Five FTC were stimulated by buried heating wires in addition to three naturally occurring FTC during winter 2005/06. Intensified FTC significantly increased aboveground production of grassland early in the following growing season. However, no reaction was found for heath. Biomass production of heath communities dropped significantly and C/N ratio increased in the freeze-thaw treated plots in the second year after the manipulation, whereas production in the grassland communities was no longer affected significantly, except for an increase in C/N ratio. The results show the high ecological importance of climate changes during winter, with the outcomes differing strongly between contrasting vegetation types. Furthermore, we show that short term climatic events cause long-lasting effects, sometimes emerging in the vegetation only after considerable lag times (here: one growing season). Figure 1. Aboveground Net Primary Production (ANPP) over each growing season (mean values and standard errors). Freeze-thaw manipulation took place only in Winter 2005/06. An asterisk marks significant treatment effects (ANOVA, Tukey HSD post hoc comparison: p < 0.05). References: Kreyling, J., Beierkuhnlein, C., Pritsch, K., Schloter, M. & Jentsch, A. 2008. Recurrent soil freeze-thaw cycles enhance grassland productivity. New Phytologist 177, 938–945.