Long-term influences of soil frost on C mineralization in a European beech and a Norway spruce stand
O 2.6 in Research in its Prime: First Results of Ongoing Research
10.10.2013, 11:00-11:15, H6, GEO
In temperate forests, winter soil frost is often followed by a pronounced spring or summer drought. Here, we tested the hypothesis, that severe soil frost affects the microbial activity and reduces C mineralization substantially during the subsequent desiccation period.
In laboratory incubations, homogenized soil samples of Oi/Oe, Oa and A horizons from a European beech and a Norway spruce stand were exposed to intensive frost of -8°C over 3 weeks. Control samples were incubated at +2°C. After thawing, soil samples were warmed up stepwise to 20°C and subsequently dried out to pF~4.5 over a period of 4 weeks. CO2 production was monitored and microbial biomass and fungal enzyme activity (chitinase) were determined.
When soils were kept at field capacity, C mineralization of previously frozen soils was significantly reduced by 17-30% after 160 days. Concomitantly, microbial biomass decreased by 17-42% in Oa and A horizons, but not in Oi/Oe horizons. Stepwise desiccation to pF 4.5 decreased C mineralization by 15-42%.
At field capacity, intensive soil frost severely affected microbial biomass in Oa and A horizons, whereas microorganisms in Oi/Oe horizons seemed well adapted to soil frost. Desiccation did not impact C mineralization, microbial biomass and fungal activity stronger in previously frozen than in previously unfrozen soils.
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