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Sources of dissolved organic carbon in surface horizons and its relevance to stability of organic matter in soil

Sarka Cepakova1, Jan Frouz2
1 Institute of Soil Biology, Biology centre ASCR
2 Charles University in Prague

P 7.4 in Controls of dissolved organic matter fluxes in ecosystems

Poster Session 1 on Monday, 16:30-18:30

Litter and rhisodeponies are a key organic C input into soil. Litter input into soil is comprised of two main origins: aboveground and belowground litter. Aboveground litter constitutes mainly from plant tissue from litter fall. Belowground input is much variable. It originates from root debris, root exudates and microbial products of symbiotic microorganisms on plant roots (De Deyn et al., 2008).

The objective of this study was to assess seasonal variability in contribution of aboveground litter input and root related input to dissolved organic carbon. In addition we explored how there pattern differ between plantations of different tree species. We hypothesized a connection between amount of labile components extractable from soil and C/N ratio of soil at individual sites.

We studied plantation of four tree species including one conifer (Pinus sylvestris) and three broadleaf species (Quercus robur, Alnus glutinosa and Salix caprea) at one large common garden experiment planted in post-mining sites near Sokolov, Czech Republic. We samples soil from Oe and A horizon, in addition we sample fresh litter and we also established sand filled ingrow cores that allow to sample roots with associated root exudates.

We extracted dissolved organic matter in two categories on the basis of their availability: HWC (Hot Water Carbon) and WSC (Water Soluble Carbon) extractions. Both extracts were determined on TOC (Total Organic Carbon) analyzer, SUVA (Specific UV Absorbance) measurement and NMR spectroscopy.

Results show two peaks of the increase in labile components availability. The first one was in June and the second one in December. These were separated by the decrease in October. We expect the first peak correspond with root derived material the second one with litter. The pattern was more pronounced in broadleaf with seasonal litter fall and less in conifer. In trees with well developed Oe layer, the trend was more apparent in Oe layer, in other in A layer. We consider HWC and WSC are good indicators responding to changes in the rhizodeposits carbon efflux as well as changes in leaf litter carbon input during seasons.

References:

De Deyn, G. B., Cornelissen, J. H. C., Bardgett, R. D., 2008. Ecology Letters 11, 516–531. Plant functional traits and soil carbon sequestration in contrasting biomes. 

Letzte Änderung 19.06.2014