New insights into the role of tannins in controlling N cycling of boreal forest soils

Bartosz Adamczyk1, Sylwia Adamczyk1, Veikko Kitunen1, Aino Smolander1
1 Vantaa, Finnish Forest Research Institute

O 4.1 in Below ground turnover of C and nutrients in forest soils

14.07.2014, 11:15-11:35, H17

Tannins are complex group of phenolic plant secondary compounds, which are especially abundant in boreal forest ecosystems with short growing season and nutrient poor acidic soil. In addition to acting as herbivore deterrents, tannins seem to control soil N cycle. Tannins may affect soil N transformations by inducing toxicity to microbial populations and by forming complexes with proteins. Tannin-protein complexes may shift N cycling from mineral to organic dominated pathway. The actual role of tannins is still under debate.

Our recent findings give new insights into tannin role in nitrogen cycle. In addition to formation of complexes with proteins, tannins may also form complexes with a wide range of organic nitrogen compounds, including polyamines, nitrogen bases, chitin and chitosan. From all proteinogenic amino acids only arginine may form complexes with tannins. Both tannin groups, hydrolysable tannins and condensed tannins showed similar pattern of reaction with organic N compounds. Formation of these complexes is influenced by pH and concentration of both tannins and organic nitrogen compounds. Formation of tannin complexes with organic nitrogen compounds other than proteins can potentially affect soil N cycling. The role of these complexes for soil N cycling is barely known. Our recent study suggested that tannin-chitin complexes are relatively recalcitrant in the soil and they may potentially conserve N similarly as tannin-protein complexes. The true role of tannin complexes with organic N compounds other than proteins needs further studies.

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last modified 2014-04-03