Characterization of high-tannin fractions from humus by carbon-13 cross-polarization and magic-angle spinning nuclear magnetic resonance

• Main Authors: Klaus Lorenz, Caroline M. Preston
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2002
• Subjects: Canada; Titus; Newfoundland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.564.4014; http://www.mf.wau.nl/hemminga/Online_articles/JEQ/LorenzJEQ(2002)31,431-436.pdf

ABSTRACT of black spruce in Newfoundland with a permanent con-version from forest to heathland (Titus et al., 1995).Condensed tannins can be found in various parts of many plants. Also, northern black spruce forests develop nutrientUnlike lignin there has been little study of their fate as they enter the soil organic matter pool and their influence on nutrient cycling, limitation and increased sequestration of N in the forest especially through their protein-binding properties. We extracted and floor with increasing stand age (Pastor et al., 1987; Smith characterized tannin-rich fractions from humus collected in 1998 from et al., 1998). Incubation experiments with black spruce a black spruce [Picea mariana (Mill.) Britton et al.] forest in Canada humus showed a decrease in mineral N cycling after where a previous study (1995) showed high levels (3.8 % by weight) addition of condensed tannins (Bradley et al., 2000). of condensed tannins. A reference tannin purified from black spruce Tannins are defined by their ability to bind proteins needles was characterized by solution 13C nuclear magnetic resonance (Hagerman et al., 1998), and ecosystem-scale effects of(NMR) as a pure procyanidin with mainly cis stereochemistry and tannins are believed to be associated with formation ofan average chain length of four to five units. The colorimetric proan-recalcitrant tannin–protein complexes and inhibition ofthocyanidin (PA) assay, standardized against the black spruce tannin, soil enzymes. However, there is little chemically explicitshowed that both extracted humus fractions had higher tannin con-tents than the original humus (2.84 % and 11.17 % vs. 0.08%), and information on the fate of tannins in humus, soil, or