The Influence of Condensed Tannin Structure on Rate of Microbial Mineralization and Reactivity to Chemical Assays

Abstract

We examined how tannin structure influences reactivity in tannin assays and carbon and nitrogen mineralization. Condensed tannins from the foliage of ten tree and shrub species and from pecan shells (Carya illinoensis) had different proportions of: (a) epicatechin (cis) and catechin (trans) isomers, (b) procyanidin (PC) and prodelphinidin (PD) monomers, and (c) different chain lengths. The response of each tannin to several widely used tannin assays was determined. Although there was some variation in response to proanthocyanidin (butanol/HCl) and Folin Ciocalteu assays, we did not deduce any predictable relationship between tannin structure and response to either assay. There was little variation in protein precipitation among the different tannins. To assess biological activity, six of the tannins were incubated with forest humus for 22 days. We determined that, while PC-based tannins remained at least partly extractable for the duration of the incubation, tannins with a high proportion of PD subunits rapidly became unextractable from soil. There was a positive correlation between net nitrogen mineralization and cis chemical structure. Carbon mineralization was enhanced initially by the addition of tannins to humus, but after 22 days, a negative correlation between the proportion of cis subunits and respiration was determined. Overall, we were not able to demonstrate consistent effects of structure on either microbial mineralization or reactivity to chemical assays; such relationships remain elusive.

Nitrogen transformations in boreal forest soils—does composition of plant secondary compounds give any explanations?

“…However, tannins in Norway spruce needles, which contain predominantly procyanidins, and tannins in Scots pine needles, which consist mostly of prodelphidines, did not have very different effects on microbial biomass or rates of C and net N mineralization (Kanerva and Smolander 2008). Moreover, Norris et al (2011) who studied condensed tannins from six different plant species was not able to demonstrate any clear and consistent effects of tannin structure on C and N mineralization rates in soil. They stated that a problem in developing better structure-function relationships is that the tannin preparations are not typically single pure compounds and the derived structural parameters are averages.…”

“…Condensed tannins of spruce needles contain more procyanidin units while pine needles contain more prodelphinidin units (Maie et al 2003;Kraus et al 2004a;Kanerva et al 2006;Norris et al 2011). …”

“…), Kalmia angustifolia L. and Abies balsamea (L.) Mill(Bradley et al 2000;Nierop et al 2006a;Norris et al 2011), Pinus muricata D. Don(Kraus et al 2004a), P. sylvestris L (Kanerva et al 2006;. …”

Bacterial fermentation of Lemna sp. as a potential substitute of fish meal in shrimp diets

“…This anti-nutritional factor can affect shrimp growth. Tannins are a highly diverse class of plant secondary phenolic compounds (Kraus et al, 2003;Norris et al, 2011) and have been found to interfere with the digestibility of proteins, carbohydrates, and the availability of vitamins and minerals (Liener, 1994). The tannin content (all treatments) of Lemna sp.…”

The effects of high-tannin leaf litter from transgenic poplars on microbial communities in microcosm soils

“…In Populus balsamifera growing in the Alaskan taiga, Schimel et al (1998) attributed major changes in soil N-cycling to the secondary compounds found in poplar leaves; poplar litter reduced N-fixation, decomposition, and N-mineralization, while increasing N-immobilization. Some reports indicate that this inhibition of N-cycling can be qualified by the molecular weight of condensed tannins, the vegetative history of the soil, and by the microbial community present (Fierer et al, 2001; Triebwasser et al, 2012); however, research in other types of plant litter has found some of these influences to be inconsistent (Norris et al, 2011). …”