Short-term and long-term effects of tannins on nitrogen mineralisation and litter decomposition in kauri (Agathis australis (D. Don) Lindl.) forests
- 275 Downloads
Kauri (Agathis australis (D. Don) Lindl.) occurs naturally in the warm temperate forest of northern New Zealand where it grows mixed with angiosperm tree species. Below mature kauri trees thick organic layers develop in which large amounts of nitrogen are accumulated. This nitrogen seems to be inaccessible to plants. While litter quality can explain the low decomposition rate below kauri, it is not known what causes the accumulation of nitrogen. We hypothesised that kauri tannins reduce nitrogen mineralisation and litter decomposition below kauri. We further hypothesised that high tannin concentrations in the soil would increase the availability of dissolved organic nitrogen relative to the availability of inorganic nitrogen. To test these hypotheses a laboratory incubation was carried out for 1 year. Purified tannins of kauri and of two other common New Zealand tree species were added to samples of the soil organic layer from under a kauri tree. The results suggest that during the first month of incubation the added tannins reduced nitrogen availability by sequestering proteins or by stimulating nitrogen immobilisation. In the long-term, the reduced nitrogen release, which was found following tannin addition, seems attributable to the complexation of proteins by tannins. It further appeared that the addition of tannins did not change the ratio of dissolved organic nitrogen to inorganic nitrogen in the long-term. We conclude that the effect of kauri tannins on nitrogen release offers a good explanation for the accumulation of nitrogen below kauri trees.
KeywordsDecomposition Kauri (Agathis australis) Nitrogen mineralisation Tannin
Unable to display preview. Download preview PDF.
The investigations were supported by the Research Council for Earth and Life Sciences (ALW) with financial aid from the Netherlands Organisation for Scientific Research (NWO). We thank J. van Walsem and F. Möller for assistance with the chemical analyses, and J. Limpens for critical comments on a previous version of this manuscript. J. Burrough advised on the English.
- Ahmed M, Ogden J (1987) Population dynamics of the emergent conifer Agathis australis (D. Don) Lindl. (kauri) in New Zealand; I. Population structures and tree growth rates in mature stands. New Zeal J Bot 25:217–229Google Scholar
- Barton IL (1982) An investigation of aspects of the physiology and ecology of kauri (Agathis australis-Salisb). Unpublished MSc thesis University of Waikato, HamiltonGoogle Scholar
- Bloomfield C (1957) A review of work on the mechanism of podzol formation. New Zeal Soil News 5:154–158Google Scholar
- Field JA, Lettinga G (1992) Toxity of tannic compounds to microorganisms. In: Hemingway RW, Laks PE (eds) Plant polyphenols. Synthesis, properties, significance. Plenum Press, New York pp 673–692Google Scholar
- Jongkind AG, Buurman P Grain size distribution and clay mineralogy under kauri (Agathis australis). Geoderma (in press)Google Scholar
- Ogden J, Stewart GH (1995) Community dynamics of the New Zealand conifers. In: Enright NJ, Hill RS (eds) Ecology of the southern conifers. Melbourne University Press, pp 81–119Google Scholar
- Schimel JP, Van Cleve K, Cates RG, Clausen TP, Reichardt PB (1996) Effects of balsam poplar (Populus balsamifera) tannins and low molecular weight phenolics on microbial activity in taiga floodplain soil: implications for changes in N cycling during succession. Can J Bot 74:84–90Google Scholar
- Silvester WB (2000) Nitrogen cycling in kauri (Agathis australis) forest: an example of extreme accumulation, fixation and immobilisation of nitrogen. New Zeal J␣Bot 38:205–220Google Scholar
- Silvester WB, Orchard TA (1999) The biology of kauri (Agathis australis Salisb.) in New Zealand. I Production, biomass, carbon storage and litterfall in four forest remnants. New Zeal J Bot 37:553–571Google Scholar
- Swindale LD (1957) The effect of kauri vegetation upon the development of soils from rhyolite and olivine basalt. New Zeal Soil News 5:115–118Google Scholar
- Waterman PG, Mole S (1994) Analysis of phenolic plant metabolites. Blackwell Scientific Publications, Oxford. The Methods in Ecology Series, p 238Google Scholar