Inhibition of net nitrification activity in a Mediterranean woodland: possible role of chemicals produced by Arbutus unedo
- 309 Downloads
Nitrification is a key biological process for the control of soil NO3 − availability and N losses from terrestrial ecosystems. The study investigates the causes for the absence of net nitrification activity in the soil of a Mediterranean monospecific woodland of Arbutus unedo, focusing in particular on the possible role of chemicals produced by this plant. The mineral N pool, net rates of mineralization and nitrification were measured in the soil top 10 cm over 18 months. Raw extracts of leaves and roots of Arbutus unedo and soil underneath Arbutus plant canopy were purified using chromatographic techniques and the structure of chemicals was defined using spectroscopic and spectrometric methods. Leaf extracts (raw, aqueous and organic fractions) were tested for their toxicity on net nitrification, using a test soil. Field and laboratory incubations showed soil NO3 − concentration below the detection limit over the whole study period, despite the significant NH4 + availability. Toxicity tests indicated that more than 400 μg of extract g−1 dry soil were needed to have more than 50% reduction of net NO3 − production. Gallocatechin and catechin were among the most abundant chemicals in the extracts of leaves, roots and soil. Their soil concentration was significantly higher than the annual calculated input via leaf litter, and it was in the range of toxic concentrations, as deduced from the dose-response curve of the toxicity test. Data support the hypothesis that plant produced chemicals might be involved in the limited net nitrate production in this Mediterranean woodland.
KeywordsAllelopathy N cycle Toxicity Leaf extract NO3− (+)-gallocatechin
Research was supported by the European Community (MIND projects EVK2-2001-00296, NitroEurope GOCE-CT-17841) and CarboItaly (FISR, Italian Ministry of Environment). We thank Alessandro Zaldei and Giorgio Alberti for their help with field work.
- Akhtardzhiev K (1966) Presence of arbutin and tannins in native representatives of family Ericaceae. Pharmazie 21:59–60Google Scholar
- Alonso MC, Puig D, Silgoner I, Grasserbauer M, Barceló D (1998) Determination of priority phenolic compounds in soil samples by various extraction methods followed by liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry. J Chromatogr A 823:231–239 doi: 10.1016/S0021-9673(98)00110-1 CrossRefGoogle Scholar
- Carnol M, Kowalchuk GA, De Boer W (1998) Liming effects on the ammonia-oxidising bacteria in acid forest soils. Poster, 8th International Symposium on Microbial Ecology, HalifaxGoogle Scholar
- FAO 1998 World reference base for soil resources. World Soil Resources, Report no. 84, RomeGoogle Scholar
- Granli T, Bøckman OC (1994) Nitrous oxide from agriculture. Nor J Agric Sci 12(supplement):128Google Scholar
- Howard PJA, Howard DM (1991) Inhibition of nitrification by aqueous extracts of tree leaf litters. Rev Ecol Biol Sol 28:255–264Google Scholar
- Kandeler E (1995a) N-mineralization under aerobic conditions. In: Schinner F, Kandeler E, Ohlinger R, Margesin R (eds) Methods in soil biology. Springer, Heidelberg, pp 139–141Google Scholar
- Kandeler E (1995b) Nitrification during long term incubation. In: Schinner F, Kandeler E, Ohlinger R, Margesin R (eds) Methods in soil biology. Springer, Heidelberg, pp 149–151Google Scholar
- McCarty GW, Bremner JM (1986) Inhibition of nitrification in soil by acetylene compounds. SSSA 50:1198–1201Google Scholar
- Putnam AR (1988) Allelochemicals from plants as herbicides. Weed Technol 2:510–518Google Scholar
- Schimel JP, VanCleve 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 74:84–90 doi: 10.1139/b96-012 CrossRefGoogle Scholar