Fluxes, stocks and availability of nitrogen in evergreen broadleaf and fir forests: similarities and differences
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ORIGINAL PAPER
Fluxes, stocks and availability of nitrogen in evergreen broadleaf and fir forests: similarities and differences Panagiotis Michopoulos1 · Athanassios Bourletsikas1 · Kostas Kaoukis1
Received: 19 May 2020 / Accepted: 24 September 2020 © Northeast Forestry University 2020
Abstract In this study, nitrogen fluxes or flows in litterfall, nitrogen stocks and available nitrogen in soils of two plots representing evergreen broadleaf and Bulgarian fir forests were assessed. Both plots are in good quality sites and for this reason, the litterfall quantities and nitrogen fluxes were relatively high. The woody litterfall flux of nitrogen was significantly higher in the fir forest than in the evergreen broadleaf one. The total nitrogen stock was higher in the soil under the fir forest. However, the percentage of the available nitrogen (ammonium + nitrates) was significantly higher in the upper 20 cm soil layer of the evergreen broadleaf forest in spite of the higher average C/N ratios in the foliar litterfall of the broadleaf forest and insignificant difference of the C/N ratios in all soil layers of the two ecosystems. The microclimatic conditions (higher soil temperatures in the evergreen broadleaf forest) is probable possible cause for this difference. The available nitrogen in the soils and its retranslocation from senescing leaves cover the nitrogen requirements of trees. It is hypothesized that trees may also take up nitrogen from deeper soil layers. Keywords Maquis · Fir · Nitrogen · Litterfall fluxes · Soil Project funding This work was supported financially by the Programme of “Effects of Atmospheric Pollutants on Forest Ecosystems” from the Ministry of Agriculture and Food, the Greek Ministry of Environment and the European Commission. The online version is available at http://www.springerlink.com. Corresponding editor: Zhu Hong * Panagiotis Michopoulos [email protected] 1
H.A.O. DEMETER-Institute of Mediterranean Forest Ecosystems, Terma Alkmanos, 115 28 Athens, Greece
Introduction Among all elements, the limitation of nitrogen (N) is one of the most critical factors affecting tree growth (Vitousek and Farrington 1997). This is not due to low quantities of this element but to its restricted availability in many soils. Because of the important role nitrogen has in plant growth, there is considerable information with regard to its cycling or flow in forest ecosystems (Keeney 1980; Cole and Rapp 1981; Carlyle 1986; Dannenmann et al. 2006; Rennenberg et al. 2009). The nitrogen paths to forest soils are throughfall, stemflow (both from atmospheric nitrogen deposition in rain/snow) and litterfall. Litterfall is the most important source for all plant nutrients with the exception of potassium for which throughfall is the primary source. Litterfall affects soil respiration, microbial biomass, and total carbon and nitrogen (Sayer 2006; Xu et al. 2013) and all its fractions are subjected to decomposition once they reach the soil. The rate of decomposition depends on the forest species, climate and the
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