Long-term effects on the nitrogen budget of a short-rotation grey alder (Alnus incana (L.) Moench) forest on abandoned agricultural land

Nitrogen mineralization and gaseous nitrogen losses from waterlogged and drained organic soils in a black alder (<i>Alnus glutinosa</i> (L.) Gaertn.) forest

“…Dittert (1992) estimated N 2 fixation rates of between 40 to 85 kg N ha −1 yr −1 for a black alder stand in northern Germany. Comparable and even higher values have also been reported for grey alder stands (e.g., Rytter et al, 1991;Lõhmus et al, 2002;Mander et al, 2005;Uri et al, 2011). Additionally, drainage of histosols supplies large amounts of N through mineralization of ancient organic matter .…”

“…High contents of available NO − 3 in the soil carry the risk of leaching or gaseous losses (Robertson, 1982). Several studies reported NO − 3 losses by leaching from soils under alder stands (e.g., Binkley et al, 1992;Van Miegroet et al, 1992;Compton et al, 2003;Uri et al, 2011). The slightly higher NO − 3 contents but lower NNM rates observed in the soil depth of 10-20 cm compared to the soil depth of 0-10 cm at the drained sites probably indicate leaching of NO − 3 into deeper soil layers.…”

“…However, the distinct differences in the C and N contents of the drained sites did not result in significantly different NNM rates in the present study. Low retranslocation of nitrogen from senescing leaves to the alder tree Lõhmus et al, 2002;Uri et al, 2011) causes high contents of N and narrow C / N ratios of the foliage, favoring the fast decomposition of the leaf litter (Struwe and Kjøller, 1990;Rytter et al, 1991;Lõhmus et al, 2002;Uri et al, 2011). The organic surface layer at the drained sites was classified as L-mull humus type, indicating the fast decomposition of the incorporated alder leaves.…”

“…This requires the presence of efficient electron acceptors (e.g., NO − 3 ) to prevent the reduction of N 2 O to N 2 (Bremner and Blackmer, 1981;Speir et al, 1995;Jungkunst et al, 2004). Due mainly to analytical difficulties in the determination of microbially produced N 2 , to date the denitrification potential from waterlogged peat soils has rarely been estimated (Watts and Seitzinger, 2000;Mander et al, 2003;Teiter and Mander, 2005;Wray and Bayley, 2007;Roobroeck et al, 2010;Soosaar et al, 2011;Uri et al, 2011). The substitution of ambient N 2 by Helium (He) in laboratory studies possibly represents the most reliable method for the direct and simultaneous determination of N 2 O and N 2 exchange rates (Butterbach-Bahl et al, 2002;Roobroeck et al, 2010;Butterbach-Bahl et al, 2013).…”

“…For measurements of N 2 , N 2 O, CO 2 and CH 4 fluxes, we applied the helium-oxygen (He-O) method (Butterbach-Bahl et al, 2002;Mander et al, 2003;Roobroeck et al, 2010;Uri et al, 2011) using four different incubation temperatures (0, 5, 15 and 25 • C). Five replications per site and moisture content were simultaneously placed in special gas-tight incubation vessels inside a climate chamber.…”