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Variability of CO 2 and N 2 O emissions during freeze‐thaw cycles: results of model experiments on undisturbed forest‐soil cores
Author(s) -
Teepe Robert,
Ludwig Bernard
Publication year - 2004
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.200321313
Subject(s) - beech , fagus sylvatica , soil water , picea abies , loam , humus , environmental science , soil texture , chemistry , soil science , botany , biology
The amounts of N 2 O released in periods of alternate freezing and thawing depend on site and freezing conditions, and contribute considerably to the annual N 2 O emissions. However, quantitative information on the N 2 O emission level of forest soils in freeze‐thaw cycles is scarce, especially with regard to the direct and indirect effect of tree species and the duration of freezing. Our objectives were (i) to quantify the CO 2 and N 2 O emissions of three soils under beech which differed in their texture, C and N contents, and humus types in freeze‐thaw cycles, and (ii) to study the effects of the tree species (beech ( Fagus sylvatica L.) and spruce ( Picea abies (L.) Karst.)) for silty soils from two adjacent sites and the duration of freezing (three and eleven days) on the emissions. Soils were adjusted to a matric potential of –0.5 kPa, and emissions were measured in 3‐hr intervals for 33 days. CO 2 emissions of all soils were similar in the two freeze‐thaw cycles, and followed the temperature course. In contrast, the N 2 O emissions during thawing differed considerably. Large N 2 O emissions were found on the loamy soil under beech (Loam‐beech) with a maximum N 2 O emission of 1200 μg N m –2 h –1 and a cumulative emission of 0.15 g N m –2 in the two thawing periods. However, the sandy soil under beech (Sand‐beech) emitted only 1 mg N 2 O‐N m –2 in the two thawing periods probably because of a low water‐filled pore space of 44 %. The N 2 O emissions of the silty soil under beech (Silt‐beech) were small (9 mg N m –2 in the two thawing periods) with a maximum emission of 150 μg N m –2 h –1 while insignificant N 2 O emissions were found on the silty soil under spruce (0.2 mg N m –2 in the two thawing periods). The cumulative N 2 O emissions of the short freeze‐thaw cycles were 17 % (Sand‐beech) or 22 % (Loam‐beech, Silt‐beech) less than those of the long freeze‐thaw cycles, but the differences between the emissions of the two periods were not significant ( P ≤ 0.05). The results of the study show that the amounts of N 2 O emitted in freeze‐thaw cycles vary markedly among different forest soils and that the tree species influence the N 2 O thawing emissions in forests considerably due to direct and indirect impacts on soil physical and chemical properties, soil structure, and properties of the humus layer.