Comparison of Soil Nitrogen Availability Indices under Two Temperate Forest Types
Author(s): ZHONG Zhe-Ke, F. MAKESCHIN
Pages: 273-283
Year: 2006 Issue: 3
Journal: PEDOSPHERE
Keyword: density fractionation; forest soils; N availability; soil N indices;
Abstract: To evaluate the validity of different indices in estimating soil readily mineralizable N, soil microbial biomass (Nmic),soil active N (SAN), soluble organic N (SON), net N mineralization rate (NNR) and gross N mineralization rate (GNR) in mineral soils (0-10 cm) from six forest stands located in central Germany were determined and compared with two sampling times: April and November. Additionally, soil density fractionation was conducted for incubated soils (with addition of 15NH4-N and glucose, 40 days) to observe the sink of added 15N in different soil fractions. The study showed that Nmic and NNR in most stands differed significantly (P ≤ 0.05) between the two sampling times, but not GNR, SAN and SON. In November, no close relationships were found between GNR and other N indices, or between Nmic, SON, and SAN and forest type. However, in April, GNR was significantly correlated (P ≤ 0.05) with Nmic, SAN, and NNR along with Nmic under beech being significantly higher (P ≤ 0.05) than under conifers. Furthermore, density fractionation revealed that the light fraction (LF, 0.063-2 mm, ＞ 1.7 g cm-3) was not correlated with the other N indices. In contrast, results from the incubation study proved that more 15N was incorporated into the heavy fraction (HF ＜ 0.063 mm, ＞ 1.7 gcm-3) than into LF, indicaing that more labile N existed in HF than in LF. These findings suggested that attention should be paid to the differences existing in N status between agricultural and forest soils.
Pages: 273-283
Year: 2006 Issue: 3
Journal: PEDOSPHERE
Keyword: density fractionation; forest soils; N availability; soil N indices;
Abstract: To evaluate the validity of different indices in estimating soil readily mineralizable N, soil microbial biomass (Nmic),soil active N (SAN), soluble organic N (SON), net N mineralization rate (NNR) and gross N mineralization rate (GNR) in mineral soils (0-10 cm) from six forest stands located in central Germany were determined and compared with two sampling times: April and November. Additionally, soil density fractionation was conducted for incubated soils (with addition of 15NH4-N and glucose, 40 days) to observe the sink of added 15N in different soil fractions. The study showed that Nmic and NNR in most stands differed significantly (P ≤ 0.05) between the two sampling times, but not GNR, SAN and SON. In November, no close relationships were found between GNR and other N indices, or between Nmic, SON, and SAN and forest type. However, in April, GNR was significantly correlated (P ≤ 0.05) with Nmic, SAN, and NNR along with Nmic under beech being significantly higher (P ≤ 0.05) than under conifers. Furthermore, density fractionation revealed that the light fraction (LF, 0.063-2 mm, ＞ 1.7 g cm-3) was not correlated with the other N indices. In contrast, results from the incubation study proved that more 15N was incorporated into the heavy fraction (HF ＜ 0.063 mm, ＞ 1.7 gcm-3) than into LF, indicaing that more labile N existed in HF than in LF. These findings suggested that attention should be paid to the differences existing in N status between agricultural and forest soils.
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