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Soluble organic nitrogen pools in adjacent native and plantation forests of subtropical Australia |
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| Authors: | Joanne Burton Chengrong Chen Hossein Ghadiri |
| Institution: | a Griffith School of Environment, Griffith University, Nathan 4111, Australia b Centre for Forestry and Horticultural Research, School of Biomolecular and Physical Sciences, Griffith University, Nathan 4111, Australia c Australian Rivers Institute, Griffith School of Environment, Griffith University, Nathan 4111, Australia |
| Abstract: | Soil soluble organic nitrogen (SON) can play an important role in soil nitrogen (N) cycling in forest ecosystems. This study examined the effect of land-use change from a native forest (NF) to a first rotation (1R) and subsequent second rotation (2R) hoop pine (Araucaria cunninghamii) plantation on soil SON pools. The impact of residue management on SON pools was also investigated in the 2R forest, where SON was measured in tree rows (2R-T) and windrows (2R-W). Various extraction techniques were used to measure SON pool size in the 0-10, 10-20 and 20-30 cm layers of soil. The results showed that land-use change had a significant impact on soil SON pools. In the 0-10 cm layer, 3.2-8.7, 14-23, 20-28, 60-160 and 127-340 mg SON kg−1 were extracted by water, 0.5 M K2SO4, 2 M KCl, hot water and hot 2 M KCl, respectively. The size of the SON pools and the potential production of SON (PPSON) were generally highest in the NF soil and lowest in the 2R-T soil, and in all forest types decreased with soil depth. The larger SON pools in the NF soil coincided with lower soil, litter and root C:N ratios, suggesting that the difference in the size of SON pools between the NF and 1R soil may be related to differences in the quality of organic matter input under the different forest ecosystems. Differences in the size of SON pools between the 1R soil and the 2R soils and between the 2R-T soil and the 2R-W soil may be related to the quantity of organic matter input and time since disturbance. Significant relationships were found between the SON extracted by 0.5 M K2SO4 (SONps) and 2 M KCl (SONKCl), and also among the SON extracted by hot 2 M KCl (SONhKCl), hot water (SONhw) and water (SONw), suggesting that the organic N released by these groups of extracts may be at least partly from similar pools. |
| Keywords: | Soluble organic nitrogen Forest soil Land-use change |
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