Application of (15NH4)2SO4 to study N dynamics in hoop pine plantation and adjacent native forest of subtropical Australia: the effects of injection depth and litter addition

J Soils Sediments (2009) 9:515525 DOI 10.1007/s11368-009-0131-8

SOILS, SEC 1 * SOIL ORGANIC MATTER DYNAMICS AND NUTRIENT RECYCLING * RESEARCH ARTICLE

Application of (15NH4)2SO4 to study N dynamics in hoop

pine plantation and adjacent native forest of subtropical Australia: the effects of injection depth and litter addition

Kaiwen Pan & Zhihong Xu & Timothy J. Blumfield &

Shane Tutua & Manxin Lu

Received: 27 March 2009 /Revised: 12 August 2009 /Accepted: 13 August 2009 /Published online: 3 September 2009 # Springer-Verlag 2009

AbstractPurpose Hoop pine (Araucaria cunninghamii) is a nitrogen(N)-demanding native Australian softwood plantation species. Litter quality and its effects on soil mineral N and 15N

transformations have not been well studied in the hoop pine plantation and adjacent native forest. The present study was conducted to determine the impact of 15N injection depth and litter additions on the dynamics and fate of mineral 15N

and also to compare the difference in litter quality, 15N

dynamics, and fate between the hoop pine plantation (HP) and the adjacent native forest (NF).

Materials and methods The experiments were done in the Yarraman State Forest (2652 S, 15151 E), southeastern Queensland. Materials of litter addition were prepared on the basis of ten random samples of litters taken from the NF and HP sites using a 11-m quadrat. Litter additions were defined as: SL represented the average condition of forest floor in the forest ecosystems and DL represented the double average amount of litters in the forest ecosystem. Experiment 1 covered 2 forest types (NF and HP)3 litter

rates (nil litter, SL, and DL)3 15N injection depths (0, 2.5, and 5.0 cm). Experiment 2 included 2 forest types (NF and HP)2 litter rates (nil litter and SL)3 injection depths (0,2.5, and 5.0 cm) of distilled water. The in situ core incubation method was used with an incubation period of 28 days. The isotope ratio of mineral N or/and total N (soil and litter) were analyzed using an isotope ratio mass spectrometer with a Eurovector elemental analyzer (Isoprime-EuroEA 3000).

Results Total N and 15N were significantly higher, and C/N ratios and 13C were significantly lower in the NF litters than in the HP litters. The NF litters had significantly lower total

15N and total 15N recovery than the HP litters...