N2O emissions in Acacia mangium stands with different ages, in Sumatra, Indonesia

Abstract

We compared nitrous oxide (N2O) emissions in different-aged (1, 3, and 5 years) Acacia mangium plantations and secondary forests for two and a half years at three areas in Sumatra, Indonesia. N2O emission was high from November to March (rainy season) and low from May to November (relatively drier season). In the first year, the average ± standard deviation of annual N2O emissions in 1-year-old sites was 8.92 ± 2.29 kg ha−1 of N, which was larger than those in 3-year-old (2.58 ± 2.28 kg ha−1 of N) and 5-year-old (2.16 ± 1.12 kg ha−1 of N) sites and secondary forests (1.38 ± 0.45 kg ha−1 of N) (p < 0.001). However, there is no significant difference in N2O flux among treatments after the second year. Although nitrogen mineralization and nitrification potential did not differ among tree ages, inorganic nitrogen and NH4/NO3 ratio in 1-year-old acacia site in the first year were significantly different from those in the other aged forests and secondary forests. Results of linear mixed model suggest that water-filled pore space and nitrogen availability are key factors for N2O emission in these sites. N2O emission within 1 year after planting contributed to 41% of total emission during the 7-year rotation period. Therefore, reduction in N2O emission within 1 year after planting is important for the total emission from acacia plantation.