ABSTRACT

Although studies in mainland states of Australia and overseas show that the conversion of native forests to plantations can reduce carbon (C) stocks in soils, no studies have been undertaken in Tasmania to assess how plantations affect soil C stocks. To address this knowledge gap, we compared soil C concentrations and C stocks to 30 cm depth in native ‘mixed’ eucalypt forests and adjacent Eucalyptus nitens plantations on Ferrosols in north-west Tasmania, using a factorial sampling strategy. Mean soil C and nitrogen (N) concentrations were significantly lower in plantations than in mixed forests; however, because the soils in plantations had higher bulk density, mean soil C stocks under the two treatments (114 Mg ha⁻¹ and 116 Mg ha⁻¹, respectively) were not significantly different. It is concluded that machine removal of 5–6 cm of topsoil into windrows during land clearing for plantations would be sufficient to explain why C concentrations were lower in plantations than in mixed forests and that, apart from this physical effect of land preparation, 17–21 years of plantation growth on Ferrosols in north-west Tasmania has not significantly affected soil C stocks in mineral soil. This result can be partly explained by the ability of Ferrosols to form stable complexes between organic matter, sesquioxides and clays.

摘要

尽管澳大利亚大陆各州和海外的研究表明，将原生森林转变为种植园可以减少土壤中的碳 (C) 储量，但塔斯马尼亚尚未进行任何研究来评估种植园如何影响土壤碳储量。为了解决这一知识差距，我们使用因子抽样策略比较了塔斯马尼亚州西北部铁溶胶上的原生“混合”桉树林和邻近的桉树人工林中 30 厘米深度的土壤 C 浓度和 C 储量。人工林的平均土壤 C 和氮 (N) 浓度显着低于混交林；然而，由于人工林土壤具有较高的容重，两种处理下的平均土壤碳储量（114 Mg ha ^-1和 116 Mg ha ^-1，分别）没有显着差异。得出的结论是，在人工林清理过程中机器将 5-6 厘米的表土清除到堆垛中就足以解释为什么人工林中的 C 浓度低于混交林，并且除了土地整理的这种物理影响之外，17-塔斯马尼亚西北部 21 年的铁溶胶种植园生长并未显着影响矿质土壤中的土壤碳储量。这一结果可以部分解释为铁溶胶能够在有机物、倍半氧化物和粘土之间形成稳定的复合物。