桂北地区桉树林及其他三种森林类型土壤有机碳含量及密度特征

以桂北地区桉树（Eucalyptus grandis×E.urophylla）林、杉木（Cunninghamia lanceolata）林、马尾松（Pinus massoniana）林和毛竹（Phyllostachys edulis）林的土层0~60 cm土壤为研究对象,对比分析了4种森林类型的土壤有机碳质量分数及密度分布特征。结果表明：（1）在4种森林类型土层中,有机碳质量分数的最大值（49.49±1.16）g·kg-1]和最小值（4.50±0.52）g·kg-1]分别出现在毛竹林土层0~15 cm和马尾松林土层45~60 cm。土层0~60 cm有机碳质量分数平均值按大小顺序排列为：毛竹林（28.16g·kg-1）〉杉木林（25.10 g·kg-1）〉桉树林（14.52 g·kg-1）〉马尾松林（9.56 g·kg-1）。桉树林、杉木林、马尾松林和毛竹林土层0~15 cm有机碳质量分数所占的比例分别为28.29%、39.14%、55.44%和43.94%。（2）4种森林类型土层中有机碳密度的最大值（6.71±1.72）kg·m-2]和最小值（1.14±0.11）kg·m-2]分别出现在杉木林土层0~15 cm和马尾松林土层40~60 cm。土层0~60 cm的有机碳密度平均值按大小顺序排列为：杉木林（19.60 kg·m-2）〉毛竹林（18.85 kg·m-2）〉桉树林（12.91 kg·m-2）〉马尾松林（8.47kg·m-2）。桉树林、杉木林、马尾松林和毛竹林土层0~15 cm有机碳密度所占的比例分别为25.12%、34.25%、52.07%和32.64%。4种森林类型土壤有机碳质量分数和有机碳密度均随着土层深度的增加呈降低的趋势。

Characteristics of content and density of soil organic carbon in Eucalptus grandisxE, urophylla forest and the other three forest types in northern Guangxi

Based on the soil horizons of 0-60cm of Eucalptus grandisxE, urophylla forest, Cunninghamia lanceolata forest, Pinus massoniana forest and Phyllostachys edulis forest planted in northern Guangxi, which the distribution characteristics of the soil organic carbon content and soil organic carbon density had studied. The results showed that the maximum value and minimum value of soil organic carbon content were occurred at the soil horizons of 0-15 cm （49.49±1.16） g kg-1] of the Phyllostachys edulis forest and at the soil horizons of 45-60 cm （4.50 ±0.52） g kg-1] of the Pinus massoniana forest, respectively. The average value of the soil organic carbon content at the soil horizons of 0-60cm of the four forest types arranged as the following order： Phyllostachys edulis forest （28.16 g kg-1 ） 〉 Cunninghamia lanceolata forest （25.10 g .kg-1 ） 〉 Eucalptus grandis ~E. urophylla forest （ 14.52 g .kg-1 ） 〉 Pinus massoniana forest （9.56 g kg-1）. The proportion of soil organic carbon content at the soil horizons of 0-15cm of the Eucalptus grandisx E. urophylla forest, Cunninghamia lanceolata forest, Pinus massoniana forest and Phyllostachys edulis forest were 28.29%, 39.14%, 55.44% and 43.94%, respectively. The maximum value and minimum value of the soil organic carbon density were occurred at the soil horizons of 0-15 cm （6.71±1.72） kg m2] of the Cunninghamia lanceolata forest and at the soil horizons of 45-60 cm （ 1.14±0.1 l） kg.m-2] of the Pinus massoniana forest, respectively. The average value of the soil organic carbon density at the soil horizons of 0-60cm of the four forest types arranged as the following order： Cunninghamia lanceolata forest （19.60 kg.m-2） 〉 Phyllostachys edulis forest 08.85 kg m-2） 〉 Eucalptus grandis~E, urophylla forest （12.91 kg m-2） 〉 Pinus massoniana forest （8.47 kg m-2）. The proportion of the soil organic carbon density at the soil horizons of 0-15 cm of the Eucalptus grandisxE, urophylla forest, Cunninghamia lanceoIata forest, Pinus massoniana forest and Phyllostachys edulis forest were 25.12%, 34.25%, 52.07% and 32.64%, respectively. The soil organic carbon content and the soil organic carbon density of the four forest types had a decreased trend with the soil horizons increasing.