秦岭典型林分土壤有机碳储量及碳氮垂直分布

以秦岭典型林分锐齿栎(马头滩林区)、油松、华山松、松栎混交林、云杉、锐齿栎(辛家山林区)为对象,研究了不同林分土壤剖面上有机碳、全氮、有机碳储量的分布规律。结果表明:在秦岭地区,随着土壤剖面深度增加,不同林分的土壤有机碳、全氮含量均逐渐降低;不同林分的土壤有机碳、氮素的积累和分解存在一定差异。其中,云杉和松栎混交林的土壤有机碳、全氮含量较高,锐齿栎(辛家山林区)含量较低,不同林分土壤剖面有机碳、全氮含量平均值分别为13.46—26.41 g/kg、4.47—9.51 g/kg,大小顺序均为云杉松栎混交林锐齿栎(马头滩林区)油松华山松锐齿栎(辛家山林区);各个林分的土壤C/N在5.93—15.47之间,C/N平均值大小为松栎混交林﹥华山松﹥油松﹥云杉﹥锐齿栎(辛家山林区)﹥锐齿栎(马头滩林区);各个林分0—60 cm土层的土壤有机碳储量大小为云杉锐齿栎(马头滩林区)松栎混交林华山松锐齿栎(辛家山林区)油松,分别为150.94、135.28、124.93、109.24、102.15、96.62 t/hm2;各个林分土壤有机碳含量与土壤全氮含量存在极显著正相关,土壤有机碳、全氮与C/N则没有明显相关性。

Soil organic carbon storage and vertical distribution of carbon and nitrogen across different forest types in the Qinling Mountains

The main forest areas of Shaanxi Province lie in the Qinling Mountains. These forests have important ecological and economic significance. The distribution patterns of soil organic carbon (SOC), total nitrogen (TN), and SOC storage in the soil profiles have not been systematically studied. The objective of this study was to estimate SOC, TN, and SOC storage for six forest types in the Matoutan forest farm and in the Xinjiashan forest farm of the Qinling mountain range. All forest types in this study were natural secondary forests: namely Quercus aliena var acuteserrata (Matoutan forest farm), Pinus tabulaeformis Carr, Pinus armandii Franch, pine-oak mixed forest, Picea asperata Mast, and Quercus aliena var acuteserrata (Xinjiashan forest farm). Five replicate samples were taken in an "S" pattern for each forest type. The profiles were divided into 0-10, 10-20, 20-40, and 40-60 cm groups and then sampled, summing up to 72 soil samples. The physical and chemical properties of the soils were measured using conventional methods. The results were analyzed using univariate analysis of variance. Differences among forest types and soil horizons were analyzed with SPSS statistics 18.0. The results showed that the content of SOC and TN of different soil layers decreased with increasing soil depth in all six soil profiles. The accumulation and decomposition of SOC and TN differed between forest types. Among the six forest types, the SOC and TN contents of Picea asperata Mast and pine-oak mixed forest were higher than in the others, and that of Quercus aliena var. acuteserrata (Xinjiashan forest farm) was the lowest. The SOC and TN content in the intervals of the six forest soils were 13.46-26.41 g/kg and 4.47-9.51 g/kg, respectively, and the order was Picea asperata Mast > pine-oak mixed forest > Quercus aliena var acuteserrata (Matoutan forest farm) > Pinus tabulaeformis Carr > Pinus armandii Franch > Quercus aliena var. acuteserrata (Xinjiashan forest farm). The ratio of carbon to nitrogen (C/N) ranged from 5.93 to 15.47, the mean C/N was in the order of pine-oak mixed forest > Pinus armandii Franch > Pinus tabulaeformis Carr > Picea asperata Mast > Quercus aliena var acuteserrata (XinJiashan forest farm) > Quercus aliena var acuteserrata (MaToutan forest farm). SOC storage of the 0-60 cm layer of the six soils was 150.94 t/hm² for Picea asperata Mast > 135.28 t/hm² for Quercus aliena var acuteserrata (Matoutan forest farm) > 124.93 t/hm² for Pine-oak mixed forest > 109.24 t/hm² for Pinus armandii Franch > 102.15 t/hm² for Quercus aliena var acuteserrata (Xinjiashan forest farm) > 96.62 t/hm² for Pinus tabulaeformis Carr, which was greater than the national average SOC storage (96.0 t/hm²). SOC storage was influenced by SOC content, soil bulk density (BD), soil thickness, and volume of gravel; therefore, the distribution regularity in the soil profile was poorer. Correlation analysis showed that there were highly significant positive correlations between SOC and TN, but no significant correlations between C/N and SOC and TN.