不同杉木林分类型土壤团聚体生态化学计量特征

在野外调查的基础上,选择成土母质相同、坡向坡度相似、海拔基本一致的杉木-米老排、杉木-火力楠和杉木纯林3种杉木人工林采集土壤样品,通过干筛法分离2 mm、2～0.25 mm和0.25 mm 3个团聚体组分,研究其土壤团聚体有机碳、全氮、全磷的含量及其生态化学计量特征,以阐明不同杉木林分类型土壤团聚体碳氮磷生态化学计量特征的指示意义。结果表明:(1)0～10 cm和10～20 cm土层有机碳、全氮和全磷含量的变异系数分别为21.37%、21.00%、21.46%和20.35%、16.51%、17.82%;全氮的变异系数低于有机碳和全磷,但三者含量呈极显著正相关关系。(2)有机碳和全氮含量集中分布于小粒径团聚体(0.25 mm)中,全磷含量在各粒径团聚体中分布较为均匀;在不同林分类型中土壤有机碳、全氮和全磷含量均表现为杉木-火力楠杉木-米老排杉木纯林;在0～10 cm和10～20 cm土层的C/N、C/P和N/P的变异系数分别为14.09%、19.75%、22.24%和19.56%、21.28%、24.49%;土壤C/N的变异性较低,土壤C/P和N/P均在大粒径团聚体(0.25 mm)中较高,土壤C/N、C/P和N/P对土壤有机碳储量具有良好的指示作用。研究表明,在杉木与火力楠混交林中,缺乏磷元素,建议及时补充P元素,避免土壤持续利用受到磷的限制。

Ecological Stoichiometry of Soil Carbon, Nitrogen, and Phosphorus within Soil Aggregates of Four Plantations in Different Cunninghamia lanceolata Stand Types

We analyzed soil samples from the plantation of Mixed plantation of Cumninghamia lanceolata and Mytilaria laosensis; C. lanceolata and Michelia macclurei and pure plantation of C. lanceolata in the Experimental Center of Tropical Forestry, Chinese Academy of Forestry. The soil aggregates were classified into >2 mm, 0.25-2 mm, and <0.25 mm fractions by a dry sieving procedure. Soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) contents, and their stoichiometric ratios were calculated, and to examine the ecological stoichiometric characteristics of C, N and P within soil aggregates. The results showed that the coefficients of variation of SOC, TN and TP were 21.37%, 21.00% and 21.46%, respectively in the 0-10 cm soil layer and were 20.35%, 16.51% and 17.82%, respectively in the 10-20 cm soil layer. The spatial variation of TN was lower than that of SOC and TP but there were significant positive correlations among them. SOC and TN were distributed in the micro aggregates and among of them had the greatest values in the C. lanceolata and M. macclurei plantation, however, the distribution of TP was relatively uniform among aggregates and ages. The coefficients of variation of C/N, C/P and N/P were 14.09%, 19.75% and 22.24%, respectively in the 0-10 cm soil layer and were 19.56%, 21.28% and 24.49%, respectively in the 10-20 cm soil layer. Variation of C/N was lower than that of C/P and N/P. Averaged C/P and N/P values in the macro aggregates were higher than that in aggregates of other sizes. C/N, C/P and N/P had good indication for SOC storage. The results showed that there was a lack of phosphorus in the mixed forest of C. lanceolata and M. macclurei. It was suggested that P should be supplemented in time to avoid the limitation of phosphorus on the sustainable utilization of soil.