思茅松人工林土壤有机碳和氮储量变化

以思茅松人工林中龄林、近熟林和过熟林及附近区域思茅松天然林和常绿阔叶林为研究对象,探讨造林对思茅松人工林土壤有机碳和氮储量大小与空间分布的影响。结果表明:各林地类型土壤有机碳、氮含量与C:N随着土层厚度增加而减少,过熟林土壤有机碳和氮含量随土层加深则显著高于其它林地类型,近熟林土壤表层有机碳和氮含量显著低于中龄林和过熟林。思茅松人工林乔木层碳储量随林龄增大而增加,过熟林乔木层碳储量最高。造林对思茅松人工林土壤氮储量的影响不显著,而土壤有机碳储量随林龄增大先减少后增加至过熟林恢复至常绿阔叶林和思茅松天然林水平,土壤有机碳与氮储量随土层加深而减少。与常绿阔叶林和思茅松天然林相比,思茅松人工林的中龄林与过熟林土壤有机碳和氮储量的年变化量高于近熟林,近熟林年变化量呈净减少;在思茅松天然林中,人工更新与在常绿阔叶林中造林相比,思茅松人工林可以累积更多的土壤有机碳和氮储量。此外,土壤含水量越大,土壤有机碳储量则越高。

Changes in Soil Organic Carbon and Nitrogen Stocks in Pinus kesiya var. langbiannesis Plantation

Taking three stand age-class(immature forest, near-mature forest and over-mature forest) of Pinus kesiya var. langbiannesis plantation and nearby green broad-leaved forest, primary coniferous forest as contrast in Pu'er city, Yunnan province. We discussed that the impacts on afforestation for size and spatial distribution of soil organic carbon and nitrogen stocks of Pinus kesiya var. langbiannesis plantation.The results show that soil organic carbon content, nitrogen content and C:N gradually decreased with increase of soil layer thickness in different forest types. Soil organic carbon and nitrogen content in the over-mature forest were significantly higher than that of other forest types as the soil layer deepen and soil organic carbon and nitrogen content of topsoil in the near-mature foretst is significantly lower than that immature forest and over-mature forest. Tree layer carbon stocks of Pinus kesiya var. langbiannesis plantation increased with stand age development, moreover, tree layer carbon stocks in the over-mature forest was significantly higher than other forest types. Afforestation had no significant effect on soil nitrogen stocks, and the soil organic carbon stocks increased, then decreased and recovered the level of green broad-leaved forest and primary coniferous forest with the stand age development. Simultaneously, soil organic carbon and nitrogen stocks decreased with the increase of soil layers depth(0-60 cm). The relative Change rate of soil organic carbon and nitrogen stock of immature and over-mature forest were higher than near-mature forest with stand age development compared with the green broad-leaved and primary coniferous forest, and the relative change rate of soil organic carbon and nirtrogen stock of near-mature forest had obviously net reduction. Artificial reforestation of priamry coniferous forest can accumulate more soil organic carbon and nitrogen stocks than green broad-leaved forest. there were a significant and extremely significant positive correlation between soil moisture and soil organic carbon stocks in the different soil layer depth.