不同林龄油松(Pinus tabulaeformis)人工林植物、凋落物与土壤C、N、P化学计量特征

在陕西省北部延安市境内子午岭林区,采用时空互代的方法选取9、23、33、47年生油松(Pinus tabuliformis)人工林为研究对象,比较油松不同器官(叶、枝、干、根)、凋落物及土壤C、N、P含量及其比值的差异,探讨它们随林龄的变化及其相互间的关系,以期为油松人工林的生产、改善和林木生长环境的调节提供参考。结果表明:除根中C含量在林龄间差异不显著外,其它器官C、N、P含量及其比值在林龄间均差异显著且随林龄增加变化趋势不尽相同。9、23、33、47年生油松林C、N、P含量及N∶P比值均在叶中最高;C∶N比值均在干中最高,根中次之;C∶P比值均在干中最高,其它器官大小次序不一。除33年生油松林叶中N∶P比值大于14外,其它各器官各林龄N∶P比值均小于14,且N∶P比值随林龄先增加后减少,故可判断油松在该区域受N限制较为严重,且随林龄的增加受N限制的情况有所缓解。不同林龄土壤和凋落物C、N、P含量及其比值差异显著,且后者均大于前者。土壤与凋落物C、P含量及C∶N、C∶P、N∶P比值随林龄增加变化趋势完全一致,表明土壤与凋落物之间有着密切的关系。叶片与凋落物N、P含量及C∶N、C∶P、N∶P比值之间显著相关,表明凋落物的养分承自植物叶片,二者之间关系紧密;植物和土壤的C、N、P含量之间均不存在显著相关性,说明土壤C、N、P供应量对乔木叶片C、N、P含量影响不大。

Variation of C, N, and P stoichiometry in plant tissue, litter, and soil during stand development in Pinus tabulaeformis plantation

To estimate the ecological stoichiometry of Pinus tabulaeformis at different plantation stand ages, we investigated P. tabulaeformis plantations of 9, 23, 33, and 47 years old in the Ziwuling of Shaanxi province. This research of ecological stoichiometry was studied in order to guide the P. tabulaeformis forest productivity, and to improve and adjust the growth environment of such plantations. To this end, we investigated the carbon (C), nitrogen (N), and phosphorus (P) concentration, as well as their ratios in plant organs (leaf, branch, stem, and root), litter, and soil during stand development. Apart from root C concentration, the C, N, and P concentrations of the different plant organs, as well as their ratios, were significantly different in all plantation age groups. For all four age groups of P. tabulaeformis plantations, the C, N, and P concentrations, as well as the N:P ratios were highest in the leaf tissue, whereas the C:N and C:P ratios were highest in the stems. For other plant organs, no consistent patterns were found. For all plantation ages, all plant organ N:P ratios were lower than 14, except for leaf tissue from the 33-year-old P. tabulaeformis forest stand. Overall, the N:P ratios first increased, and then decreased with increasing forest age. These results imply that in this region, P. tabulaeformis is limited by N, and this N limitation decreases with increasing forest age. The litter and soil C, N, and P concentrations, as well as their ratios, were significantly different among the plantation age groups, with litter having higher concentrations than soil. Soil and litter C and P concentrations, as well as their C:N, C:P, and N:P ratios changed similarly with the increasing forest age, indicating a close relationships between soil and litter stoichiometry. There were significant correlations between the leaf tissue and litter N and P concentrations, as well as between their C:N, C:P, and N:P ratios. However, no significant correlations between the leaf tissue and soil C, N, and P concentrations were found, suggesting that the supply of C, N, and P from the soil had little influence on plant tissue C, N, and P concentrations.