黄土丘陵区不同森林类型叶片-凋落物-土壤生态化学计量特征

采用野外调查与室内分析相结合的方法,测定了黄土丘陵区主要人工林(刺槐、小叶杨和油松)和天然次生林(辽东栎、麻栎和白桦)中乔叶、凋落物以及土壤的碳(C)、氮(N)和磷(P)含量,探讨不同森林类型叶片-凋落物-土壤生态化学计量特征差异,旨在进一步了解研究区森林生态系统的养分供求现状。结果表明:1)人工林叶片和凋落物的C含量大于天然次生林,N、P含量均小于天然次生林,叶片和凋落物C∶N和C∶P值均表现为人工林大于天然次生林;2)人工林中土壤的C、N、P含量及化学计量比的显著性差异主要集中在土壤表层(0—10 cm),而天然次生林则集中在10—50 cm的土层,随着土层深度增加,二者的C、N、P含量逐渐减小;3)人工林N含量在叶片与凋落物间为显著正相关,天然次生林N含量在凋落物与土壤间为极显著正相关、C∶P值在叶片与土壤间则为显著负相关,其余各指标无显著相关性。揭示了除刺槐和辽东栎的生长受P限制外,其余各树种均受N限制,人工林凋落物的分解速率较快,且人工林土壤P有效性高于天然次生林,这些研究结果可为我国黄土丘陵区的植被恢复与重建工作提供理论依据。

Ecological stoichiometry characteristics of leaf-litter-soil interactions in different forest types in the Loess hilly-gully region of China

This study measured the C, N, and P concentrations in the leaves, litter, and soil of plantations (Robinia pseudoacacia, Populus simonii, and Pinus tabuliformis) and natural secondary forests (Quercus wutaishanica, Quercus acutissima, and Betula platyphylla) in the hilly-gully region of the Loess Plateau by combining field investigations with laboratory analyses. We explored the ecological stoichiometry characteristics of leaf-litter-soil interactions in different forest types in order to understand the nutrient supply-demand status of different forest ecosystems. The results showed that 1) for leaves and litter, the C concentration was higher in plantations than in natural secondary forests, whereas the concentrations of N and P were higher in natural secondary forests than in plantations. The C:N and C:P ratios of the leaves and litter were higher in plantations than in natural secondary forests. 2) The significant differences between C, N, and P regarding the stoichiometric ratios of soil were mainly concentrated at the soil surface (0-10 cm) in plantations, while in natural secondary forests these differences were found deeper in the soil layer (10-50 cm). With an increase in soil depth, the C, N, and P concentrations gradually decreased. 3) The N concentration in the leaves showed significant positive correlation with the litter in the plantations; the N concentration of litter showed significant positive correlation with the soil in the natural secondary forests, and the C:P ratio in the leaves showed significant negative correlation with that of the soil (P < 0.05); and there were no significant differences in the remaining indicators. These results revealed that the growths of R. pseudoacacia and Q. wutaishanica were limited by P, other trees were restricted by N, the decomposition rate of litter was higher in plantations than in natural secondary forests, and the soil P was higher in plantations than in natural secondary forests. The results of this study could provide a theoretical basis for vegetation restoration and reconstruction in the Loess hilly-gully region of China.