黄土丘陵区刺槐与油松人工林生态系统生态化学计量特征

为阐明不同人工林生态系统间生态化学计量特征的差异,采用野外采样与室内分析相结合的方式分析了陕北黄土丘陵区落叶阔叶树种刺槐和常绿针叶树种油松人工林乔木、灌草、枯落物和土壤(土层深度0—100cm)C、N、P化学计量特征。结果表明:1)刺槐乔木各器官(叶、枝、干、皮、根)C含量显著低于油松,但N和P含量显著高于油松。因此,油松的C∶N和C∶P显著大于刺槐,而N∶P小于刺槐。2)刺槐林下枯落物N和P含量显著高于油松,但C含量显著小于油松。此外,油松林下枯落物C∶N(70.21)大于刺槐林下枯落物C∶N(19.71),说明油松林下枯落物分解较慢,有利于养分的存储。3)刺槐和油松人工林土壤C、N含量均随土壤深度增加而减少,P含量则基本保持不变。刺槐人工林土壤中C含量低于油松,N、P含量在两者之间无显著差异。4)刺槐人工林内乔灌草叶、枯落物与土壤C、N、P及其计量比的相关性多集中在10—20、20—30cm土层,而油松林中各组分与土壤营养元素的相关性相对较小,其中20—30cm土层中无显著相关性,说明相比刺槐人工林而言,油松人工林内土壤层N、P供应量对植物叶片N、P含量影响不显著。本研究为深入了解黄土丘陵区生态系统养分耦合循环机制奠定了基础,同时也为黄土丘陵区的植被恢复工作提供了一定的指导意义。

Stoichiometric characteristics of Robinia pseudoacacia and Pinus tabuliformis plantation ecosystems in the Loess hilly-gully region, China

To comprehensively understand the stoichiometric characteristics of different plantation ecosystems, field investigations and laboratory analyses were performed to study the carbon (C), nitrogen (N), and phosphorus (P) stoichiometries in the arbor, shrub, herb, litter, and soil (soil depth 0-100cm) of the deciduous broad-leaved tree species Robinia pseudoacacia and evergreen coniferous tree species Pinus tabuliformis plantations in the Loess hilly-gully region, northern Shaanxi, China. The results showed that 1) the C concentrations of arbor organs were significantly lower in Robinia than in the Pinus plantations, while the N and P concentrations were significantly higher in Robinia than in the Pinus plantations. Thus, the C:N and C:P ratios were significantly higher in Pinus than in the Robinia plantations, but the N:P ratio in Pinus was less than that in the Robinia plantation. 2) The litter N and P concentrations were significantly higher in Robinia than in the Pinus plantations, but the C concentration was significantly lower in Robinia than in the Pinus plantations. In addition, the litter C:N ratio was higher in Pinus (70.21) than in the Robinia (19.71) plantations. This indicated that the lower decomposition rate of litter was advantageous to nutrient storage in the Pinus plantation. 3) The soil C and N concentrations decreased with increasing soil depth, but the P concentrations remained constant in both plantations. The soil C concentration in Robinia was less than that in the Pinus plantation, but no difference was observed in N and P concentrations. 4) The correlations between the C, N, P, and nutrient ratios of the arbor leaf, shrub leaf, herb leaf, litter, and soil in the Robinia plantation were more focused in the 10-20, and 20-30cm soil layers, and these correlations in the Pinus plantation were relatively lower, with no significant correlation even in 20-30cm soil layer. This indicated that compared with the Robinia plantation, the supply of N and P had no significant impact on the N and P content of leaf in the Pinus plantation. This study establishes the foundation for illuminating the ecosystem nutrient coupling mechanism in Loess hilly-gully region, as well as provides a guiding significance for the vegetation restoration in the Loess hilly-gully region.