不同林龄尾巨桉人工林凋落物和土壤C、N、P化学计量特征

为正确认识桉树(Eucalyptus spp.)人工林凋落物和土壤C、N、P时空分配格局及两者间的关系,对5个林龄尾巨桉林分凋落物及土壤C、N、P含量及化学计量比进行测定分析。结果表明,凋落物的C含量均显著大于土壤,且不同林龄间凋落物C含量无显著差异,1年生人工林土壤表层(0~20 cm)的C含量显著小于3~7年生,其他土层C含量在不同林龄间差异不显著。凋落物的N含量均显著高于土壤,且1年生人工林显著大于其他林龄的,而土壤表层的N含量以7年生人工林最大,1年生的最小。凋落物的P含量除1年生人工林显著大于3年生外,其他林龄间均无显著差异,土壤的P含量在不同林龄间的差异均不显著。凋落物C∶N随林龄呈逐渐增大趋势,且显著大于土壤层。凋落物的C∶P和N∶P在不同林龄间的差异不显著,但均显著大于土壤层。凋落物的N含量与表层土壤的C、N含量呈极显著负相关,凋落物的C∶N与表层土壤的C∶P,N∶P呈显著正相关,表层土壤C、N积累受到凋落物N的制约。因此,在桉树人工林经营管理过程中如何降低凋落物分解的N限制性、提高养分传递效率及合理施肥显得十分重要。

Ecological Stoichiometric Characteristrics of Carbon, Nitrogen and Phosphorus in Litter and Soil of Eucalyptus urophylla × E. grandis Plantation at Different Forest Ages

In order to understand the temporal and spatial distribution pattern and stoichiometry characteristics of carbon, nitrogen, phosphorus in litter and soil of Eucalyptus plantation, the contents of carbon, nitrogen, phosphorus in litter and soil of E. urophylla×E. grandis plantation under five forest ages were analyzed. The results showed that the C content in litter was significantly higher than that in soil, and had no significant difference among forest ages. The C content in surface soil (0-20 cm) at 1-year-old forest was the lowest, and that in other soil layers had no significant difference among forest ages. The N content of litter was higher significantly than that in soil, and which at 1-year-old forest was the highest. The N content of surface soil in 7-year-old forest was the highest, which in 1-year-old forest was the smallest. The P content of litter had no significant difference among forest ages except 1-year-old forest was obviously bigger than 3-year-old forest. The P content in soil had no significant difference among forest ages. The C:N in litter increased with forest ages, which was significantly higher than that in soil. The C:N, N:P in litter had no significant difference among forest ages, which were higher than soil. The N content in litter was negatively correlated with C and N contents in soil, and there were significant relation between C:N in litter and C:P, N:P in surface soil. The C and N accumulation in surface soil was restricted by N content in litter. Therefore, it was important in sustainable management of Eucalyptus plantation for reduce N limitation in litter, increase nutrient transfer efficiency and rational application of fertilizer.