无患子初果期人工林土壤和叶片C、N、P化学计量特征

【目的】了解无患子无性系人工林初果期C、N、P化学计量差异及其养分元素间相互作用。【方法】以福建省建宁县无患子无性系媛华人工林为研究对象,选择其初果期具有代表性的地段,分别设置3块20 m×10 m样地,测定了土壤(有机碳、全氮、全磷、全钾、有效磷、有效钾、碱解氮)和叶片(碳、氮、磷、钾)养分含量,并计算土壤和叶片的碳、氮、磷元素计量比(记为C/N、C/P、N/P),分析处于初果期的无患子人工林土壤和叶片养分含量及化学计量特征。【结果】无患子无性系媛华人工林土壤有机碳、全氮、全钾、有效磷含量在初果期随林龄增大而增加,土壤全磷变化不明显且含量较低(0.36 g/kg);土壤C/N随林龄增加逐步减小,而C/P和N/P有一定增加趋势;叶片碳和磷含量随林龄增加而逐渐增大,氮含量逐渐降低,钾含量无显著变化,其人工林叶片C/N有一定程度升高,C/P和N/P随林龄增加出现逐渐降低的趋势。此外,无患子人工林土壤有机碳和全氮含量具有显著正相关;无患子叶片碳与氮之间呈负相关,但碳与磷、钾呈正相关。同时,无患子无性系人工林叶片C含量与土壤有机碳含量在0~20和≥40~60 cm的土层呈显著正相关,在≥20~40 cm的土层中呈极显著正相关;叶片磷P含量与土壤有机碳含量在0~20 cm呈极显著正相关,在≥20~40和≥40~60 cm的土层中呈显著正相关;N/P与土壤有机碳含量在0~20 和≥40~60 cm呈极显著负相关,在≥20~40 cm土层中呈显著负相关。【结论】在无患子人工林初果期,土壤养分主要受P的限制,因此,苗木定植后的结果初期,可适当增加磷肥的投入。

Stoichiometric characteristics of soil and leaves in Sapindus mukorossi plantation at an early fruiting stage

【Objective】 This study aimed to elucidate differences in C, N and P in a soapberry (Sapindus mukorossi) plantation at the first fruit stage of clones and their nutrient element interactions. 【Method】 A clonal plantation in Jianning County, Fujian Province, was used to establish three plots of 20 m×10 m. Soil parameters (organic C, total N, total P, total K, effective P, available P, and alkali N) and leaf parameters (C, N, P and K) were measured, and the C, N and P element ratios were calculated. Nutrient contents and chemical characteristics of soil and leaves at different forest ages at the initial fruit stage were analyzed. 【Result】 The content of organic C, total N, total P and available P increased with forest age, while no change in total P in soil was observed, and the content was low (0.36 g/kg). Soil C/N ratios decreased gradually with the increase of forest age, while C/P and N/P ratios increased to a certain extent. With the increase of forest age, the contents of C and P in leaves increased gradually, while the contents of N decreased gradually, while the contents of K had no significant change. The C/N ratio of leaves increased to a certain extent, while the C/P and N/P ratios decreased gradually. In addition, there was a significant positive correlation between soil organic carbon (SOC) and total N in Sapindus mukorossi plantation. There was a negative correlation between C and N, but a positive correlation between C and P, K. At the same time, there was a significant positive correlation between leaf C content and SOC content in 0-20 cm and ≥ 40-60 cm soil layers, and a very significant positive correlation in ≥20-40 cm soil layers. There was a significant positive correlation between leaf P content and SOC content in 0-20 cm, and a significant positive correlation between leaf P content and SOC content in ≥20-40 and ≥ 40-60 cm soil layers; N/P was significantly negatively correlated with SOC content in 0-20 cm and ≥40-60 cm soil layers, and significantly negatively correlated with SOC content in ≥ 20-40 cm soil layers. 【Conclusion】 Plantation soils at the early fruiting stage were mainly limited regarding P, thus P fertilization should be increased accordingly for future planting processes.