土壤和叶面中的天然同位素丰度可以提供与森林生态系统中碳(C)和氮(N)循环的长期变化有关的综合信息。我们评估了总碳(TC),总氮(TN),针叶林(CPF)土壤和叶面中C(δ13C)和N(δ15N)的同位素自然丰度,天然阔叶林(NBF),和混交林在三个不同的土壤深度(即,0-10、10-20和20-40厘米)。这项研究还探讨了不同森林类型对土壤有效养分的影响。路头森林研究站,位于湖南省,中国中部,被用作研究区域。结果表明,表层土层在混交林中具有较高的TC和TN含量,导致混交林表层土壤层中有机材料的质量优于NBF和CPF。总的来说,土壤TC,TN,和δ15N在不同的土壤深度和森林类型中显着变化。然而,森林类型对δ13C没有显着影响。总的来说,土壤δ13C在CPF中显著富集,和δ15N值在混交林中富集。不同森林类型的叶面碳含量差异显著,而叶面氮含量没有显着差异。不同森林类型的叶面δ15N和δ13C没有大的差异。然而,叶面δ13C和δ15N与土壤δ13C和δ15N呈正相关,分别。FoliarN,土壤和叶面碳氮比,土壤水分含量(SMC),和森林类型是影响同位素自然丰度的主要影响因素,而土壤pH没有显着相关。此外,森林类型变化和土壤深度增量对土壤养分有效性有显著影响。总的来说,混交林土壤养分有效性较高。我们的发现暗示森林类型和土壤深度会改变TC,TN,和土壤δ15N,而δ13C仅由土壤深度驱动。此外,与NBF和混交林分相比,人工林导致土壤有效养分含量下降。
Natural isotopic abundance in soil and foliar can provide integrated information related to the long-term alterations of carbon (C) and nitrogen (N) cycles in forest ecosystems. We evaluated total carbon (TC), total nitrogen (TN), and isotopic natural abundance of C (δ13C) and N (δ15N) in soil and foliar of coniferous plantation (CPF), natural broadleaved forest (NBF), and mixed forest stands at three different soil depths (i.e., 0-10, 10-20, and 20-40 cm). This study also explored how soil available nutrients are affected by different forest types. Lutou forest research station, located in Hunan Province, central
China, was used as the study area. Results demonstrated that the topsoil layer had higher TC and TN content in the mixed forest stand, resulting in a better quality of organic materials in the topsoil layer in the mixed forest than NBF and CPF. In general, soil TC, TN, and δ15N varied significantly in different soil depths and forest types. However, the forest type did not exhibit any significant effect on δ13C. Overall, soil δ13C was significantly enriched in CPF, and δ15N values were enriched in mixed forest. Foliar C content varied significantly among forest types, whereas foliar N content was not significantly different. No big differences were observed for foliar δ15N and δ13C across forest types. However, foliar δ13C and δ15N were positively related to soil δ13C and δ15N, respectively. Foliar N, soil and foliar C:N ratio, soil moisture content (SMC), and forest type were observed as the major influential factors affecting isotopic natural abundance, whereas soil pH was not significantly correlated. In addition, forest type change and soil depth increment had a significant effect on soil nutrient availability. In general, soil nutrient availability was higher in mixed forest. Our findings implied that forest type and soil depth alter TC, TN, and soil δ15N, whereas δ13C was only driven by soil depth. Moreover, plantations led to a decline in soil available nutrient content compared with NBF and mixed forest stands.