间伐对杉木人工林不同组分碳、氮、磷含量及其生态化学计量关系的影响

目的 研究间伐后杉木人工林碳（C）、氮（N）、磷（P）生态化学计量关系变化，为杉木人工林养分循环研究提供参考。 方法 在浙江开化县林场17年生杉木人工纯林内，建立9块20 m×20 m的固定样地，测定分析了未间伐、中度间伐（20%间伐强度）和强度间伐（37%间伐强度）处理地表凋落物、林下植被、杉木细根和土壤C、N、P含量及其计量关系。 结果 间伐2 a后，强度间伐处理地表凋落物和杉木细根生物量显著降低，林下植被生物量显著增加。强度间伐处理下地表凋落物总氮（TN）含量显著降低，林下植被总氮（TN）含量则显著增加，土壤有机碳（SOC）和总氮（TN）含量也显著增加，杉木细根C、N、P含量在未间伐、中度间伐和强度间伐之间无显著差异。地表凋落物C/N和C/P随着间伐强度增加而增大；林下植被C/N随着间伐强度增加而减小，N/P比随着间伐强度增加而增大；杉木细根和土壤C/N、C/P和N/P在不同间伐处理之间差异不显著。土壤与林下植被C、N、P含量及其比值具有显著相关性。 结论 间伐后短期内杉木人工林地表凋落物、林下植被和土壤C、N含量受间伐强度显著影响，间伐改变了地表凋落物和林下植被C、N、P生态化学计量关系，但对杉木细根和土壤C、N、P生态化学计量关系无显著影响。

Effects of Thinning on Contents and Stoichiometry of C,N, and P in Different Components of Chinese Fir Plantation

Objective To study the changes of carbon (C), nitrogen (N) and phosphorus (P) stoichiometry in Chinese fir (Cunninghamia lanceolata) plantations after thinning. Method Nine 20 m×20 m plots were established in 17-years-old Chinese fir plantation in Kaihua Forest Farm of Zhejiang. The contents and stoichiometry of C, N, and P in litter, understory, fine roots and soil were studied under three thinning intensities, i.e. unthinning, moderate thinning (20%), and heavy thinning (37%). Result After 2 years of thinning, the litter biomass and fine root biomass of Chinese fir decreased significantly (P < 0.05) in the heavy thinning treatment, while the understory vegetation biomass increased significantly. Compared with the unthinned stands, the total N content decreased significantly in the litter and increased in the understory vegetation in the heavy thinning treatment (P < 0.05), and the contents of soil organic carbon and total nitrogen also increased significantly in the heavy thinning treatment (P < 0.05). The contents of C, N, and P in the fine roots of Chinese fir showed no significant difference among the unthinned, 20% thinned and 37% thinned stands. The ratios of C/N and C/P in the litter increased with increasing thinning intensity. The C/N ratio of the understory vegetation decreased with increasing thinning intensity, and N/P ratio increased with increasing thinning intensity. The ratios of C/N, C/P and N/P in the fine root and soil showed no significant difference among the three thinning treatments. There was positive correlation in the contents of C, N and P and their ratios between soil and understory vegetation. Conclusion The contents of C and N in the litter, understory vegetation and soil are strongly affected by thinning intensity during a short time after thinning. Thinning alters C, N and P stoichiometry in litter and understory vegetation, but has no effect on fine roots of Chinese fir and soil.