黄土高原子午岭地区人工油松林碳氮磷生态化学计量特征

分析人工植被重建背景下,森林植物、枯落物与土壤的碳(C)、氮(N)、磷(P)化学计量特征有助于深入理解森林生态系统养分循环规律和系统稳定机制。以黄土高原子午岭地区的3个林龄(10、25 a和40 a)的人工油松林为对象,通过测定油松林叶片、枯落物和土壤的碳(C)、氮(N)、磷(P)含量,研究人工油松林不同林龄叶片、枯落物和土壤的化学计量学特征。结果表明,不同林龄油松叶片C、N、P含量分别为538.85—560.54 g/kg、9.00—10.47 g/kg和1.04—1.13 g/kg。在3个林龄油松林中,除叶片C含量外,叶片N、P含量存在显著差异(P0.05);枯落物层以及土壤层的C、N、P含量均存在显著差异(P0.05),且枯落物层含量大于土壤层。随着林龄的增加,叶片C∶N比呈现先减小后增大的变化,N∶P和C∶P比呈显著增加趋势,而枯落物层C∶N、C∶P和N∶P比无显著差异。同时,随着林龄的增加,除10—20 cm土层的C∶N比外,土壤的C∶N比在0—10 cm土层和C∶P和N∶P比在0—10和10—20 cm皆呈显著增加趋势。研究区油松林叶片N∶P比平均值为9.13,低于14,表明油松林生长主要受氮的限制。土壤的N含量与叶片和枯落物层的N含量、以及三者间N∶P比呈显著线性相关(P0.05),充分体现了油松林植物、枯落物与土壤之间的互动关系。研究结果可为我国黄土高原脆弱生态区的生态功能恢复与植被重建提供科学依据。

C, N, and P stoichiometric characteristics of Pinus tabulaeformis plantation in the Ziwuling Region of the Loess Plateau

In this study, Characterization of the C, N, and P stoichiometry of the "plant-litter-soil" continuum was to guide the Pinus tabulaeformis forest productivity, and to understand the nutrient cycling and stability mechanisms of the forest ecosystem on the Loess Plateau. The P. tabulaeformis plantation grown for 10-, 25-, and 40-years in the Ziwuling area on the Loess Plateau was selected to determine the carbon (C), nitrogen (N) and phosphorus (P), as well as the stoichiometric characteristics in the leaves, litter, and soil during stand development. The results showed that the content of C, N, and P in leaves from the P. tabulaeformis plantations ranged from 538.85 to 560.54, 9.00 to 10.47, and 1.04 to 1.13 g/kg, respectively. Except for the C content in leaf, the N and P contents in the leaves were significantly different for the three stand ages (P < 0.05). The C, N and P contents in litter and soil were also significantly different for the three stand ages (P < 0.05), with litter having higher contents than soil. As the forest age increased, the leaf C:N ratios first decreased, and then increased; whereas the N:P and C:P ratios of the leaves were significantly increased. Meanwhile the C:N, C:P and N:P ratios of the litter did not significantly differ with the age of the P. tabulaeformis plantations. The contents of C and N in soil increased with increasing forest age, and were significantly higher (P < 0.05) at 0-10 depth than at the 10-20 cm depth in all plantation ages. However, the content of P changed litter in the soil profile. As the forest age increased, the soil C:P and N:P ratios at 0-10 and 10-20 cm depth and the soil C:N ratios at 0-10 cm depth increased, the soil C:N ratios at 10-20 cm depth decreased. For all plantation ages, the value of the N:P ratio in leaves was less than 14 under P. tabulaeformis plantations, which indicated that the growth of the plant in this study was limited by N. Correlations analysis showed that significantly positive correlations (P < 0.05) between the N content and N:P ratios existed for the leaves, litter, and soil, which indicated that content of N in the plant was affected by the supply of N in the soil. Overall, vegetation restoration improved soil quality in the Loess Plateau. The results can provide a scientific basis for the restoration of ecological function and vegetation in the fragile ecological region of the Loess Plateau in China.