黄土高原不同林龄刺槐林碳、氮、磷化学计量特征

C,N and P stoichiometry characteristics of different-aged Robinia pseudoacacia plantations on the Loess Plateau,China

以黄土高原幼龄林、中龄林、成熟林(分别为5~10、11~15、21~30年生)刺槐人工林为对象,研究刺槐根、茎、叶、枯落物的碳、氮、磷化学计量学特征及其相互关系.结果表明:不同林龄刺槐林各组分的碳、氮、磷含量分别为376.74~486.67、8.66~29.70和0.79~1.95g·kg^(-1),刺槐各组分碳含量变异较小,磷含量变异较大.中龄林碳含量较高,成熟林氮、磷含量较高.不同组分间叶碳、氮、磷含量较高,茎的氮含量较低.不同林龄刺槐林各组分的C/N、C/P和N/P分别为15.74~53.40、242.47~606.39和8.10~20.57;中龄林和幼龄林中茎C/N、C/P和N/P显著高于成熟林,不同组分间茎C/N、C/P较高,叶C/N、C/P较低.刺槐叶片和根的碳氮磷含量间不存在相关关系,枯落物与茎的氮含量和磷含量间存在显著相关关系,反映出枯落物和茎的建成过程中对氮磷按比例投入的依赖.与全球尺度相比,黄土高原人工刺槐林具有较高的储碳能力,氮含量丰富,而磷相对缺乏,成为刺槐人工林生长的主要限制因子.

Three different stand ages of Robinia pseudoacacia plantations, including young plantation （5-10 years old）, middle-age plantation （11-15 years old）, and mature plantation （21-30 years old）, were selected as the objects, to explore the contents of C, N and P and their ecological stoichiometry characteristics in roots, stems, leaves and litter. The results showed that carbon, ni- trogen and phosphorus contents varied in the range of 376.74-486.67, 8.66-29.70 and 0.79-1.95 g· kg^-1, respectively in different components of R. pseudoacacia plantations with different ages. There was a low variability of C content, a high variability of P content. The high C content was found in middle-age plantation, and the high N and P contents were found in mature plantation. The high C, N and P contents were found in leaves, and the low N content was found in stems for different-aged R. pseudoacacia plantations. C/N, C/P and N/P in different components of R. pseudoacacia plantation were 15.74-53.40, 242.47-606.39 and 8.10-20.57, respectively. C/N, C/P and N/P of stems in mid-mature plantation and young plantation were significantly higher than those in mature plantation. C/N and C/P were high in stems, and C/N and C/P was low in leaves in different-aged R. pseudoacacia plantations. There was no correlation among carbon, nitrogen and phosphorus contents in leaves and roots of R. pseudoacacia plantations, but significant positive correlation between the nitrogen content and phosphorus content in litter and stems. It indicated that the litter and stems were built on the proportional input of nitrogen and phosphorus elements. Compared with the global scale, R. pseudoacacia plantation in the Loess Plateau had the high carbon storage capacity, abundant nitrogen content and relative lack of phosphorus, which became the major limiting factor for growth of R. pseudoacacia plantation.