林龄对重庆武陵山区马尾松天然次生林C、N、P生态化学计量特征的影响

在国家碳达峰和碳中和背景下，为准确评估区域植被固碳增汇功能和科学指导其经营管理，以重庆武陵山区14、25、38、45、62年生马尾松天然次生林为研究对象，对马尾松各器官（叶、枝、干、根和皮）、凋落物以及土壤C、N、P含量及其生态化学计量特征进行研究。结果表明：（1）马尾松针叶C、N、P含量分别变化在444.48-518.03 g/kg、12.31-16.15 g/kg、1.75-2.21 g/kg之间，总体呈"C适中、N缺乏及P充足"的养分格局，且马尾松生长主要受N限制。（2）马尾松各器官C、N、P生态化学计量受林龄影响及其变化规律各有不同，但不同器官差异显著（P<0.05），其中C含量以皮最大，N、P含量则以针叶最大。（3）林龄对马尾松凋落物C、N、P生态化学计量影响不显著（P>0.05）；马尾松林土壤P含量低（变化在0.09-0.41 g/kg之间），但各土层生态化学计量比却普遍较高，且受林龄影响各不相同。（4） C、N、P生态化学计量在马尾松各器官-凋落物-土壤之间总体呈显著相关性（P<0.05），其中，针叶C、N含量均与土壤N含量呈显著正相关，但针叶P含量与土壤N含量呈显著负相关。因此，对于该区域的马尾松天然次生林，应采取适当增施氮肥或林下补植固氮树种的营林措施，以提升马尾松天然次生林的固碳增汇能力。

Effects of stand ages on C, N and P stoichiometry of Pinus massoniana secondary forests in Wuling Mountain Area of Chongqing

As the essential nutrient elements of plants and the most basic constituent elements of ecosystem, carbon (C), nitrogen (N), and phosphorus (P) play an important role in biogeochemical cycle and maintaining stability of ecosystem structure and function. Under the background of carbon peak and carbon neutralization, in order to accurately evaluate the carbon sequestration and sink increasing function of regional vegetation and scientifically guide vegetation management, we investigated Pinus massoniana secondary forests of 14, 25, 38, 45 and 62 years old in Wuling Mountains Area of Chongqing. Contents and stoichiometry of C, N and P in various organs (leaf, branch, stem, root and bark), litter and soil of P. massoniana forests at five different stand ages were studied. The results showed that C, N and P contents of P. massoniana leaf ranged from 444.48 to 518.03 g/kg, 12.31 to 16.15 g/kg, and 1.75 to 2.21 g/kg, respectively, and overall presented a nutrient pattern of "moderate C, deficient N and sufficient P", and the growth of P. massoniana in this study was mainly limited by N. C, N and P contents in various organs of P. massoniana, as well as their stoichiometry, were differently affected by stand ages and their variations were different, but were significantly affected by organs (P<0.05). C content in bark was the largest, and N and P contents in leaf were the largest in various organs. Litter C, N and P contents of P. massoniana forests, as well as their stoichiometry, were not significantly affected by stand ages (P>0.05). The soil P contents of P. massoniana forests were lower (ranging from 0.09 to 0.41 g/kg), but their stoichiometric ratios of various soil layers were generally higher and differently affected by stand ages. C, N and P contents, as well as their stoichiometry presented the significant correlation between various organs and litter and soil of P. massoniana forests (P<0.05). C and N contents in leaves were significantly positively correlated with soil N content, but P content in leaves was significantly negatively correlated with soil N content. Therefore, for the P. massoniana secondary forests in this region, our findings suggest that appropriate forest management measures such as increasing soil nitrogen fertilizer or replanting nitrogen fixation trees under forest should be taken to enhance the capacity of forest carbon sequestration and sink increasing.