遮阴对云南松幼苗针叶非结构性碳水化合物和碳氮磷化学计量特征的影响OA

[Objective]The study aims to elucidate the shading adaptation mechanism of Pinus yunnanensis seedlings at different ages,to provide a reference for age-class silviculture and forest environmental adaptation theory.[Method]One-year-old and three-year-old Pinus yunnanensis seedlings were used to conduct the shade test with five light gradients(100%,80%,45%,30%and 5%full light).Phenotypic plasticity index,correla-tion analysis and principal component analysis were used to assess the chlorophyll content,non-structural carbo-hydrates(NSC),and carbon,nitrogen and phosphorus stoichiometric characteristics of needles from Pinus yun-nanensis seedlings of different ages.[Result]Compared with CK,photosynthetic pigments(Chl a,Chl b)and NSC contents were significantly higher in one-year-old Pinus yunnanensis seedlings under light shade(80%full light,L1)treatment.Under heavy shade(5%full light,L4),however,carbon enrichment resulted in a 19.86%increase in the C/P ratio,and the seedling growth was mainly limited by N(N/P<14).Compared with CK,3-year-old Pinus yunnanensis seedlings under shade significantly alleviated nutrient limitation through optimiza-tion of photosynthetic efficiency(29.78%increase in Chl(a+b))and enhancement of phosphorus uptake(15.56%increase in P content),which resulted in the accumulation of NSC(44.95%increase in soluble sugar content compared with one-year-old Pinus yunnanensis)and the synergistic regulation of carbon and nitrogen(49.33%decrease in C/N).The results of phenotypic plasticity analysis showed that the plasticity indices of photosynthetic pigments,NSC and N utilization of 3-year-old Pinus yunnanensis seedlings(0.13-0.70)were significantly higher than those of one-year-old Pinus yunnanensis seedlings(0.05-0.63).[Conclusion]Shade adaptation strategies for Pinus yunnanensis seedlings differed according to seedling age,with one-year-old Pinus yunnanensis seedlings maintaining metabolic balance by regulating photosynthetic pigments and short-term car-bon allocation,and three-year-old Pinus yunnanensis seedlings optimizing resource allocation by enhancing phos-phorus uptake efficiency and long-term carbon storage.It is suggested that in Pinus yunnanensis plantation forest management,30%-80%full light condition should be maintained to balance carbon metabolism in younger seedlings,and phosphorus supplementation should be used to improve the shade tolerance of older seedlings.