黄土高原两种针叶树种不同器官水碳氮磷分配格局及其生态化学计量特征

Distribution patterns and ecological stoichiometry of water, carbon, nitrogen and phosphorus in different organs of two conifer species on the Loess Plateau

植物不同器官水、碳、氮、磷等元素含量及其生态化学计量特征能够反映植物的生态策略及其环境适应性。本研究以黄土高原两种乡土树种油松(Pinus tabulaeformis)和柴松(Pinus tabulaefirmis f.shekanensis)为研究对象,分析了研究区两种树种水、碳、氮和磷在不同器官的含量及其生态化学计量特征,探讨了两种树种基于水、碳、氮和磷分配格局的生态适应策略。结果表明:(1)油松和柴松对水分和碳素的分配格局总体表现为根和叶最大,其次为枝和干,树皮最小;对氮、磷的分配格局则表现为叶片显著高于其他器官。(2)油松将更多的水和氮分配给叶、根等生产性器官,而柴松将更多的水和碳分配给枝、干等防御性器官,反映了柴松较油松具有更加保守的生长策略,能够更好适应逆境条件。(3)植物器官不同元素间通过相互耦合后可以表现出较好的相关性,反映了植物元素之间具有高度复杂的协同关系,这种协同关系的体现形式可能与植物类型及其对外界环境变化的生长适应策略密切相关。

Background,aim,and scope Stoichiometry is one of the hotspots in currently ecological study that it mainly focuses on the mass balance of multiple chemical elements in living systems.The contents of water,carbon,nitrogen and phosphorus in different organs of plants and their ecological stoichiometry can reflect the ecological strategy and environmental adaptability of plants.In this study,two native species of Pinus tabulaeformis and Pinus tabulaefirmis f.shekanensis on the Loess Plateau were taken as research target,and the contents of water,carbon,nitrogen and phosphorus in different organs and their ecological stoichiometry were analyzed to investigate the ecological adaptation strategies of the two coniferous species.Materials and methods A 20 m×20 m standard plots were established in both P.tabulaeformis and P.tabulaefirmis f.shekanensis community when the plant biomass peaked.Five standard trees that can represent the average growth of trees within each plot were selected to collect the samples of leaf,branch,bark and stem of each species.And the roots in 0-20 cm soil depth of the two communities were sampled by using a 9 cm diameter root corer.All the plant organic samples were oven-dried at 65℃and weighed to within 0.01 g.The contents of water,carbon,nitrogen and phosphorus in different organs were analyzed referring to Lu(2000).The one-Way analysis of variance(ANOVA),Pearson correlation analysis and regression analysis among all the elements and their ratio in each organic of the two species were conducted by SPSS 16.0,and LSD test was used for multiple comparison tests.Results The water,carbon,nitrogen,and phosphorus content in each organic of the two species ranged from 207‰to 625‰,434.0 g.kg-1 to 596.8 g.kg-1,1.1 g.kg-1 to 13.0 g.kg-1 and 1.3 g.kg-1 to 2.4 g.kg-1.The distribution pattern of water and carbon in different organs of P.tabulaeformis and P.tabulaefirmis f.shekanensis was the highest in roots and leaves,followed by branches and roots,and the bark was the smallest;and the nitrogen and phosphorus was significantly higher in leaf than that of other organs.The water/carbon ratio,water/nitrogen ratio,water/phosphorus ratio,carbon/nitrogen ratio,carbon/phosphorus ratio and nitrogen/phosphorus ratio were from 0.77-1.14,44.8-499.1,121.6-491.7,45.9-524.9,250.5-443.4 and 0.6-5.5.Generally,the water/carbon ratios in leaf,branch and stem,and nitrogen/phosphorus ratio in bark of P.tabulaeformis were higher than that in P.tabulaefirmis f.shekanensis(P<0.05);however,the water/nitrogen ratio,carbon/nitrogen ratio and carbon/phosphorus ratio in stem and bark of P.tabulaeformis were lower than that in P.tabulaefirmis f.shekanensis(P<0.05);while the water/phosphorus ratio in each organic were not different significantly between the two species.Moreover,most of the elements and their stoichiometry between the two species have significant positive and negative relationship.Discussion The water content was significantly higher in leaves and lower in stem of P.tabulaeformis than that of P.tabulaefirmis f.shekanensis,which indicated P.tabulaeformis had more active water use strategy.Under the condition of better water condition,the growth of P.tabulaeformis was faster than that of P.tabulaefirmis f.shekanensis,but P.tabulaefirmis f.shekanensis could better adapt to the relatively dry environment.The allocation strategy of carbon and nitrogen in the two species reflects that more nitrogen was allocated to the plant-producing organs of P.tabulaeformis.In contrast,more carbon would allocate to the plant’s defensive organs of P.tabulaefirmis f.shekanensis,which also indicates that P.tabulaefirmis f.shekanensis has more conservative growth strategy to better adapt to adversity conditions.There was no significant difference in the total phosphorus content of Pinus tabulaeformis and P.tabulaefirmis f.shekanensis in different organs which indicated the utilization strategies of phosphorus were similar between the two species.And it also indicated that phosphorus was not a limiting element for plant growth in comparing to water and nitrogen in this area.Conclusions P.tabulaeformis will allocate more water and nitrogen to productive organs of leaf and root,and P.tabulaefirmis f.shekanensis will allocate more water and carbon to defensive organs of branch and stem.The allocation pattern water,carbon,nitrogen and phosphorus in different organs and their ecological stoichiometry indicates P.tabulaefirmis f.shekanensis has a more conservative ecological strategy than P.tabulaeformis and is better to adapt to adversity conditions on the Loess Plateau in China.Recommendations and perspectives The elements in plant organ can be shown to be well correlated after their intercoupling which reflects the highly complex synergistic relationship among different elements.And the expression of these synergistic relationships may be closely related to the plant types and their adaptive strategies to the external environment.The stoichiometry characteristic of plant organic could be well indicated the adaptive strategies of species on the Loess Plateau.