不同坡向及径级油松异龄叶的功能性状

【目的】研究植物叶功能性状特征,以了解植物生存的适应性策略。【方法】以松山地区油松天然林及人工林为对象,通过测定不同叶龄油松的比叶面积(SLA)、叶干物质含量(LDMC)、叶氮量(LNC)、叶磷量(LPC)及氮磷比(m(N):m(P),缩写为N/P),得到不同坡向上不同径级油松异龄叶的功能性状特征。【结果】①在天然林和人工林内,不同坡向油松的SLA、LDMC差异均显著(P<0.05),SLA在阴坡较高,而LDMC在阳坡较高。②SLA与LDMC呈显著负相关(P<0.01,其中当年生叶相关系数r=-0.86,往年生叶r=-0.84); LPC与m(N):m(P)呈现显著负相关(P<0.01, 当年生叶r=-0.47,往年生叶r=-0.70); LNC与m(N):m(P)呈显著正相关(当年生叶P<0.05,r=0.23; 往年生叶P<0.01,r=0.45)。③不同发育阶段中,小径级油松的SLA显著高于中、大径级(P<0.05),LDMC趋势则相反,且大径级的LDMC最大。④各径级中当年生叶的LNC和m(N):m(P)均低于往年生叶相应值,但其LPC均比往年生叶的高。【结论】坡向显著影响油松叶对资源和能量的分配策略,阴坡叶的比叶面积性状特征明显,而阳坡叶注重叶干物质含量的积累; 松山地区油松营养限制类型为氮限制,且新叶生长更易受氮限制。异龄叶在不同坡向和各个发育阶段的叶功能性状,表明该地区油松为了最大限度地减少环境的不利影响而采取了适应性权衡对策。

Effect of age,slope aspects and diameter classes on leaf functional traits of Pinus tabulaeformis in Songshan,Beijing

Objective] Determine characteristics of leaf functional traits that reflected the adaptability of plants.Method] We measured five leaf functioual traits of Pinus tabulaeformis,including specific leaf area (SLA),leaf dry matter content (LDMC),leaf nitrogen concentration (LNC),leaf phosphorus concentration (LPC) and N/P,respectively,across age,slope aspect and diameter class in natural and artificial forests in the Songshan Nature Reserve.Result]① The SLA from north-facing slopes was significantly greater than that from south-facing slopes (P＜ 0.05).The LDMC from north-facing slopes was significantly lower than that from south-facing slopes (P ＜ 0.05).② SLA was significantly negatively correlated with LDMC (P ＜ 0.01),LPC was significantly negatively correlated with the N/P ratio (P＜ 0.01),and LNC was significantly positively correlated with LPC (current-year leaf,P ＜ 0.05;perennial leaf,P ＜0.01).③ The SLA of the small class diameter was significantly higher than that of medium diameter and large diameter classes.Conversely,the LDMC of the large diameter class was higher than other that of other diameter classes.④ In each diameter class,the LNP and N/P ratio of current-year needles were lower than those of perennial needles,but the LPC of current-year needles was higher than that of perennial needles.Conclusion] Characteristics of functional leaf traits indicated that slope aspect was an important factor significantly affecting the resources and energy distribution strategy of leaves.Needles from north-facing slopes tended to use more resources on specific leaf area.However,needles from south-facing slopes tended to accumulate more dry matter.P.tabulaeformis,especially the new growing needles,were found to be limited by nitrogen in Songshan.The leaf functional traits of P.tabulaeformis were an embodiment of a tradeoff strategy to minimize the impacts of negative environmental factors.