太白山栎属树种气孔特征沿海拔梯度的变化规律

气孔是植物与外界环境进行水分和气体交换的主要通道,调节植物碳同化和水分散失的平衡关系,在一定程度上反映植物对外界环境变化的适应。沿太白山北坡1100—2300 m海拔,测定4种栎属树种的气孔性状,分析气孔性状沿海拔的变化规律和其对环境因子的响应。结果表明:(1)气孔密度与气孔长度间的负相关在4个树种间均显著存在(P0.05);除栓皮栎(Quercus variabilis)外,气孔密度与潜在气孔导度指数的正相关关系均达显著水平;而气孔宽度与气孔长度之间只在栓皮栎和锐齿栎(Q. aliena var. acuteserrata)达到显著水平。(2)栓皮栎和槲栎(Q. aliena)的气孔长度和宽度随海拔升高而下降,气孔密度、潜在气孔导度指数增加,辽东栎(Q. wutaishansea)变化形式则相反;锐齿栎气孔宽度减小,其余性状沿海拔呈单峰变化,在约1600 m处气孔长度达到最小值,气孔密度和潜在气孔导度指数达到最大值。(3)与土壤因子相比,气孔性状主要受气候因素的影响。潜在气孔导度指数与大气温度、空气湿度成极显著正相关(P0.01),与降水量显著负相关(P0.05)。其中,空气相对湿度是影响潜在气孔导度指数的主要因素,能够解释气孔变异的22.9%。本研究结果对于深入认识秦岭太白山地区栎属树种对环境变化的响应和适应提供理论证据。

Variation of leaf stomatal traits in Quercus species along the altitudinal gradient in Taibai Mountain, China

Stomata are the main channels for water and gas exchange between plants and their environment; this exchange adjusts the balance between plant carbon assimilation and water loss and reflects to some extent the adaptability of plants to environmental changes. In this study, we investigated stomatal traits in four Quercus species along an elevation gradient (1100-2300 m) in the northern slope of Taibai Mountain (China) and explored the patterns of stomatal traits and responses to environmental variables. The results obtained were as follows. (1) There was a significant positive correlation between the potential conductance index and stomatal density in all species except Q. variabilis. Moreover, a significant positive correlation between stomatal width and length was found in Q. variabilis and Q. aliena var. acuteserrata, whereas a significant negative correlation between stomatal density and length was observed in all species (P < 0.05). (2) The stomatal width and length of Q. variabilis and Q. aliena decreased with altitude while their stomatal density and potential conductance index increased. However, the opposite trends were observed in Q. wutaishansea. Furthermore, along the elevation gradient, the stomatal width of Q. aliena var. acuteserrata decreased and the other stomatal traits showed a single-peak pattern. Particularly, the stomatal length was the shortest at around 1600 m while the stomatal density and potential conductance index reached their maxima. (3) Climate factors had greater influence than soil factors on the variation of stomatal traits along the elevation gradient. For instance, the potential conductance index was mainly positively correlated with atmospheric temperature and air humidity but negatively correlated with precipitation (P < 0.05). Of all the factors considered, air humidity explained the largest percentage (22.9%) of stomatal trait variations. Our results enhance our understanding about the adaptation response of Quercus species to future environmental changes.