若尔盖典型高寒湿地植物叶功能性状对水深梯度的响应

Responses of leaf functional traits to water depth gradient in Zoige typical alpine wetland

高寒泥炭沼泽湿地储存着大量有机碳,影响全球碳库的收支平衡,作为重要的生态因子,植物功能性状显著影响着生态系统的碳输入与输出过程.为了解水位变化对高原高寒湿地植物功能性状的影响并深入理解水位下降下的高寒泥炭沼泽碳循环,以青藏高原东部若尔盖典型沼泽湿地两种优势植物——木里苔草(Carex muliensis;湿生植物,即喜欢潮湿环境而不能忍受长时间水位不足的陆生植物)和斑唇马先蒿(Pedicularis longiflora var.tubiformis;中生植物,即介于湿生与旱生植物之间而不能忍受严重干旱或长期水涝的植物)为研究对象,采用“中宇宙”水位模拟试验,分析两种植物在10 cm(D_(10))、0 cm(D_(0))、–20 cm(D_(-20))和–50 cm(D_(-50))水位梯度下叶形态性状的差异,以及叶片光合气体交换参数、叶绿素荧光参数等的变化规律.结果表明:(1)木里苔草通过减小叶长、叶面积、比叶面积、叶干重和增加叶厚以适应水位下降,斑唇马先蒿则通过减小叶长、叶宽、叶面积、比叶面积和叶干重来适应水位上升.(2)随着水位下降,木里苔草的净光合速率、蒸腾速率、气孔导度、电子传递量子效率和光化学淬灭系数显著减小,而胞间CO_(2)浓度和非光化学淬灭系数显著增加;斑唇马先蒿表现为净光合速率、蒸腾速率、气孔导度、电子传递量子效率和光化学淬灭系数增加,而胞间CO_(2)浓度和非光化学淬灭系数逐渐减小.(3)木里苔草叶干重与叶长、比叶面积呈极显著正相关关系(P<0.001),与叶面积呈显著正相关关系(P<0.05),而与叶厚呈极显著负相关关系(P<0.001);斑唇马先蒿的叶干重除与叶厚无显著相关关系外,与叶长、叶宽、叶面积、比叶面积呈极显著正相关关系(P<0.001).总体而言,水位增加对斑唇马先蒿生长产生抑制作用,而水位下降对木里苔草生长产生抑制作用,并且木里苔草(湿生植物)对水位下降的敏感程度要大于斑唇马先蒿(中生植物).(图4表1参46)

Alpine peat bogs store large amounts of organic carbon and affect the balance of the global carbon pool.As an important ecological factor,plant functional traits significantly affect carbon input and output processes in ecosystems.To explore the effects of water level change on the leaf functional traits of plants in alpine wetlands and understand the carbon cycle of alpine peat bogs under declining water levels,we selected two dominant species(Carex muliensis and Pedicularis longiflora var.tubiformis)from a typical zoige wetland on the eastern Tibetan Plateau.C.muliensis is a hygrophyte(a terrestrial plant that thrives in wet environment and cannot tolerate low water levels for long periods),whereas P.longiflora var.tubiformis is a mesophyte(a plant between hygrophytes and xerophytes,that does not tolerate severe drought or long-term waterlogging).The differences in leaf morphological characteristics,photosynthetic gas exchange parameters,and chlorophyll fluorescence parameters of the two species were studied under four levels of water depth(10 cm(D_(10)),0 cm(D_(0)),-20 cm(D_(-20))and-50 cm(D_(-50)))using a“mesocosm”water level simulation experiment.The results showed that:(1)C.muliensis increased leaf thickness by decreasing leaf length,area,specific area,and dry weight to adapt to a decreased water level,whereas P.longiflora var.tubiformis decreased leaf length,width,area,specific area,and dry weight to adapt to rising water levels.(2)With a decrease in water level,the net photosynthetic rate,transpiration rate,stomatal conductance,electron transfer quantum efficiency(ETR),and photochemical quenching coefficient(qP)of C.muliensis decreased significantly,whereas the intercellular CO_(2)concentration and non-photochemical quenching coefficient(NPQ)increased significantly;P.longiflora var.tubiformis showed an increased net photosynthetic rate,transpiration rate,stomatal conductance,ETR,and q_(P),and a gradual decreased intercellular CO_(2)concentration and NPQ.(3)Leaf dry weight of C.muliensis positively correlated with leaf length and specific leaf area(P<0.001),as well as leaf area(P<0.05),and negatively correlated with leaf thickness(P<0.001).We found no significant correlation between leaf thickness and leaf dry weight in P.longiflora var.tubiformis;however,leaf length,width,area,and specific area were positively correlated with leaf dry weight(P<0.001).Globally,an increase in the water level inhibited the growth of P.longiflora var.tubiformis,whereas the decrease in water level inhibited the growth of C.muliensis,and the latter(hygrophyte)was more sensitive to the decrease in water level than the former(mesophyte).