荒漠植物梭梭稳定碳同位素组成与环境因子的关系

摘要

Haloxylon ammodendron is a dominant shrub widely distributed in the desert in the Xinjiang Uygur Autonomous Region,northwest China.In the present study,we investigated the variation in the stable carbon isotope composition (δ13C) in an assimilating branch of H.ammodendron and the relationship of δ13C from H.ammodendron with environmental factors (altitude,duration of sunshine,evaporation,mean annual precipitation,and mean annual temperature) using a dataset collected from 101 communities and 23 ecosystem sites.Our results showed that:(1) δ13C in the assimilating branch of H.ammodendron averaged 14.15‰ with a range from-13.14 to-15.38‰ at a 95％ confidence interval,which indicated that H.ammodendron was characterized by a C4photosynthetic pathway.(2) Along an environmental gradient,δ13C values of H.ammodendron was negatively and significantly correlated with mean annual precipitation and mean annual temperature,but positively correlated with altitude,duration of sunshine,and evaporation.We inferred that the different response patterns of δ13C values to environmental factors were possibly caused by stomatal limitation in the assimilating branch of H.ammodendron,which was considered an adaptation to the dry desert conditions.(3) δ13C values of H.ammodendron varied significantly among different habitats.The highest δ13C values appeared when H.ammodendron was found with Nitraria tangutorum and Reaumuria Linn.in grey and grey-brown desert soils,and distributed in plain,mountainous and hill habitats,whereas the lowest δ13C values were observed when H.ammodendron was found with Ceratoides arborescens and Calligonum mongolicum located in aeolian sandy and chisley soils,and distributed in Junggar Basin.Together,our results demonstrated that water use efficiency of H.ammodendron varied significantly along environmental gradients and habitats,indicating a divergent adaptation strategy for water use efficiency.%以广泛分布于新疆荒漠地区的建群种植物——梭梭(Haloxylon ammodendron)为研究对象,通过对23个样地101份梭梭同化枝样品δ13C值的测定,分析了梭梭稳定碳同位素组成的变化特征及其与环境因子(海拔、日照时数、潜在蒸散量、年平均降水量和年平均温度)的关系,并讨论了不同生境下梭梭同化枝δ13C值的变化特征.研究结果显示:(1)梭梭同化枝δ13C平均值为-14.15‰,其在95％置信区间的变化范围为-13.14‰-15.38‰,表明梭梭是C4光合途径的植物.(2)梭梭同化枝δ13C值与年平均降水量和年平均温度呈显著负相关关系,而与日照时数、潜在蒸散量和海拔呈显著正相关关系.我们推测梭梭同化枝δ13C值对各环境因子响应趋势的不同,可能是由气孔限制因素造成的,它是梭梭适应干旱荒漠环境的一种策略.(3)在不同生境下,梭梭同化枝的碳同位素组成存在显著差异.当梭梭群落中的主要伴生种为白刺、红砂时,其δ13C值最高,当主要伴生种为沙拐枣和假木贼时,其δ13C值最低.在灰漠土与灰棕漠土样地中的梭梭δ13C值高于棕钙土、风沙土、石质土样地;盆地中梭梭同化枝δ13C值低于平原、山地、丘陵地形条件下的样地.以上结果表明:梭梭水分利用效率在不同环境梯度和生境中,存在着显著不同,表现出显著的适应策略差异.