东北大兴安岭演替初期泰加林灌草层典型植物开花物候与生长对模拟暖干化气候的响应

Flowering phenology and growth of typical shrub grass plants in response to simulated warmer and drier climate in early succession Taiga forests in the Da Hinggan Ling of northeast China

为了揭示暖干化气候变化趋势对演替初期泰加林灌草层植物开花物候和生长的影响,以东北大兴安岭演替初期泰加林灌草层(高度<50 cm)植物为研究对象,根据植物生活史,选择典型的早花植物圆锥薹草(Carex diandra)和水葡萄茶藨子(Ribes procumbens),中花植物杜香(Ledum palustre)及晚花植物齿叶风毛菊(Saussurea neoserrata),监测模拟增温和排水处理2年后其完整的开花物候及生长状况,以期为认识气候变化下泰加林火后植被恢复演替提供依据。结果显示:1)模拟增温和排水处理后,早花植物开花温度限制的提早解除使其花期提前,而水分限制使得晚花植物花期呈延后趋势,这可能为中花植物提供更大的生态位空隙,使其开花数量趋向于增加,花期提前且呈延长趋势;2)模拟增温和排水处理后,圆锥薹草、杜香和齿叶风毛菊的盖度和频度均呈增加的趋势,以杜香最显著,而水葡萄茶藨子的盖度和频度均下降;3)模拟增温与排水处理对植物开花物候的影响无显著交互作用,但土壤水分降低影响部分植物生长对增温的响应。研究结果表明,植物开花物候对暖干化气候的响应表现出明显的种间差异,因植物开花功能群而异。早、中花植物花期趋于提前,晚花期植物花期趋于延后,一方面可能导致群落生态位变化,对种间竞争产生潜在影响,引发群落组成和结构改变;另一方面可能成为群落调节其整体物候,以适应气候变化的重要途径。

Aims We studied flowering phenology and growth of four typical shrub grass plants （Carex diandra, Ribes procumbens, Ledum palustre, Saussurea neoserrata） with different life histories in the Da Hinggan Ling of north- east China to explore changes of flowering phenology and growth of early succession Taiga forests and to learn about the post-fire succession of the Taiga forests in warmer and drier climate. Methods Open-top chambers （OTCs） and artificial drainage ditches were used to simulate the warmer and drier climate in the field. After two years of experimental wanning and drainage, we recorded the flowering phenology and growth indices of four typical shrub grass plants. Flowering phenology included the first flowering date, peak flowering date, last flowering date, flowering duration and maximum flowering number. The growth indices of plants included height, coverage, frequency and above-ground biomass. Important findings Our results revealed that： 1） Under experimental warming and drainage treatment, the first flowering dates for Carex diandra and Ribes procumbens were advanced due to early elimination of the temperature limit, which for Saussurea neoserrata were delayed by the water stress. Moreover, the Ledum palustre had longer flowering duration and more followers under the experimental warming and drainage because of the adverse shift in flowering phenology of the earlier flowering plant and the later flowering plant. 2） The Carex diandra, Saussurea neoserrata and Ledum palustre had higher coverage and frequency under experimental warming and drainage, especially in Ledum palustre, while the coverage and frequency of Ribes procumbens were declined. 3） There was no significant interaction effect between the warming and drainage on plant flowering phenology, but the responses of plant growth characteristics to warming were affected by drainage. These results indicated that species respond differently to warmer and drier climate due to different flower functional groups they belong to. The first flowering date of the early flowering plants had been progressed, and that of the late flowering plants was delayed. On the one hand, these changes can change niches in the community and interspecific competition and further alter the composition and structure of the community. On the other hand, these changes could be a way for the community to regulate community phenology to adapt climate change.