Mechanisms of abundance decline and potential responses to climate warming in C3 grass species

（1）虽然多年生草本植物鸭茅（Dactylis glomerata L.）自19世纪70年代首次引进以来在日本已确立了优势种群，但其丰富度在东北地区南部显示出明显的减少。在这项研究中，丰富的下降机制和潜在的响应气候变暖的自然种群的D. glomerata。（2）对东北和关东地区43个样地的鸭茅归化种群的丰度进行了测定，并分析了其与气候因子的关系。多度与9月最高气温呈极显著正相关，表明多度的下降与炎热气候的持续时间密切相关，而与盛夏最高气温无关。（3）在26 ~ 40℃温度范围内，以2 ℃为间隔，用A-Ci曲线测定了光响应和暗响应的光合效率。光反应最大效率Jmax随温度的升高而下降，而暗反应最大效率Jcmax随温度的升高没有下降。这些结果表明，高温胁迫下光合作用的下降是由于光捕获或光传递反应功能的降低所致。

(1)Although the perennial grass Dactylis glomerata L.has established dominant populations in Japan since the first introduction in the 1870s', its abundance shows a marked reduction in the southern part of Tohoku regions. In this study, mechanisms of abundance decline and potential responses to climate warming of the naturalized populations of D.glomerata.(2)Abundancs of naturalized populations of D.glomerata were measured in 43 sites of Tohoku and Kantoh regions and their relationships with climate factors were examined. There were highly positie correlation between abundance and maximum temperature in September, which suggests that abundance decline is closely related to duration of hot climate rather than by highest temperature of mid summer.(3)Photosynthetic efficiency of light response and dark response were measured by A-Ci curve during 26℃ to 40℃ at two degree intervals. The decline of Jmax, which represent the maximum efficiency of light reaction, showed a large decline with increasing temperature, but no deline was found for Jcmax, which is the maximum efficiency of dark reaction. These results show that decline of photosynthesis under heat stress is caused by decreased function of light harvesting or light transfer reactions.