关键词: 生命表, 有效积温, 温度, 发育起点温度, 种群趋势指数

Abstract: Merremia boisiana is a native species in Hainan Province of China, and its population quantity has been rapidly increasing in recent two decades, which poses a heavy threat to many secondary forests, planted forests and shrublands. There are different light and water quantity conditions in habitats where populations of M. boisiana have broken out, and outbreak species usually adapt to diverse environmental conditions through high phenotypic plasticity. To reveal the ecophysiological mechanisms underlying the adaptation of the outbreak species M. boisiana to diverse environmental conditions, this study assessed the effects of different light and water availability on the growth, morphological traits and their plasticity, and allelopathy of M. boisiana through a greenhouse pot experiment. Biomass of M. boisiana decreased under high light intensity and drought. Low light increased total stem length, specific stem length, and specific leaf area, and decreased the root/shoot ratio of M. boisiana. The mean phenotypic plasticity index of these morphological traits was 0.36. Under high light and drought, aqueous leachates from dry leaves of M. boisiana were least inhibitory to seed germination and seedling shoot growth of Lactuca sativa var. ramosa, possibly because M. boisiana decreased its resource allocation to competition (allelopathy) under stress conditions. Plasticity in morphology might facilitate M. boisiana to better capture light as well as grow to the canopy at a faster rate under low light availability in the forest understory, while plasticity in allelopathy indicates that M. boisiana might adjust its resource allocation to competition (allelopathy) to adapt to various water conditions. We conclude that plasticity of M. boisiana in morphological traits and allelopathy might be one of the ecophysiological mechanisms of M. boisiana adapting to various environmental conditions and causing outbreak.

Key words: life table, effective accumulated temperature, population trend index, developmental threshold temperature, temperature