不同生境条件下紫茎泽兰幼苗生长动态

紫茎泽兰(Eupatorium adenophorum)种子属投机式萌发, 一年内只要有适合的温湿条件都可以萌发。种子萌发的高峰期主要集中在雨季, 而干旱的冬、春季节萌发率很低。未开花结实的紫茎泽兰个体可终年持续生长, 生长速率受光照、湿度和温度影响显著。秋季萌发的紫茎泽兰幼苗在冬季及干旱季节中, 各项生长指标(包括主茎长度、总叶面积、基径等)增长缓慢。在不同生境中, 紫茎泽兰平均月增长量由高到低依次为: 偏阳生境＞全荫湿润生境＞灌丛遮荫生境, 生长旺季为6–10月份的雨季。实生苗越年后通常在第一个旱季即可开花结实; 但萌发较晚以及生长发育不良的个体一般并不开花而是保持营养生长。未开花结实的越年生实生苗的生长节律与当年生实生苗相似, 但需要再经过一个生长季节甚至更长的生长发育期才能进行开花结实, 完成其生活史周期。本研究结果进一步揭示了紫茎泽兰是通过有性生殖与无性生殖相互补充的繁殖策略进行种群更新与种群扩张的。

Growth trends of Crofton weed (Eupatorium adenophorum) seedlings in different habitats

Crofton weed () seeds took a speculative strategy to germinate, and its seeds would germinate at any time all the year round as long as the conditions were suitable. The peak of the seeds’ germination occurred in the rainy season while few seeds germinated during the dry seasons. The un-flowering individuals of Crofton weed keep growing all year, and its growth rate would be influenced by the illumination intensity, humidity and temperature distinctly. The results showed that all of the growth pa-rameters of seedlings germinating during autumn changed slowly in the dry season. The optimum habitat was the sunny sites, then entirely shaded ones, and the shrub habitats were the last. The fastest growth of the seedlings period began in June and ended in October. Usually the seedling would flower and seed during the first dry season, but those germinated later or did not develop well would keep vegetative growth without flowering. The growth dynamic of un-flowering seedlings was similar to those flowering and seeding, but the life history periods between them were different: only those crossing two or enven more winters could the former seedlings bloom and fructify to finish their life history circle. The result of this study further indicated that reinforcement each other of both sexual reproduction and clone would promote the renewal and spread of their population increase of Crofton weed.