入侵植物小花山桃草种群构件生物量结构及种子萌发特征

通过野外设置样方调查和室内萌发试验,研究小花山桃草种群各构件生物量的结构特征和它们之间的关系模型、繁殖分配以及种子萌发特点。结果表明:(1)小花山桃草根、茎、叶、花(果)序生物量与植株高度之间以及各构件生物量之间均呈正相关关系,可用幂函数模型或线性函数模型较好地表达;(2)各构件生物量在个体生物量中所占的比率表现为茎>花序>叶>根;(3)小花山桃草的繁殖投入和繁殖分配都随植株个体的增大而增加;(4)小花山桃草个体大小和繁殖投入之间为线性关系,而个体大小和繁殖分配之间为幂函数关系;(5)小花山桃草存在一个较小的繁殖阈值(0.6043g);(6)小花山桃草种子在有光照(12h)和黑暗条件下发芽率均可达到85%以上;未经贮藏的种子不萌发,低温沙藏(1～2℃)和室温干藏(14～32℃)一个半月种子萌发率分别可达92.5%和79%;低温沙藏时种子即可发芽,且发芽率可达61%。在研究地区,小花山桃草几乎整个生长季都可萌发,甚至初冬还有幼苗产生。小花山桃草构件生物量结构和繁殖分配特征、种子萌发特点等都有助于其入侵能力的提高,是其成功入侵我国的重要原因。

Module biomass structure and seed germination traits of the exotic invasive plant Gaura parviflora

Gaura parviflora is native to the North America,but it has now become one of the main exotic invasive plants in China.Through field investigations and the seed germination experiments in the labor-atory,the biomass structure traits,the correlation models among different modules,the reproductive allocation and the seed germination traits of G.parviflora population were studied.The results showed that:(1) The biomass of root,stem,leaf and capitulum(and fruit) of G.parviflora had remarkable positive correlations with plant height,and the biomass of each module also had remarkable positive correlation,which could be described respectively by power function or linear function;(2) The biomass proportion of each module to the whole plant decreased in the sequence of stem,capitulum(and fruit) ,leaf,root;(3) The reproducetive investment and reproductive allocation increased as the individual size increased;(4) A linear function relationship was found between the individual size and reproductive investment whereas a power function relationship between the individual size and reproductive allocation was detected;(5) Reproductive threshold in this plant was comparably small(0.6043 g) ;(6) The seed of G.parviflora was non-photoblastic.Its seed germination percentage was more than 85% both under 12 h light or continuous dark condition.The seed germination rate reached 79% and 92.5% respectively in seeds stored for 45 d at ambient temperature(14-32 ℃) and seeds stored for 45 d at cold stratification(1-2 ℃) while the seed germination did not occur without being stored.In the natural habitat in Luoyang,seedling of G.parviflora emerge almost during the growing season,even in the early winter.It was concluded that the traits of module biomass structure and reproductive allocation,seed germination all facilitated its invasions.