Chemical Ecology of an Invader (Podocarpus Nagi)

日本中部奈良县首府奈良市的东北部，一座小山的西坡上覆盖着以Podocarpus nagi为主的小鲤鱼林，山顶海拔294米。在1400多年的历史长河中，它作为Kasuga神社的背景受到了保护。自从大约一千年前，为了表达人们对神道教神的尊敬，人们在山脚下人工种植了一些紫菖蒲树以来，这些树已经侵入了原生植被——日本的常绿阔叶林。由于其化感化学物质nagi -内酯具有六种光学异构体，这种入侵者对其他植物具有侵略性。本研究关注的是一种具有侵略性的入侵植物紫菀所采取的一种生存策略的化学生态学。这些化学物质明显地抑制了原生树木的发芽和初始生长，并从食草动物中释放出长叶蓟，其主要成分是生活在森林中的1000只鹿，这些鹿在神社中被保护为神道神的冬青动物。在凋落物中，化学物质从林冠流向林底，在雨中，化学物质从林冠流向林底。因此，森林生态系统中化学物质的循环与碳和养分循环高度相关，表明入侵者的自中毒。森林土壤受到化学物质的污染，导致森林结构和植物组成较差。入侵者是一种雌雄同株的物种，性别比例为1:1。其幼苗分布格局取决于雄树。该物种的物候特征表明其原产地为热带，每4年一次结实，与ENSO有较高的相关性。

A podocarp forest with Podocarpus nagi dominant covers the west slope of a small hill, Mt. Mikasa with a peak of 294 m in altitude, situated on the north-eastern part of Nara City, the capital of Nara Prefecture, Central Japan. It has been protected for a background of the Kasuga Shinto Shrine through long historical time over 1400 years. Since some podocarp trees was artificially planted on a foot of the hill about a thousand years ago to express man's respect to the Shinto Gods, the trees has been invading into the native vegetation, Japanese broadleaved evergreen forest. This invader is aggressive to other plants owing to its allelopatic chemicals, Nagi-lactones with six optical isomers. This study is concerned with chemical ecology of a life strategy adopted by an aggressive invader P. nagi.The chemicals clearly inhibited the germination and initial growth of native trees and released P. nagi from grazers, whose major component was one thousand deers living in the forest and has been protected as a holly animal of the Shinto Gods at the Shrine. There was substantia '1 flow of chemicals from forest canopy to forest floor in litterfall and the others : throughfall and stemflow in rain. Therefore the cycle of the chemicals in the forest ecosystem was highly correlated with carbon and nutrient cyclings, suggesting the auto-intoxication of the invader.Forest soil was polluted by the chemicals and resulted in the poor forest architecture and frolal composition. The invader is a monoecious species with a sex ratio of 1 : 1. The distribution pattern of seedlings of the invader depend on the male trees. The phenological phenomena of the invader suggested its tropical origin and its mast fruiting was observed every four years implying the high correlation with the ENSO.