Chemical Ecology of an Invader (Podocarpus Nagi)

一片以罗汉果为优势的罗汉果林覆盖在一座小山的西坡上。米卡萨，海拔294米，位于日本中部奈良县首府奈良市东北部。在1400多年的漫长历史中，它一直被保护在Kasuga神社的背景下。自从大约一千年前在山脚下人工种植了一些罗汉果树以表达人们对神道神的敬意以来，这些树一直在入侵当地的植被--日本常绿阔叶林。由于其化感物质--含有六种光学异构体的NaGI-内酯类化合物，该种入侵植物对其他植物具有侵袭性。这项研究是关于侵略性入侵者P.nagi采取的一种生活策略的化学生态学。这些化学物质明显地抑制了当地树木的萌发和初始生长，并从食草动物中释放了P.nagi，其主要成分是生活在森林中的1000头鹿，并作为神道神的冬青动物在靖国神社受到保护。森林生态系统中化学物质的循环与碳、养分循环密切相关，表明森林土壤受到化学物质的污染，导致森林结构和植被组成较差。入侵种为雌雄同株种，性别比为1：1。入侵种苗木的分布格局依赖于雄树。入侵种的物候现象表明，入侵种起源于热带，盛果与ENSO有很高的相关性。

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.