Christopher Kettle, Biodiversity International's director for forest genetic resources and restoration in Rome, says that the need for infrastructure — things such as mechanisms for collecting and storing seeds, and nurseries to raise seedlings — might be most desperate here because many trees are 'masting' species, which don't produce seeds every year.
罗马生物多样性国际组织森林遗传资源与恢复主任克里斯托弗·凯特尔表示,基础设施的需求——例如收集和储存种子的机制,以及培育幼苗的苗圃——在这里可能最为迫切,因为许多树木是“ mast 结实”物种,它们不是每年都产种子。
这是一个三层嵌套结构:第一层是 "that" 引导的宾语从句作 "says" 的宾语;第二层是 "because" 引导的原因状语从句嵌套在 that 从句内;第三层是 "which" 引导的非限定性定语从句嵌套在 because 从句内,修饰 "masting species"。此外,从句内部还包含不定式和分词短语作后置定语,形成了从句、从句、非谓语的混合嵌套。