Why do we have amber forests? The relationship between resin production and amber deposits

植物产生的树脂是一种复杂的化学混合物，但通常树脂有挥发性成分和非挥发性成分，正是这些成分中的化合物混合物往往是物种所特有的。植物树脂通常用于防御目的，如保护免受草食动物或病原体的伤害，或密封裂缝和其他损害，尽管尚不清楚为什么所有树脂植物都会产生这些分泌物。琥珀是一种化石树脂，人们认为它的挥发性成分丢失了，非挥发性部分发生了聚合和其他化学变化。在整个岩石记录中，琥珀是罕见的，但有三个例子，在世界各地出现了大量的、往往是大量的沉积物，被称为琥珀爆发。它们发生在始新世至中新世(5500万至1700万年前)、早至中白垩世(145至80Mya)和晚三叠世(约230Mya)。为什么琥珀会在这个时候出现，数量如此之大，在世界各地出现的地方如此之多，这一点尚不清楚。为什么产生树脂的物种会产生如此多的树脂，在这个时候作为琥珀爆裂而被保存下来？有几种解释，比如新型钻木昆虫的进化或火灾风险的增加，但到目前为止，这些想法还没有得到证实。该项目旨在对现代世界树脂生产的想法进行经验性测试，并评估这些原因是否可能是岩石记录中发现的琥珀破裂的原因，并发现现代树脂中是否存在独特的化学特征，这些特征指向过去树脂涌出的一个特定原因。该项目的重点是当今树脂含量最高的针叶树种，即新西兰和新喀里多尼亚的阿拉伯树科树种。通过结合现场观察和重复的树实验，它将测试是否可以检测到因不同原因释放的现代树脂中不同的化学特征，并使用这些特征来区分这些树脂。这样的化学差异将在来自新西兰的较古老的树脂和琥珀中进行勘探，这些树脂和琥珀被认为也是由珍稀物种产生的。树脂和琥珀将通过一系列方法进行化学比较，包括标准热解-气相色谱-质谱仪和傅立叶变换红外光谱，以确定树脂的化学成分，以及新的ToF-SIMS方法，测试树脂的化学均一性。这是第一项结合测试自然界树脂生产的多种生态原因的研究，并通过重复实验，使用一系列技术和专业知识。作为这个项目的结果，我们对琥珀森林的生态以及它们为什么会产生树脂的了解将得到显著提高。

Plants produce resins which are a complex mixture of chemicals, but generally resins have a volatile and a non-volatile component, and it is this mixture of chemical compounds in the components that is often unique to a species. Plant resins are generally for defensive purposes, such as protection from herbivores or pathogens, or to seal cracks and other damage, although it is not clear why all resinous plants produce these exudates. Amber is fossilised resin, where it is thought that the volatile component is lost, and polymerization and other chemical changes occurred in the non-volatile fraction. Amber is rare throughout the rock record, but there are three instances where numerous, often large deposits occur worldwide, and are called amber bursts. These occur in the Eocene to Miocene (55-17 Million years ago, Mya), Early to mid-Cretaceous (145-80 Mya), and Late Triassic (c. 230 Mya). Why amber should occur at these times in such large quantities and in so many localities worldwide is not understood. Why did the resin producing species produce so much resin that became preserved as amber bursts at these times? There are several explanations, such as the evolution of new wood-boring insects or heightened fire risk but there has been no substantiating of these ideas to date. This project aims to empirically test ideas for resin production in the modern world and evaluates whether these reasons could be the causes of the amber bursts found in the rock record, and to discover whether there are distinctive chemical signatures in the modern resins that point to one particular reason for a resin outpouring in the past. The focus of this project is on the most resinous conifers today; the Araucariaceae of New Zealand and New Caledonia. By combining field observations and replicate tree experimentation it will test if differing chemical signatures in modern resins released in response to different causes can be detected and used to tell such resins apart. Such chemical differences would then be prospected for in older resins and ambers from New Zealand, which are thought to have also been produced by araucarian species. The resins and ambers will be chemically compared through a range of methods including standard pyrolysis-gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy identifying the resin chemistry to the new ToF-SIMS method testing the chemical homogeneity of resins. This is the first study to combine the testing of multiple ecological reasons for resin production in the natural world and through replicate experiments, using a range of techniques and expertise. As a result of this project, our understanding of the ecology of amber forests and why they produced their resins will be significantly improved.