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物质混合物，但通常树脂具有挥发性和非挥发性组分，并且这种组分中的化合物混合物通常是物种所特有的。植物树脂通常用于防御目的，例如保护免受食草动物或病原体的侵害，或密封裂缝和其他损害，尽管目前尚不清楚为什么所有的植物都产生这些分泌物。琥珀是一种树脂，人们认为它的挥发性成分丢失了，而聚合和其他化学变化发生在非挥发性部分。琥珀在整个岩石记录中是罕见的，但有三种情况下，世界各地出现了大量的，通常是大型的矿床，被称为琥珀爆发。它们发生在始新世到中新世（5500 - 1700万年前，Mya），早白垩世到中白垩世（14500 - 8000万年前）和晚三叠世（c. 230 Mya）。为什么琥珀会在这些时候出现在如此大的数量和世界各地的如此多的地方还不清楚。为什么产树脂的物种会产生如此多的树脂，并在这些时候以琥珀爆裂的形式保存下来呢？有几种解释，例如新的钻木昆虫的进化或火灾风险的增加，但迄今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实证测试，并评估这些原因是否可能是岩石记录中发现的琥珀爆裂的原因，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最多的针叶树;新西兰和新喀里多尼亚的南洋杉科。通过结合实地观察和复制树实验，它将测试是否可以检测到现代树脂中因不同原因而释放的不同化学特征，并用于区分这些树脂。这样的化学差异将在来自新西兰的更古老的树脂和琥珀中被发现，这些树脂和琥珀被认为也是由南洋杉物种产生的。将通过一系列方法对树脂和琥珀进行化学比较，包括标准热解-气相色谱-质谱法和傅里叶变换红外光谱法，用于识别树脂化学成分，以及新的ToF-SIMS方法，用于测试树脂的化学均匀性。这是第一项联合收割机的研究，通过重复实验，使用一系列技术和专业知识，在自然界中测试树脂生产的多种生态原因。由于这个项目，我们对琥珀森林生态的理解以及为什么它们会产生树脂将得到显着提高。

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.