What are the large-scale diversity, distributions and fates of forest mycorrhizal communities?

森林里藏着一个惊人的秘密。虽然树木主导着这些生态系统，创造了一个复杂的栖息地，庇护了许多物种，同时遮蔽了许多其他物种，但这种主导地位依赖于与真菌的隐藏关系。这些真菌很少见到，但它们的丝状细丝（称为菌丝）缠绕在树木的根部，形成一种紧密的共生关系，帮助树木和真菌生长——一种互惠的相互作用。这两种生物都需要碳水化合物和矿物质来生长，而树木擅长从空气中捕获和储存碳，真菌的微小菌丝擅长从土壤中提取水和营养物质，如氮和磷。树木和真菌之间的交换量非常高：真菌中的所有碳都可以直接从它的伴侣树木中获得，而树木中的大部分氮直接来自它的伴侣真菌。这些不同种类的真菌被称为外生菌根（ECM）真菌，以修饰的细根或外生菌根命名，树木和真菌在那里相互连接。这些共生关系非常普遍：大多数欧洲树木依赖于ECM真菌，并且有许多不同的真菌形成这些关系。其中一些真菌以其性子实体而闻名，例如毒蝇木耳毒菌和可食用的松露和小圆面包蘑菇。然而，令人担忧的是，我们对外生菌根真菌的多样性知之甚少。虽然一些真菌可能与各种各样的树木和其他植物一起生长，但其他真菌可能仅限于密切相关的树种。虽然已经描述了大约8000种ECM真菌，但可能还有更多未被发现的。此外，我们在很大程度上忽略了这些真菌的地理分布范围。有些可能广泛分布，但其他可能仅限于少数几个小地点。我们确实知道，至少有一些可以入侵其他大陆，而另一些可能在当地灭绝。最令人担忧的是，我们知道外生菌根真菌对环境变化很敏感，尤其是污染、降雨和温度的变化。但我们不知道这些观察结果如何转化为大地理尺度上的变化。在此，我们提出填补我们对树木真菌共生更广泛的多样性和分布的理解的空白，并帮助我们集中选择实验和遗传模型。为了做到这一点，我们提出使用地球上最广泛的生物监测点网络之一，在这个网络中，污染和森林土壤质量变化的影响已经被密切监测。我们的目标是利用这些地块对欧洲三种主要森林类型（山毛榉、苏格兰松和挪威云杉）的菌根真菌进行首次精确测绘。在150个密集监测的地块中，我们将使用优化的分子生态学技术从外生菌根中获得DNA序列。一旦我们知道欧洲的主要真菌是谁和在哪里，我们就打算使用来自这些地块的监测数据以及最新的环境变化预测来了解控制这些隐藏的共生体的过程以及它们在不断变化的世界中可能的命运。

Forests harbour a surprising secret. Although trees dominate these ecosystems, creating a complex habitat that shelters many species while shading out many others, this dominance relies on a hidden relationship with fungi. These fungi are rarely seen but their thread-like filaments, called hyphae, are intertwined among the roots of trees, forming a close symbiosis that helps both tree and fungus grow - a mutualistic interaction. Both organisms need carbohydrates and minerals to grow and, while trees excel at capturing and storing carbon from the air, the tiny hyphae of fungi excel at extracting water and nutrients, like nitrogen and phosphorus, from the soil. The amounts exchanged between trees and fungi is extremely high: all of the carbon in a fungus can be obtained directly from its partner trees, while most of the nitrogen in a tree comes directly from its partner fungi. The diverse groups of fungi involved are called ectomycorrhizal (or ECM) fungi, after the modified fine roots, or ectomycorrhizas, where the tree and fungus join each other.These symbiotic relationships are remarkably common: the majority of European trees depend on ECM fungi and there are many different fungi that form these relationships. Some of these fungi are well known for their sexual fruiting bodies, for example the poisonous fly agaric toadstools and the edible truffles and penny bun mushrooms. However, we know worryingly little about the diversity of ectomycorrhizal fungi. While some fungi may grow with a wide variety of trees and other plants, others may be specialists restricted to closely related tree species. And while around 8,000 species of ECM fungi have been described, there may be many more undiscovered. In addition, we largely ignore the geographic ranges of these fungi. Some may be widely distributed, but others may be restricted to a handful of small locations. We do know that at least some can invade in other continents and that others may be locally extinct. Most worryingly of all, we know that ectomycorrhizal fungi are sensitive to environmental change, particularly pollution and changes in rainfall and temperature. But we do not know how these observations translate to changes at large geographical scales.Here we propose to fill the gap in our understanding of the wider diversity and distribution of tree-fungi symbioses, and help focus our selection of experimental and genetic models. In order to do this, we put forward the use of one of the most extensive biomonitoring plot networks on Earth in which the effects of pollution and changes in forest soil quality have been closely monitored. We aim to use these plots to carry out the first precise mapping of mycorrhizal fungi across Europe's three major forest types: beech, Scots pine and Norway spruce. At each of 150 intensively-monitored plots, we will use optimised molecular ecology techniques to obtain DNA sequences from ectomycorrhizas. Once we know who and where are the dominant fungi in Europe, we intend to use the monitored data from the plots along with the latest environmental change predictions to understand the processes that control these hidden symbioses and their likely fate in our changing world.