Mighty to Microscopic - The Mycorrhizal Relationships of Alaska’s Trees and Fungi

Alaska, known for its pristine landscapes and rugged wilderness, is home to some of the most intricate and mysterious interactions between fungi and trees. This unique ecosystem, with its stunted spruce and birch trees, hosts a variety of fungi that play a crucial role in the health and survival of these hardy forests. In this article, we will delve into the fascinating interactions of trees and fungi in Alaska, highlighting the vital roles these organisms play in this northern wilderness.

What are fungi really?

Let’s start by talking about exactly what a fungus is. Fungi are organisms completely separate from plants and animals. The majority of a fungus’s mass and reach is in its mycelium, a lacy substance that generally lives underground or inside trees. Mushrooms, what we normally think of as a fungus, is actually only the fruiting body of that fungus. A mushroom is to a fungus as a blueberry is to a blueberry bush. The fruiting body distributes spores in various ways that will then go on to create new fungi of their own!

Mycorrhizal relationships

One of the most significant and well-studied interactions between fungi and trees is mycorrhizal symbiosis. Mycorrhizal fungi establish mutually beneficial relationships with trees, aiding in nutrient and water uptake, disease resistance, and overall tree health.

Mycorrhizal relationships also aid trees by allowing them a pathway of communication. They allow trees to send warning signals to their neighbors about pests entering the area, incoming droughts, opportunistic herbivores, and much more. In fact, this is such a tight-knit community that members can be excluded for breaking the status quo. If a tree starts outcompeting its neighbors and negatively impacting them, they may shut it off from the network, leaving it far more vulnerable to pests, disease, and changing climates!

Decomposition and nutrient cycling

In the chilly Alaskan climate, the decomposition of organic matter can be incredibly slow due to the low temperatures. The stark cold also plays a part in the lack of common decomposers in mmany Alaskan ecosystems. For this reason, fungi play an vital role than they usually do in breaking down dead plant material, returning essential nutrients to the forest ecosystem.

Species like the oyster mushroom (Pleurotus ostreatus) and various wood-decaying polypores are crucial decomposers in Alaskan forests. They help recycle carbon, nitrogen, and other nutrients, contributing to the forest's overall health and vitality.

Unfortunately, these types of wood-decaying fungi can also be detrimental to individual trees, as they will sometimes start decomposing a tree before it’s dead and effectively kill it. In fact, if you ever see a fungus of any type growing out of a living tree, that tree WILL die soon. It may be a few years, but once the fruiting body (mushroom) of a fungus appears on a tree, its days are numbered.

Disease management

In Alaska's harsh climate, trees often face the threat of various pathogens and pests. Fungi come to the rescue by acting as both protectors and antagonists against these threats. Some fungi, such as Trichoderma spp., which appear in the Alaskan wilds, are known for their ability to suppress harmful pathogens and protect trees from diseases. Other mycorrhizal fungi will also act as armor around the fragile outlying roots of trees, and fight off other harmful fungi and even some pests.

Endophytic fungi are often overlooked because of the comparatively new research going into them, yet from what we understand they have a significant role in tree health and survival. There are both harmful and beneficial endophytic fungi, and they live inside the plant tissues. Beneficial endophytes are likely to enhance the tree's resistance to herbivores and pathogens. Alaskan trees, including the Sitka spruce and black spruce, host a range of endophytic fungi that help them thrive in challenging conditions.

Affects of climate change on fungi and their arboreal hosts

As climate change brings warmer temperatures to Alaska, fungi are adapting alongside their tree hosts. These symbiotic relationships are evolving in response to changing environmental conditions, which could have far-reaching consequences for the forests of Alaska.

Since fungi and the trees they are symbiotic with are so closely linked, the disappearance of one could likely mean the disappearance of the other as well. As the spruce beetle continues to ravage Alaska’s spruce forests, the future of both Alaska’s widespread boreal and taiga forests as well as the fungi that depend on them seem to be in question.

Conclusion

Alaska's forests are a testament to the intricate and interconnected web of life that thrives in this rugged landscape. Fungi, often hidden beneath the towering trees and dense canopies, play an essential role in maintaining the health and balance of this unique ecosystem. From mycorrhizal partnerships to nutrient cycling, disease management, and adaptation to climate change, the intricate relationships between fungi and trees in Alaska continue to be a subject of fascination and scientific exploration. These interactions underscore the importance of preserving and understanding this vital ecological balance in the face of environmental challenges.