Hunting for bryophytes in the mountains

By Konsta

Part of the Edge Lab’s field campaign last year was to do a bryophyte survey of the plots around Latnjajávri in the Scandinavian mountains in which we also monitor microclimate. The ultimate aim of the project is to be able to relate bryophytes’ traits to their niches. Most work on this aspect of bryophyte functional ecology has been done on categorical traits or with qualitative methods; our focus is on developing and testing hypotheses using quantitative data on both traits and environmental conditions. That work is still ongoing though, so in this post, I will share some of my favourite bryophyte observations instead, along with a bunch of bryophyte factoids!

A stereotypical botanist makes hikes miserable for their friends by stopping constantly to look at interesting species growing in e.g. gutters and other lovely habitats. When in the mountains, it’s important to keep an eye out for poo and rotting animal corpses. If one does, they might spot Tetraplodon pallidus, a coprophilous species that occupies short-lived nutrient-rich habitats such as reindeer droppings and pellets spit out by meat-eating birds. Species in this genus are often quite beautiful with bunches of brightly-colored sporophytes, but looks can be deceiving, in this case literally! Tetraplodon species use devious tactics involving visual and chemical attractants to trick flies into unwilling dispersal agents. Because the species’ habitat is so short-lived it needs an effective strategy for locating new patches of dung or animal remains. The colonization of new habitat patches is greatly aided by the flies that the moss attracts by emitting volatile compounds. I know of no study that has quantified the volatiles emitted by just this species, but other species in the family use compounds such as dimethyl disulfite (the smell of rotting flesh), octane-derivatives (smells of fungi), and indole and phenols (also present in herbivore feces). The sticky-sticky spores get attached to the unknowing insects, effectively turning them into silver bullet -solutions to the problem of finding a suitable habitat patch from the vast tundra landscape. Even though flies provide a crucial service for the mosses, they get nothing in return; the colorful divas of the tundra are not generous.

Probably Polytrichastrum hyperboreum (I forgot to write down the species when I took the picture), with something that looks a lot like mycorrhiza. But it’s not! Mosses are not known to form true mycorrhizal symbioses. The fungi colonizing the moss might well be a species capable of forming mycorrhizal symbiosis with vascular plants, but here it is likely just degrading the senescent bryophyte stem. In fact, the ability of ecto- and ericoid mycorrhizal species to break down organic matter is an important reason for why plants capable of hosting such fungi (Empetrum, Betula, Vaccinium, just to name a few genera) can be so dominant in severely nutrient-limited environments such as in many parts of the Arctic.

The liverwort Tetralophozia setiformis mixed with what are likely Dicranum shoots. I’ve always found liverworts to be mysterious, a view which has not been weakened by the fact that many species can only be identified by microscopic features that are only observable in fresh samples. Luckily there are also easily identifiable species, such as Tetralophozia. One interesting feature of liverworts is that more than 90% of the species have oil bodies in some of their cells. Oil bodies, as their name implies, are tiny droplets of essential oils and other terpenoids. Their number and shape are some of the microscopic features used to identify liverwort species. But what is the function of these oil bodies? There are many hypotheses. They might provide protection against herbivores, pathogens, radiation, cold temperatures, and desiccation, but much research still needs to be done to verify this. In any case, terpenoids from liverworts have been demonstrated to have among antiviral, antimicrobial, and insect-repelling properties, which makes liverworts seem like a negative bunch. In many environments this cocktail of anti-life substances combined with hard-to-digest structural compounds and relatively low energy and nutrient concentrations seem to make liverworts unappealing targets to gnaw upon, especially for vertebrates.

Although some moss species are hard to identify so that microscopic characteristics and/or mature spore capsules are needed for a certain ID, others are easily recognizable. One easy species even for a beginner is Conostomum tetragonum with its bright blue-green coloration setting it apart from other species. This beautiful moss can be found growing high up in the mountains on heaths and at the edges of late-lying snow patches. Such easy species are in my opinion psychologically important for learning to identify mosses. The self-doubt caused by confusing forms of common mosses like Dicranum scoparium is most effectively remedied by the feeling of accomplishment one gets from firmly recognizing distinctive species. The characteristic blue gloss of Conostomum is caused by a mesh-like layer of wax that covers the leaf surface. One might think that being covered by wax would impair the water uptake of these plants that don’t have roots, but leaf-wax is actually a pretty common trait in endohydric mosses, i.e. mosses that can transport water within their tissues. The reduced uptake of water from the leaf surface is more than compensated by the increased desiccation resistance.

Concluding remarks

Mosses/

Are the bosses/

Me and liverworts/

Click with the frequency of a gigahertz

Bryophytes in the Arctic tundra (including its altitudinal extension in the Scandinavian mountains) exhibit an interesting variety of life cycles and life forms and partake in a multitude of ecological interactions. Getting to study them is well worth the time needed to invest in species identification.

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