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Ferns and mosses will grow with global warming

In Siberia rampant moss is already hindering the establishment of larch seedlings. The accumulation of carbon dioxide acidifies the soil, in the same way that CO$_2$ acidifies the ocean, suffocation other plants.

In the Carboniferous period, when the atmosphere had a lot less oxygen than now, mosses and ferns like horsetails were dozens of feet high, mostrous triffid-like plants that gorged themselves on carbon dioxide. The triumph of the gymnosperms and angiosperms - coniferous and deciduous woody plants that slowly oxygenated the atmosphere - cut the equiseta, ferns and mosses down to size. With current warming, we can expect them to rise again, with serious consequences for forestry and agriculture as acidic air empowers the moss, choking fields.

Implied violoence of brutalist forest architecture

The palette of the hill is red with moss, pink from the granite, bright green with shoots of blaeberry, the orange and red and white of lichen, all set against the blanket grey of heavy rainclouds pressing down. Below me the forest is an unending green, punctuated by trucks on the highway and the iron grey of the River Spey looping through the trees. Far off are the bare burned-brown grouse moors and the geometric blocks of plantations that now appear to me to have all the implied violence of brutalist concrete architecture.

Trees can see and hear

Monoterpenes are volatile organic chemicals produced by pines that the trees use to send signals to each other - to deter herbivores or insects or to coordinate seed release. Monoterpenes are tiny molecules that carry pine scent and bounce sunlight back into space. When pines are metabolising in sunlight there can be as many as 1000-2000 particles per cubic centimetre in the air around the tree, reducing the amount of solar radiation hitting the earth. Via the density of the chemical signal and the availability of light, they can detect the presence of other trees. In fact, they see the space in polygons, growing away from their neighbours and towards the light, creating a five-sided tesselation in the canopy that is the basis of self-organisation in the forest${}^{10}$. Through the structure of their cells, trees can capture reverberations and ‘hear’ sounds around them as well as ultrasound far away${}^{11}$. Pines can detect the familiar presence of rustling needles or the crack of a falling tree, and of course they communicate and look after each other through the rich mycorrhizal network underground. Scots pines have one of the most developed fungal networks in the soil, with over nineteen known ecto-mycorrhizal relationships for sharing carbon, nitrogen, eseential acids and other nutrients.

• ${}^{10}$ Vladimir Gavrikov and Pavel Grabarnik et al., ‘Trunk-Top Relations in a Siberian Pine Forest’, Biometrical Journal 35, 1993
• ${}^{11}$ Diana Beresford-Kroeger, The Global Forest: 40 Ways Trees Can Save Us (Particular Books, 2011)

Personal note: There seems to be a lot of speculation here that trees look after each other (the more than controversial Mother Tree hypothesis) and share resources through mycorrhizal fungi. Probably they rather compete for resources through that fungal network.

The shift from rights of usage to rights of ownership

The shift from rights of usage to rights of ownership, seen as the mercantile spirit of northern Europe inveigled or imposed itself across the world, was, it seems, the crucial shift, as forests ceased to be seen as sacred places of wonder, mystery and sustenance and instead became a standing crop with a value expressed in pounds, shillings and pence calculated by the acre and the ton.

The real tragedy is the enclosure of common land

The so-called tragedy of the commons (that humans cannot be trusted to manage a common resource sensibly) might be a problem for individualistic societies unable to restrain pollution and over-exploitation, but as a histrocial explanatio for the British landscape it doesn’t hold except perhaps as a retrospective ideological justification for the real tragedy to follow: the enclosure of common land.

In any carbon cycle, death is the engine of life.

Twisted pines grow in the most unlikely of cracks in the rocks. Dead trees, standing and fallen, are everywhere. This is the signature characteristic of wildwood - dead trees are allowed to rest where they fall. Dead trees support far more life than living ones, hence the density of bird life. Some species like tree pipits and redstarts associate only with old-grown forests because of the volume and species of insects. The great spooted woodpecker nests only in dead Scots pines. Even more niche, the pine hoverfly breeds exclusively in wet hollows of dead Scots pines. No wonder it is almost extinct in Scotland.

In any carbon cycle, death is the engine of life. When a tree dies, wood-boring beetles enter the sapwood and begin the process of decay. Then fungi enter the spaces along with wasps, spiders and other insects, and invite other fungi. And in the final stages, the humification phase, soil organisms convert the last of the wood molecule lignin to soil. The cycle is complete. Because of its high resin content, a mature Scots pine takes forty years to decay, releasing nitrogen slowly into the soil, feeding the grubs and bacteria that are bottom of the food chain for insects and birds.

Modified source-sink dynamics govern resource exchange in ectomycorrhizal symbiosis

Summary

Symbiosis between tree roots and fungi as a trade explains mutualism development on evolutionary timescale but not experimental results. Instead think of it as source-sink dynamics.

I. Introduction

• sometimes C invest and N return are uncorrelated or even negatively correlated
• reward schemes depend on the scale

II. Source-sink dynamics remain a useful model for resource movement

• source-sink dynamics: flow from high concentration to low concentration
• gradient and conductivity govern speed
• fungal biomass drives C sink strength which can lead to positive feedback
• fungi can monompolize N if it’s available at high level, induce artificial N scarcity
• nutrients and water also move according to source-sink dynamics
• plant, fungi, and environment change rates making thinkgs more complex

III. Beyond source-sink: modifications to resource movement

• plant and fungi have different interests, modify simple source-sink dynamics
• plant defense might change resource transfer
• C transfer sometimes mostly explained by expression of genes involved in defense and stress response
• high variation of fungi and immune responses lead to a variety of altered source-sink dynamics
• other functional diversities have also influence
• molecular tools not yet completely understood
• fungal competition also a factor in favor of the plant

IV. Conclusions

• source-sink dynamics a good first approximation
• altered by a lot of factors

Box 1 - Future research directions

1. How does strength of resource gradient affect dynamics?
   • Physics?
2. Extent of fungal diversity improving N access of the plant
   • Plant benefits from fungal competition
3. At what level of resource do fungi stop helping?
   • Tragedy of the commons?
4. Plant sensitivity to shift from helpful to unhelpful fungus
   • Makes only sense if there are more fungi or fungus-independent nutrient uptake pathway.
5. Spatial scale on which plant can discriminate between fungal partners. How?
   • Plays a role for C allocation to different fungi.
6. Can we predict plant-fungal compatibility from genomic data?
   • How fast are those genomic gata changing? Does it make sense to identify genes if they change too fast?
7. Differences in resource transfers with adult trees and seedlings.
   • Also adult fungi and youg ones? Have different levels of need?

My remarks

• no citation of “The mycorrhizal tragedy of the commons”
• So what do we learn? That it’s complex, lots of interests, strategies, external factors. Thanks.
• We probably learn about the future research directions. This thought is supported by the relatively new references.

Scotlands signature landscape - the bog - is a ruined landscape

Rackham argues that pine wood never stretched from shore to shore., but it certainly covered most of Scotland until Mesolithic humans began to clear the forest for agriculture, hunting and construction. Managing the forest rhrough felling, clearing or burning for game played a role in creating biodiverse habitats of heath and moor, but also set the stage for the creeping blanket bog that has become upland Britain’s signature landscape. The bog is, in a sense, a ruined ecosystem as tree clearance has allowed minerals and iron to be washed into the lower layers of the soil, creating a pan impermeable to water. Unable to drain, the rundra-type landscape becomes waterlogged, and plants do not fully decompose, forming peat.

Migration of Scots pine to Scotland supported by humans

Before driving north, I read a scientific paper by Lithuanian researchers demonstrating that the DNA of Scots pine in the eastern half of Scotland came from a refugium - a place where species survived the last ice age - near Moscow around 9000-8000 BCE. Previous DNA analysis has shown that the surviving pines in the west of Scotland came from the Iberian peninsula in modern-day Portugal and Spain. In both cases the seed migrated to Scotland on timescales hundreds of times faster than is possible through natural succession. The most likely vehicle for such rapid migration was humans.

The first expression of an economic system founded on overreach

The Romanes, Danes and the nobles of England were in search of natural resources, principally timber. The colonisation of Wales was the first expression of an economic system founded on overreach: having exceeded the limits of what their own environment could sustain, early mercantilists applied force to acquire tribute and resources elsewhere. Empire, whether British, Viking, Roman or otherwise, is by definition overreach. And colonialism, capitalism and white supremacy share a common, perverse philospoph: limits on some human’s freedom of action are seen as an affront to the principle of freedom itself. The excat opposite of the co-evolutionary dynamic of the forest.