The amazing hidden world of tree root systems

Some fine examples of tree root systems - and (scroll down) the micro-habitat they sometimes create:



An old oak tree rooted in a rock face at Plankey Mill in Northumberland.

Sycamore, beside the river Tees at The Meeting of the Waters in Teesdale, where winter floods scoured the soil away, exposing the roots ...

.... so that a lot of tree seems to be balanced on quite a small root system!

Young beech roots at Allen Banks in Northumberland, again exposed by water erosion. Interestingly, you can see how the roots autograft on to each other when they come into direct contact. In a few decades it might look like this....




.......a wonderful mature beech near Wolsingham in Weardale, where the mass of autografted roots seem almost to have melted into the ground.

The hollows formed where roots have grafted onto one another often house small pools of water, known as phytotelmata, which are home to transient communities of small organisms. These mini-ponds, trapped in a cavity formed by the coalesced roots, can contain vast numbers of small organisms, feeding in bacteria and fungi growing on the rotting leaves trapped in the water. The pool is fed by rivulets of water that trickle down the trunk when it rains. Temporary pools of water trapped in plants like this are known as phytotelmata. The pools in this beech tree's roots hosted nothing larger than rat-tailed maggots - the larval stages of drone flies. But while the species diversity in the beech-tree pool might have been low, the sheer abundance of the tiny single-celled protists that are present can be staggering ..............

These little organisms, taken from one of these beech root pools, are called Colpidium colpoda.  They're single-cell protists that swim with incredible speed using ciliary hairs on their surface, that beat in rhythm. Here they're magnified one hundred times. This single drop of  water on a microscope slide probably contained about five hundred...

Here they are magnified two hundred times. The circles that you can see in some of them are contractile vacuoles that constantly expel water from the cell cytoplasm.

At 400 times magnification you can see the fine cilia (top right) that are arranged in rows over the surface of the cell - you can just make out their dark parallel lines and you can also see algae that the Paramecium has ingested, inside the cell.

Static images don't really do justice to the helter-skelter movement of these little protists, so click here and click here to take a look at these two video clips of this sample, which give a much better impression of what is going on in those little temporary pools of water that you find trapped in beech tree root systems.

A magnificent veteran beech tree

There are some fine stands of native trees scattered throughout Hamsterley Forest's commercial conifer plantations here in country Durham. None is more impressive than this venerable beech tree, growing next to an old dry stone wall that must have been part of the field system before the forest was planted. 

This is one of the largest and most impressive beeches that I've encountered and it probably benefits from the shelter of the surrounding conifers, although the top of its crown is taller than they are. But it's real glory lies in its magnificent convoluted bole - folded, fissured and branching from low down in a way that suggests that it must have been pollarded or lost its leading shoot earlier in its life. 

Now all those folds and cavities make it an excellent wildlife habitat. Over the last decade or so it has acquired a fine fungal flora, in the form of ......

....... these massive brackets of Ganoderma australe, commonly known as the southern bracket. The fungus is undoubtedly killing the tree very slowly. The crown is still as leafy as I remember it when I first saw it, almost 40 years ago. I would not be in the least surprised it it survives for several more decades.

Ganoderma is a perennial bracket fungus, producing a new hymenial layer (the spore producing tissue) annually over a decade or more. Here you can see this year's fresh white hymenium on the underside of the brackets.

The tan-coloured stain on the trunk is a coating of spores, that are released in billions.

The 'shelf' formed by the upper surface of the old brackets has become carpeted with mosses ......

..... while the upper surfaces of those immediately below becomes covered with a thick layer of spores, like a coating of cocoa powder. The dark area under this bracket is one of several temporary pools formed when rainwater trickles down the trunk and collects in folds and rot-holes. Temporary pools like this are known as phytotelmata and are home to vast numbers of tiny protists and animals. When I took a sample from this one and looked at it under the microscope it was seething with oligochaete worms and tardigrades, feeding on the single-celled protists which in turn were feeding on the soup of fungal spores in the water.