Posts tagged ‘forest’
Next time you crunch or squelch through a rich leaf litter under trees, stop and get your eyes down to the forest floor. Carefully tease apart the rotting leaves, twigs and decaying branches and you may be lucky enough to see some fungal or mycelial cords.
Fungal cords running between a rotting silver birch log and the leaf litter on the forest floor
Quite a number of saprotrophic fungi, particularly the wood-decaying Basidiomycetes (e.g. including some of the stinkhorns, bracket fungi, or puffballs), can form mycelial cords. Cords are collections of hyphae that aggregate to form long cords. These cords can create vast webs across the floors of forests, in both temperate and tropical regions, where they link nutrient resources together.
Fungal cords and hyphae on a decomposing silver birch log on the forest floor. One cord can be seen top right linking to the leaf litter. Bottom left, visible as a network of dark strands, are probably the cords of the Honey Fungus Armillaria mellea
The cords can be visible as creamy white strands, varying in thickness from thin cotton threads to chunky spaghetti. Carefully roll over a well-rotten log (don’t forget to roll it back afterwards) and you may see cords running from the leaf litter on the forest floor, and onto and into the log . Sometimes you may find rotting leaves stuck together by tiny nets of white threads. Cords also travel at the surface of the soil, running along underneath a carpet of leaf litter, where you can track them to their source; often a substantial rotting log.
Fungal cords running along underneath the leaf litter (cleared away for the photograph). The cords rarely penetrate the soil.
It is thought that fungal cords play an extremely important role in recycling carbon and mineral nutrients, but little is actually known about their diversity and behaviour; for instance it is thought that fungi species that form cords can be highly competitive. Their ability to redistribute nutrients across the forest is extremely important but only just beginning to be understood and appreciated.
Gabriel Hemery
These photographs were taken during fieldwork where I was assisting the Sylva Foundation’s scholar, Kirsty Monk, in her DPhil research programme read more
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The relascope is a forester’s tool used for forest mensuration, or tree and forest stand measurements. The Spiegel relascope is the bee’s knees of forest inventory tools; allowing the user to estimate tree heights, stem diameters at different heights, and Basal Areas. It comes at a high price though as it’s a complex surveying tool (expect to pay £1500/€1750/$2400), so it is only used typically by professionals who measure a lot of trees. There are cheaper ways of measuring trees, such as a diameter tape for stem diameter or a clinometer for tree height (or even use a smartphone to estimate tree height). To assess Basal Area there is a different type of relascope available; the wedge prism relascope. This post aims to provide a simple explanation of how to use a wedge prism but first some background information.
What is basal area?
Basal Area (BA) is the cross-sectional area of a tree at dbh (stem diameter at breast height – measured at 1.3m), and is normally described per hectare of land area (G m2 ha-1). The Basal Area provides an indication of the productivity of the land, and the growth rate of the trees when one or basal area estimates are compared.
How to measure basal area of a stand the hard way
To estimate the Basal Area of a single tree, measure the tree’s diameter at breast height (dbh) and convert to BA with the following formula:
BA = 0.00007854 x dbh2 dbh is in cm.
The result will be in m2.
You can them estimate the Basal Area of a forest stand by adding together the basal areas (as calculated above) of all of the single trees in the area, and then by dividing this figure by the area of land (in m2) in which the trees were measured (e.g. /10,000 if in one hectare). As you can imagine, estimating Basal Area for a forest stand with this method is hard work; this is where a wedge prism relascope comes into its own.
Using a wedge prism relascope
A wedge prism can be used to estimate quickly the Basal Area per hectare, and one costs only 2% the price of a Spiegel relascope! It is a simple wedge-shaped prism of glass or see-through plastic, typically 5 x 2 cm. It distorts the light and shifts the position of a tree stem when looked at through the prism. Different factors of prism relascopes are available, with common Basal Area Factors being 5, 8, or 10.
How to use a wedge prism relascope
I created this diagram to explain simply how a wedge prism relascope is used in the forest. The technique with the relascope is to stand at one point among the trees and to complete a 360 degree sweep around, counting all the trees that are ‘in’. Those that are ‘borderline’ should be counted every other time, and those that are ‘out’ discounted. To estimate the Basal Area simply multiply the number of counted trees by the Basal Area Factor (e.g. 5, 8 or 10).
Using a wedge prism relascope. Count (left), borderline (centre), and Don't count (right). Click to enlarge.
You should conduct as many sweeps around the stand of trees as you can, as this will provide a more accurate estimate when averaged over the stand.
Gabriel Hemery
Regular readers will have noticed that I did not post a feature last week. In fact I was in southern Kyrgyzstan visiting the beautiful and remote walnut fruit forests that nestle in the Fergana Valley, among the south-western Tian Shan.
In 1997 I spent three and a half weeks in Kyrgyzstan, which is one of the most mountainous countries in the world. In places it has very high biodiversity and yet is devastatingly desolate in others. Fourteen years ago I was collecting walnut seeds as part of a scientific expedition (read more).
This time I was invited back to this fascinating country to give a presentation at an International Conference discussing the future of the walnut fruit forests. Both meeting and travel were inspiring and I have much to write and share. For now, here is a short slideshow highlighting some of my favourite photographs from the trip:
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Gabriel Hemery
In modern English forest and woodland are used interchangeably. Forest is more often used to describe a large area of trees in the landscape, sometimes being linked with economic productivity, than the term woodland. However, they are very loosely defined terms, at least in popular language. I explore the origins for forest and woodland, and some other collective nouns for trees.
Non-English terms
Like the French forêt, the English word forest has at its root the Medieval Latin foresta, in turn probably derived from late-Latin foras meaning ‘outside’. The word developed in Norman areas. Elsewhere in Europe other terms for forest were founded on different roots:
- Dutch bos means forest. It has a similar root to the French bocage meaning grove or a landscape of mixed trees/hedges and fields.
- German wald is thought to have come from the Proto-Germanic word “walpu” (meaning foliage or branches). Forst, is commonly used to describe economically-managed areas of trees.
- Italian for woodland, selva, comes from classical Latin silva although foresta is now commonly used to describe forest.
- Portuguese floresta means forest (as well as flowers in French).
- Spanish, monte, is sometimes used for forest although it has many other meanings including mountain. More usually silva is used for woodland and forestales for forest.
Forest or woodland
Historically, forest originally meant an area outside (foras) ordinary jurisdiction, being subject to separate ‘forest law’. Forest law was primarily designed to protect and provide game for the King’s table. A Forest would include large areas of land that were not covered with trees, such as farmland, and even whole towns and villages. Its woodlands and other tree features (e.g. hedges) would have been important in providing the habitat for the game. The forest law was enforced, often with harsh consequences, by foresters.
We have now lost the clear definition of forest in English, and an area of trees can be forest or woodland, and of course just a wood too. Forest is normally linked to large areas of trees (e.g. Affric Forest, New Forest, Grizedale Forest), although the scale at which a woodland becomes a forest is undefined. Areas managed economically for timber production are often referred to as forest, but not exclusively, whereas woodland is a term now closely associated with naturalness. We talk about ancient woodland or native woodland, not forest: the popular British NGO The Woodland Trust focusses almost exclusively on these two aspects.
Copse, spinney, grove, thicket, coppice …
There are dozens of other names for a group of trees in the English language. Their definitions are also rather loose but we can delight in celebrating the diversity they bring to conversation:
- avenue – a line of trees, one or more rows deep, each side of a road or vista
(e.g. Clipsham Yew Tree Avenue). - brake – a clump of shrubs, brushwood, briars or fallen trees (see also thicket).
- coombe – the head of a wood in a valley
(cym – woods in the Welsh language). - coppice – an area of woodland where the shrubs (e.g. hazel) are cut regularly to produce products.
- copse – a very small woodland (perhaps less than 0.25 hectares?).
- covert – a dense groups of trees or shrubs, often connected with game.
- dingle – a deep wooded valley or dell.
- grove – a small group of trees without undergrowth. Also used to describe a productive system (e.g.orange grove).
- spinney – often used to describe a copse that shelters game.
- stand – a small group of trees. Also used by foresters to describe a particular group of trees under similar management.
- thicket – a dense growth of shrubs and briars.
- wood is used interchangeably with woodland.
Gabriel Hemery
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Many people are interested in how big a tree’s crown will grow. It can be important in planning gardens, managing street trees, forest silviculture and in assessing the health of ancient trees.
Estimating tree height is very imprecise as it is dependent on so many different factors. However, I wrote recently about the very good relationship statistically between a tree’s stem diameter and its crown diameter (read more). I have received several requests for more information, and for this to be presented in a way that could be used by those who care for and manage trees.
So I have reworked the graph to produce a simple plot of tree crown diameter and stem diameter for the following nine species: ash (Fraxinus excelsior), beech (Fagus sylvatica), silver birch (Betula pendula), wild cherry (Prunus avium), sweet chestnut (Castanea sativa), oak (Quercus robur & Q. petraea) poplar (Populus spp.), sycamore (Acer pseudoplatanus) and common walnut (Juglans regia).
Tree crown diameter and stem diameter for nine broadleaved species. Click to enlarge.
Here is a simple summary of the same data in a table, presented in 0.10m stem diameter (dbh) increments.
| crown diameter (m) | |||||||||
| dbh (m) | walnut | ash | oak | sweet chestnut | wild cherry | beech | sycamore | silver birch | poplar |
| 0.10 | 4.47 | 2.65 | 2.50 | 3.86 | 3.30 | 2.52 | 2.48 | 2.58 | 2.71 |
| 0.20 | 6.23 | 4.54 | 4.28 | 4.93 | 4.84 | 4.10 | 4.37 | 4.19 | 4.60 |
| 0.30 | 7.99 | 6.43 | 6.05 | 5.99 | 6.38 | 5.67 | 6.26 | 5.81 | 6.50 |
| 0.40 | 9.75 | 8.32 | 7.82 | 7.06 | 7.92 | 7.24 | 8.15 | 7.43 | 8.39 |
| 0.50 | 11.51 | 10.21 | 9.59 | 8.13 | 9.46 | 8.82 | 10.04 | 9.05 | 10.29 |
| 0.60 | 13.27 | 12.10 | 11.36 | 9.19 | 11.00 | 10.39 | 11.93 | 10.67 | 12.18 |
| 0.70 | 15.03 | 13.99 | 13.14 | 10.26 | 12.54 | 11.96 | 13.82 | 12.29 | 14.08 |
The data for this work was collected from open grown trees. Note therefore that trees grown in forest conditions, where they will have been affected by light levels and other competition factors, will not follow closely the data presented here.
I hope that this data may prove useful for those who are interested in scoring the condition of ancient trees, in planning tree avenues, and in garden planning or landscape architecture. Remember that the results presented here are based on peer-reviewed scientific work: if you want a reference for this work you can find it in my previous post on this subject (click here). Let me know if you find a use for this data.
Gabriel Hemery
