Posts tagged ‘forest’
The old growth forests of the Pacific northwest of America are home to many of the ‘exotic’ conifers that have been planted in Britain over the last two to three hundred years. Many of the species were introduced by foresters and planted in regimental rows in dense plantations, and have earned an unjust reputation among the public. The fault lies not with the trees but with how and where they were planted. The Sitka spruce (Picea sitchensis), Douglas-fir (Pseudotsuga menziesii), western red cedar (Thuja plicata) and western hemlock (Tsuga heterophylla) are all examples of beautiful coniferous trees native to areas such as Vancouver Island and the Olympic Peninsula.
As part of the research for my book, The New Sylva, I visited recently a remarkable place in Scotland where all these species are not only thriving but are forming a functioning forest ecosystem similar to that found in the Pacific northwest. Pucks Glen, owned and managed by the Forestry Commission, is located on a steep west-facing mountainside, and like its counterpart in America, is very wet. The conifers at Pucks Glen were planted in the 19th Century but have since been left mostly unmanaged. The forest is regenerating naturally and becoming an old-growth forest with the four main structures found in the Pacific northwest forests:
- There are large trees that store most of the biomass and form an upper canopy that towers above. Their needles and branches drop to provide nutrients to the forest floor. Their living structures host a multitude of life, from birds and mammals, to mosses, lichens and fungi. Even other trees and vascular plants grow among the crevices of their giant bark, or along horizontal branches.
- Large trees may die and remain standing, providing a rich source of nutrients and homes for other life forms.
- Trees eventually fall to the forest floor. On the steep-sided slopes, some even slip and remain living; often forming unique leaning trees in unusual locations. Dead trees rot to release nutrients and support a vast range of life especially invertebrates, fungi, mosses and lichens.
- The forest is multi-layered. The older trees do not form a continuous canopy and in the gaps of light between them, other trees will germinate and form small stands. Shade-tolerant species such as western hemlock will thrive in even the darkest places waiting for more light before shooting up to the upper canopy.
All these structures exist in Scotland at Pucks Glen, while another characteristic feature of these Pacific northwest forests can also be found: tree regeneration on nurse logs. The stems of large fallen trees become clad in a thick mat of mosses, and when tree seed falls on this, the seeds germinate and the resulting seedlings start to grow on top of the log. From the Pacific northwest we know that many of the seedlings will slough off, jettisoning some of the young trees with them. Eventually the host nurse log will rot away completely. Often the trees nursed on logs survive with amazing raised root systems; indicating where the nurse log once nurtured the tree when younger. Currently none of the logs at Pucks Glen are at this stage but some of the trees regenerating on nurse logs now reach 2m in height. Below are a few photos of the nurse logs at Pucks Glen.
Check out my tree photography blog at www.theTreePhotographer.com to see details about these and many more photographs of the trees and forest at Pucks Glen.
December 14, 2012
April 28, 2012
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.
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.
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.
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.
These photographs were taken during fieldwork where I was assisting the Sylva Foundation’s scholar, Kirsty Monk, in her DPhil research programme read more
December 5, 2011
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 breast height (at 1.3m above ground level), and is normally described per as the tree stem area per hectare (m2 ha-1). 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.
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).
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.
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:
August 1, 2011
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.
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
(cwm – valley (often wooded) 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.