The oak is a keystone species.  Just as building an arch, the stability of the arch is gained from the positioning of the central stone - the keystone, so in many woodlands oak trees are what holds the woodland together; offering both stability and diversity.  There are two types of oak : The pedunculate oak, which ‘likes’ richer and somewhat heavier soils.  It can be distinguished from the sessile oak as Its acorns grow on long stalks [called peduncles]. The sessile oak, which can grow and survive on poorer and somewhat acidic soils, so can be found in upland areas.  Its acorns sit more or less directly on a twig. Both these oak trees contribute to many woodlands across the UK, and have done so for thousands of years.  Some have great age and are veteran trees. Their life can be between 300 and 800 years.    An oak woodland often represents the climax community in lowland Britain, which has considerable stability.  Because of their long lifespan and great biomass, they also represent significant stores of carbon.  Their extensive canopy also moderates the temperature and humidity of the woodland beneath, allowing for the growth of shade tolerate species such as hazel and holly. The trees also support an amazing diversity of life,  some two thousand species are known to find a ‘home’ in oak trees.  Feeding on the leaves or flowers are hundreds of species of insects - notably moths and butterflies.  The leaves provide food for many species of caterpillars, which in turn are a food source for birds, like the tits and warblers.  The branches of the trees provide nesting and roosting sites for many bird species.  The acorns of the oaks are a rich source of nutrients and energy not only for squirrels, but also mice, deer and other mammals.  Birds, like the jay, also take them.  Jays and squirrels create ‘caches of acorns’, that is they bury them as a store for later.  However, many are forgotten so they effectively distribute the acorns over a wider area and ‘plant’ future oak trees. The bark of the oak is rough and corrugated offering specialised niches for lichens and mosses.  When an oak dies , it is then home to a variety of fungi and beetles, which feed upon the rotting wood (saproxylic beetles).   The roots of an oak penetrate deep into the soil, which helps improve drainage, and the roots establish mycorrhizal connections with soil fungi.  These connections are symbiotic in nature, in that both partners benefit from the association.   The tree gets mineral nutrients from the fungi, and, in return, diverts some of its carbohydrate material to the fungi.  The breakdown of the oak leaves in autumn returns vital nutrients to the soil and provides food to a variety of decomposer organisms, from bacteria to earthworms.  Thus, oaks are a vital part of many woodland food chains.   Sadly, our oaks face a number of threats.  In elizabethan times, the main threat was that of being cut down and used in ship building.  At the height of Nelson’s navy in the late eighteenth century / early nineteenth century it took some 4,000 oak trees, to build a single 100-gun ship, and the navy had some 300 ships!  More recently, there have been problems with acute oak decline and infestation by the oak processionary moth.  The caterpillars of this moth feed on oak trees and large populations can strip an oak tree bare.  This leaves the tree vulnerable to other pests, and stresses such as drought.    Incidentally, contact with the hairs of the older caterpillars of this moth can cause itching, skin rashes and eye irritations, plus sore throats and breathing difficulties in us and other animals.   

The Turkey Oak (or Quercus cerris) is is a fast growing, tough tree; capable of surviving exposure in coastal regions. It was introduced as an ornamental tree into the UK in the eighteenth century,  being native to south east France across to the Balkans and Turkey.   It often has a long straight trunk (or bole), with branches that are somewhat more slender than those seen on English oaks. The leaves are distinctive and different from those of the native oaks (sessile or pedunculate). Whereas the leaf of the latter is quite broad, the leaf of the Turkey Oak is quite narrow and more ‘angular’ (see featured image);  it is also hairy or downy on its lower surface. One of the tree’s distinctive features is the bark, which has orange fissures near to the base of the trunk. Unfortunately, its timber is of little use as it splits and warps during seasoning. [caption id="attachment_37670" align="aligncenter" width="675"] Turkey oak bark[/caption] The Turkey Oak is considered by some to be a "weed species or pest species" because: it is fast growing it will hybridise with the English oak. it is a host to the Knopper Gall wasp Acorns form and mature some 18 months after pollination and are quite large. They may be an orange / brown at the base,  to a green-brown at the tip. The acorn 'cup' is 'hairy' (see image). The galls that form on the tree are abnormal growths.These galls are caused, in this case, by the development of wasp eggs within the plant’s tissues. The wasp (Andricus quercuscalicis) lays eggs in the catkins of the Turkey Oak, these hatch and develop into wasps which in turn lay their eggs in the flowers of the pedunculate oak. The acorns that form are grossly mis-shapen – and are called Knopper Galls. [caption id="attachment_40042" align="alignleft" width="150"] Gall[/caption] [caption id="attachment_40046" align="alignright" width="150"] Gall[/caption]       In some areas there are now systematic attempts to remove Turkey Oak and other non-native species from woodlands and forests.  

The oak has long been regarded as the King of the Forest and emblematic of the UK.  It is the largest of our native, broad-leaved trees.  There are two native species of oak; the sessile oak (Quercus petraea) and the pedunculate oak (Quercus robur).  Oaks belong to the beech family, Fagaceae. Read more...