Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines, and shrubs. It overlays the wood and consists of the inner bark and the outer bark. Products used by people that are derived from bark include: bark shingle siding and wall coverings, spices and other flavorings, tanbark for tannin, resin, latex, medicines, poisons, various hallucinogenic chemicals and cork. Bark has been used to make cloth, canoes, and ropes and used as a surface for paintings and map making. A number of plants are also grown for their attractive or interesting bark colorations and surface textures or their bark is used as landscape mulch. What is commonly called bark includes a number of different tissues. Cork is an external, secondary tissue that is impermeable to water and gases, and is also called the phellem. Bark contains strong fibres known as bast, and there is a long tradition in northern Europe of using bark from coppiced young branches of the small-leaved lime tree to produce cordage and rope, used for example in the rigging of Viking age longships. Among the commercial products made from bark are cork, cinnamon and aspirin from the bark of willow trees. Many trees have chemicals within their bark, which protect against fungal and insect attack. Birch bark is high in volatile oils, and is so waterproof and resistant to decay that tubes of birch bark can still be found on the forest floor after the wood inside has decayed. The bark of some trees such as oak are a good source of tannic acid, which is used in tanning. A number of living organisms live in or on bark, including insects, fungi and other plants like mosses, algae and other vascular plants. Many of these organisms are pathogens or parasites but some also have symbiotic relationships. The degree to which trees are able to repair physical damage to their bark is very variable. Some are able to produce a callus growth which heals over the wound rapidly, but leaves a clear scar, whilst others such as oaks do not produce an extensive callus repair. The bark of different trees has evolved to make best use of the environment in which each species occurs. Scots pine bark offers protection from fire. In prehistoric times, parts of Scotland’s woodlands would have been influenced by fires, which would have occasionally swept through areas of forest. While this may seem devastating, when forests were more extensive, pinewood ecosystems would actually have benefited from such natural disturbance, as it can clear away rank vegetation, leaving a fertile bed on which pine seeds can germinate. Many Scots pines have very characteristic thick protective plates on their bark, and it is thought that in areas more prone to fire the bark may become locally adapted to offer extra protection. Different species of trees have very characteristic textures to their bark, that influence what other species live on it. The deep fissures and crevices on the bark of an old oak or Scots pine are a haven for many species of insects and spiders. These invertebrates attract birds, which feed on them. The crested tit is very much a pinewood bird that includes in its diet insects picked from the bark and twigs in the branches. The treecreeper is a specialist bark forager, hopping up the trunk, and probing the crevices with its specially adapted, thin, curved beak. Even after a tree has died, bark can be a haven for all sorts of wildlife. Bats, such as the brown long-eared bat, sometimes roost beneath loose bark, and a multitude of invertebrates also live out their lives in this hidden world. While bark does an excellent job of protecting the tree, there are some very determined creatures that are keen to get to the wood beneath it. Voles often eat the bark at the base of young trees, killing young saplings. Deer also strip bark as well as damaging it by ‘fraying’ their antlers on it to shed the velvet coating. And the bark of aspen and willow is an important food source for the European beaver. Drifting 2 by Audionautix is licensed under a Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/) Artist: http://audionautix.com/ For more videos, photos and blog posts like this please visit http://www.wholesomeday.com Twitter: https://twitter.com/wholesomeday/ Tumblr: http://wholesomeday.tumblr.com/ Pinterest: http://www.pinterest.com/wholesomed/ Facebook: https://www.facebook.com/wholesomeday

• published: 06 Sep 2015
• views: 301