Sap flow in desert trees

Many horticultural professional and home gardeners get concerned when they see sap oozing from the branches or trunks of trees in the land­scape. While it is not a common occurrence it does happen for an array of reasons and not all of them are detrimental to the long-term health and survival of trees. Ask any Vermont Maple Syrup producer.

The comparison of trees’ vascular system and sap to blood and blood vessels in our bodies is a bit over used, but a worthy analogy. Like our blood vessels, the vascular system in a tree is a dense network of tiny tubes that transport essential fluids from one part of the plant to another. The two parts of this conducting tissue are xylem (which moves water and mineral nutrients, found in the soil, through the roots to the upper portions of the tree) and phloem (which conducts sugars manufactured in the leaves to the other parts of the tree, including back to the roots). In trees, tissues are lo­cated just beneath the surface or bark of trees. Any breaks or imperfections in the bark tissue can lead to fluids leaking from the vascular system and appearing as clear to amber color, sticky globs of sap.

Most often we see sap oozing during the spring and early summer, as the growing season gets underway in the desert southwest, when fluids be­gins to flow within the tree. Almost any injury to the bark that can lead to sap escaping include the use of pruning and trimming tools, bird feeding (particularly woodpeckers), insect feeding and egg laying, sun injury, and vandalism. Probably the most overlooked source of sap leakage is the rapid expansion or radial growth of trunk and branches in response to op­timal growth conditions. As you inflate a cylindrical balloon, it increases in both length and girth or width at about the same rate. Tree trunks and branches grow in the same way but tree bark is not as elastic or forgiving as the rubber of a balloon. If radial growth (increase in caliper) exceeds the growth of the bark weak areas and crack (microscopic to several inches in length) can occur. These cracks become areas where sap can leak.

The good news about the appearance of sap is that it is an indicator of active growth in both the xylem and phloem and a general sign of vigorous growth. Or put another way that both the canopy and root system of the tree are growing vigorously and sap is moving. It is also an indicator that there are injuries or imperfection in the bark and you may want to explore further to understand their causes and preventions.

The association between sapping and woodborers is incorrect, at least within the majority of landscape trees grown in the desert southwest. With the exception of the Palo Verde Borer, that feeds exclusively underground, aboveground wood boring insects only attack and feed on dead wood. Some of the injuries mentioned above can lead to the death of tissues that can be colonized by woodborers and perhaps this is the source of the con­fusion. There is also a disease of citrus where excessive and conspicuous gumming or sap release along the lower trunk is associated with Phy­tophthora Root Rot. This is a very unique situation limited almost exclu­sively to citrus.

(3203 signs)

 

Birch

Birch (figure 12.1) is agenerally small to medium-size tree, mostly of northern temperate climates. The simple leaves may be toothed or lobed. The fruit is a small samara, although the wings may be obscure in some species.The botanic name Betula is from the original Latin.Both the Latin and the Germanic come ultimately from the proto-Indo-European root bherəg-, meaning ‘to shine; bright, white’, i.e. birch was the “white tree”. The birch is considered a national tree of Russia, where it used to be worshipped as a goddess during the Green Week in early June. Birches are versatile trees. The sap, bark, leaves, wood, twigs, and roots are used for food, construction materials, drums, medicinal treatments, lubricants, and other practical applications. Due to birch pulp’s short-fibre qualities, this hardwood can be used to make printing paper. In northern latitudes birch is however considered to be the most important allergenic tree pollen, with an estimated 15-20% of hay fever sufferers sensitive to birch pollen grainsu were mean 2 me. Extracts of birch are used for flavoring or leather oil, and in cosmetics such as soap or shampoo. In the past, commercial oil of wintergreen was used as a lubricant or glue and also for medicinal pur­poses. Xylitol can also be extracted from birch, a sugar alhohol artifical sweetener, which has shown effectiveness in preventing, and in some cases repairing, tooth decay. In Belarus, Russia, the Baltic States, Finland and parts of northern China, birch sap is drunk as a refreshing beverage, and is believed to have tonic qualities. It is watery and pale green in color, with a slightly sweet flavor, and is bottled commercially. Birch sap may also made into kvass. The sap of particular birch species may also be rendered into birch syrip, vinegar, beer, soft drinks, and other foods. In contrast to maple syrup, birch syrup is very difficult to produce, making it more ex­pensive than other food syrups. It is also considerably less sweet than ma­ple syrup and the sap for syrup production is not available until a month later than maple’s. The syrup is made mainly in Alaska (from Alaska Birch) and Russia (from several species), and more rarely elsewhere. Silver Birch is Finland’s national tree.

Occasionally one uses leafy, fragrant twigs of silver birch to gently beat oneself in sauna. The twigs are called vihta or vasta. This has a relaxing effect on the muscles. Birch is used as firewood due to its high calorificvalue per unit weight and unit volume. Birch leaves are used to make extracts for dyes and cosmetics. Birch twigs were bound in a bundle, also called birch, to be used for birching, a form of corporal punishment. The chaga mushroom is an adaptogen that grows on white birch trees, extracting the birch constituents and is used as a remedy for cancer. The bark is high in betulin and betulinic acid, phytochemicals which have potential as pharmaceuticals, and other chemicals which show promise as industrial lubricants. Many of the First Nations of North America prized the birch for its bark, which due to its light weight, flexibility, and the ease with which it could be stripped from fallen trees, was often used for the construction of strong, waterproof but lightweight canoes, bowls, and tipis. Birch bark can be soaked until moist in hot water, and then formed into a cast for a broken arm. It is also used in starting fires. The bark will burn very well, even when wet, because of the oils it contains. With care, the bark can be split into very thin sheets that will ignite from even the smallest of sparks. Birches also have spiritual importance in several religions, both modern and historical. Birch wood is also used to make drums. They produce boosted high and low frequencies with loud low end punch that is ideal for studio recordings.

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Kapok Tree

Why the kapok tree (figure 11.1) is often described as majestic? The Kapok tree is an emergent tree of the tropical rainforests, and is often described as majestic. It can grow to a height of 150 feet or more, towering over other trees in the rainforest. Originally a native to South America it now has spread to the primary rainforests of West Africa, and the Southeast Asian rainforests of the Malay Peninsula, and the Indonesian archipelago.

The straight trunks are cylindrical, smooth and gray in color, and can reach a diameter of 9 feet. Large spines protrude from the trunk to discourage damage to the trunk. Thin, plank type buttresses stabilize the giant and can extend to 30 feet. The wood is a pinkish white to ashy brown in color, with a straight grain. The branches grow in horizontal tiers, and spread widely.

The crown has an open umbrella shape. Many plants and animals grow and live in the branches of the kapok tree. Birds nest in it, and mammals use the huge branches as highways. Frogs breed in the pools of water that collect in the bromeliads.

Kapoks are drought deciduous. This means they shed most or all of their leaves during the tropical dry season. The dry season occurs during the northern hemisphere winter.

In many places the straight trunks of the kapok tree are used to make dugout canoes. The white, fluffy seed covering is used in pillows and mattresses. Since it is buoyant and water resistant it is often used in flotation devices and padding. The seeds, leaves, bark and resin have been used to treat dysentery, fever, asthma, and kidney disease. In Mayan myths the kapok tree was sacred. They believed that the souls of the dead would climb up into the branches which reached into heaven.

The kapok tree is widely spread around the world and occupies an important niche in the ecosystem of a rainforest. Emergent trees like the kapok rise above the canopy of the rainforest and provide a home for plants dependent on sunlight. Their branches provide a habitat for countless epiphytes, which provide food and shelter for many types or animals. They allow animals to move around the rainforest without coming down to the ground. Monkeys who venture out to the tops of emergent trees are easy prey for eagles.

There is no status on the kapok tree. Its timber is desirable because of the great length of its trunks, the beautiful color of its wood, and its straight grain. People of the rainforest have many uses for the kapok tree. As with many desirable things, too many people may want to exploit the kapok tree and put its future in jeopardy.

(2566 signs)

 

Common Lime

The common lime is a tall, stately tree, which grows in the deciduous forests of Europe, the British Isles, and the USA. In the USA it is known as a linden tree. It is the tallest broad-leaved tree in Britain. In the past it was found growing throughout the old growth forests of Europe. Today there are no original forests left there, but the common lime is still widespread because it is frequently planted along avenues and in gardens. The common lime can live up to 500 years.

The tree can grow to a height of 120-130 ft (25 m). Bushy side shoots grow along the trunk from near the ground. The lower branches arch out, giving the tree an upside-down pyramid look.

The leaves of the common lime (figure 12.1) grow singly along a stem but not opposite each other, and about 4-7 inches (5-10 cm) wide. They are roundish and slightly heart shaped with small, fine-toothed edges. Their color is a dull, dark green color above and lighter green underneath. The tops of the leaves are hairless but have tufts of white hairs at the junction of the veins underneath. The leaves often have small blisters caused by aphids and other sap-sucking insects. Flowers of the common lime are yellowish to dull white in color and are sweetly scented. They hang from slender stalks in flattened clusters of 4-10 on a stalk. They have five petals and are about 1/2 inch (15 mm) wide. Insects attracted by the abundant nectar pollinate them. The common lime blooms in June and July. The common lime fruit is a small round nutlet about the size and shape of a pea. Hairy and faintlyribbed, they hang together on green bracts. In October they float away from the parent tree on the wind. The bark is smooth and a dull grey color when young. As it grows older, the bark becomes brownish-grey with perpendicular, shallow cracks. The stringy inner bark is called bass or bast. It is used to make mats, ropes, and fancy baskets.

The wood is white, smooth and close-grained. It is a light wood and doesn’t become worm-eaten. It is useful for small things that don’t need much strength. It is often used for carvings and the sounding boards for pianos, and for artist’s charcoal.

The common lime has been used as a home remedy for colds, flu, coughs, epilepsy and indigestion. The inner bark contains a gelatin-like material that was applied to soothe skin irritations. Tea made from leaves and flowers is used to treat cold symptoms. However, drinking too much flower tea may cause heart damage. During the Middle Ages statues of the Virgin Mary were carved from lime wood. They called the wood sacred wood. In Germany the tree was thought to bring fertility and prosperity, and was considered the sacred tree for people in love.

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13 The Oak-Hickory Forest

The typical upland forests of southern New England have a different appearance from the northern hardwood forests. First, the trees themselves are different. Here oaks are the most common trees; their lustrous dark green leaves provide a sharp contrast to the delicate greens of the northern hardwoods. Hickory and red maple are also common trees on drier sites.

Where there is a bit more moisture, the variety of trees increases. A number of southern trees including black birch, sweet gum (in southwestern Connecticut), tulip tree, and dogwood join the tree community. In extreme southern New England, however, hemlock and the northern hardwoods become limited to shady ravines and moist, north-facing slopes. White pine, so common in central New England, also becomes scarce in the extreme southern part.

The oak forests in southern New England also appear drier and more open than those of the north. In place of the lush undergrowth of the northern forest, large patches of the forest floor are entirely bare of vegetation or support only monotonous growth of blueberry, sheep laurel, or huckleberry. Generally speaking, the southern woods arc drier than those farther north. Although both areas receive about the same yearly rainfall, the hot sun and longer summer season dries out the southern woods more rapidly. Where some ground water is available, however, the southern New England woods support thick undergrowth.

Another characteristic of the southern New England woodlands is the relatively small size of the trees. The miles of stone walls that crisscross the woods point out how much of the land was once cleared.

Coppice trees – that is, trees with several trunks growing in a clump from one set of roots – are a common sight in the oak-hickory forest. Oaks, hickories, and several other hardwoods that are common in these wood­lands have the ability to send up sprouts from burned or cut stumps. Al­though one set of roots can support several generations of trees, the later generations are almost always several-trunked coppice trees. The trunks are usually bent or crowded, the wood unfit for timber. So common are these sprouted, second-growth trees that the oak-hickory region is some­times referred to as the “sprout hardwoods” region.

The majority of young trees and stump sprouts point to the tremen­dous influence of man upon these woodlands. It is clear that most of the forests are still in the process of renewal from large-scale disturbances that have taken place since the arrival of the first European settlers about 350 years ago.

The line between the oak-hickory forests and the northern hardwoods region is indistinct The two meet and blend together along an irregular band stretching from northwestern Connecticut to southern Maine, form­ing what foresters call the “transition forest”. The oaks are generally southern trees, but persist in the woodlands up the Connecticut and Merri­mack Valleys deep into the hardwood regions.

It may be a century or more before the southern New England wood­lands reach a size to be of much value. In Rhode Island, for example, a woodland survey conducted in the 1940s showed that 30 percent of the trees in the woodlands of the state were still too small even to be of use for firewood; only 1 percent of the trees were large enough for saw timber, and these few were too widely scattered to be of any real economic value. No doubt the situation has improved somewhat in the last 20 years, but oak and hardwoods grow slowly. In addition, most of the older trees are cop­pices that rarely yield salable timber.

Nevertheless, all of the states have natural woodland areas that, barring fire or hurricane, will eventually return to a primeval state. These are either part of the state park systems or are owned by private organizations such as the Audubon Society or Nature Conservancy. Many already support mature woodland that can probably give visitors at least an approximate idea of the natural vegetation of this region.

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Temperate forest

Temperate forests are located almost entirely in the Northern Hemisphere, although they do occur in the Southern Hemisphere at the tips of Africa, South America and Australasia.

The rainfall in this biome averages 80-150 cm a year and is fairly evenly spread over the year. The summers are typically warm and the winters are cold, often falling below zero degrees Celsius.

Temperate forests usually consist of two layers - the canopy and an understorey of shrubs. Unlike in the rainforests where little light penetrates to the forest floor, in temperate forests there is enough light for herbaceous plants and moss to grow. There are also less tree species in temperate forests than in the rainforest. The perennial plants that grow on the forest floor tend to die away in the winter and come up again in the spring.

There are several different types of temperate forest. These are:

· Broad-leaved deciduous woodland (western Europe, eastern North America), including oak, beech, chestnut and ash.

· Coniferous forest (Pacific coast of North America), made up of redwood, red cedar and hemlock.

· Mixed conifer and deciduous (Great Lakes region), containing birch, oak, hemlock, pine and maple.

· Broad-leaved evergreen forests (Japan and Tasmania), include southern beech and chinquapin.

At higher latitudes the forests are typically coniferous, and in warmer regions they tend to be deciduous.

The leaves of deciduous trees change colour in the autumn, as chlorophyll, the green pigment, breaks down. The leaves turn golden, red or brown before falling off the branches. This is because water is in short supply, and so to conserve this precious resource, the trees sacrifice their leaves in the winter.

This is one of the most heavily populated biomes. If it were not for the long history of forest clearance for agriculture, industry and cities, a great deal more of the temperate world would be covered by woodland. Much of the ancient forest has been replaced by heathland and moorland. Ten thousand years ago the UK was almost entirely covered by forest, with coniferous pines in the north and oak, lime, elm, hazel, birch, alder and ash in the south.

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