Forest management in Pennsylvania, USA
Forest management in Pennsylvania, USA
How making use of low-grade timber — sometimes called low-use wood — for energy can support the sustainable management of forests
A
AFor a long time, woodland owners in Latvia prized their trees for one thing only: high-grade sawtimber. When a stand was cut, the finest, straightest stems were taken out and the misshapen trees — those least suited to the ground they stood on — were left behind. This habit, called 'high-grading', has handed today's forests a legacy of 'low-use wood'. Foresters sometimes dismiss such trees as 'weed trees', and across the country they are far from scarce. They fetch little in conventional timber markets, crowd better stems as they compete for room, shade out the seedlings meant to replace them and sap a stand's overall vigour, leaving the forest more exposed to storms and disease. Cutting aimed squarely at this low-use wood helps owners tackle these problems, and markets for wood energy give them a reason to do so.
B
BThose markets are useful because they will take timber of a lower grade, and price, than any sawmill would consider. In Latvia most wood burned for energy is turned into heat or electricity by combustion: many schools and hospitals run their heating on wood-chip boilers, countless homes rely on wood for warmth, and several power stations blend wood into the peat they burn for electricity. Wood can also be turned into gas for power, or processed into liquid fuels such as ethanol and petrol — the very fuels that drive lorries and cars. Every one of these products draws chiefly on low-use wood, and several cutting methods, each able to improve a forest's long-term quality, are built around supplying it.
C
CJust how much any tree is 'worth', though, is far from fixed. It turns on a range of things — species, size, shape, condition, quality, the part it plays in the wood and how easily it can be reached — and on what the owner wants from the forest. The same tree may strike two people quite differently. To a timber merchant, a tall oak with a clean, straight trunk is a valuable saw-log or future furniture; to an owner who cares about wildlife, that trunk's worth lies in the food and shelter it gives animals. Likewise, once fungal decay — a defect foresters call heart-rot — has crept into a stem, its timber value drops sharply, yet the figured wood it yields may be just what a bowl-turner treasures.
D
DThe first method is the Timber Stand Improvement, or TSI, Cut. Here the poorest trees and plants are felled so that the space, light and other resources they used pass to the best stems still standing; removing invasive plants may be a second aim. Freed from crowding, the trees left behind can thicken, put out more foliage and spread wider crowns, giving better cover to wildlife and a greater chance of regenerating. A TSI Cut can be shaped to fit whatever an owner is trying to do with their land.
E
EA Shelterwood Cut is possible only in a mature wood already thinned more than once. Once a new generation of seedlings has taken hold, the mature trees are removed together, letting the forester decide which species come up in their place and leaving a young stand whose trees are all at much the same stage of growth. It can also create a forest of two layers, yielding two harvests and stretching the owner's income across ten years or more.
F
FA Salvage Cut, by contrast, tends to produce a great deal of low-use wood. Forests today face all manner of pests and diseases — the European spruce bark beetle, the large pine weevil, the nun moth and the pine-tree lappet moth are only a handful — and those who work among the trees can ease the pressure through well-judged felling. Such cuts thin out the sickened trees and check how far a pest may spread, while sparing the sturdy trees that came through the attack unharmed.
G
GThinning, and the clearing of dense or dead material to lessen the danger of wildfire, likewise yields low-use wood. Yet keeping back a certain amount of what most would write off as low-use wood matters greatly. Stripping it away is partly a way of taking off the fuel that a fire would burn; but when a tree is felled, its top is best left where it falls, so that the minerals locked inside it seep back into the earth. Trunks pitted with hollows are, likewise, priceless as homes for the creatures that prey on insects — woodpeckers, bats and other small mammals — which keep troublesome insect numbers down and make the forest healthier. Nor is every small tree low-use: some, such as the rowan, are a ready source of food for birds and other animals. And any species that is uncommon in a given wood should be left to grow, for it adds to the forest's structural variety.
Question 1 - 5
Which paragraph contains the following information?
1
harmful effects on a wood that arise when owners judge it purely by profit
A
B
C
D
E
F
G
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