段落A

A tree’s ‘value’ depends on several factors including its species, size, form, condition, quality, function, and accessibility, and depends on the management goals for a given forest. The same tree can be valued very differently by each person who looks at it. A large, straight black cherry tree has high value as timber to be cut into logs or made into furniture, but for a landowner more interested in wildlife habitat, the real value of that stem (or trunk) may be the food it provides to animals. Likewise, if the tree suffers from black knot disease, its value for timber decreases, but to a woodworker interested in making bowls, it brings an opportunity for a unique and beautiful piece of art.

段落B

In the past, Pennsylvania landowners were solely interested in the value of their trees as high-quality timber. The norm was to remove the stems of highest quality and leave behind poorly formed trees that were not as well suited to the site where they grew. This practice, called ‘high-grading’, has left a legacy of ‘low-use wood’ in the forests. Some people even call these ‘junk trees’, and they are abundant in Pennsylvania. These trees have lower economic value for traditional timber markets, compete for growth with higher-value trees, shade out desirable regeneration and decrease the health of a stand leaving it more vulnerable to poor weather and disease. Management that specifically targets low-use wood can help landowners manage these forest health issues, and wood energy markets help promote this.

段落C

Wood energy markets can accept less expensive wood material of lower quality than would be suitable for traditional timber markets. Most wood used for energy in Pennsylvania is used to produce heat or electricity through combustion. Many schools and hospitals use wood boiler systems to heat and power their facilities, many homes are primarily heated with wood, and some coal plants incorporate wood into their coal streams to produce electricity. Wood can also be gasified for electrical generation and can even be made into liquid fuels like ethanol and gasoline for lorries and cars. All these products are made primarily from low-use wood. Several tree- and plant-cutting approaches, which could greatly improve the long-term quality of a forest, focus strongly or solely on the use of wood for those markets.

段落D

One such approach is called a Timber Stand Improvement (TSI) Cut. In a TSI Cut, really poor-quality tree and plant material is cut down to allow more space, light, and other resources to the highest-valued stems that remain.  Removing invasive plants might be another primary goal of a TSI Cut. The stems that are left behind might then grow in size and develop more foliage and larger crowns or tops that produce more coverage for wildlife; they have a better chance to regenerate in a less crowded environment. TSI Cutscan be tailored to one farmer’s specific management goals for his or her land.

段落E

Another approach that might yield a high amount of low-use wood is a Salvage Cut. With many pests and pathogens visiting forests including hemlock wooly adelgid, Asian long-horned beetle, emerald ash borer, and gypsy moth, to name just a few, it is important to remember that those working in the forests can help ease these issues through cutting procedures. These types of cut reduce the number of sick trees and seek to manage the future spread of a pest problem. They leave vigorous trees that have stayed healthy enough to survive the outbreak.

段落F

A Shelterwood Cut, which only takes place in a mature forest that has already been thinned several times, involves removing all the mature trees when other seedlings have become established. This then allows the forester to decide which tree species are regenerated. It leaves a young forest where all trees are at a similar point in their growth. It can also be used to develop a two-tier forest so that there are two harvests and the money that comes in is spread out over a decade or more.

段落G

Thinnings and dense and dead wood removal for fire prevention also center on the production of low-use wood. However, it is important to remember that some retention of what many would classify as low-use wood is very important. The tops of trees that have been cut down should be left on the site so that their nutrients cycle back into the soil. In addition, trees with many cavities are extremely important habitats for insect predators like woodpeckers, bats and small mammals. They help control problem insects and increase the health and resilience of the forest. It is also important to remember that not all small trees are low-use. For example, many species like hawthorn provide food for wildlife. Finally, rare species of trees in a forest should also stay behind as they add to its structural diversity.

    段落A
一棵树的“价值”取决于其物种、大小、形态、状态、品质、功能和可及性等多个因素，并且取决于对给定森林的管理目标。同一棵树在每个看它的人眼中的价值可能会有很大不同。一棵又大又直的黑樱桃树作为木材，可以被用来制成原木或家具，因此具有较高的价值；但对于更关注野生动物栖息地的土地所有者来说，这颗树的真正价值可能是为动物提供的食物。同样，如果这棵树遭受了黑瘤病的侵害，它作为木材的价值就会降低，但对于一位对制作碗感兴趣的木匠来说，这里面却蕴含了制作独特而美丽的艺术品的机会。

段落B
过去，宾夕法尼亚州的土地所有者只关心树木作为高品质木材的价值。通常的做法是移除最高品质的树干，留下在生长地点上不太适合的形态较差的树木。这种被称为“高选择”的做法在森林中留下了大量的“低价值木材”。有人甚至将这些树木称为“垃圾树”，它们在宾夕法尼亚州很常见。这些树木在传统的木材市场上的经济价值较低，与高价值树木竞争生长，遮荫了期望的更新，降低了林地的健康状况，使其更容易受到恶劣天气和疾病的影响。专门针对低价值木材进行管理可以帮助土地所有者解决森林健康问题，而木材能源市场有助于推动这一点。

段落C
木材能源市场可以接受比传统木材市场更便宜、质量较低的木材材料。宾夕法尼亚州使用的大多数木材用于通过燃烧产生热能或电能。许多学校和医院使用木质锅炉系统来供暖和发电，许多家庭主要使用木材供暖，一些燃煤厂将木材混入煤流以发电。木材也可以气化发电，甚至可以制成乙醇和汽油等液体燃料用于卡车和汽车。所有这些产品主要都是由低价值木材制成的。几种针对树木和植物的砍伐方法，可以显著改善森林的长期质量，强调或仅仅以这些市场的木材为重点。

段落D
一种这样的方法被称为抚育采伐（Timber Stand Improvement，TSI）。在抚育采伐中，非常质量差的树木和植物材料被砍伐，以便为保留的最有价值的树木提供更多的空间、光线和其他资源。除此之外，还可以把清除入侵植物作为抚育采伐的主要目标。留下的树木可能会在较少拥挤的环境中生长并增加叶面积和更大的冠幅，为野生动物提供更多的遮蔽；它们在更少的竞争中更有机会再生。抚育采伐可以根据农民对土地的具体管理目标进行调整。

段落E
另一种可能产生大量低价值木材的方法是抢救性砍伐。由于包括蓝细胞松蚧、亚洲天牛、翡翠灰蠹和裳纹尺蛾在内的许多害虫和病原体经常侵袭森林，因此重要的是记住，在森林工作的人可以通过砍伐程序来缓解这些问题。这种类型的砍伐减少了患病树木的数量，并寻求管理未来害虫传播的问题。它们留下了能够保持足够健康以在爆发中存活下来的活力树木。

段落F
护林砍伐（Shelterwood Cut）只在已经经过多次间伐的成熟森林中进行，它涉及到当其他幼苗已经成长时移除所有的成熟树木。然后，林务员可以决定哪些树种进行再生。这样留下了一个所有树木处于相似生长阶段的年轻森林。它还可以用于发展双层森林，以便有两个收获期，并且分散在十年甚至更长的时间内获取利益。

段落G
稀疏和清除密集和死木以预防火灾也是以生产低价值木材为中心的。“但是重要的是记住，保留许多人会将之归类为低价值木材的树木非常重要。砍伐掉的树木的树顶应该留在现场，以便它们的养分循环回土壤中。此外，具有许多树洞的树木对于啄木鸟、蝙蝠和小型哺乳动物等昆虫捕食者来说非常重要。它们帮助控制问题昆虫，并增加森林的健康和抗逆性。还应该记住，并不是所有的小树都是低价值的。例如，像山楂这样的许多树种为野生动物提供食物。最后，森林中的稀有树种也应该保留，因为它们增加了森林的结构多样性。