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woodland,
P1 observation→ 科学家发现现在地球上二氧化碳的排放量比他们原来计算的要稍少一些
推测原因→ 有人提出,woodland原来是source of CO2,现在已经成为 CO2 sink,吸收二氧化碳并转化成木头
P2 test→ 1920年以前树因为烧啊灾害啊毁坏很厉害,所以释放二氧化碳;但是1920年-1985年种树多了,新增树木超过deforestation,树木吸收了二氧化碳,二氧化碳就变少了
{考题}
1. 主旨题:好像选的是explain paradox,全文就一个理论,之后是这个理论的detail
2.下面哪一项如果是对的,科学家的理论就被削弱了
这道题选项不记得了,当时好像选了一个大致意思树木数量/吸收速度小于co2排出的什么的。。。
这篇是卤煮第一篇,文章不难,逻辑很清楚,细节题文章都有定位
是原文吗?
The quantity of wood in the forests is the key to the puzzle. To estimate its volume, Auclair began with traditional measurements of factors affecting the area and density of a forest, such as logging, fires, pests, and the regrowth and replanting of logged land. Such measurements have been recorded for northern forests for a century. But, significantly, Auclair also included estimates of tree growth rates in uncut forests, derived from recent studies in Europe and North America of tree ring width. This is important because increases in the area of a forest and the number of trees are not the only way that the volume of wood in a forest can increase: it can also increase simply because the trees are growing faster. Any gain in the overall volume of wood ndicates the forest is acting as a carbon sink, turning CO2 into wood
From sink to source
To determine whether the forest as a whole is releasing or absorbing carbon, the volume of wood added to the forest must be compared with the wood lost. Auclair’s analysis of the past hundred years shows the forest changing from a carbon source to a carbon sink and, more recently, back into a source again.
Before 1890, boreal forests were a source of C02, mainly because of forest fires and tree felling. Deforestation releases CO2 largely because debris from the forest floor rots more quickly when the trees are cleared. After 1920, a steep increase in tree growth outstripped the losses due to fire and the felling of trees, turning the northern forests from a carbon source into a carbon sink and storing C02 from fossil fuel burning for the next fifty years.
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