| Directions: Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need. | |
a result of climate change, according to a study of trees in eastern America. The trees appear to have faster growth rates due to longer growing seasons and higher concentrations (浓度) of carbon dioxide in the 1______. Geoffrey Parker, a scientist at the Smithsonian Environmental Research Centre in Edgewater. Maryland, said that the increase ha the rate of growth was unexpected and might be 2______ to the higher temperatures and longer growing seasons documented in the region. The growth may also be influenced by the significant 3______ in atmospheric CO2, he said. "We made a list of reasons these forests could be growing faster and then excluded half of them," Dr Parker said. Their study suggests that northern forests may become increasingly important in 4______ the influence of man-made CO2 on the climate. Dr Parker and his colleagues have 5______ out a detailed record of the trees on a(n) 6______ basis since 1987. They calculated that due to the global warming the forest is producing 7______ tons of wood each year. The scientists 8______ the land with trees at different stages of growth and found that both young and old trees were showing increased growth rate. More than 90 per cent of the tree groups had grown by between two and four times faster than the scientists had 9______ from estimates of the long-term rates of growth. |