2012年3月18日托福阅读考试机经回忆

第一篇：真菌(fungi)

　　>考生回忆：

　　·在欧洲，过去采集真菌相对容易;而现在不仅数量减少了，外形也变小了。真菌有很强的环境敏感度，这同树木不同;故环境出现问题则真菌首当其冲。真菌也可以储存养分供给树木。

　　·在北美，那里的人食用真菌类食物(如蘑菇)比较少，且历史较短。人们把其他蘑菇等都算进真菌里面。虽然没有显著减少，但是也有危险。

　　·里面用了很多TPO文章The Arrival of Plant Life in Hawaii的很多内容;

　　>参考文献说明

　　“欧洲真菌减少”的回忆似乎并不太合常识。经过对自然科学类期刊论文数据库检索后，找到了发表于1990年的一篇论文”Decline of ectomycorrhizal fungi in Europe”，探讨了欧洲“外生菌”(Ectomycorrhizal Fungi)的数量减少，其中提到的主要原因便是环境因素，同回忆相符。该论述如下(参考阅读中划线句子)：

　　“It is argued that changes in the populations of ectomycorrhizal fungi are most likely to be attributable to indirect effects of air pollution, in particular to increases in amounts of available nitrogen (possibly in combination with acidification) and/or to decreased tree vitality wity consequent reductions in the transport of current assimilates to roots and mycorrhizas.”

　　该论文由学术数据库ScienceDirect收录，来源如下：

　　Eef Arnolds , “Decline of ectomycorrhizal fungi in Europe “, Agriculture, Ecosystems & Environment, Volume 35, Issues 2-3, April 1991, Pages 209-244

　　>参考阅读(上述论文摘要部分)

　　Abstract

　　Recent changes in the species diversity and sporocarp production of ectomycorrhizal fungi in different regions of, and forest communities within, Europe are discussed with special emphasis on events in The Netherlands. In some forests in some regions fewer ectomycorrhizal fungi are now producing sporocarps, notably those associated with trees more than 40 years old and in particular conifers, for instance species of Phellodon, Hydnellum, Suillus, Tricholoma and Cortinarius. It is argued that this decline in different parts of Europe is coincident with decreased numbers of mycorrhizas. A scheme of progressive changes with three phases of ectomycorrhizal impoverishment and seven subphases is presented. The more probable causes ofdecline are discussed, namely forest succession, the collection of sporocarps (of edible mycorrhizal fungi), changes in forest management, direct influences of air pollutants, acidification of forest soils and consequent increased availability of aluminium in soil solution, nitrogen deposition, increased litter accumulation, changes in the herb layer of forests and reduced tree vitality.

　　It is argued that changes in the populations of ectomycorrhizal fungi are most likely to be attributable to indirect effects of air pollution, in particular to increases in amounts of available nitrogen (possibly in combination with acidification) and/or to decreased tree vitality wity consequent reductions in the transport of current assimilates to roots and mycorrhizas. The relative importance of these different factors, and their interactions, are likely to differ in different locations. It is supposed that liming and applications of other corrective fertilizers are unlikely to restore the diversity and sporocarp production of ectomycorrhizal fungi; they may even have adverse effects. In the circumstances therefore it seems that the abatement of emissions is likely to be the only effective way of improving and sustaining stable forest ecosystems in areas at risk, notably in densely populated Europe.