They noted at that timethat only two of thebogs contained palsas, whereas aerial photos takenin 1957 showed palsas present in all of thebogs.
他们注意到那时只有两个沼泽有泥炭丘，而1957年空中拍摄的该地区照片显示所有沼泽都有泥炭丘。
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For the last fifteen years, Ellison and University of Vermont biologist Nicholas Gotelli have slogged through thebogs of New England, studying the life that exists in each pool.
The poor soil of bogs, for example, offers little nitrogen and phosphorus, so carnivorous plants enjoy an advantage over plants that obtain these nutrients by more conventional means.