香蕉视频

"Cultivated trees grow faster [than their natural counterparts] because in the early years much effort is spent weeding out the competition," points out David Wees, Faculty Lecturer in the Department of Plant Science at McGill's Macdonald Campus. "The fir trees that grow naturally in the forest are for their part in competition with all their neighbours, and they often develop in partially shaded areas, whereas in the fields where fir trees are grown, there are only fir trees whose conical shape does not cast a shadow on neighbours."

the article (in French) in Le Devoir.