摘要
北美不毛之地的驯鹿(Rangifer tarandus)群可达到相当的规模,并从北极苔原至北方针叶林进行大尺度的季节性迁移。为了验证驯鹿减少与当地捕猎和野火有关的假说,我们采用了与众不同的方法来研究驯鹿活动的长期趋势:用树木年轮来确定Riviere-aux-Feuilles鹿群(RAF鹿群,北魁北克哈得逊湾东部)冬夏活动区内广布的鹿道上鹿蹄践踏瘢痕的时间。遍及整个RAF活动范围的地衣林地中践踏瘢痕的年龄结构数据证实了从18世纪末至今驯鹿活动的总体规律。近200年来,RAF鹿群经历了两次高峰,分别在18世纪末和20世纪,中间间隔着19世纪末中等规模的活动格局。当地捕猎可能与20世纪初期的鹿群减少(尽管是在中等水平上)有关。在此期间驯鹿活动的数量减少,但这并未影响高峰低谷的自然循环,这意味着有其它的种群统计学因素在控制着驯鹿的数量变化。我们的数据也显示出,只有异常的大火可以对驯鹿迁移造成微弱的短期影响,而对驯鹿数量无影响。
Barren-ground caribou ( Rangifer tarandus) herds in North America may reach cnsiderable size and undertake large-scale seasonal migrations from the Arctic tundra to the boreal forest. To test the caribou decline hypothesis associated with native harvesting and fire,we have documented the long-term trends of caribou activity based on a novel approach which uses tree-ring dated trampling scars produced by caribou hooves in the extensive trails distributed over the summer and winter ranges of the Riviere-aux-Feuilles herd (RAF herd,east of Hudson Bay in northern Quebec).The age structure data of trampling scars from lichen woodlands distributed over the entire RAF range confirmed the overall trends of caribou activity from the late 1700s to present time.Over the last 200 years,the RAF herd has undergone two highs in the late 1700s and 1900s separated by a moderate activity pattern in the late 1800s.Native harvesting was possibly involved in the early 1900s decline,although at a moderate level.The reduced magnitude of caribou activity during this period has not modified the natural cycle of highs and lows,which suggests that other demographic factors were controlling the changing caribou abundance.Our data also show that only exceptionally large fires may have a minor, short-lived impact on caribou migrations but not on caribou numbers.
