首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4篇
  免费   0篇
  2009年   1篇
  2000年   1篇
  1967年   1篇
  1950年   1篇
排序方式: 共有4条查询结果,搜索用时 31 毫秒
1
1.
Characterizing the use of carbon (C) reserves in trees is important for understanding regional and global C cycles, stress responses, asynchrony between photosynthetic activity and growth demand, and isotopic exchanges in studies of tree physiology and ecosystem C cycling. Using an inadvertent, whole-ecosystem radiocarbon (14C) release in a temperate deciduous oak forest and numerical modeling, we estimated that the mean age of stored C used to grow both leaf buds and new roots is 0.7 years and about 55% of new-root growth annually comes from stored C. Therefore, the calculated mean age of C used to grow new-root tissue is ∼0.4 years. In short, new roots contain a lot of stored C but it is young in age. Additionally, the type of structure used to model stored C input is important. Model structures that did not include storage, or that assumed stored and new C mixed well (within root or shoot tissues) before being used for root growth, did not fit the data nearly as well as when a distinct storage pool was used. Consistent with these whole-ecosystem labeling results, the mean age of C in new-root tissues determined using 'bomb-14C' in three additional forest sites in North America and Europe (one deciduous, two coniferous) was less than 1–2 years. The effect of stored reserves on estimated ages of fine roots is unlikely to be large in most natural abundance isotope studies. However, models of root C dynamics should take stored reserves into account, particularly for pulse-labeling studies and fast-cycling roots (<1 years).  相似文献   
2.
Ecological studies of timber wolves (Canis lupus) in a forestedenvironment have always been difficult to undertake in the past,particularly during the summer months, because of the lack ofa suitable technique. In 1960 Pimlott devised a technique whichemployed the use of broadcast wolf howls in locating wolvesin the field. This report reviews the success of this techniquein studying the movements of two packs of wolves, and theiruse of home sites in Algonquin Park, Ontario. Wolves responded by howling a total of 476 occasions or approximately13% of the occasions that broadcast howls were given. Humanimitations were more successful than tape-recordings in inducingresponses. Wolves responded at any time of day, but dusk wasthe most favorable period. They also responded more frequentlyin July and August than in May and June. Two types of home sites were found: the den site, occupied duringthe early life of the pups, and the rendezvous site, a placeoccupied by wolves during later development of pups. All ofhe home sites were adjacent to some immediate source of water.The movement of wolves appeared also to be concentrated alongthe water courses. The locations of the home sites and the evidence obtained fromhowling responses, tracks, and scats suggested that the summerrange comprised a minimum area of eight square miles. The samerange was utilized by a pack in 1961 and 1963.  相似文献   
3.
Effects of altered water regimes on forest root systems   总被引:21,自引:0,他引:21  
  相似文献   
4.
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号