Henriksson Janne
Section of Ecology, Department of Biology, University of Turku, 20014, Turku, Finland.
Kevo Subarctic Research Institute, University of Turku, 20014, Turku, Finland.
Oecologia. 2001 Feb;126(4):482-486. doi: 10.1007/s004420000547. Epub 2001 Feb 1.
This study compared the effects of shading individual branches or whole trees on the survival, growth and reproduction of branches of mountain birch [Betula pubescens ssp. czerepanovii (Orlova) Hämet-Ahti]. When a single branch was shaded its performance decreased drastically, while individual branches performed relatively well if the whole tree was shaded. For instance, after two summers 90% of the individually shaded branches were dead, while none of the study branches died following shading of entire trees. These results indicate that the fate of a branch depended more on shading-induced asymmetric competition among branches than on the shading itself. Furthermore, the increased growth of non-shaded branches in the trees where only two branches were shaded suggests that resources were preferentially allocated to branches in more favorable positions. Branch autonomy may promote environmental screening and growth towards favorable directions, optimizing the use of available light resources. In addition, branch autonomy may buffer the genet against environmental hazards, thus increasing the fitness of the genet at the cost of an increased mortality for individual modules.
本研究比较了对单个树枝或整棵树进行遮荫处理对欧洲山桦[Betula pubescens ssp. czerepanovii (Orlova) Hämet - Ahti]树枝的存活、生长和繁殖的影响。当单个树枝被遮荫时，其表现急剧下降，而如果整棵树被遮荫，单个树枝的表现相对较好。例如，经过两个夏天，90%被单独遮荫的树枝死亡，而在整棵树被遮荫后，没有一个研究树枝死亡。这些结果表明，树枝的命运更多地取决于遮荫引起的树枝间不对称竞争，而非遮荫本身。此外，在仅对两根树枝进行遮荫处理的树木中，未被遮荫树枝的生长增加，这表明资源优先分配给了处于更有利位置的树枝。树枝自主性可能促进对环境的筛选以及朝着有利方向生长，从而优化可用光资源的利用。此外，树枝自主性可能使基株免受环境危害，从而以单个模块死亡率增加为代价提高基株的适合度。
