Department of Forest Resources, University of Minnesota, Green Hall, St Paul, MN 55108, USA Present address: University of Wisconsin-Milwaukee, PO Box 413, Milwaukee, WI 53201, USA Department of Ecology, Evolution, and Behavior, University of Minnesota, St Paul, MN 55108, USA.
Ecol Lett. 2005 Nov;8(11):1191-200. doi: 10.1111/j.1461-0248.2005.00822.x.
Little is known of the co-occurrence and implications of competitive and facilitative interactions within sites. Here we show spatially disjunct competition and facilitation at forest edges, with beneficial influences of trees on seedling growth via increased ectomycorrhizal infection apparent from 12 to 20 m while closer to trees seedling growth is negatively correlated with canopy closure. As a result, seedling growth is maximized at intermediate distances. Facilitative interactions were nonlinear: being within 15.7 m of a tree maximized seedling mycorrhizal infection; while competitive effects were correlated with canopy closure, which was related to distance and generally scales with density. These patterns result in a positive correlation of tree density and seedling growth at low densities of trees, and negative correlation at higher densities because of competition. A spatial model suggests that plant communities are a mosaic of positive and negative interactions, which may contribute to population homeostasis and plant diversity.
目前对于同一地点内的竞争和促进作用的同时发生及其影响还知之甚少。在这里，我们发现森林边缘存在空间上的分离的竞争和促进作用，树木通过增加外生菌根感染对幼苗生长有有益的影响，这种影响在 12 到 20 米的范围内是明显的，而在离树木更近的地方，树冠闭合与幼苗生长呈负相关。因此，幼苗生长在中等距离处达到最大值。促进作用是非线性的：距离树木 15.7 米以内可使幼苗的菌根感染最大化；而竞争作用与树冠闭合有关，树冠闭合与距离有关，通常与密度有关。这些模式导致在树木密度较低时，树木密度和幼苗生长呈正相关，而在树木密度较高时，由于竞争，它们呈负相关。一个空间模型表明，植物群落是正、负相互作用的镶嵌体，这可能有助于种群的内稳性和植物多样性。
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