A vegetation switch as the cause of a forest/mire ecotone in New Zealand
A vegetation switch as the cause of a forest/mire ecotone in New Zealand
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植被转换是新西兰森林/沼泽交错带的原因
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
M. Sykes
中科院分区：
文献类型：
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作者：
A. Agnew;J. Wilson;M. Sykes
。植被转换是植被和环境之间存在正反馈的过程，即植被状态改变其环境，产生对自身更有利的条件（Wilson & Agnew 1992）。转换可以在植物群落之间产生并维持突然的生态交错带。
新西兰西南部的深层泥炭上，山毛榉罗汉松森林和沼泽植被之间存在着如此尖锐的生态交错带。我们对这样一个地点进行了检查。对于当前地形和基质中的交错带没有明显的解释。
穿过森林的水平横断面表明，大多数幼苗的建立都发生在枯死的倒下的树干上。这些微场地的氮、磷和钾含量明显高于湿污水坑微场地。我们认为，这是一种机制，树木可以在森林中生长，但不能在开阔的泥沼中生长。在森林中，树木的存在确保了地面上存在死木微点，使树苗能够生长。在泥沼中，没有这样的微型场所，树木也无法生长。
由于森林和沼泽之间存在小树 Leptospermum sco-parium 的生态交错带，生态交错带可能会变得尖锐。该物种可以通过泥沼中的根吸盘进行无性繁殖。它的树干很轻，即使掉落到泥沼表面，也不足以形成树苗生长的基质。较大的树种可以通过森林的避风作用和轻子植物区来防止掉落到泥沼中。
假设的过程将代表一种新型的水/营养介导的转换，类型 1（“单侧”）。它可能发生在全世界许多浸水的森林中。
. Vegetation switches are those processes in which there is positive-feedback between vegetation and environment, i.e. a vegetation state modifies its environment producing conditions more favourable to itself (Wilson & Agnew 1992). Switches can produce and maintain abrupt ecotones between plant communities.
Such a sharp ecotone exists between beech-podocarp forest and mire vegetation, both on deep peat, in southwest New Zealand. One such site was examined. There was no apparent explanation for the ecotone in the present topography nor in the substrate.
Levelled transects through the forest demonstrated that most seedling establishment occurred on dead fallen tree boles. These microsites were significantly richer in N, P and K than the wet sump microsites. We argue that this is a mechanism whereby trees can become established in the forest, but not in the open mire. In the forest, the presence of trees ensures the presence of dead-log microsites on the ground, permitting tree seedlings to grow. In the mire, there are no such micro-sites, and trees cannot establish.
The ecotone may be sharpened because of the presence of an ecotonal band of the small tree Leptospermum sco-parium between forest and mire. This species can reproduce vegetatively by root suckers in the mire. Its boles are light, and even if they fall to the mire surface they are not thick enough to form a substrate for tree-seedling establishment. The larger tree species may be prevented from falling onto the mire by the wind-sheltering of the forest, and by the zone of Leptospermum.
The postulated process would represent a new kind of water-/nutrient-mediated switch, of Type 1 (‘One-sided’). It may occur in many waterlogged forests worldwide.