We evaluated the ecological significance of the boundary form between two patches with contrasting vegetation (mine grassland and adjacent forest) on woody colonization and forest expansion in open-cast coal mines in Northern Spain. Woody colonization and browsing traces were measured on three mine sites, along 24 transects that were laid out perpendicular to the forest-mine boundary and classified according to their shape (concave, convex, straight). Mine sites were colonized from the close forest by woody species, whose colonization intensity depends on the boundary form. The overall colonization intensity decreased with increasing distance to the forest and differed depending on the boundary form. The more intense colonization was found in concave boundaries and the strongest decrease in convex boundaries close to the forest, whereas straight boundaries showed an intermediate colonization pattern. Concave boundaries reached higher woody cover in the basal strata of the mines than convex (up to 2 m) or straight boundaries (up to 1 m) from 11 m to the forest edge, mainly by the presence of dense patches of Cytisus scoparius (L.) Link, with a scattered overstory of Genista florida L. These shrubs might reduce the browsing intensity and act as nurse plants facilitating the establishment of Quercus petraea (Matt.) Liebl. in mine areas at greater distances from the forest edge. The forest-mine boundary form does not affect the forest vertical structure that is homogenous and does not help explain the woody colonization pattern in the mines. We conclude that edge characteristics have a strong potential to be used in the restoration of native forests based on natural processes. The implications of our results for sessile oak (Quercus petraea (Matt.) Liebl.) forest expansion along edges in fragmented Mediterranean forest landscapes were discussed.

中文翻译：

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森林-矿山边界形式对退化生态系统中木本定植和森林扩张的影响

我们评估了两个具有对比植被的斑块（矿山草原和邻近森林）之间的边界形式对西班牙北部露天煤矿木本殖民和森林扩张的生态意义。在三个矿场沿垂直于林矿边界布置并根据其形状（凹、凸、直）进行分类的 24 条断面测量了木质定植和浏览痕迹。矿区由密林中的木本物种殖民，其殖民强度取决于边界形式。总体定植强度随着与森林距离的增加而降低，并因边界形式而异。在凹边界处发现更强烈的殖民化，而在靠近森林的凸边界处发现的减少最强，而直线边界显示出中间的定植模式。从 11 m 到森林边缘，凹形边界在矿山的基底地层中达到比凸形（高达 2 m）或直线边界（高达 1 m）更高的木质覆盖，主要是由于存在密集的斑块Cytisus scoparius (L.) Link，散布着Genista florida L 的覆盖层。这些灌木可能会降低浏览强度并充当促进Quercus petraea (Matt.) Liebl建立的护生植物。在距离森林边缘更远的矿区。森林-矿山边界形式不影响同质的森林垂直结构，也无助于解释矿山中的木本殖民模式。我们得出结论，边缘特征在基于自然过程的原始森林恢复中具有强大的潜力。讨论了我们的结果对无柄橡树（Quercus petraea (Matt.) Liebl.）森林沿破碎的地中海森林景观边缘扩张的影响。