Light is a vital factor affecting tree growth, survival and reproduction. In forests, natural and anthropogenic disturbances are the main drivers of abrupt changes in environmental conditions, including solar irradiance. We examined interspecific differences in the responses of European beech and silver fir to canopy gap characteristics and positions within gaps across various life stages (small seedlings, tall seedlings and saplings) in old-growth stands in Świętokrzyski National Park, Central Poland. Additionally, we analyzed sapling architectural responses to light. Regeneration densities were strongly affected by gap characteristics. The largest interspecific differences in responses to gap characteristics were found for small seedlings, which indicated their different preferences not only for light conditions created within gaps, but also toward various microsites distributed on a fine-scale after gap creation. Small beech seedlings responded only to the position within the gap, but small fir seedlings reacted in a more complex way, including such variables as gap size, shape and distance from a gap border. Gap size and the distance from its border had the most noticeable positive effect on tall seedlings and saplings, indicating that successful transition of regeneration to taller life stages may be possible only in larger gaps and in places further from a canopy border. Light conditions did not affect sapling length to diameter ratio. However, both direct and diffuse light had a negative effect on beech and fir crown area and length. Fir had wider but shorter crowns compared with beech in the whole light spectrum. This result indicates that these two species might have contrasting strategies regarding light interception, with fir being better adapted to increase a crown laterally, and with beech either being more tolerant to self-shading than fir or able to keep a favorable spatial leaf arrangement to avoid self-shading. Beech had the highest height growth increments in low levels of direct light, but its height growth was positively affected by diffuse light. Fir height growth rates showed no response to direct light, but were highest in medium levels of diffuse light. No effect of light on beech height to lateral growth rate ratio was found. The effect of direct light on this parameter for fir was negative, and nonlinear in the case of diffuse light, with the highest ratios observed in medium light levels. Our results stress the need of using both direct and diffuse light when analyzing light effects on sapling architecture.

光是影响树木生长，存活和繁殖的重要因素。在森林中，自然和人为干扰是环境条件（包括太阳辐射）突然变化的主要驱动力。我们在波兰中部Świętokrzyski国家公园的老林中研究了欧洲山毛榉和银冷杉对树冠间隙特征和间隙在不同生命阶段（小幼苗，高大幼苗和幼树）中间隙中位置的种间差异。此外，我们分析了树苗对光的响应。间隙密度强烈影响再生密度。发现小型幼苗对间隙特性的响应之间存在最大的种间差异，这表明它们不仅对间隙内产生的光照条件有不同的偏好，而且还可以在创建缺口后针对各种微型站点进行精细分布。小山毛榉幼苗仅对间隙内的位置响应，但是小杉树幼苗以更复杂的方式反应，包括诸如间隙大小，形状和距间隙边界的距离等变量。间隙的大小和与边界的距离对高大的幼苗和幼树有最显着的积极影响，表明只有在较大的间隙和距冠层边界较远的地方，才有可能成功地将再生成功过渡到较高的生命阶段。光照条件不影响树苗的长径比。但是，直射光和漫射光都对山毛榉和杉木冠的面积和长度产生负面影响。在整个光谱上，与山毛榉相比，冷杉的冠冠更宽但更短。该结果表明，这两个物种在光拦截方面可能具有相反的策略，冷杉更适合于横向增加树冠，而山毛榉比冷杉更耐自遮荫，或者能够保持良好的空间叶片排列以避免自我遮蔽。在低水平的直射光下，山毛榉的高度增长增量最高，但其高度增长受到散射光的积极影响。杉木高度的增长速度表明对直射光无反应，但在中等水平的漫射光中最高。没有发现光对山毛榉高度与侧向生长速率之比的影响。直射光对该冷杉参数的影响为负，而对于漫射光则为非线性，在中等光照水平下观察到的比率最高。