To restore secondary forests (major forest resources worldwide), it is essential to accelerate the natural regeneration of dominant trees by altering micro-environments. Forest gaps are products of various disturbances, ranging from natural storms or wildfires to anthropogenic events like logging and slashing-and-burning, and sprouts of most tree species with non-structural carbohydrates (NSCs) storage can regenerate from stumps after gap formation. However, how the stump sprouts with diverse NSCs storages and stump sizes (i.e., diameters) adapt to various micro-environments of within-gap positions remains unclear. Therefore in this study, we monitored the stump sprout regeneration (density, survival, and growth) and NSCs concentrations of three dominant tree species with different shade tolerances and varying stump diameters at five within-gap positions for the first two consecutive years after gap formation. Stump diameter was positively correlated with sprout density, growth, and survival of all three tree species, but insignificantly related with sprout NSCs concentrations at the early stage after gap formation. The effect of within-gap position on sprout NSCs concentrations was different among species. After an environmental adaptation of two growing seasons, the north of gap (higher light availability and lower soil moisture habitat) was the least conducive for shade-intolerant Quercus mongolica to accumulate leaf NSCs, and the east of gap (shadier and drier habitat) was conducive to increasing the leaf NSCs concentrations of shade-tolerant Tilia mandshurica. Within-gap position significantly affected leaf NSCs concentrations of all three tree species, but most of the sprout growth, survival, and stem NSCs concentrations were independent of the various within-gap positions. Besides stump diameter, the NSCs stored in stump and root systems and the interspecific differences in shade tolerance also contributed more in sprout regeneration at the early stage (2 years) of gap formation. A prolonged monitoring (> 10 years) is needed to further examine the long-term effects of stump diameter and within-gap position on sprout regeneration. All of these findings could be applied to gap-based silviculture by promoting sprout regeneration of dominant tree species with different shade tolerances, which would help accelerate the restoration of temperate secondary forests.

中文翻译：

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不同树荫容忍度的树种之间，树桩大小和间隙位置对发芽非结构性碳水化合物浓度和森林间隙再生的影响各不相同

为了恢复次生林（全球主要森林资源），必须通过改变微环境来加速优势林的自然再生。森林缺口是各种干扰的产物，范围从自然风暴或野火到人为事件，例如伐木和砍伐和燃烧，大多数树种的非结构性碳水化合物（NSC）存储的新芽可在缺口形成后从树桩中再生。但是，尚不清楚具有不同NSC贮藏量和树桩大小（即直径）的树桩芽如何适应间隙内位置的各种微环境。因此，在这项研究中，我们监测了树桩新芽的再生（密度，存活率，和生长）以及在间隙形成后的前两年中，在五个内部间隙位置处具有不同的阴影容差和不同的树桩直径的三种优势树种的NSC浓度。树桩直径与这三种树种的树苗密度，生长和存活率均呈正相关，而与缺口形成后早期树苗中的NSCs浓度无关。间隙内位置对种苗NSCs浓度的影响是不同的。经过两个生长季节的环境适应后，空白区的北部（较高的光可利用性和较低的土壤水分栖息地）最不利于耐荫的蒙古栎积累叶片NSC，缝隙的东部（阴凉干燥的生境）有利于提高耐荫紫T的叶片NSCs浓度。间隙内位置显着影响所有这三种树种的叶片NSCs浓度，但是大多数芽苗的生长，存活和茎NSCs浓度均独立于各个间隙内位置。除树桩直径外，存储在树桩和根系中的NSC以及种间耐荫性的差异也对间隙形成的早期（2年）中的新芽再生起了更大的作用。需要长期监测（> 10年）以进一步检查树桩直径和间隙位置对新芽再生的长期影响。