Sapling richness and composition in canopy gaps of a southern Appalachian mixed Quercus forest1
Sapling richness and composition in canopy gaps of a southern Appalachian mixed Quercus forest1
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阿巴拉契亚南部栎树混交林树冠间隙的树苗丰富度和组成1
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
J. Kupfer
中科院分区：
文献类型：
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作者：
J. Hart;J. Kupfer
摘要 树冠间隙在更广泛的森林环境中创造了独特的微环境，并提供了再生和补充的机制。在这项研究中，我们调查了田纳西州坎伯兰高原的次生栎树混交林中 40 个树冠间隙的树苗丰富度和组成模式。我们发现树苗丰富度很高，树冠间隙中有 34 种树苗。物种间隙面积曲线显示，树苗丰富度稳步增加，间隙大小可达约 100 倍。 200 平方米，但随后趋于平稳。虽然主要森林冠层中的次要成分，但糖枫、大叶水青冈和红枫是林隙中分布最广、最丰富的物种。我们使用排序（NMS）和随机化技术（MRPP）对植物区系组成进行分析，阐明了负责构建间隙组成模式和物种-环境关系的机制，包括个体因素（间隙形成机制、间隙大小、方面和土壤）的影响及其集体影响。障碍物形成的间隙尺寸较小，最常见于南部石质壤土。由连根拔起的树木形成的间隙更大，并且最常见于具有浅层砾质壤土的朝北斜坡。间隙组成沿着这些梯度变化。目前树冠优势属（栎属和山核桃）的幼树主要局限于干旱地区的小间隙，这表明间隙阶段演替将导致从栎属-山核桃系统向具有更强的宏碁-水青冈成分的系统转变。
Abstract Canopy gaps create distinct microenvironments within the broader forest environment and provide a mechanism for regeneration and recruitment. In this study, we investigated patterns of sapling richness and composition in 40 canopy gaps in a secondary, mixed Quercus forest on the Cumberland Plateau in Tennessee. We found that sapling richness was high, with 34 species represented in canopy gaps. A species-gap area curve revealed that sapling richness increased steadily with gap sizes up to ca. 200 m2, but then tended to level off. While minor components in the main forest canopy, Acer saccharum, Fagus grandifolia, and Acer rubrum were the most widespread and abundant species in gaps. Our analyses of floristic composition using ordination (NMS) and randomization techniques (MRPP) clarified the mechanisms responsible for structuring patterns of gap composition and species-environment relationships, including the effects of individual factors (gap formation mechanism, gap size, aspect, and soils) and their collective impacts. Snag-formed gaps were smaller in size and most common on southern exposures with stony loam soils. Gaps formed by uprooted trees were larger and most common on north-facing slopes with shallow, gravelly loam soils. Gap composition varied along these gradients. Saplings of current canopy dominant genera (Quercus and Carya) were largely restricted to small gaps on xeric sites, suggesting that gap-phase succession will result in a transition from a Quercus–Carya system to one with a much stronger Acer–Fagus component.