Site and neighborhood effects on growth of tree saplings in subtropical plantations (China)
Site and neighborhood effects on growth of tree saplings in subtropical plantations (China)
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DOI：
10.1016/j.foreco.2014.04.039
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发表时间：
2014-09
影响因子：
3.7
通讯作者：
Ying Li;W. Härdtle;H. Bruelheide;K. Nadrowski;T. Scholten;H. Wehrden;G. Oheimb
中科院分区：
文献类型：
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作者：
Ying Li;W. Härdtle;H. Bruelheide;K. Nadrowski;T. Scholten;H. Wehrden;G. Oheimb
重新造林和植树造林往往以单一作物的形式进行。这些作物越来越受到批评，因为它们更容易受到不利环境条件和病原体的影响，并对土壤肥力产生长期的负面影响。此外，对于单一栽培是否是最大限度地提高生物量生产力的唯一途径，经常有人持保留意见。中国亚热带森林不仅树种丰富，而且地形多样。然而，历史上的皆伐和对木材的高需求意味着这些森林的相当大的面积已经退化或完全消失。近年来，中国在亚热带地区进行了大规模的恢复和绿化工作。然而，由于缺乏关于多样性与生态系统功能之间关系的数据，以及对该区域人工林中本地阔叶树种生长情况的了解有限，针叶树单一栽培人工林仍然很普遍。在这项研究中，我们调查了在一个大规模的森林生物多样性和生态系统功能（BEF）的实验中建立在一个高度异质性的环境中，在中国亚热带（BEF-China）的生长反应。该实验是在2008年11月至2009年4月期间建立的，包括261个地块（每个地块0.067公顷）的24个树种的物种库和每个地块1-24个物种的广泛丰富度梯度。以24个树种的6723株幼树的树高、茎粗和冠幅的年生长率为响应变量。利用混合效应模型分析了初始大小、局部非生物立地条件和局部邻域对生长性能的影响。初始大小，当地地形（方面，坡度，曲率，海拔）和土壤变量（总氮，C/N比）以及当地的邻居变量（竞争指数，香农指数）作为固定效应。随机效应是地块和物种标识。结果表明，苗木生长表现出明显的种特异性，并受初始大小和当地立地条件的强烈影响。在实验的早期阶段，当地的香农多样性还不能解释树苗生长的显著变化。然而，相邻树木的大小增加的显着影响表明，树树之间的相互作用已经发生。以牺牲径生长为代价，加大对树高生长的投入，表明光截获是幼树生长的优先选择。这项研究强调了更好地了解当地立地条件对混种人工林初始生长的影响的重要性。
Reforestation and afforestation often takes place in the form of monocultures. These have increasingly come under criticism due to their greater susceptibility to adverse environmental conditions and pathogens and because of the negative long-term impacts they have on soil fertility. Moreover, reservations have frequently been expressed as to whether monoculture is the only way to maximize biomass productivity. Subtropical forests in China are not only rich in tree species but are also diverse in terms of topography. However, historical clear-cutting and the high demand for wood have meant that considerable areas of these forests have been degraded or lost entirely. In recent years, great efforts have been made in subtropical China to restore and afforest vast areas. Nonetheless, conifer monoculture plantations are still prevalent owing to the lack of data on the relationship between diversity and ecosystem functioning and the limited knowledge of the growth performance of native broad-leaved tree species in plantations in this region. In this study, we investigated the growth response of individual tree saplings in a large-scale forest biodiversity and ecosystem functioning (BEF) experiment established in a highly heterogeneous environment in subtropical China (BEF-China). The experiment was established during the period November 2008 to April 2009 and incorporates a species pool of 24 tree species across 261 plots (0.067 ha each) and a broad richness gradient with 1–24 species per plot. Annual growth rates of tree height, stem diameter and crown width for 6723 saplings of 24 species in the third year after establishment were used as response variables. We analyzed the effects of initial size, local abiotic site conditions and local neighborhood on growth performance using mixed effects models. Initial size, local topographic (aspect, slope, curvature, elevation) and edaphic variables (total nitrogen, C/N ratio) as well as local neighborhood variables (competition index, Shannon index) were included as fixed effects. Random effects were plot and species identity. The results showed that growth performance of tree saplings was markedly species-specific and strongly affected by initial size and local site conditions. In this early stage of the experiment, local Shannon diversity did not yet explain a significant amount of variation in sapling growth. However, the significant effect of the increasing size of neighboring trees indicated that tree–tree interactions had already occurred. A greater investment in height growth at the expense of diameter growth suggested that light intercept is the priority for tree sapling growth. This study stresses the importance of better understanding the effects of local site conditions on initial growth in mixed-species plantations.