Seedling planting plays a key role in active forest restoration and regeneration of managed stands. Plant attributes at outplanting can determine tree seedling survival and consequently early success of forest plantations. Although many studies show that large seedlings of the same age within a species have higher survival than small ones, others report the opposite. This may be due to differences in environmental conditions at the planting site and in the inherent functional characteristics of species. Here, we conducted a global-scale meta-analysis to evaluate the effect of seedling size on early outplanting survival. Our meta-analysis covered 86 tree species and 142 planting locations distributed worldwide. We also assessed whether planting site aridity and key plant functional traits related to abiotic and biotic stress resistance and growth capacity, namely specific leaf area and wood density, modulate this effect. Planting large seedlings within a species consistently increases survival in forest plantations worldwide. Species’ functional traits modulate the magnitude of the positive seedling size–outplanting survival relationship, showing contrasting effects due to aridity and between angiosperms and gymnosperms. For angiosperms planted in arid/semiarid sites and gymnosperms in subhumid/humid sites the magnitude of the positive effect of seedling size on survival was maximized in species with low specific leaf area and high wood density, characteristics linked to high stress resistance and slow growth. By contrast, high specific leaf area and low wood density maximized the positive effect of seedling size on survival for angiosperms planted in subhumid/humid sites. Results have key implications for implementing forest plantations globally, especially for adjusting nursery cultivation to species’ functional characteristics and planting site aridity. Nursery cultivation should promote large seedlings, especially for stress sensitive angiosperms planted in humid sites and for stress-resistant species planted in dry sites.

中文翻译：

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气候和物种抗逆性调节全球森林恢复中大苗的更高存活率

苗木种植在积极的森林恢复和管理林分更新中起着关键作用。外植时的植物属性可以决定树木幼苗的存活率，从而决定森林种植的早期成功。尽管许多研究表明一个物种内相同年龄的大幼苗比小幼苗存活率更高，但其他研究则相反。这可能是由于种植地点的环境条件和物种固有的功能特征不同。在这里，我们进行了一项全球范围的荟萃分析，以评估幼苗大小对早期外植成活率的影响。我们的荟萃分析涵盖了分布于全球的 86 种树种和 142 个种植地点。我们还评估了种植地点的干旱和与非生物和生物胁迫抗性和生长能力相关的关键植物功能特性，即比叶面积和木材密度，是否会调节这种影响。在一个物种内种植大苗会持续提高全球森林种植园的存活率。物种的功能性状调节着幼苗大小-外植成活率正相关的大小，显示出由于干旱以及被子植物和裸子植物之间的对比效应。对于种植在干旱/半干旱地区的被子植物和半湿润/湿润地区的裸子植物，幼苗大小对存活的积极影响在比叶面积低和木材密度高的物种中最大化，这些特性与高抗逆性和生长缓慢有关。相比之下，高比叶面积和低木材密度最大限度地提高了幼苗大小对种植在半湿润/潮湿地区的被子植物存活率的积极影响。结果对在全球范围内实施人工林具有重要意义，尤其是根据物种的功能特征和种植地点的干旱调整苗圃栽培。苗圃栽培应促进大苗，特别是种植在潮湿地区的胁迫敏感被子植物和种植在干旱地区的抗逆品种。