Data from: Topsoil removal through scarification improves natural regeneration in high-graded Nothofagus old-growth forests

1.High grading by removing the majority of trees with superior timber quality has led to loss of productivity and biodiversity in forests. Typically, after high grading, little attention is given to tree regeneration. Thus, undesirable understory vegetation often dominates for a long time, leading to stagnation in forest recovery and so-called arrested succession. In such settings, managing understory vegetation using topsoil removal through scarification has been proposed as a restoration tool to encourage tree regeneration. 2.We investigated the effectiveness of topsoil removal as a restoration technique in high-graded Nothofagus old-growth forests in the Chilean Andes. In these forests, high grading often leads to understories being dominated by dense thickets of native bamboo, Chusquea culeou. These understory conditions typically delay succession by preventing tree regeneration. 3.T-tests were used to compare vegetation development in areas with topsoil removal against those without. Non-parametric multiplicative regression (NPMR) was used to investigate which environmental variables were mainly related to regeneration of different plant groups (short and long-lived early and late-seral tree species) and C. culeou abundance in areas with and without topsoil removal. 4.Topsoil removal improved the regeneration of early-seral tree species and constrained C. culeou. In areas without topsoil scarification, higher abundances of C. culeou were reflected in a higher transmitted radiation and litter cover. In these areas, the presence of early-seral tree species was related to higher soil water content and transmitted radiation. However, topsoil removal altered these response patterns for early-seral trees. For instance, the interaction between higher soil water content and more exposed mineral soil was reflected in a higher likelihood of finding early-seral tree seedlings. 5.Synthesis and applications. Topsoil removal was a successful restoration tool for overcoming arrested succession in Nothofagus old-growth forests in the Chilean Andes by encouraging the regeneration of early-seral trees in high-graded forests. Contrasting environmental conditions of pre- and post-topsoil removal allowed insights into the processes and mechanisms responsible for forests with arrested succession and for succession progression. This understanding provides guidance regarding the range of conditions under which topsoil removal can be used as a successful restoration practice.

1. 优质林木择伐（high grading）——即移除大部分优质用材林木——已造成森林生产力与生物多样性的双重损失。通常而言，经优质木择伐干扰后，人们对林木天然更新的关注严重不足，致使劣质林下植被长期占据群落主导地位，最终引发森林恢复停滞，即所谓的受阻演替（arrested succession）。针对此类场景，业内已提出通过划破整地（scarification）移除表层土壤以管控林下植被，作为促进林木更新的修复手段。
2. 本研究针对智利安第斯山脉受优质木择伐干扰的南山毛榉（Nothofagus）老龄原始林，探究了表层土壤移除技术作为森林修复手段的有效性。在该类森林中，优质木择伐后，林下植被常被密集丛生的本土竹种智利竹（Chusquea culeou）所主导，此类林下环境会通过阻碍林木天然更新，进而延缓群落演替进程。
3. 研究采用t检验（t-test）对比了表层土壤移除区域与未处理对照区域的植被发育动态；同时采用非参数乘性回归（Non-parametric multiplicative regression, NPMR），分析了在有/无表层土壤移除的样地中，哪些环境变量与不同植物类群（短寿命与长寿命的早期演替、晚期演替林木物种）的更新情况以及智利竹的种群丰度显著相关。
4. 结果表明，表层土壤移除可显著提升早期演替林木物种的更新能力，并抑制智利竹的种群扩张。在未进行划破整地的对照样地中，智利竹的高丰度与更高的林下透射辐射及枯落物覆盖度呈显著正相关；在此类样地中，早期演替林木物种的存在与更高的土壤含水量及林下透射辐射密切相关。然而，表层土壤移除改变了早期演替林木的上述环境响应模式：例如，较高的土壤含水量与更多裸露矿质土壤的交互作用，可显著提升早期演替林木幼苗的出现概率。
5. 综合与应用：表层土壤移除技术可通过促进受优质木择伐干扰的森林中早期演替林木的天然更新，有效克服智利安第斯山脉南山毛榉老龄原始林的受阻演替问题。表层土壤移除前后的环境条件差异，为解析受阻演替森林的形成机制与演替推进过程提供了关键研究视角。本研究结果可为表层土壤移除作为高效森林修复实践的适用条件范围提供科学指导依据。