Data from: Nurse-based restoration of degraded tropical forests with tussock grasses: experimental support from the Andean cloud forest

1. The degradation of the Andean cloud forest raises strong biological conservation issues and threatens the sustainability of a crucial water resource. The idea that nurse-based restoration can accelerate the recovery of these forests is underexplored, despite its promise as a restoration technique. Recent conceptual models predict that facilitation among plants may be an important mechanism, but there is a lack of strong empirical support. We gathered experimental data to test this prediction and explore the relevance of using nurse-based forest restoration in these environments. 2. A 20-month factorial experimental design in the Andean tropical cloud forest was established. We measured the survival and estimated the biomass production of transplanted seedlings of a keystone canopy forest species, Ceroxylon echinulatum (Arecaceae), in a deforested area in the presence/absence of herbivory, a potential nurse plant (the tussock grass Setaria sphacelata, Poaceae), and artificial shade. 3. The joint effects of deforestation and herbivory led to the death of all seedlings, whereas most seedlings survived in the adjacent forest, which was used as the control. The presence of nurse plants led to significantly higher survival and growth of Ceroxylon seedlings throughout the experiment, regardless of herbivore presence. 4. The nurse effects were explained by a reduction of the relative abiotic stress experienced by the seedlings outside the forest, i.e. the consistently decreasing maximum vapour pressure deficit. Furthermore, nurse tussocks delayed and reduced the effects of herbivory by offering physical protection and a refuge for seedlings against detection by herbivores. However, the effects of herbivory and abiotic stress on facilitation were not additive. 5. Synthesis and applications: Facilitation in degraded cloud forest can be intense as soon as the beneficiary plants are driven away from their physiological optimum (relative abiotic stress) and/or are confronted by herbivory. Using pre-established exotic tussock grasses as a nurse-based restoration technique in degraded cloud forest is a low-cost, non-detrimental (to biodiversity) option, especially in the absence of nurse trees and shrubs. The success of this method requires transplanting seedlings at the base of tussocks.1. 安第斯云雾林（Andean cloud forest）的退化引发了严峻的生物保护问题，同时威胁到关键水资源的可持续性。尽管基于保育植物的修复（nurse-based restoration）技术颇具应用前景，但针对其可加速这类森林恢复的设想，相关研究仍有待深入探索。现有概念模型预测，植物间的促进作用或许是关键机制之一，但目前仍缺乏强有力的实证支撑。本研究通过收集实验数据，对该预测进行验证，并探究基于保育植物的森林修复技术在这类生境中的应用可行性。 2. 本研究在安第斯热带云雾林中设置了为期20个月的析因实验设计。我们在一片已遭砍伐的区域中，针对植食作用存在/缺失、潜在保育植物（丛生禾草：Setaria sphacelata，禾本科（Poaceae））以及人工遮阴这三个变量，测定了关键冠层物种棘茎蜡椰（Ceroxylon echinulatum，棕榈科（Arecaceae））移栽幼苗的存活率，并估算其生物量生产情况。 3. 砍伐迹地与植食作用的联合效应导致所有幼苗全部死亡，而作为对照的相邻原生森林中，绝大多数幼苗得以存活。整个实验过程中，无论植食作用是否存在，保育植物的存在均可显著提升棘茎蜡椰幼苗的存活率与生长速率。 4. 保育植物的促进效应可归因于：森林外生境中幼苗所承受的相对非生物胁迫（abiotic stress）得以缓解，具体表现为最大水汽压亏缺（vapour pressure deficit）持续降低。此外，保育丛生禾草可为幼苗提供物理庇护与躲避植食者探测的避难所，从而延缓并削弱植食作用的负面影响。不过，植食作用与非生物胁迫对植物促进作用的影响并非叠加效应。 5. 总结与应用：当受益植物脱离其生理最适条件（即承受相对非生物胁迫）且/或遭遇植食作用时，退化云雾林中的植物促进作用可表现得极为显著。在退化安第斯云雾林中，利用预先定植的外来丛生禾草作为基于保育植物的修复技术，是一种低成本、对生物多样性无损害的修复方案，尤其适用于缺乏原生保育乔灌木的生境。该方法的成功实施需将幼苗移栽至丛生禾草的基部。