Gan Jelaine L, Grainger Matthew J, Shirley Mark David Foster, Davis Sheena, Watson Molly, Dube Shreya, Pfeifer Marion
School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, UK.
Institute of Biology, College of Science, University of the Philippines Diliman, Quezon City, Philippines.
Environ Evid. 2025 Jun 14;14(1):10. doi: 10.1186/s13750-025-00363-8.
Assisted Natural Regeneration (ANR) is an increasingly popular cost-effective approach to restore forests for climate change mitigation and biodiversity conservation. One ANR strategy is the use of perches to attract avian seed dispersers to degraded landscapes for increased seed supply and seedling establishment. This systematic review sought to determine the effectiveness of artificial, semi-natural, and natural perches in promoting natural forest regeneration, specifically in driving four outcomes: seed richness, seed density, seedling richness, and seedling density.
In September 2023, we searched for studies in eight bibliographic sources, which include an organizational library and a web-based search engine, using a refined search string in English. After deduplication, we conducted double screening at title and abstract, then at full text level to check for eligibility (e.g., compared perches versus control). The final list of studies underwent critical appraisal based on risk of bias and method validity, then data extraction. We used Hedges' g as our effect size and fitted each outcome in a three-level meta-regression model. We also tested the effect of matrix type, bioregion, and precipitation variation as modifiers, and conducted sensitivity analysis based on risk of bias and method validity.
After screening, we accepted a total of 396 studies in 79 articles for the review. The majority of these studies examined seed (49%) and seedling density (28%) outcomes over richness, using mostly natural perches (68%) and, to a lesser frequency, artificial and semi-natural perches. Most studies that included distance to forest edge as a factor reported no effects (n = 68). We then analysed 333 studies in a meta-analysis. Results showed that natural perches had overall positive effects in increasing seed and seedling density and richness, while artificial and semi-natural perches were effective only for seed outcomes. We found high heterogeneity in our models, with perch effectiveness affected by matrix type, bioregion, precipitation variation, method specificity, as well as study quality. In general, perches showed robust positive effects in shrublands and grasslands in tropical, subtropical, and mediterranean biomes.
The use of perches can be an effective ANR strategy to increase seed rain and seedling establishment in a variety of degraded landscapes. We recommend that natural perches be preserved in the matrix, but in areas lacking these natural features, to explore the use of artificial or semi-natural perches to increase seed rain and follow it up with additional treatments, such as soil amelioration and weeding, to improve seedling establishment. Due to insufficient data, we could not analyse the effect of distance to forest edge as a moderator in our meta-regression models. This gap can be addressed by examining perches placed at increasing distances from the edge and having better data sharing practices. We also emphasize a need for improving the quality of reporting, such as variances and detailed methodologies, in order for research to be useful for systematic reviews and meta-analysis.
辅助自然更新（ANR）是一种越来越受欢迎的具有成本效益的方法，用于恢复森林以缓解气候变化和保护生物多样性。一种ANR策略是使用栖木来吸引鸟类种子传播者到退化的景观中，以增加种子供应和幼苗定植。本系统评价旨在确定人工、半自然和自然栖木在促进天然森林更新方面的有效性，特别是在推动四个结果方面：种子丰富度、种子密度、幼苗丰富度和幼苗密度。
2023年9月，我们使用英文的精确搜索字符串在八个文献来源中搜索研究，这些来源包括一个组织图书馆和一个基于网络的搜索引擎。在去重后，我们在标题和摘要层面进行了双重筛选，然后在全文层面检查是否符合条件（例如，比较栖木与对照）。最终的研究列表根据偏倚风险和方法有效性进行了严格评估，然后进行了数据提取。我们使用Hedges' g作为效应量，并将每个结果拟合到一个三级元回归模型中。我们还测试了基质类型、生物区域和降水变化作为调节因素的影响，并基于偏倚风险和方法有效性进行了敏感性分析。
筛选后，我们共接受了79篇文章中的396项研究进行综述。这些研究中的大多数考察了种子（49%）和幼苗密度（28%）结果而非丰富度，大多使用自然栖木（68%），较少使用人工和半自然栖木。大多数将到森林边缘的距离作为一个因素纳入的研究报告没有影响（n = 68）。然后我们在一项元分析中分析了333项研究。结果表明，自然栖木在增加种子和幼苗密度及丰富度方面总体具有积极影响，而人工和半自然栖木仅对种子结果有效。我们发现我们的模型中存在高度异质性，栖木的有效性受到基质类型、生物区域、降水变化、方法特异性以及研究质量的影响。一般来说，栖木在热带、亚热带和地中海生物群落的灌木林和草原中显示出强劲的积极影响。
使用栖木可以是一种有效的ANR策略，以增加各种退化景观中的种子雨和幼苗定植。我们建议在基质中保留自然栖木，但在缺乏这些自然特征的地区，探索使用人工或半自然栖木来增加种子雨，并随后进行额外的处理，如土壤改良和除草，以改善幼苗定植。由于数据不足，我们无法在元回归模型中分析到森林边缘的距离作为调节因素的影响。通过检查放置在离边缘越来越远的栖木并采用更好的数据共享做法，可以解决这一差距。我们还强调需要提高报告质量，如方差和详细方法，以便研究对系统评价和元分析有用。
