# The Role of Trees in Sand Dune Rehabilitation: Insights from Global Experiences
## 2 Materials and Methods  
We started this study with a bibliometric analysis intended to evaluate the global scientific research about the use of trees on sand dunes between 1995-2024. We have used the Science Citation Index Expanded (SCI-Expanded) from the Web of Science database,complemented by Scopus. This has allowed us to identify relevant publications and to test different search strategies. After testing different keywords, we have selected the phrase \"trees on sand dunes\" as our main search term.  
We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, which provide a standardized framework to enhance the transparency and completeness of systematic reviews [39]. The PRISMA statement, originally published in 2009, is designed to help authors clearly report the rationale, methodology, and findings of their reviews. In line with open science practices, we have made our database, including the full list of included and excluded studies, available on the Open Science Framework (OSF); our registration number is osf.io/ruz7y. The OSF is a free and open platform that supports the sharing of research materials to promote transparency, collaboration, and reproducibility in scientific research [40].  
The selection process of the papers included in this review is illustrated in Figure 1. In total, 461 publications were retrieved from Scopus and 476 from Web of Science, accounting for 937 publications. After removing 301 duplicates, 636 unique records remained. Titles and abstracts of these records were screened based on the following inclusion criteria: studies published in English, and articles whose title and/or abstract referred to the specific topic. The following exclusion criteria were adopted: papers not in English, previous reviews, non-scientific articles, non-published materials, and letters to editors were excluded. After this manually performed screening, 57 bibliographic sources were excluded, and 1 full-paper was not retrieved. The remaining 578 full-text records were deeply inspected. A total of 148 articles were excluded because they were irrelevant to the topic and another 8 were excluded because they did not have abstracts. Finally, 422 papers were included in this systematic review (Figure 1). The overlap between the databases was substantial: 301 articles (approximately 32%) were identified as duplicates found in both Scopus and Web of Science. This indicates a significant but not complete overlap between the two sources, supporting the decision to include both databases to ensure comprehensive coverage.  
Figure 1: Selection process of the eligible reports based on the PRISMA 2020 flow diagram.  
As such, our bibliometric approach focused on nine key aspects: (1) types of publications, (2) research domains, (3) year of publication, (4) countries of publications, (5) authors, (6) institutions, (7) journals, (8) publishers, (9) keywords. We processed the obtained data with the Web of Science Core tools (version 5.35, Clarivate), Scopus, Excel (version 2024), and Geochart [41; 42; 43; 44]. In addition, we used VOSviewer (version 1.6.20) to realize visual maps and clusters [45].  
In the second stage of our analysis, we used a more traditional approach. This took the form of a literature review that allowed us to conduct a more detailed analysis of the 422 selected articles. Our findings were then grouped into four research clusters: (1) Tree species used in the afforestation of sand dunes, (2) Local results from all over the world, (3) Factors that influence the success of afforestation works from sand dunes, and (4) The effects of afforestation on sand dunes. Figure 2 showcases our methodology.