Mapping the global research landscape of sap flow studies in forest ecosystems: a bibliometric analysis (2000–2024)

Sap flow techniques are widely applied in forest research to examine tree water use and forest–atmosphere interactions across diverse climatic and ecological settings. Over the past two decades, the volume of sap flow–based studies has increased substantially, spanning multiple disciplines, regions, and research contexts. Despite this growth, a quantitative overview of how sap flow research has evolved in terms of publication trends, thematic focus, and collaboration patterns remains limited. This study presents a bibliometric analysis of global sap flow research in forest ecosystems published between 2000 and 2024, based on 1,989 peer-reviewed journal articles and reviews indexed in the Scopus database. Using bibliometric performance indicators and science-mapping techniques implemented through the bibliometrix package and VOSviewer, we analysed temporal publication dynamics, citation structures, leading journals and authors, international collaboration networks, keyword co-occurrence patterns, and thematic evolution. The results show a steady increase in publication output after 2010, accompanied by expanding international collaboration and diversification of research themes. Keywords related to established sap flow measurement approaches, particularly thermal dissipation and heat-pulse methods, remain consistently prominent throughout the study period. At the same time, increasing co-occurrence of sap flow with terms associated with drought, soil moisture, atmospheric demand, and climate variability reflects a broadening research emphasis in recent years. Co-citation and thematic analyses reveal a well-defined research structure linking methodological foundations with ecohydrological and climate-oriented research context. These findings provide an objective overview of research trends and emerging thematic directions.