Global Trends and Research Gaps in Surface Biomass, Water Retention and Soil Erosion in European Temperate Forest: A Bibliometric Analysis (2005–2025)

Surface biomass, including litter, organic matter and ground vegetation, plays a very important role in forest ecosystems for regulating water retention and soil erosion. At the global and European temperate forest scale, no bibliometric analysis has previously been conducted, even though the scientific interest has been growing. This bibliometric analysis studied 1189 global and 178 European temperate forest articles retrieved from Scopus from 2005 to 2025 using RStudio (bibliometrix) and VOSviewer. The global output grew at an annual growth rate of almost 20.83%, coinciding with the Paris Agreement 2015 and the European Green Deal 2019 that may have brought scientific attention to climate change, hydrological process, forest ecosystem services and sustainable forest management, leading to the increases, while European research accounted for only 14.9% of global output and was mainly influenced by Mediterranean fire-related research, which limits its direct applicability to central European forest conditions. China and the USA dominated the global research output. Despite being the country with 30% of its area covered with forests, no Polish institution appeared in the top 10 contributors in both the global and European datasets. Thematic analysis showed that infiltration and surface runoff are poorly integrated with forest management and climate change research. Litter and soil organic carbon appeared as an emerging topic in the European Temperate Forest dataset. Three dominant tree species of the central European temperate forest, Scots Pine (Pinus sylvestris L.), Norway Spruce (Picea abies), and European aspen (Populus tremula L.), were each mentioned just once in 178 European publications, indicating the need for species-specific research about water retention and erosion susceptibility and surface runoff. This bibliometric analysis identified the significant species-specific, institutional, and regional knowledge gaps in European temperate forest research, most importantly, for the central European ecosystem and the dominant Polish forest. The study highlighted the limited incorporation of hydrological processes with forest management and climate adaptation strategies. Future research direction should focus on long-term field research analysing biomass changes, water retention and erosion susceptibility in the European temperate forest ecosystem, while promoting stronger international research collaborations.