Forest Soil and Water Biogeochemistry

For us as editors, the whole-ecosystem approach is undoubtedly the most compelling way to study forests. We do not view the forest as merely a collection of trees, but as a complex ecosystem that both influences and is influenced by the surrounding environments. There is a continuous exchange of elements with the atmosphere and—through soils—with surface waters. Accordingly, the research presented in this Special Issue addresses the broader field of biogeochemistry of forested areas, including atmospheric deposition, the chemistry and biochemistry of forest soils, and the chemistry and biochemistry of water (e.g., lakes).

The Special Issue features six papers presenting original data, highlighting the impact of diffuse pollution on soils and water, as well as examining the status of nitrogen, phosphorus, and carbon in various components of forest ecosystems—from natural forests to plantations and urban/peri-urban forests. The studies were carried out across a wide range of locations, from the Baltics, Central Europe, and the Balkans to China and Malaysia. The papers reveal biogeochemical flows through forest ecosystems and show how natural or anthropogenic forest disturbances can affect ecosystem functions and increase the risk of soil and land degradation.

Metal pollution remains an important issue, with half of the papers in this Special Issue focusing on mercury (Hg). Klavina et al. [1] examined the levels of carbon, other nutrients, and methylmercury in runoff water from eight small forest watersheds in Latvia. The disturbances of organic soils were caused by various forest management operations. This research contributes to our understanding of the impact of less-studied management operations—such as ditch cleaning—on carbon, nutrient, and methylmercury concentrations in runoff water.

Given the risks Hg pollution poses to natural ecosystems, the study from the Czech Republic by Pecina et al. [2] evaluates the vertical distribution of mercury in forest soils and its transfer to edible mushrooms in mature Norway spruce and European beech forests, in relation to tree species. The content of Hg in soil and its interactions across the soil–tree–mushroom pathway help explain potential differences in Hg accumulation. Notably, foraging for edible mushrooms in forests holds special significance for people in the Czech Republic.

Diffuse pollution and ecological risk assessment in soil and water in two Serbian Special Nature Reserves—nominated as potential Natura 2000 areas—were analyzed by Caković et al. [3]. Their analyses identified diffuse water pollution from agriculture as one of the major factors contributing to contamination in the lakes. They highlighted the areas with the highest pollution and assessed the environmental risks posed by phosphorus, nitrogen, and the accumulation of heavy metals (Zn, Cu, Pb, Cr, Ni, Mn, Cd, and Hg).

Another study from the Balkans assessed soil physical and chemical properties among urban and peri-urban forests. Enescu et al. [4] demonstrated the impact of rapid urbanization (influence of potential toxic elements) on changes in soil properties within the metropolitan area of Brasov, Romania. The study is especially relevant in light of the EU Soil Strategy, which outlines a framework and concrete measures to protect and restore soil health.

Yang and Luo [5] examined nitrogen and phosphorus distribution and their relationship in soils under Chinese fir plantations of different ages, as well as in different organs of Chinese fir. Their analysis of nutrient status offers insight but only partially explains the balance of nutrients within the plant–soil ecosystem. In a related study from Malaysia, Hamad-Sheip et al. [6] explored the effects of the Acacia mangium canopy on the physicochemical characteristics and nutrient concentrations in the soil.

We would like to thank all the authors for their contributions to these important topics. Understanding biogeochemical cycles across ecosystems is essential for addressing today’s environmental challenges—not only global climate change but also anthropogenic pollution. We therefore believe that this Special Issue of Forests will not be the last to explore such a vital topic.