Impacts of felling and forest road construction on surface water quality in a managed forested catchment in Latvia

While forests are generally regarded as beneficial for water quality, forest management can significantly impact water quality, even if sustainable forest management practices are applied. Fellings alter water balance and nutrient cycling, while forest roads with impermeable surfaces fragment ecosystems and enhance runoff. Road construction often requires extensive landscape modification and material relocation, which increases substance leaching and erosion. In the present study, water quality parameters and nutrient export were monitored over eight years (2016–2023) in a forested catchment (2212 ha) and its sub-catchments. During this period, 15.8 km of forest roads were constructed, and fellings occurred across 18.8% of the catchment. Fellings increased nitrogen compound concentrations and export, with effects persisting for four-five years. Runoff patterns strongly controlled the export of total nitrogen, calcium, and dissolved organic carbon. The onset of fellings and higher felling intensities raised total suspended solids levels, though high variability masked statistical significance. Calcium and potassium concentrations also increased during periods of more intense felling, though their export patterns closely followed runoff dynamics. Road construction increased calcium and total suspended solids concentrations.