Vegetation composition, chemical element flows and their interactions in the forested riparian zone: An example from a small stream in Latvia

Riparian vegetation plays a major role in maintaining biodiversity and reducing the negative impact of nutrient leaching into aquatic ecosystems. However, the knowledge on the interactions between riparian vegetation and other environmental factors is still incomplete for planning sustainable riparian forest management. The aim of this study was to explore interactions between riparian forest ecosystem components along a small stream. Interactions between vegetation structure, chemical composition of soil and groundwater, as well as chemical element flows via litterfall and precipitation were studied in seven 50 m long transects located in the riparian forest of different characteristics along a 1.4 km river section in the northern part of Latvia. Our results showed that throughfall input of total nitrogen (TN) and potassium (K) was higher in transects with predominantly deciduous tree stands, but the concentration of TN in forest floor was higher in coniferous tree stands. At some soil layers, a positive correlation between organic soil carbon (OC) and the concentration of TN in groundwater was detected. The concentration of TN and nitrate-nitrogen (N-NO3-) in groundwater correlated positively with the deciduous tree basal area. The obtained results suggested that element flows are strongly dependent on tree species' composition and a comparatively small riparian area is able to provide diverse ecological conditions.