A new method for estimation of dry deposition of particles based on throughfall measurements in a forest edge

Throughfall measurements are very often used to calculate the atmospheric input to ecosystems. Such attempts are normally complicated by canopy interaction processes which are difficult to assess. This study presents an approach to calculate dry deposition and canopy leaching of Ca²⁺, Mg²⁺ and K⁺ to forests. The calculations are based on throughfall measurements in a forest edge of a spruce stand and by use of Na⁺ as a model substance for dry deposition of particles. This ‘forest edge approach’ is compared with an approach based on equal Na⁺ to base cation ratios in wet and dry deposition (‘wet/dry ratio approach’), which has been widely used in the literature. Our calculations show that the wet/dry ratio approach may overestimate the dry deposition of Ca²⁺, Mg²⁺ and K⁺ by up to 100% and leaching will correspondingly be underestimated. The assumptions underlying the different approaches and the use of throughfall measurements to estimate dry deposition are discussed and it is suggested that throughfall measurements in forest edges may be a valuable improvement to studies of atmospheric deposition in forests.