Nutrient input through occult and wet deposition into a subtropical montane cloud forest

Beiderwieden E, Schmidt A, Hsia YJ, Chang SC, Wrzesinsky T, Klemm O

Abstract

Chemical composition of fog and rain water was studied during a 47- day experimental period. The differences between the fog and rain water were found to be significantly for most analyzed ions. H+, NH4+, NO3-, and SO42- made up 85% of the total median ion concentration in fog and 84% in rain water. The total mean equivalent concentration was 15 times higher in the fog than in the rain water. The fog water samples were classified according to their air mass history. The analysis of the 120 h backward trajectory led to the identification of three advection regimes. Significant differences of ion concentrations between the respective classes were found. Air masses of class I travelled exclusively over the Pacific Ocean, class II were carried over the Philippines, and class III were advected from mainland China. The turbulent fog water deposition was determined by the means of the eddy covariance method. The total (turbulent plus gravitational) fog water fluxes ranged between +31.7 mg m(-2) s(-1) and -56.6 mg m(-2) s(-1). Fog water droplets with mean diameters between 15 mu m and 25 mu m contributed most to the liquid water flux. The sample based nutrient input was calculated on the basis of the occult and wet deposition, and the concentrations of the simultaneously collected fog and rainwater samples, respectively. The nutrient input through wet deposition was about 13 times higher than through occult deposition.