Nutrient Fluxes in Rainfall, Throughfall, and Stemflow in Pinus densata Natural Forest of Tibetan Plateau

This study aimed to measure the chemical components of the rainfall, throughfall, and stemflow, and to evaluate the characteristics of the solutes in the Pinus densata forest in Tibetan plateau. Rainfall, throughfall, and stemflow were monitored from March 2011 to November 2013. The pH and concentrations of NH4+-N, NO3--N; SO42--S; Cl-, Na+,K+, Ca2+, and Mg2+ were measured. Depositions of rainfall, throughfall, and stemflow, and canopy budget of different solutes were calculated. There were significant correlations among throughfall, stemflow, and rainfall. The monthly pH of the three forms of water was significantly different between each other. The annual average concentrations of the solutes showed the following order: stemflow> throughfall> rainfall. The annual mean rainfall depositions of rainfall, throughfall, and stemflow were 104.20, 175.54, and 16.60 kg ha(-1).per year, respectively. Annual net throughfall and stemflow deposit was 87.94 kg ha(-1).per year. The main source of NH4+ N and NH3- N came from rainfall while SO42- -S; Cl-, Na+, K+, Ca2+, and Mg2+ input mainly came from the throughfall. Settlement of NH4+-N was close to the global average, NO3--N; SO42--S; Cl-, K+, Mg2+ were above the global average, and Na+ and Ca2+ were slightly lower than the global average. The rainfall may have the potential to supply nutrients in the P. densata forest in the Tibetan plateau.