The Sources and Atmospheric Pathway of Phosphorus to a High Alpine Forest in Eastern Tibetan Plateau, China

Atmospheric deposition is considered as an important source of phosphorus (P) to P-limited ecosystems. The PM_2.5 samples were collected from a high alpine P-limited forest of Gongga Mountain (Mt. Gongga), eastern Tibetan Plateau from May 2015 to May 2016. Total P (TP) exhibited a higher concentration in the dry season (November to April, 96 ± 30 ng/m³) than that in the wet season (May to October, 77 ± 21 ng/m³). Source apportionment exhibited that 22% and 44% of TP in the dry season were contributed by soil dust and biomass burning, respectively. During the wet season, soil dust, biomass burning, and anthropogenic sources were estimated to contribute to 19%, 26%, and 41% of TP, respectively. Dissolved organic P (DOP) was found to be the significant fraction of total dissolved P (TDP), accounting for 65% and 53% of TDP in the dry and wet season, respectively. The significant correlations between DOP and K_BB ⁺ suggested that the soluble P originating from biomass burning was possible mainly in the form of DOP. In addition, the acidification of apatite during the transport could explain the dissolved inorganic P level in the wet season. Supposing that all the soluble P was bioavailable, the atmospheric deposition of TDP was estimated to result in a fixation of 0.1394 kg C/m²/yr, accounting for 23% of net primary productivity in a forest of Mt. Gongga. The data showed herein highlighted the importance of atmospheric dry deposition of P to the long-term fertility of high-elevation soils.