Soil phosphorus fractionation as a tool for monitoring dust phosphorus signature underneath a Blue Pine (Pinus wallichiana) canopy in a Temperate Forest

Aim of the study: This study aims (i) to monitor the amount of dust deposition during dry season in the moist temperate forest; (ii) to study nature of P fractions in the dust samples falling on the trees in the region; (iii) to study soil P fractions as influenced by the processes of throughfall and stemflow of a Blue Pine (Pinus wallichiana) canopy and to finger print the contribution of dust towards P input in the temperate forest ecosystem. Area of study: The site used for the collection of soil samples was situated at an elevation of 6900 feet above sea level (temperate forest in Himalaya region) in the Thandani area national forest located in the north west of Pakistan. Material and methods: For soil sampling and processing, three forest sites with three old tree plants per site were selected at approximately leveled plain for surface soil sampling. Two dust samples were collected and analyzed for different physicochemical properties along with different P fractions. First dust sample was collected from a site situated at an elevation of 4000 feet and second one was collected from an elevation of 6500 feet above sea levels. Modified Hedley procedure for the fractionation of P in the dust and soil samples were used. Main results: The input of dust was 43 and 20 kg ha(-1) during drier months of the year (September-June) at lower and higher elevation sites respectively, and the dust from lower elevation site had relative more all P fractions than the other dust sample. However, HCl-P-i fraction was dominant in both samples. Both labile (water plus NaHCO3) and non-labile (NaOH plus HCl) inorganic P (P-i) fractions were significantly increased in the surface soil by both stemflow and throughfall compared to the open field soil. The buildup of NaOH and HCl-P-i pools in soils underneath the canopy might prove useful in fingerprinting the contribution of atmospheric dust towards P cycling in this temperate forest. Research highlights: The role of dust in the cycling of P in temperate forest in Himalaya region.