Research On The Effect Of Canopy Interception Of Nitrogen And Phosphorus Sulfur In Pinus Massoniana Plantations

The interception function of atmospheric pollutants by forest vegetation had received a widespread attention. The effect of forest ecosystem interception on pollutants such as nitrogen, phosphorus and sulfur were generally accomplished by reciprocal transformation of pollutants among the aerial part (e.g. arbor forests and shrubs),surface part (e.g.herbs and litter), and underground part such as plant roots and soil (e.g. microbial) in forest ecosystem. Especially, the influence process of tree layer of aerial part on ionic contamination of rainfall is the key to pollutants intercept effects. Pinus massoniana is an important timber species in southwest Chaina, and it is also a pioneer tree species for barren hills forestations. So it has great significance for research the canopy interception effect of Pinus massoniana plantation. But till now, the impacts of forest canopy of masson pine pure or mixed forest on redistribution of rainfall and the content of N, P, S during different periods of dry season and rainy season was rarely discussed. Therefore, The penetration of rainfall, throughfall stem flow throughout one year were observed by the method of artificial observation and total phosphorus (TP), nitrate nitrogen (NO3-N), ammonium nitrogen (NH4+-N) and sulfur (S) within them were also sampled and analyzed simultaneously in 18a pure and broadleaf-conifer mixed forest and 32a pure forest of Pinus massoniana plantations in LaiFu town of Yibin city. In order to provide certain scientific basis for deeply understand the effects of canopy interception on pollutants in pine forest.The results were as follows:(1) Canopy interception and nitrogen, phosphorus, sulfur concentrations were influenced by the rainfall class. In the different age of pure masson pine forests, the rainfall, interception of throughfall and stemflow were positively correlated with the rainfall class, the higher the rainfall class was, the higher the interception was, and the interception in dry season was less than that in rain season. Rainfall interception capability of 18-year-old Masson Pine Plantation was higher than the 32-year-old Masson Pine Plantation. In the Pinus massoniana plantation mixed forests, the rainfall, interception of throughfall and stemflow were also positively correlated with the rainfall class, the higher the rainfall class was, the higher the interception was. Rainfall interception capability of mixed broadleaf-conifer forest was higher than pure masson pine, and it was reduced significantly after the litterfall of mixed forest.(2) Nitrogen, phosphorus, sulfur concentrations were influenced by the rainfall class. In the different age of pure masson pine forests and the Pinus massoniana plantation mixed forests, the result indicated that there was a significant negative correlation between nitrogen, phosphorus and sulfur concentrations with rainfall, throughfall and stemflow, and the nitrogen, phosphorus and sulfur concentrations declined significantly with rainfall increasing, during one year.The monthly average concentration of TP, NO3-N, NH4+-N, S in the dry season was significantly higher than that in rain season, and there were significantly difference between months, whereas there were no significant differences in canopy interception of total nitrogen, phosphorus and sulfur concentrations between the 32-year-old Masson Pine Plantation and the 18-year-old Masson Pine Plantation. Forest age had no significant impact on the monthly average content of P、NO3-N、NH4+-N and S in throughfall and stem flow, NO2--N、NH4+-N in mixed broadleaf-conifer forest was significantly lower than two pure pine forest. After the leaves fallen, the P^ NO3--N、NH4+-N and S’monthly average contents reduced significantly, during the rainy season. From view of total content of nitrogen, phosphorus and sulfur of throughfall and stem flow,32-year-old Masson Pine Plantation was highest and mixed broadleaf-conifer forest was lowest, total content of P、NO3-N、NH4+-N and S in throughfall through canopy decreased, during the rainy season. Forest type had a significant impact on the total N、S content of stemflow and throughfall, but no significant effect on P content.(3)In the In the different age of pure masson pine forests and the Pinus massoniana plantation mixed.forests, the mutrient inputs via rainfall were 0.028kg.hm-2 of P,0.2378 kg.hm"2 of NH4+N,0.3442 kg.hm-2 of N03--N, and 5.471 kg.hm-2 of S. Negative fluxes were found for S in the net input across three plantation canopy, showing that canopy of three plantation had certain adsorption capacity to S. The total net input of N、P and S were all negative through mixed forest, showing that’s canopy had adsorption ability in N、P and S. Therefore, the pure Pinus massoniana plantations mixing broadleaf species can improve intercept filtering ability to N、P、S.