Effect of Canopy Interception on Nitrogen, Phosphorus and Sulfur in Pinus Massoniana Plantations
The penetration of rainfall,throughfall and stemflow during the rainy season were observed in Pinus massoniana plantations of 18,32-years-old and mixed broadleaf-conifer forest at Laifu town of Yibin city,and its total phosphorus(TP),nitrate(NO3--N),ammonium(NH4+-N),sulfur(S) were sampled and analyzed simultaneously.The results showed that:Rainfall interception capability of mixed broadleaf-conifer forest was higher than that of pure masson pine,and it reduced significantly after the litterfall of mixed forest.Forest age had no significant impact on the monthly average content of P,NO3--N,NH4+-N and S in throughfall and stemflow,NO3--N,NH4+-N in mixed broadleaf-conifer forest was significantly lower than that in two pure masson pine forest.After the leaves fallen,the P,NO3--N,NH4+-N and S' monthly average contents reduced significantly.From view of total content of nitrogen,phosphorus and sulfur of throughfall and stemflow,32-year-old masson pine plantation was highest and mixed broadleaf-conifer forest was lowest,the content of TP,NO3--N,NH4+-N and S in throughfall through canopy decreased.Forest type had a significant impact on the TN,S content of stemflow and throughfall,but no significant effect on P content.Nutrient inputs via rainfall were 0.028 kg/hm2 of P,0.238 kg/hm2 of NH4+-N,0.344 kg/hm2 of NO3--N,and 5.471 kg/hm2 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 which canopy had adsorption ability in N,P and S.Therefore,the pure Pinus massoniana plantations mixing broadleaf species could improve intercept filtering ability to N,P and S.
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