| An field experiment was conducted to study the effects of simulated nitrogen deposition on contents of soil soluble sugar, phenolics, free amino acid and soluble organic nitrogen for one Cunninghamia lanceolata plantation (CUL), and two Cinnamomum chekiangense (CIC), and Castanopsis fabric (CAF) natural forests in Wanmulin Nature Reserve in Jianou of Fujian Province, where three nitrogen levels were designed for the experiment of CK (0kg·hm-2·yr-1),low N (30kg·hm-2·yr-1), and high N (100kg·hm-2·yr-1).The main results are summarized as follows:(1) After three months of N addition, the soil tannin contents of three forest stands decreased significantly (except HN at CUL), litter layers increased the polyphenols and tannin contents of each forest stand while decreased soluble sugar significantly. Litter layers induced a significant increase in soluble sugar and a decrease in polyphenol at LN and a significant increase in tannin at HN of each forest stand. The effects of N addition on soil free amino acid contents in each forest stand were not significant, except a significant increase in CUL at HN. Litter have induced a significant increase in soil free amino acid at HN of CUL and CAF. N addition and litter reservation almost did not make any significant difference to soil soluble organic nitrogen. Soluble organic nitrogen contents in CUL were much lower than those in CIC and CAF.(2) After3days of N addition, content of soil soluble sugar, phenolics, free amino acid and soluble organic nitrogen did not change much. Litter induced a significant decrease in soil tannin of each forest stand at LN and a significant increase of CUL and CIC at HN. The effects of N addition on soil free amino acid and soluble organic nitrogen in each forest stands were not significant. Soluble organic nitrogen contents in CUL were much lower than those in CIC and CAF. |
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