模拟氮沉降对森林土壤酚类物质和可溶性糖含量的影响

采用野外原位试验模拟氮沉降,研究其对福建建瓯万木林自然保护区杉木林(CUL)、浙江桂(CIC)和罗浮栲林(CAF)3种林分土壤多酚、单宁和可溶性糖含量的影响。每个林分设置对照(CK,0 kg/(hm2·a))、低氮(LN,30 kg/(hm2·a))和高氮(HN,100 kg/(hm2·a))3个处理。结果表明:针叶杉木林土壤多酚含量最高,单宁和可溶性糖含量最低,且均与另两个阔叶树种林分差异显著。杉木和罗浮栲林土壤多酚含量随着氮添加量的增加而显著降低,浙江桂多酚受HN处理影响不大,仅LN处理显著降低49.4%。氮沉降主要表现为降低土壤单宁含量,LN处理分别显著降低杉木林、浙江桂和罗浮栲林单宁含量43.5%、70.0%和79.5%;而HN处理仅降低阔叶林土壤单宁含量。然而,氮沉降增加土壤可溶性糖含量,与对照处理相比,LN处理分别显著增加杉木、浙江桂和罗浮栲林土壤可溶性糖48.8%、19.2%和19.8%。各林分凋落物中多酚、单宁和可溶性糖含量受氮沉降的影响不显著。

Effects of Simulated Nitrogen Deposition on Phenolics and Soluble Sugar in Forest Soils

An in situ field experiment was conducted to study the effects of simulated nitrogen deposition on soil polyphenols, tannin and soluble sugar in Cunninghamia lanceolata plantation (CUL), Cinnamomum chekiangense (CIC), and Castanopsis fabric (CAF) natural forests in Wanmulin Nature Reserve in Jianou of Fujian Province. Three nitrogen levels were installed, i.e., CK (0 kg/(hm2·a)), low N (30 kg/(hm2·a)), and high N (100 kg/(hm2·a)). The results showed that soil polyphenols was highest in CUL while lowest for tannin and soluble sugar, which all had significant difference compared to both CIC and CAF. Soil polyphenols content in CUF and CAF decreased with nitrogen deposition, and in CIC it significantly decreased by 49.4% at LN only. Soil tannin content had been significantly decreased by 43.5%, 70% and 79.5% in CUL, CIC and CAF at LN compared to CK, respectively. However, it was decreased only for broadleaf soil under HN. An increase of 48.8%, 19.2% and 19.8% was found due to nitrogen deposition for soil soluble sugar in CUL, CIC and CIC at LN, respectively. The effects of N addition on litter polyphenols, tannin and soluble sugar in 3 forest litters were not significant.