施肥对杉木林土壤酶和活性有机碳的影响

Impact of fertilization on soil organic carbon and enzyme activities in a Cunninghamia lanceolata plantation

以中亚热带地区的5年生杉木(Cunninghamia lanceolata)人工林为研究对象,探讨施肥对土壤酶活性和活性有机碳含量的影响,实验包括对照(CK)、施氮肥(200 kg N·hm^(-2)·a^(-1))、施磷肥(50 kg P·hm^(-2)·a^(-1))、施氮磷肥(200 kg N·hm^(-2)·a^(-1)和50 kg P·hm^(-2)·a^(-1))等4个处理。结果表明:在表层(0~10 cm)土壤中,施NP肥处理的土壤蔗糖酶和过氧化氢酶活性分别比CK降低了40.2%和36.5%,β-葡萄糖苷酶活性比施P肥处理降低了31.1%;亚表层(10~20 cm)土壤中,施N肥处理的脲酶活性显著低于CK;施N肥、P肥和NP肥处理的蔗糖酶活性分别比CK降低了46.9%、37.8%和42.4%;施NP肥处理的过氧化氢酶活性比施P肥处理降低了22.6%;在表层土壤中,施N肥、P肥处理的土壤水溶性有机碳含量分别比CK降低24.1%和29.4%;施NP肥处理的微生物生物量碳显著低于CK;土壤活性有机碳组分在不同土层之间差异显著,均表现为表层土壤活性有机碳含量高于亚表层土壤。相关性分析结果显示:蔗糖酶活性与硝态氮含量呈极显著负相关,表明施NP肥增加了硝态氮含量,一定程度上抑制了蔗糖酶的活性;水溶性有机碳与脲酶活性呈显著正相关,土壤微生物生物量碳与脲酶、过氧化氢酶和β-葡萄糖苷酶活性呈显著正相关。研究表明,水溶性有机碳、微生物生物量碳和土壤酶活性的降低可能会抑制土壤碳的释放,从而增加土壤碳的固定。

A fertilization experiment was conducted in a 5-year-old Chinese fir （ Cunninghamia lanceolata） plantation in Huitong, Hunan Province, China, to study effects of fertilization on soil organic carbon and enzymatic activity. In this experiment, four treatments were： no fertilization as control （CK） ; 200 kg N·hm^-2·a^-1（N） ; 50 kg P ·hm^-2·a^-1（P） ; and 200 kg N ·hm^-2·a^-1and 50 kg P ·hm^-2·a^-1（NP）. The results showed that sucrase and catalase activities in 0-10 cm soil layer were decreased in NP treatment by 40.2% and 36.5% compared to the CK treatment. In 0-10 cm soil layer, β-glucosidase activity was decreased by 31.1% in NP treatment than in P treatment. In 10-20 cm soil layer, urease activity was significantly decreased in N treatment compared with the CK. Sucrase activity in 10-20 cm soil layer was significantly decreased by 46.9%, 37.8%, and 42.4% in N, P and NP treatments, respectively. Catalase activity in 10-20 cm soil layer was decreased by 22.6% in NP treatment than in P treatment. The concentration of dissolved organic carbon in 0-10 cm soil layer was significantly decreased in the N and P treatments by 24.1% and 29.4% compared to the CK treatment, respectively. In addition,soil microbial biomass carbon in 0-10 cm layer was significantly lower in the NP treatment than in the CK treatment. The effects of fertilization on labile organic carbon were mainly found in 0- 10 cm soil layer. Labile organic carbon in 0-10 cm soil layer was higher than in 10-20 cm soil layer. Correlation analysis showed that sucrase activity had a significant negative correlation with nitrate nitrogen content, indicating that the increasing nitrate nitrogen content by NP treatment suppressed the activity of sucrase. Dissolved organic carbon was positively related to urease activi- ty. There were positive relationships between soil microbial biomass carbon and urease, catalase, 13-glucosidase activities. Our findings suggest that the release of soil carbon to the atmosphere is probably suppressed by decreasing soil microbial biomass carbon, dissolved organic carbon content and soil enzyme activities, thus enhancing the potential of carbon sequestration in forest ecosystems.