常绿阔叶林改造为板栗林对土壤氮磷钾库及酶活性的影响

研究天然林改造为人工林对土壤养分库的影响,对于森林的可持续经营具有非常重要的意义。论文为探明天然常绿阔叶林改造为板栗林对土壤氮磷钾库及酶活性的影响,在浙江省临安市三口镇采集了相邻的天然常绿阔叶林和板栗林（板栗林由天然常绿阔叶林改造而来）的表层（0~20 cm）与亚表层（20~40 cm）土壤,测定土壤不同形态氮磷钾素和蔗糖酶、脲酶、过氧化氢酶和酸性磷酸酶的活性。结果表明：表层和亚表层土壤pH值、水溶性有机氮（WSON）和微生物量氮（MBN）均显著降低,而铵态氮和硝态氮含量均显著增加（P < 0.05）;表层土壤全氮含量显著增加,而亚表层土壤全氮含量无显著变化;表层土壤树脂提取态磷（Resin-P_i）、碳酸氢钠提取态无机磷（NaHCO₃-P_i）、氢氧化钠提取态无机磷（NaOH-P_i）、盐酸提取态磷（HCl-P_i）和残余态磷（Residual-P）含量分别增加了61.4%、53.5%、19.2%、55.1%和25.3%,亚表层土壤Resin-P_i、NaHCO₃-P_i、HCl-P_i和Residual-P含量分别增加了64.6%、61.2%、13.7%和17.3%;而表层土壤碳酸氢钠提取态有机磷（NaHCO₃-P_o）和氢氧化钠提取态有机磷（NaOH-P_o）含量分别下降了24.8%和18.3%,亚表层土壤NaHCO₃-P_o和NaOH-P_o含量分别下降了20.5%和7.7%;表层土壤的速效钾、缓效钾、矿物态钾和全钾含量均显著增加,亚表层土壤速效钾、缓效钾含量显著增加,而矿物态钾和全钾无显著变化;表层土壤蔗糖酶、脲酶、过氧化氢酶和酸性磷酸酶活性显著下降,亚表层土壤脲酶和酸性磷酸酶活性显著下降（P < 0.05）。综上,上述林分转变对土壤无机氮磷钾库具有正面效应,而对土壤有机氮磷钾库与酶活性具有负面效应。

Effects of Converting Evergreen Broad-leaved Forests to Chinese Chestnut Forests on Soil Nitrogen,Phosphorous and Potassium Pools and Enzyme Activity

Study on the effects of converting natural forests to plantations on soil nutrient pools has very important significance for sustainable management of forests. In order to investigate the effects of converting evergreen broad-leaved forest (EBLF) to Chinese chestnut forest (MBF) on nitrogen (N), phosphorous (P), potassium (K) pools and enzyme activity in soil, we collected soil samples at the soil surface (0-20 cm) and subsurface layers (20-40 cm) in EBLF and adjacent MBF that was converted from EBLF in Sankou Township, Lin’an City, Zhejiang Province. Different forms of N, P, K and soil invertase, urease, catalase and acid phosphatase activity of the soil sample were determined. The results showed that soil pH, WSON and MBN concentrations decreased significantly and the NH4+-N and NO3--N concentrations increased significantly in both surface and subsurface layers after converting EBLF to MBF. The total N concentrations in the surface layer increased significantly, but those in the subsurface layer had no significant change after the conversion. The Resin-P_i, NaHCO₃-P_i, NaOH-P_i, HCl-P_i and Residual-P concentrations in the surface layer increased 61.4%, 53.5%, 19.2%, 55.1% and 25.3% respectively. Resin-P_i, NaHCO₃-P_i, HCl-P_i and Residual-P concentrations in the subsurface layer increased 64.6%, 61.2%, 13.7% and 17.3% respectively. The NaHCO₃-P_o and NaOH-P_o concentrations in the soil surface layer decreased 24.8% and 18.3% respectively, while those in the subsurface layer decreased 20.5% and 7.7% respectively after the conversion. The available K, slowly available K, mineral K and total K concentrations in the soil surface layer increased significantly and the available K and slowly available K concentrations in the subsurface layer also increased, but the mineral K and total K concentrations in the subsurface layer had no significant changes after the conversion. Soil invertase, urease, catalase and acid phosphatase activities in the surface layer decreased significantly; urease and acid phosphatase activities in the subsurface layer decreased significantly, but invertase and catalase activities had no significant decrease after the conversion (P < 0.05). To conclude, this forest type conversion has positive effects on soil inorganic N, P and K pools, while has negative effects on soil organic N, P and K pools and enzyme activities.