氮磷添加对华南地区2种人工林土壤氮磷循环酶活性的影响

Effects of Long-term Nitrogen and Phosphorus Additions on Soil Enzyme Activities Related N and P Cycle in Two Plantations in South China

摘要:

为探究亚热带森林土壤中与氮、磷循环相关的土壤酶对长期氮、磷沉降的响应，在我国南方大叶相思（Acacia auriculiformis）和尾叶桉（Eucalyptus urophylla）人工林施N、P肥8 a，对土壤中磷循环酶[磷酸单脂酶（PME）和磷酸二脂酶（PDE）]和氮循环酶[β-1，4-乙酰氨基葡糖苷酶（NAG）和l-亮氨酸氨基肽酶（LAP）]的活性进行测定。结果表明，施50 kg/（hm²·a）氮肥对土壤氮和磷循环酶活性没有显著影响，施50 kg/（hm²·a）磷肥和氮磷肥[N、P各50 kg/（hm²·a）]均显著降低了土壤中PME和PDE活性，而对NAG和LAP活性没有显著影响。华南地区亚热带人工林的微生物和植物生长可能受磷限制而非氮限制，施P可以缓解P限制，这为人工林的管理与恢复提供依据。

关键词:氮沉降;磷添加;亚热带森林;土壤酶;磷限制

Abstract:

Nitrogen (N) deposition has been increasing during recent decades and may affect supply of soil nutrients and resources acquired by organism. Soil enzyme activity is an important indicator for reflecting the nutrient acquisition of plants and microorganisms. To explore the effects of long-term N and phosphorus (P) additions on activities of N and P cycling enzymes in subtropical forest soil, two plantations of Acacia auriculiformis and Eucalyptus urophylla in south China were applied N and P fertilizers for 8 years, each with 50 kg/(hm²·a), and then the activities of soil enzymes, including P-cycling enzymes[phosphomonolipase (PME) and phosphodiesterase (PDE)] and N-cycling enzymes[β-1,4-acetylglucosaminidase (NAG) and l-leucine aminopeptidase (LAP)] were measured. The results showed that N addition had no significant effect on activities of soil N and P cycling enzymes. P and N+P additions had significant negative effects on activities of PME and PDE, but which had no effect on activities of NAG and LAP. The growth of soil microorganisms and plants of subtropical plantations in south China may be limited by P rather than by N, and P fertilization could alleviate soil P limitation on plants and microorganisms. Therefore, these would provide an important insight for forest management in the future.

Key words:N deposition;P addition;Subtropical forest;Soil enzyme;P limitation