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

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