[Effects of nitrogen addition on the kinetic parameters of soil acid phosphomonoesterase in a Moso bamboo forest]. / æ°®æ·»åŠ å¯¹æ¯›ç«¹æž—åœŸå£¤é ¸æ€§ç£·é ¸å•é ¯é ¶åŠ¨åŠ›å­¦å‚æ•°çš„å½±å“.

ABSTRACT

Soil phosphatases are important in the mineralization of organophosphates and in the phosphorus (P) cycle. The kinetic mechanisms of phosphatases in response to nitrogen (N) deposition remain unclear. We carried out a field experiment with four different concentrations of N 0 g N·hm-2·a-1(control), 20 g N·hm-2·a-1(low N), 40 g N·hm-2·a-1(medium N), and 80 g N·hm-2·a-1(high N) in a subtropical Moso bamboo forest. Soil samples were then collected from 0 to 15 cm depth, after 3, 5 and 7 years of N addition. We analyzed soil chemical properties and microbial biomass. Acid phosphatase (ACP) was investigated on the basis of maximum reaction velocity (Vm), Michaelis constant (Km), and catalytic efficiency (Ka). Results showed that N addition significantly decreased soil dissolved organic carbon (DOC), available phosphorus, and organophosphate content, but significantly increased soil ammonium, nitrate-N content, and Vm. There was a significant relationship between Vm and the concentrations of available phosphorus, organophosphate, and soil DOC. In general, N addition substantially increased Ka, but did not affect Km. The Km value in the high N treatment group was higher than that in the control group after five years of N addition. Km was significantly negatively associated with both available phosphorus and organophosphate. Medium and high N treatments had stronger effects on the kinetic parameters of ACP than low N treatment. Results of variation partition analysis showed that changes in soil chemical properties, rather than microbial biomass, dominated changes in Vm(47%) and Km(33%). In summary, N addition significantly affected substrate availability in Moso bamboo forest soil and modulated soil P cycle by regulating ACP kinetic parameters (especially Vm). The study would improve the understanding of the mechanisms underlying soil microorganisms-regulated soil P cycle under N enrichment. These mechanisms would identify the important parameters for improving soil P cycling models under global change scenarios.