A comparison of lignin-degrading enzyme activities in forest floor layers across a global climatic gradient

Abstract

Rapid litter turnover in tropical forests and during summer seasons might be due to increases in ligninolytic enzyme activities during warmer periods. We compared ligninolytic enzyme activity [lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac)] in the organic layers of forest soils across a global climate gradient. As expected, MnP activities in fresh litter layers increased with increasing air temperature. Litter Mn/lignin ratios correlate positively with MnP activity and more rapid litter turnover in warmer climates. In contrast, LiP and Lac activities are regulated by site-specific conditions. Lac activity is commonly observed in less acidic fresh litter layers, while LiP activity localizes in acidified and lignin-rich deeper organic layers. The widespread occurrence of MnP and an increase in MnP activities in warmer climates support efficient lignin degradation in the tropics and during summer seasons. High Mn/lignin ratios in fresh litter could be an indicator of lignin degradability by MnP-producing fungi across global climate gradients.