The effect of lignin and nitrogen on the decomposition of litter in nutrient-poor ecosystems: a theoretical approach

Abstract

A model is developed to study the dynamics of carbon and nitrogen in decomposing substrates that contain different organic compounds: (i) lignin, (ii) carbohydrates "masked" by lignin compounds, and (iii) free carbohydrates. Under conditions both of carbon limitation and of nitrogen limitation the model predicts a negative linear relationship between lignin concentration and rate of mass loss. The coefficients of this relationship are determined by microbial properties and by the ratio (ac) between the amount of "masked" carbohydrates and the amount of lignin in the litter. Litter decomposition data of three different ecosystems are used to obtain estimates of the ratio ac. The calculated values are in the same range as values estimated on the basis of the course of the cellulose/lignin ratio during the decomposition process. When nitrogen limits microbial growth, the model predicts a positive linear relationship between rate of mass loss and initial lignin concentration.