Effect of lignin concentration on CO2 emissions in forest soils of the Sierra Nevada

Abstract

Objective: To evaluate the effect of the concentration of lignin contained in leaf litter on the mineralization rate and accumulated mineralization in forest soils.

Design/methodology/approach: 25 g of soil from the Abies religiosa forest in the Sierra Nevada were incubated with increasing concentrations of leaf litter and branch lignin, with a humidity of 60 % at 35°C. CO₂ was recovered in a solution of 0.5 N NaOH and 0.5 N barium chloride, and titrated with 0.5 N H₂SO₄. A completely randomized experimental design with two factors was used. Mineralization rate and cumulative mineralization were determined. Linear regression analysis and ANOVA were performed with the statistical package SAS OnDemand for Academics.

Results: CO₂ emissions fit a linear model for lignin and soil levels, with mineralization rates ranging from 12.06 mg day^-1 of CO₂ to 33.68 mg day^-1 of CO₂. There are highly significant differences between lignin levels. The Site-Lignin Concentration interaction shows statistical differences. There is a positive and highly significant relationship between soil nitrogen and phosphorus.

Limitations on study/implications: It is suggested to consider the climate factor throughout the year as a source of variation in CO₂ emissions and its interaction with the quality of the leaf litter, as well as microbial activity.

Findings/conclusions: CO₂ emissions show a linear and positive trend with lignin concentration. Mineralization rates and accumulated minerali-zation show statistical differences in lignin levels, as well as in total nitrogen content, as well as in the interaction between sites and lignin concentration.