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

Resumen

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

Design/methodology/approach: Twenty-five grams of soil from an Abies religiosa forest in the Sierra Nevada were incubated with increasing concentrations of lignin from leaf litter and branches, at 60% humidity and 35 °C. CO₂ was captured in a 0.5 N NaOH and 0.5 N barium chloride solution, 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 using the SAS OnDemand for Academics statistical package.

Results: CO₂ emissions followed a linear model for both lignin and soil levels, with mineralization rates ranging from 12.06 mg CO₂ day⁻¹ to 33.68 mg CO₂ day⁻¹. There were highly significant differences between lignin concentrations. The interaction between plot and lignin concentration also showed statistically significant differences. A positive and highly significant relationship was found between soil nitrogen and phosphorus content.

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

Findings/conclusions: CO₂ emissions exhibit a linear and positive trend with increasing lignin concentration. Both mineralization rates and cumulative mineralization show statistically significant differences across lignin levels and total nitrogen content, as well as in the interaction between plot and lignin concentration.