No abstract

No abstract

No abstract

Lignin is an abundant and complex plant polymer that may limit litter decomposition, yet lignin is sometimes a minor constituent of soil organic carbon (SOC). Accounting for diversity in soil characteristics might reconcile this apparent contradiction. Tracking decomposition of a lignin/litter mixture and SOC across different North American mineral soils using lab and field incubations, here we show that cumulative lignin decomposition varies 18-fold among soils and is strongly correlated with bulk litter decomposition, but not SOC decomposition. Climate legacy predicts decomposition in the lab, and impacts of nitrogen availability are minor compared with geochemical and microbial properties. Lignin decomposition increases with some metals and fungal taxa, whereas SOC decomposition decreases with metals and is weakly related with fungi. Decoupling of lignin and SOC decomposition and their contrasting biogeochemical drivers indicate that lignin is not necessarily a bottleneck for SOC decomposition and can explain variable contributions of lignin to SOC among ecosystems.

Lignin is an abundant and complex plant polymer that may limit litter decomposition, yet lignin is sometimes a minor constituent of soil organic carbon (SOC). Accounting for geographic diversity in soil characteristics might reconcile this apparent contradiction. We tracked decomposition of a lignin/litter mixture across North American mineral soils using lab and field incubations. Cumulative lignin decomposition varied 18-fold among soils and was strongly correlated with bulk litter decomposition, but not SOC decomposition. Legacy climate predicted decomposition even in the lab. Impacts of nitrogen availability were minor compared with geochemical and microbial properties, which had contradictory relationships with lignin and SOC decomposition. Lignin decomposition increased with some metals and fungi, whereas SOC decomposition decreased with all metals and was weakly related with fungi. Soil properties differentially impact decomposition of lignin and litter vs. SOC across broad geographic scales, linking short-term decomposition to differences in organic matter among ecosystems.