The coordination between leaf and fine root litter decomposition and the difference in their controlling factors

Aim As the two largest components of plant detritus input, leaf and root litter together determine ecosystem vegetation turnover and nutrient cycling rates. However, the similarities and differences between the factors controlling their decomposition remain unknown. We evaluated the relationship between leaf and fine root litter decomposition across biomes and analysed how litter traits, climate, soil conditions and decomposers shape their relationship. Location Global. Time period 1984-2020. Major taxa studied Vascular plants. Methods We collected 352 paired leaf and fine root decomposition rates (k values) and ancillary traits, climate, soil condition and decomposer abundance data from 88 sites spanning the major global biomes. Boosted regression trees (BRTs) were applied to partition the factors that control root and leaf decomposition rates. Results Averaged across all biomes, leaf litter decomposes significantly faster (k(leaf) = .72) than fine root litter (k(root) = .42). The BRTs indicated that plant traits best explained the variance in both leaf and root litter decomposition. The key chemical traits of leaf litter and fine root litter, including C:N, [P], N:P, [lignin], [cellulose], [non-structural carbohydrates] and [tannins], were positively correlated. Therefore, leaf and fine root k values were positively correlated within and across biomes, even after removing the influence of climate, soil conditions and decomposers. However, climate and decomposers had different impacts on leaf and fine root decomposition. Climate induced a greater impact on fine root litter decomposition, whereas decomposers had a greater influence on leaf litter decomposition. Main conclusions Our finding indicates that plants evolve a coordinated nutrient supply-and-demand strategy. The plants with high nutrient demand produce labile leaf and fine root litter, which decomposes fast to meet their high nutrient requirements. However, leaf and fine root decomposition are also mediated by different combinations of trait, climate, soil condition and decomposer factors, which weakens the coordination between leaf and fine root decomposition.

Automated summary

The study reveals that plants have evolved a coordinated nutrient supply-and-demand strategy, where high-nutrient-demand plants produce labile leaf and fine root litter that decomposes quickly to meet their nutrient requirements. Although leaf and fine root decomposition are positively correlated, they are also influenced by different combinations of traits, climate, soil conditions, and decomposers, weakening the coordination between leaf and fine root decomposition.