NITROGEN ADDITIONS AND LITTER DECOMPOSITION: A META-ANALYSIS

TLDR

The study aimed to synthesize existing data to quantitatively assess how environmental and experimental factors interact with nitrogen additions to influence litter mass loss. We performed a meta‑analysis of previously published empirical studies examining the effects of nitrogen enrichment on litter decomposition. Across all studies, nitrogen enrichment had no overall effect on litter decay, but significant effects depended on fertilization rate, ambient deposition level, and litter quality, with inhibition at high rates or high ambient deposition and stimulation at low deposition and high‑quality litters, while fertilizer type, mesh size, and climate had no influence.

Abstract

We conducted a meta-analysis of previously published empirical studies that have examined the effects of nitrogen (N) enrichment on litter decomposition. Our objective was to provide a synthesis of existing data that comprehensively and quantitatively evaluates how environmental and experimental factors interact with N additions to influence litter mass loss. Nitrogen enrichment, when averaged across all studies, had no statistically significant effect on litter decay. However, we observed significant effects of fertilization rate, site-specific ambient N-deposition level, and litter quality. Litter decomposition was inhibited by N additions when fertilization rates were 2–20 times the anthropogenic N-deposition level, when ambient N deposition was 5–10 kg N·ha−1·yr−1, or when litter quality was low (typically high-lignin litters). Decomposition was stimulated at field sites exposed to low ambient N deposition (<5 kg N·ha−1·yr−1) and for high-quality (low-lignin) litters. Fertilizer type, litterbag mesh size, and climate did not influence the litter decay response to N additions.