Determinants of the pathways of litter chemical decomposition in a tropical region

• Published in: The New phytologist 2014-08, Vol.203 (3), p.873-882
• Main Authors: Parsons, Scott A, Congdon, Robert A, Lawler, Ivan R
• Format: Article
• Language: English
• Subjects: Australia; carbon; Chemical composition; Chemical decomposition; Chemical degradation; chemical pathways; Chemicals; climate change; Convergence; Correlation analysis; Decay; Decomposition; Divergence; Drying; ecosystems; Forest soils; Infrared spectroscopy; Leaf litter; Leaves; lignin; Linear Models; Litter fall; litter quality; Near infrared radiation; phenolic compounds; Phenols; Phosphorus; Plant Leaves - chemistry; Plant litter; Rainforest; Rainforests; Sodium; Soil; Soil chemistry; Soil moisture; soil organic matter; Soil samples; Soil water; Soils; Spectrometry; spectroscopy; Statistics, Nonparametric; Tropical Climate; Tropical environment; Tropical environments; Tropical rain forests; tropical rainforest; Tropical regions; tropics
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.12852

Litter decomposition is a key ecosystem process, yet our understanding of the drivers in chemical changes in leaves during decay is limited. Our aim was to determine the comparative differences (chemical divergence or convergence) between sites and the drivers of decay pathways. We used the litterbag method (‘in situ’ litterfall and standardized ‘control’ leaves) in Australian tropical rainforests and near‐infrared spectrometry to show the chemical pathways during decomposition (c. 360 d; 12 control sites; 17 in situ sites). Chemical convergence/divergence was determined from spectral dissimilarity and quantile regression along a mass loss moving average. The influence of environment (climate and soil) and litter quality on decay pathways was determined between sites using correlation analysis. Throughout the region, litter composition in both treatments converged chemically during decay. However, divergent chemical pathways were shown for some samples/sites (especially with high initial lignin, phenolics and carbon (C), poor soil phosphorus (P), sodium (Na) and more seasonal moisture), and the diversity of decay residues increased with mass loss despite overall chemical convergence. Our study suggests that there is general chemical convergence of leaf litter during early decay, but also that divergent chemical pathways occur in locations that experience more intense seasonal drying, and contain species or conditions that promote poor‐quality litter.