Ecosphere (Apr 2018)
Litter moisture adsorption is tied to tissue structure, chemistry, and energy concentration
Abstract
Abstract The ability of plant litter to adsorb water is important for wildland fire, hydrological, and biogeochemical processes. Variation in water adsorption has largely been attributed to physical differences across species, with the role of litter chemistry in moisture dynamics receiving little attention. We hypothesized that lower specific leaf area (SLA, cm2/g) and higher concentrations of hydrophobic lignin and lipid biomolecules would be associated with decreased litter water adsorption. Because plant biochemistry is tied to litter elemental and structural traits via biophysics and leaf economics, we expected to observe a suite of linked traits that were related to water adsorption, including element concentrations, carbon oxidation state, and energy concentration (ΔHc). In litter from 22 species, we observed greater than fourfold variation in the maximum amount of liquid water adsorbed (adsorption capacity, g/g) and in the rate at which dry litter adsorbed water vapor (adsorption rate, mg g−1 min−1); there was a significant positive relationship between adsorption capacity and adsorption rate. Broadly, litter with low SLA had a low carbon oxidation state, low oxygen and ash concentrations, and high concentrations of carbon, hydrogen, lignin, and lipids. The two metrics of water adsorption had significant negative relationships with concentrations of energy, lignin, carbon, and hydrogen, and positive relationships with litter SLA and carbon oxidation state. However, water adsorption was better predicted by combinations of SLA with chemical and energy traits. Several traits associated with decreased litter water adsorption, such as concentrations of lignin and energy, also directly influence some of the same ecosystem processes affected by litter moisture (e.g., decomposition, wildland fires). In particular, because plants with the hydrophobic traits identified in this study are more abundant in dry environments, our observations suggest a mechanism that could accentuate the influence of litter traits on ecosystem processes and which merits further research. Understanding the role of these traits in water adsorption could be used to help predict shifts in ecosystem function as plant communities reassemble as result of climate change as well as provide quantitative information on how plant species influence wildland fire dynamics.
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