Fig 1.
Mass remaining of recalcitrant (lignin) to non-recalcitrant (cellulose, hemicellulose, and soluble sugars) C over time.
Across sampling times, the ratio was significantly lower in the warming treatment (P = 0.032), but there was a significant interaction between treatment and time (P = 0.046). Data are means ± SE, with n = 5 plots. †P < 0.10 for sampling date.
Fig 2.
Percentage total mass remaining in spruce needles over time.
Decomposition was significantly slower in the warming treatment compared to the control (P = 0.009). Data are means ± SE, with n = 5 plots. *P < 0.05 for sampling date.
Fig 3.
Percentage of mass remaining of lignin, cellulose, hemicellulose, and soluble sugar in spruce needles over time.
Warming did not significantly affect lignin breakdown (P = 0.108) or hemicellulose breakdown (P = 0.179). In contrast, warming slowed the breakdown of cellulose significantly (P = 0.019) and soluble sugars marginally significantly (P = 0.077). Data are means ± SE, with n = 5 plots. *P < 0.05, †P < 0.10 for sampling date.
Fig 4.
Extracellular enzyme activity (EEA) ratios of recalcitrant to non-recalcitrant C on litter retrieved at 12 months.
Recalcitrant enzyme activity is polyphenol oxidase, while non-recalcitrant enzymes are the sum of cellobiohydrolase, β-xylosidase, and β-glucosidase. Warming significantly increased the ratio of recalcitrant C decay enzymes to non-recalcitrant C decay enzymes (P = 0.002). Activities were measured in units of nmol h-1 g-1 dry litter. Data are means ± SE, with n = 5 plots.