Figure 2. Differences in extracellular enzyme activities among treatments of litter and nitrogen in a mixed pine/oak forest in central North China.

Treatments began in September 2009 and were applied annually. Vertical bars indicate one standard error of means (n = 5). BG, β-glucosidase; NAG, N-acetyl-β-glucosaminidase; PO, phenol oxidase; PER, peroxidase; N₀, zero rate of nitrogen addition; N₅, nitrogen addition at 5 g∙m⁻²∙a⁻¹; N₁₀, nitrogen addition at 10 g∙m⁻²∙a⁻¹; Litt_nil, litter removal; Litt_woody, fine woody litter; Litt_leaf, leaf litter; Litt_mix, mixed leaf and fine woody litter.