Supplementary Materials

Understanding drivers of peatland extracellular enzyme activity in the PEATcosm experiment: mixed evidence for enzymic latch hypothesis

Romanowicz KJ, ES Kane, LR Potvin, AL Daniels, RK Kolka, EA Lilleskov

Corresponding Author:

Author: Karl J Romanowicz

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Affiliation: School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI 48109, USA

Table S1 Oxidative and hydrolytic extracellular enzymes assayed in bulk peat and porewater collected from PEATcosm chambers, their enzyme commission number (EC), role in nutrient cycling, and corresponding substrate

Extracellular Enzymes / Abbreviation / EC / Type / Nutrient Cycle / Substrate
Phenol oxidase / POX / 1.10.3.2 / Oxidative / Carbon / L-DOPA
Peroxidase / PER / 1.11.1.7 / Oxidative / Carbon / L-DOPA
β-1,4-glucosidase / BG / 3.2.1.21 / Hydrolytic / Carbon / 4-MUB-β-D-glucoside
β-1,4-cellobiohydrolase / CBH / 3.2.1.91 / Hydrolytic / Carbon / 4-MUB-β-D-cellobioside
β-1,4-N-acetyl-glucosaminidase / NAG / 3.1.6.1 / Hydrolytic / Nitrogen / 4-MUB-N-acetyl-β-D-glucosaminide
Acid-phosphatase / AP / 3.1.3.2 / Hydrolytic / Phosphorus / 4-MUB-phosphate

L-DOPA = L-3,4-dihydroxyphenylalanine; 4-MUB = 4-methylumbelliferyl


Table S2 Mean physical and porewater chemical data (± standard deviation) by WT treatment over the 2012 growing season

July / August / September
HWT / LWT / HWT / LWT / HWT / LWT
Physical
WC (% moisture) / 93.1 ± 1.33 / 92.4 ± 0.90 / 93.1 ± 1.15 / 89.7 ± 0.81 / 91.8 ± 0.74 / 89.0 ± 0.89
ORP (Eh7 mV) / -147.4 ± 45.0 / -155.0 ± 50.6 / -174.8 ± 31.1 / -99.1 ± 58.7 / -75.2 ± 66.2 / -51.1 ± 90.0
Temp (°C) / 19.9 ± 0.74 / 19.8 ± 0.40 / 17.7 ± 1.61 / 17.8 ± 0.70 / 17.5 ± 0.70 / 17.2 ± 0.59
Porewater Chemistry
Total Phenolics (mg L-1) / 11.3 ± 2.83 / 12.3 ± 2.96 / 17.1 ± 5.00 / 17.7 ± 4.78 / 17.0 ± 3.43 / 12.3 ± 4.32
DOC (mg L-1) / 73.8 ± 15.6 / 82.5 ± 14.9 / 84.4 ± 21.7 / 90.6 ± 17.8 / 89.9 ± 16.4 / 87.1 ± 17.3

WC = water content; ORP = oxidation-reduction potential; Temp = temperature; ER = ecosystem respiration; GPP = gross primary productivity; DOC = dissolved organic carbon


Table S3 Mean EEA rates (± standard deviation) for bulk peat phase PER activity (umol h-1 g-1) and porewater phase AP activity (nmol h-1 mL-1) separated by water table treatment (HWT or LWT) over the 2012 growing season (n = 12/WT treatment/month)

June / July / August / September / October
HWT / LWT / HWT / LWT / HWT / LWT / HWT / LWT / HWT / LWT
Bulk Peat
PER (umol h-1 g-1) / 23.4 ± 11.0 / 22.6 ± 12.0 / 18.3 ± 6.9 / 14.3 ± 5.4 / 18.9 ± 7.1 / 8.1 ± 4.5 / 11.3 ± 4.0 / 6.8 ± 4.2 / 13.1 ± 3.7 / 9.0 ± 5.2
Porewater
AP (nmol h-1 mL-1) / 4.4 ± 0.7 / 5.2 ± 1.6 / 5.5 ± 1.1 / 6.9 ± 2.6 / 3.3 ± 1.3 / 4.5 ± 2.3 / 2.7 ± 0.6 / 3.9 ± 1.1 / 2.4 ± 0.6 / 2.3 ± 0.7

Fig. S1 Comparison of monthly mean EEAs over the 2012 growing season. Results presented for oxidative EEAs (A-D; closed circles) between the bulk peat phase (A, C) and porewater phase (B, D) and comparison of hydrolytic EEAs (E-L; open circles) between the bulk peat phase (E, G, I, K) and porewater phase (F, H, J, L). Mean ± SD are shown with Tukey’s HSD post-hoc analysis indicated by lowercase letters. EEAs based on mean monthly enzyme assays from mesocosm bins (n = 24/month)