Litter decomposition in peatlands is promoted by mixed plants

Abstract

Purpose. The carbon sink function of peatlands is primarily driven by a higher production than decomposition of the litter Sphagnum mosses. The observed increase of vascular plants in peatlands could alter the decomposition rate and the carbon (C) cycle through a litter mixing effect, which is still poorly studied. Here, we examine the litter mixing effect of a peat moss (Sphagnum fallax) and two vascular plants (Pinus uncinata and Eriophorum vaginatum) in the field and laboratory-based experiment. Materials and methods. During the laboratory incubation, mass loss, CO 2 production and dissolved organic carbon concentration were periodically monitored during 51 days. The collected data were then processed in a C dynamics model. The calculated enzymatic activity was correlated to the measured β-glucosidase activity in the litter. In the field experiment, mass loss and CO 2 production from litter bags were annually measured for three years. Results and discussion. Both laboratory and field experiments clearly show that the litter mixture, i.e. Sphagnum-Pinus-Eriophorum, had a synergistic effect on decomposition by enhancing the mass loss. Such enhanced mass loss increased the water extractable C and CO 2 production in the litter mixture during the laboratory experiment. The synergistic effect was mainly controlled by the Sphagnum-Eriophorum mixture that significantly enhanced both mass loss and CO 2 production. Although the β-glucosidase activity is often considered as a major driver of decomposition, mixing the litters did not cause any increase of the activity of this exo-enzyme in the laboratory experiment suggesting that other enzymes can play an important role in the observed effect. Conclusions. Mixing litters of graminoid and Sphagnum species led to a synergistic effect on litter decomposition. In a context of vegetation dynamics in response to environmental change, such a mixing effect could alter the C dynamics at a larger scale. Identifying the key mechanisms responsible for the synergistic effect on litter decomposition, with a specific focus on the enzymatic activities, is crucial to better predict the capacity of peatlands to act as C sinks. Keywords β-glucosidase • Carbon dynamics models • Catalysis • CO 2 production • Dissolved organic carbon • Litter mixture effect

Enzymatic stoichiometry in tropical soil under pure and mixed plantations of eucalyptus with N2-fixing trees

“…In this study, no differences were observed to Cacquiring enzymes between treatments (Figure 1B) and these enzymes did not correlate with any differences between the C content in the litter (Table 1). In addition, different types of litter, such as those found in mixed plantations, do not seem to stimulate specifically the activity of β-glucosidase, since other enzymes can play significant roles in this condition (e.g., cellulase) (Leroy et al, 2018).…”

Comment on soil-2021-86

“…Highly decomposed Sphagnum and Molinia peats were sampled in duplicate (samples A and B) in sites which were intensively studied by D' Angelo et al (2016), Bernard-Jannin et al (2018 and Leroy et al (2018Leroy et al ( , 2019aLeroy et al ( and 2019b. Large undisturbed samples (15´15´25 cm 3 ) were collected between 25 and 40 cm depth when the groundwater table level was close to the soil surface.…”

Impact of Temperature and Moisture on the Decomposition of Peat-Forming Plants: Results of a Two-Year Incubation Experiment

“…The residues of peat-forming plants can be divided into two groups based on their resistance to decomposition: (1) the rapidly decomposing fraction, which is not fixed in the botanical composition of the organic layer of peat soils (including leaves of Chamaedaphne calyculata, Menyanthes trifoliata, and other grasses), and (2) the stable fraction, which is permanently fixed in the botanical composition of peat (encompassing all fractions of most shrubs, roots of grasses like Carex (sedges), Scheuchzeria (Scheuchzeria), Eriophorum (cotton grass), and all sphagnum mosses) [9,22,[25][26][27]. Of particular interest is the non-additive effect that arises when the residues of different plant species is mixed [28,29].…”