Litter mixing promoted decomposition and altered microbial community in common bean root litter

Abstract

Background: Decomposition of plant litter is a key driver of carbon and nutrient cycling in terrestrial ecosystems. Mixing litters of different plant species may alter the decomposition rate, but its effect on the microbial decomposer community in plant litter is not fully understood. Here, we tested the effects of mixing with maize (Zea mays L.) and soybean [Glycine max (Linn.) Merr.] stalk litters on the decomposition and microbial decomposer communities of common bean (Phaseolus vulgaris L.) root litter at the early decomposition stage in a litterbag experiment.

Results: Mixing with maize stalk litter, soybean stalk litter, and both of these litters increased the decomposition rate of common bean root litter at 56 day but not 14 day after incubation. Litter mixing also increased the decomposition rate of the whole liter mixture at 56 day after incubation. Amplicon sequencing found that litter mixing altered the composition of bacterial (at 56 day after incubation) and fungal communities (at both 14 and 56 day after incubation) in common bean root litter. Litter mixing increased the abundance and alpha diversity of fungal communities in common bean root litter at 56 day after incubation. Particularly, litter mixing stimulated certain microbial taxa, such as Fusarium, Aspergillus and Stachybotrys spp. In addition, a pot experiment with adding litters in the soil showed that litter mixing promoted growth of common bean seedlings and increased soil nitrogen and phosphorus contents.

Conclusions: This study showed that litter mixing can promote the decomposition rate and cause shifts in microbial decomposer communities, which may positively affect crop growth.

Keywords: Litter mixing; Microbial community abundance; Microbial community composition; Microbial decomposer; Weight loss.

Fig. 1

Weight loss of single litters (A), the observed and expected weight losses of the whole liter mixture (B), and weight loss of common bean root litter in the mixture (C). B: common bean root litter, S: soybean stalk litter, M: maize stalk litter. BS, BM, BSM represent common bean root litter mixed with soybean stalk litter, maize stalk litter, and both soybean and maize stalk litters, respectively. –B: common bean root litter in the mixture. ***values were significantly different at P < 0.001

Fig. 2

Abundances (A) and alpha diversities (B) of bacterial and fungal communities in common bean root litter. B: common bean root litter. BS, BM, BSM represent common bean root litter mixed with soybean stalk litter, maize stalk litter, and both soybean and maize stalk litters, respectively. –B: common bean root litter in the mixture. Different letters indicate significant difference between treatments (Tukey’s HSD test, P < 0.05)

Fig. 3

Principal coordinate analysis (PCoA) plots of bacterial (A) and fungal (B) communities at each sampling time. B: common bean root litter. BS, BM, BSM represent common bean root litter mixed with soybean litter, maize litter, and both soybean and maize litter, respectively. –B: common bean root litter in the mixture

Fig. 4

Bacterial (A, B) and fungal (C, D) genera altered by litter mixing at 14 and 56 day after incubation. B: common bean root litter. BS, BM, BSM represent common bean root litter mixed with soybean stalk litter, maize stalk litter, and both soybean and maize stalk litter, respectively. –B: common bean root litter in the mixture. Different letters indicate significant difference between treatments (Tukey’s HSD test, P < 0.05)

Fig. 5

Dendrogram showing fungal OTUs altered by litter mixing. The first strip indicates the phylum-level affiliation of each. The second strip indicates in which treatment each differential OTU is enriched. The third strip indicates sampling time. The size of each circle indicates the relative abundance of each differential OTU. B: common bean root litter. BS, BM, BSM represent common bean root litter mixed with soybean stalk litter, maize stalk litter, and both soybean and maize stalk litter, respectively. –B: common bean root litter in the mixture

Fig. 6

Common bean seedling growth (A) and soil nutrient contents (B) in the pot experiment (mean ± SE). B: common bean root litter. BS, BM, BSM represent common bean root litter mixed with soybean stalk litter, maize stalk litter, and both soybean and maize stalk litter, respectively. Different letters indicate significant difference between treatments (Tukey’s HSD test, P < 0.05)