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Background: In boreal peatlands, climate warming and associated soil drying facilitate the growth of vascular plants at the cost of moss species, resulting in an alteration of species dominance in plant communities. However, how altered dominant species and evenness affect litter mixture decomposition is still unclear in these ecosystems. Methods: We collected fresh litter from Larix gmelinii (tree), Betula fruticosa (shrub), Eriophorum vaginatum (sedge), and Sphagnum magellanicum (moss), and determined mass loss and nitrogen (N) release of four-species mixtures with varying dominant species and evenness at 10 and 20 oC during 360-day decomposition. Results: Irrespective of the incubation temperature, B. fruticosa-dominated litter mixtures had greatest mass loss and N release throughout decomposition, while S. magellanicum-dominated litter mixtures had lowest values. Moreover, mass loss and N release of B. fruticosa-dominated litter mixtures decreased with elevating evenness after 360 days of decomposition, but the opposite trends were observed for litter mixtures dominated by the other three species. Increasing incubation temperature facilitated decomposition of all litter mixtures, with the lowest magnitude for S. magellanicum-dominated mixtures. Non-additive effects, especially positive effects, on mass loss and N release were common, which played a key role in enhancing the influences of dominant species and evenness on litter mixture decomposition. Moreover, the incidence of positive non-additive effects on mass loss decreased at 20 oC as litter decomposition proceeded. Conclusions: Warming-induced increased dominance of vascular plants, especially shrubs, will amplify the warming effect on litter decomposition and N availability in boreal peatlands, thus generating positive feedback to climate warming. [ABSTRACT FROM AUTHOR]

Aims The conifer litter is fairly recalcitrant and nutrient poor, and broadleaved litter promotes coniferous litter decomposition by increasing degradable nutrients and promoting microbial metabolism. Mixing Pinus massoniana litter and three broadleaved litters may increase the diversity and abundance of fungal decomposers compared with those in P. massoniana litter and vary depending on the number and proportion of broadleaved species included. Methods We analysed the composition and diversity of fungal communities during mixed litter decomposition in southwestern China with 35 treatments (P. massoniana , Toona sinensis , Cinnamomum camphora and Sassafras tzumu litter) using Illumina high-throughput sequencing. Important Findings The mixed litters increased fungal diversity and richness compared with those in the single-species litter, except in the following treatments: P. massoniana litter accounting for 70%–80% in the P. massoniana + T. sinensis , P. massoniana + S. tzumu + T. sinensis and P. massoniana + S. tzumu + C. camphora combinations, and P. massoniana + S. tzumu + C. camphora + T. sinensis combination with small proportion of T. sinensis litter. The diversity and richness of the 7:1:2 combination of P. massoniana + C. camphora + T. sinensis were significantly higher than those in the other treatments. Ascomycota and Basidiomycota were the dominant phyla, and Aspergillus was the most abundant genus. The decomposition of litters from one needleleaf and one broadleaved species (6:4) and one needleleaf species and two broadleaved species (broadleaved litter accounting for 30%–40%) exhibited synergistic interactions throughout the decomposition process, and the relative abundance of fungi that decompose refractory substances increased. The P. massoniana + C. camphora + T. sinensis combination and a 30%–40% broadleaf litter proportion increased fungal diversity and accelerated the decomposition of recalcitrant coniferous litter. Therefore, C. camphora and T. sinensis are a potential candidate species for mixed planting with P. massoniana. [ABSTRACT FROM AUTHOR]

Aims: Larix kaempferi planting with broad-leaved trees can increase production and alleviate soil degradation; however, the mechanism is unclear, especially on large scales and in different climate regions. This paper attempts to explain the underlying mechanism in a temperate region and northern subtropical alpine region of China. Methods: Litter decomposition rates, nutrient release, enzyme activity and microbial community composition were determined in conifer litter, broad-leaved litter and mixed litter by the litterbag method during about 500 days in the two regions. Results: Decomposition rate was increased by 4.00% in temperate region and 3.38% in the subtropical region after litter mixing and the synergistic effect increased with decomposition progress. However, nutrients release was not always enhanced, and enzyme activities were enhanced at the most of decomposition time and higher in the subtropical region. After litter mixing, a few new dominant taxa emerged, and the microbial gene quantities were increased in the temperate region, but not in the subtropical region. The dominant bacterial taxa were similar, while most of the dominant fungal taxa shifted with decomposition. In addition, the dominant fungi completely differed between the two regions. The environmental variables with greater influence on microbial community were similar in the two regions, including C:N, C:P and pH. Conclusions: After mixing with broad-leaved litter, the decomposition of Larix kaempferi was enhanced by increasing enzyme activities and microbial quantities in the temperate region, but the mechanisms were not clear in the subtropical region. [ABSTRACT FROM AUTHOR]

Aims: Improvement cutting or harvesting can change the coverage of understory vegetation, which can significantly influence the litter decomposition process in plantations. However, difference in potential non-additive mass loss in response to understory vegetation changes is poorly studied. Methods: A field litterbag experiment involving various litter types and treatments with no understory vegetation removal, shrub removal, herb removal and whole-understory vegetation removal was conducted to examine non-additive mass loss. Results: During approximately 2 years of decomposition, the decomposition rate of shrub and herb components was accelerated in the mixed litter with full understory vegetation. There was significant non-additive mass loss during decomposition in the plots with trees, shrubs and herbs, while the incidence of non-additive mass loss was lower in the plots with understory vegetation removal. Statistical analysis revealed a significant difference between the expected mass loss calculated with the data from the corresponding decomposition plots and that calculated with the data from the plots with whole-understory vegetation removal. Conclusions: Our results show that understory vegetation removal can inhibit litter decomposition in Masson pine plantation ecosystems in subtropical China. We highlight that non-additive litter decomposition should be assessed on the basis of litter species composition and decomposition microenvironments in situ. [ABSTRACT FROM AUTHOR]

Litter mixing effects during decomposition remain inconclusive for boreal peatlands, and such effects may vary with climate warming and associated shifts in vegetation composition. Here, litters were collected from four common species (deciduous shrub Betula fruticosa , evergreen shrub Ledum palustre , graminoid Eriophorum vaginatum , and moss Sphagnum divinum) in a boreal peatland of northeast China, resulting in 15 species combinations with species richness ranging from one to four. We determined litter mixing effects on carbon (C) mineralization rate and mass loss under aerobic conditions at 10 °C and 20 °C in a 315-d incubation experiment, and assessed the differences in litter mass loss for the individual species within monocultures and mixtures. Non-additive effects on C mineralization and mass loss were prevalent during decomposition of litter mixtures. Moreover, the sensitivity of C mineralization and mass loss to rising incubation temperature (Q 10) was found to be non-additive in five and three out of 11 mixtures, respectively. Notably, mass loss of other litters in the mixtures was generally promoted by B. fruticosa , but inhibited by S. divinum in two- and three-species litter mixtures. Furthermore, B. fruticosa increased and S. divinum decreased Q 10 values for mass loss of other litters in four out of seven cases. These findings suggest that the shifts in plant community composition will not only influence community-level litter decomposition through altered litter mixing effects during decomposition, but also modulate the response of litter decomposition to rising temperature in boreal peatlands. • Non-additive effects were predominant during litter mixture decomposition. • Litter mixing effects on decomposition varied with incubation temperature. • B. fruticosa litter promoted mass loss of other litters in the mixtures. • S. divinum litter often inhibited mass loss of other litters in the mixtures. [ABSTRACT FROM AUTHOR]