Non-additive effects of litter diversity on greenhouse gas emissions from alpine steppe soil in Northern Tibet

Scientific Reports, Dec 2015

While litter decomposition is a fundamental ecological process, previous studies have mainly focused on the decay of single species. In this study, we conducted a litter-mixing experiment to investigate litter diversity effects on greenhouse gas (GHG) emissions from an alpine steppe soil in Northern Tibet. Significant non-additive effects of litter diversity on GHG dynamics can be detected; these non-additive effects were the result of species composition rather than species richness. Synergistic effects were frequent for CO2 and N2O emissions, as they were found to occur in 70.5% and 47.1% of total cases, respectively; antagonistic effects on CH4 uptake predominated in 60.3% of the cases examined. The degree of synergism and antagonism may be significantly impacted by litter chemical traits, such as lignin and N, lignin:N ratio, and total phenols during decomposition (P < 0.05). In addition, the relationship between chemical traits and litter-mixing effects changed over incubation time. Our study provides an opportunity to gain insight into the relationship between litter diversity and soil ecological processes. The results indicate that higher plant diversity may generally enhance CO2 and N2O emissions while inhibiting CH4 uptake; meanwhile, the direction and strength of non-additive effects appear to be related to litter chemical traits.

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Non-additive effects of litter diversity on greenhouse gas emissions from alpine steppe soil in Northern Tibet

Abstract While litter decomposition is a fundamental ecological process, previous studies have mainly focused on the decay of single species. In this study, we conducted a litter-mixing experiment to investigate litter diversity effects on greenhouse gas (GHG) emissions from an alpine steppe soil in Northern Tibet. Significant non-additive effects of litter diversity on GHG dynamics can be detected; these non-additive effects were the result of species composition rather than species richness. Synergistic effects were frequent for CO2 and N2O emissions, as they were found to occur in 70.5% and 47.1% of total cases, respectively; antagonistic effects on CH4 uptake predominated in 60.3% of the cases examined. The degree of synergism and antagonism may be significantly impacted by litter chemical traits, such as lignin and N, lignin:N ratio, and total phenols during decomposition (P < 0.05). In addition, the relationship between chemical traits and litter-mixing effects changed over incubation time. Our study provides an opportunity to gain insight into the relationship between litter diversity and soil ecological processes. The results indicate that higher plant diversity may generally enhance CO2 and N2O emissions while inhibiting CH4 uptake; meanwhile, the direction and strength of non-additive effects appear to be related to litter chemical traits. Introduction Over the past century, rates of species extinction have accelerated to 2–3 orders of magnitude higher than the ambient levels recorded in the fossil record1. Changes in ecosystem functioning are a major consequence of decreasing diversity, because some ecosystem processes depend on the presence of a specific number of functional groups, species, and genotypes of organisms2. Within the field of biodiversity-ecosystem functioning research, the majority of works have focused on how plant diversity affects above-ground ecosystem processes3,4. However, the mechanisms by which plant diversity can affect other key ecosystem processes, such as litter decomposition and soil ecological processes, are still being examined5,6,7. Litter decomposition is a fundamental multitrophic process that supplies organic and inorganic elements to soil in natural ecosystems8. Most terrestrial ecosystems consist of a mixture of plant species, and litter-mixing studies indicate that litter decomposition processes in mixtures can be quite different from those of a single species2,9. In the litter-mixing experiment, litters from at least two species are mixed together and the effects of the mixture are compared with what would be expected based on the additive effects of all the component species in monoculture10. Previous studies demonstrated that the effects of litter-mixing on decomposition rate were unpredictable, because additive and non-additive (synergistic and antagonistic) effects were observed, and non-additivity seemed to be predominant2,9,11,12. If non-additive effects occur, results of litter effect in mixture cannot be predicted as simply the sum of single species results, thus, litter decomposition of a single species did not sufficiently represent litter decomposition processes at an ecosystem level. Mixed litters from species with varying resource quality and structure change the chemical environment and physically alter the total litter surface where decomposition is occurring13,14. These alterations can also affect soil ecological processes such as soil respiration, net N mineralization, and microbial activity. Although there have been some studies examining how litter mixing affects these soil ecological processes11,15,16, the direction of the specific effects and the role that diversity itself plays in mediating the non-additivity of soil processes remains unclear, and our understanding of how soil ecological processes can be altered by litter diversity is still limited. Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are three important GHGs contributing to global warming in the atmosphere17. Soils play an important role in the global budgets of these GHGs, as they are able to act both as sources and sinks for the GHGs18. Plant litter provides a source of readily available C, N, and other chemical components (e.g., condensed tannin and terpenes) into the soil during decomposition, and subsequently influences CO2, CH4, and N2O emissions from soil19,20. Nevertheless, the majority of litter mixing studies have focused on mass loss and nutrient dynamics6,21,22, as well as decomposer community11, with less information available on how GHGs respond to litter mixture decomposition. Considering the ecological significance of GHGs, a thorough understanding of the dynamics of the GHG response to plant litter diversity is, therefore, indispensable for an accurate comprehension of terrestrial ecosystem functioning and for climate change projects23. Litter diversity can be defined as species richness and composition or interactions among species5 (...truncated)


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Youchao Chen, Jian Sun, Fangting Xie, Yan Yan, Xiaodan Wang, Genwei Cheng, Xuyang Lu. Non-additive effects of litter diversity on greenhouse gas emissions from alpine steppe soil in Northern Tibet, Scientific Reports, 2015, Issue: 5, DOI: 10.1038/srep17664