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More is not always better: Peat moss mixtures slightly enhance peatland stability

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Dec 05, 2023 version files 56.16 KB
Dec 13, 2023 version files 56.15 KB

Abstract

Species-poor peatlands challenge biodiversity–ecosystem function theory, which generally links high species diversity to stable ecosystem functions. An open question in ecosystem ecology is whether assemblages of naturally co-occurring peat mosses contribute to the stability of peatland ecosystem processes. We used a replacement series mesocosm experiment with mixtures of Sphagnum cuspidatum and S. medium to assess resistance, resilience, and recovery rates of net ecosystem CO2 exchange (NEE) under a mild and a deep water table drawdown event. Our results show a positive effect of mild water table drawdown on NEE with no apparent role for the composition of the peat moss assemblage. Our study indicates that the carbon uptake capacity by peat moss assemblages is rather resilient to mild water table drawdown, but seriously affected by deeper drought conditions. Co-occurring peat moss species seem to enhance the resilience of the carbon uptake function – i.e. ability of NEE to return to pre-perturbation levels – of peat moss mixtures only slightly. These findings suggest that assemblages of co-occurring Sphagnum moss species do only marginally contribute to the stability of ecosystem functions in peatlands under drought conditions. We did find increased recovery with a larger share of S. cuspidatum in the mixtures, aiding in the ecosystem’s role as carbon sink. Above all, our results highlight that predicted severe droughts can gravely affect the sink capacity of peatlands, with only a small extenuating role for peat moss mixtures.