Abstract
Arctic ecosystems are characterized by a broad range of plant functional types that are highly heterogeneous at small (~1–2 m) spatial scales. Climatic changes can impact vegetation distribution directly, and also indirectly via impacts on disturbance regimes. Consequent changes in vegetation structure and function have implications for surface energy dynamics that may alter permafrost thermal dynamics, and are therefore of interest in the context of permafrost related climate feedbacks. In this study we examine small-scale heterogeneity in soil thermal properties and ecosystem carbon and water fluxes associated with varying understory vegetation in open-canopy larch forests in northeastern Siberia. We found that lichen mats comprise 16% of understory vegetation cover on average in open canopy larch forests, and lichen abundance was inversely related to canopy cover. Relative to adjacent areas dominated by shrubs and moss, lichen mats had 2–3 times deeper permafrost thaw depths and surface soils warmer by 1–2°C in summer and less than 1°C in autumn. Despite deeper thaw depths, ecosystem respiration did not differ across vegetation types, indicating that autotrophic respiration likely dominates areas with shrubs and moss. Summertime net ecosystem exchange of CO2 was negative (i.e. net uptake) in areas with high shrub cover, while positive (i.e. net loss) in lichen mats and areas with less shrub cover. Our results highlight relationships between vegetation and soil thermal dynamics in permafrost ecosystems, and underscore the necessity of considering both vegetation and permafrost dynamics in shaping carbon cycling in permafrost ecosystems.
Highlights
We examine spatial variability in active layer depth and ecosystem carbon fluxes associated with understory vegetation composition and biomass in an open-canopy larch forest in northeastern Siberia
We address two research questions: 1) do thaw depth and soil temperature vary between common understory vegetation types? and 2) does ecosystem respiration differ among key vegetation types, and if so are these differences related to active layer depth?
Our study is broadly inline with these previous results; we found that lichen mats had both thinner organic layers with less organic matter and correspondingly higher thermal conductivity, and higher surface temperatures associated with lower latent heat dissipation
Summary
Widespread observations of increasing permafrost (perennially frozen ground) temperatures throughout the northern hemisphere in recent decades [1] indicate that large-scale permafrost. Larch understory vegetation and active layer dynamics. 0732944, OPP-1044610, and PLR-1417700 to SN; and PLR-1304040 to HA. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have