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Transition zones between vegetation patches in a heterogeneous Arctic landscape: how plant growth and photosynthesis change with abundance at small scales
Authors:Benjamin J. Fletcher  Malcolm C. Press  Robert Baxter  Gareth K. Phoenix
Affiliation:1. Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK
2. College of Life and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
3. School of Biological and Biomedical Sciences, Durham University, Durham, DH1 3LE, UK
Abstract:Arctic vegetation is often highly heterogeneous, consisting of mosaics of vegetation patches. Vegetation transition zones at the boundaries between patches can therefore make up a significant proportion of the landscape, yet performance of plants in transition zones, compared with their main patches, has not been previously investigated. Not only does this limit our understanding of plant productivity in highly heterogeneous landscapes, this knowledge is also needed to improve our understanding of the controls on Arctic ecosystem productivity, and improve modelling uncertainty in estimates of landscape C fluxes. We investigated changes in annual growth and photosynthetic capacity (A max) of two widely distributed dwarf shrubs (Empetrum hermaphroditum and Vaccinium uliginosum) in these species’ own patches where they dominate, in transition zones at their patch edges and vegetation beyond these in vegetation where the species had lowest abundance. Maximum shoot growth occurred not in the study species’ own patches but in patches where both species mixed with a taller dwarf shrub Betula nana. Here shoot growth was 23 and 25% higher for E. hermaphroditum and V. uliginosum, respectively, compared to within their own patches. However, A max was maintained at similar levels at all sites, with a slight tendency toward increased rates in vegetation towards more nutrient-rich, wetter areas compared to the species’ own patches, despite these more nutrient-rich areas having greater shading. There was only a very minor tendency towards decreased A max in vegetation towards drier, more exposed areas compared to the species’ own patches. We show that, despite large changes in abundance and growth, A max is not highly variable at small scales, meaning that variation in A max is unlikely to be a large source of error when modelling whole-landscape C fluxes using measurements made within patches.
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