The role of the understory in litter DOC and nutrient leaching in boreal forests

Geert Hensgens,Matthias Peichl,Quan Zhou,Hjalmar Laudon,Martin Berggren,Itziar Aguinaga Gil

doi:10.1007/s10533-020-00668-5

Geert Hensgens, Matthias Peichl + Show 4 more

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https://doi.org/10.1007/s10533-020-00668-5

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Abstract

Dissolved organic carbon (DOC) derived from plant litter plays an important role in the ecosystem carbon balance and soil biogeochemistry. However, in boreal coniferous forests no integrated understanding exists of how understory vegetation contributes to litter leaching of DOC, nitrogen (N) and phosphorus (P) with different bioavailability at the forest stand level. We characterized water extractable leachates from fresh and decayed litter of dominant canopy and understory sources in a boreal coniferous forest, in order to explore the contribution of understory vegetation as a source of both total and bioavailable forms of DOC, N and P. Recently produced litter from deciduous species (including Vaccinium myrtillus) yielded the highest amounts of DOC. However, this leaching potential decreased exponentially with mass loss through litter decay. The DOC lability generally showed little interspecific variation, although wood derived DOC was more recalcitrant. Lability decreased progressively with litter aging. Water extractable nutrients increased proportionally with DOC, and roughly a quarter (N) or half (P) had directly bioavailable inorganic forms. Scaled to annual litterfall at the forest stand, understory vegetation contributed ~ 80% of the water extractable DOC and nutrients from fresh litter, with > 60% coming from Vaccinium myrtillus alone. However, as litter decomposes, the data suggest a lower leaching potential is maintained with a larger contribution from needle, wood and moss litter. Our study shows that understory vegetation, especially V. myrtillus, is a key driver of litter DOC and nutrient leaching in boreal coniferous forests.

Highlights

IntroductionProduction rates of dissolved organic carbon (DOC) represent a substantial part of the ecosystem carbon (C) balance (Neff and Asner 2001)
In boreal terrestrial ecosystems, production rates of dissolved organic carbon (DOC) represent a substantial part of the ecosystem carbon (C) balance (Neff and Asner 2001)
Our study shows that understory vegetation, especially V. myrtillus, is a key driver of litter DOC and nutrient leaching in boreal coniferous forests

Summary

Introduction

Production rates of dissolved organic carbon (DOC) represent a substantial part of the ecosystem carbon (C) balance (Neff and Asner 2001). Adsorbed DOC contributes to the formation of soil organic matter, which is the largest terrestrial C pool in the global C cycle (Schlesinger and Bernhardt 2013), while mineralized DOC returns to the atmosphere as CO2. The DOC that is not immobilized or degraded may travel with hydrological paths and contribute to the globally significant transfer of C from terrestrial to aquatic ecosystems (Cole et al 2007; Battin et al 2009; Drake et al 2018). Knowledge on the production and turnover of DOC is important for the understanding of how terrestrial ecosystems function and how they interact with other components in the biosphere

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