6th Annual ARCUS Award for Arctic Research Excellence

Honorable Mention Interdisciplinary Research

Submitted by		Wendy Loya
Authors		Wendy M. Loya, L.C. Johnson, and K.J. Nadelhoffer
Category		Interdisciplinary Research
Title		Annual dynamics of leaf and root derived carbon in arctic tundra soils
Affiliation		Division of Biology, Kansas State University, Manhattan, KS, USA

Abstract

We investigated the contribution of plant derived carbon (C) in the form of leaf litter, root litter, and root-derived materials incorporated into soil organic matter (SOM) to C storage and cycling. By adding ¹⁴C-labeled leaf or root litter to unlabeled soils or replacing soils with labeled soil, it was possible to trace C movement among four soil C fractions across a simulated year in growth chambers. In addition, we examined how the presence of living plants affected decomposition of litter and SOM by planting half the cores with shoots of the dominant sedge, Eriophorum vaginatum. The greatest losses of ¹⁴C occurred from leaf litter in planted cores (~45% lost), whereas losses from root litter and SOM cores were greater from unplanted cores (~30% lost). The unplanted leaf litter and planted root and SOM treatments lost ~20% of the ¹⁴C added. In general, litter decomposition was more dynamic than SOM decomposition, particularly that of leaf litter. All treatments showed reductions in ¹⁴C activity in the acid-insoluble fraction between the fall and spring harvests, indicating that recalcitrant C compounds might be utilized by microbes when soil temperatures drop below 0ºC. Despite seasonal increases in non-polar extractable compounds in some treatments, little ¹⁴C (<15% of the ¹⁴C added) was stored in this fraction after 1 year of decomposition. Similarly, little C remained in the water-soluble fraction (<10%), except in unplanted root and SOM cores, which had high levels of ¹⁴C remaining in this fraction (17% and 24%, respectively) at the end of the experiment. Most of the ¹⁴C remaining at the end of the simulated year was in the acid-soluble fraction in unplanted leaf litter cores (60%) and planted and unplanted root litter cores (30% for both). In planted leaf litter cores and planted and unplanted SOM cores, the greatest levels of ¹⁴C at the end of the experiment were found in the acid-insoluble fraction. Overall, the presence of living plants stimulated decomposition of leaf litter, presumably by creating more favorable temperature and moisture conditions for decomposition at the soils surface. In contrast, plants appeared to inhibit decomposition of root litter and SOM, perhaps as microbes utilized new inputs of root-derived C supplied by living plants.