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Midwestern forests are currently impacted by two prominent invaders, the emerald ash borer (EAB; Agrilus planipennis) and Amur honeysuckle (AHS; Lonicera maackii). The loss of ash (Fraxinus spp.) trees due to EAB invasion can further facilitate AHS invasion, driving changes in the composition of forest leaf litter to reflect a greater portion of labile, more easily decomposed litter. To evaluate the extent to which these changes alter ecosystem function, we conducted litter bag and culture-based decomposition experiments using leaf litter from sugar maple (Acer saccharum), oak (Quercus spp.), black ash (Fraxinus nigra), green ash (Fraxinus pennsylvanica), spicebush (Lindera benzoin) and AHS. To further understand the mechanism driving differences in decay rates, we inoculated six species of decomposing fungi separately onto both single species and multispecies (half AHS and half native species) leaf litter and measured decomposition rate, fungal growth and enzymatic activity in laboratory-based cultures. AHS leaf litter decomposed faster, had increased fungal growth, and had higher activity for carbon degrading enzymes compared to native species leaf litter. Furthermore, multispecies mixtures followed the same patterns as AHS, suggesting that the addition of AHS to leaf litter to native litter will accelerate ecosystem functions related to carbon breakdown. Consequently, forests that experience the invasion of AHS and EAB induced loss of ash are likely to have faster rates of decomposition, potentially resulting in an influx of available nutrients.
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This content will become publicly available on May 12, 2026
Direct and indirect interactions among warming, water, and growing condition slow decomposition rates of temperate-boreal tree litter
Plant litter decomposition is a primary control on carbon fluxes in terrestrial ecosystems around the world. Individually, the key mediators of decomposition rates—litter traits, temperature, and moisture—are relatively well understood. However, our understanding of how combined drivers influence decomposition remains limited. To test how multiple, interactive climate change factors directly alter decomposition rates and indirectly influence leaf litter decomposition rates by altering substrate chemistry, we conducted two decomposition experiments within the Boreal Forest Warming at an Ecotone in Danger (B4WarmED) study in Minnesota, USA. Our first experiment decomposed ambient-grown leaf litter from eight common tree species under a factorial combination of warming and rainfall reduction treatments. We found that the direct effects of combined warming and rainfall reduction increased litter half-life by 42% ± 11% in comparison to ambient plots with no warming or rainfall reduction. In contrast, only rainfall reduction influenced litter mean residence time, which increased by 37% ± 18% in comparison to ambient rainfall plots. Our second experiment decomposed ambient- and warm-grown leaf litter from the same eight species under ambient and warmed conditions. We found that warming slowed decomposition of both litter types, but warm-grown litter had a 22% ± 6.5% shorter half-life than ambient-grown leaf tissue under ambient environmental conditions. Warm grown litter half-life then increased by 36% ± 11% with warmed environmental conditions. Our results highlight that climate change could slow carbon and nutrient cycling in systems where moisture becomes a limiting factor. In addition, our study demonstrates that there may be an overlooked relationship between the growth conditions of plants and the temperature of decomposition. This nuanced understanding of decomposition can then support carbon cycling models and more effective nature-based climate mitigation efforts.
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- Award ID(s):
- 2021898
- PAR ID:
- 10632277
- Publisher / Repository:
- EcoEvorxiv
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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