Abstract
The Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment has operated five whole-ecosystem warming manipulations (+0, +2.25, +4.5, +6.75, and +9°C) with paired ambient and elevated CO2 atmospheres (eCO2, +500 ppm) for 8 full calendar years (since August 2015). We tracked shrub-layer vegetation responses to the treatments using annual destructive plot sampling. Tree (Picea and Larix) responses were assessed annually using nondestructive dimensional analyses and allometric conversions. Shrub community changes were assessed for key ericaceous shrubs (Rhododendron, Chamaedaphne, and Kalmia), two Vaccinium species (V. angustifolium, V. oxycoccos), graminoid species (mostly Eriophorum), and one common forb (Maianthemum trifolium), plus minor understory species. We tracked annual aboveground net primary production (ANPP) for vascular plant species in gC m−2 y−1 and overall stand contribution in dry mass. We observed a linear increase in shrub-layer aboveground biomass accumulation with warming over time due primarily to an increase in ericaceous shrub abundance. Cumulative biomass increases across the shrub community showed overall positive responses to eCO2 after 8 years. Community composition also changed with warming, with increases in woody shrub density, and the reduction or loss of forbs. The tree community showed minimal initial responses to warming early in the treatments, but since 2020, has shown significant increases in ANPP and individual tree growth with warming. The main driver of change in the vascular plant community was temperature, with less pronounced effects of eCO2 evident. These results indicate an overall increase in ANPP with warming from both the tree and shrub layers of peatland vegetation.
| Original language | English |
|---|---|
| Article number | e2024JG008511 |
| Journal | Journal of Geophysical Research: Biogeosciences |
| Volume | 130 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 2025 |
Funding
The authors would like to thank the following individuals for their participation in the collection of midwinter tree growth data: Kenneth A. Lowe, Zak T. Moore, W. Robert Nettles, Jennifer Peters, Donald E. Todd, Eric J. Wood, and Stan D. Wullschleger. We would also like to thank Deanne Brice and Kenneth A. Lowe for multiyear participation in the collection of the shrub-layer vegetation assessments. Lucas Spaete deserves special recognition for the initial development of the TLS sampling design used for plot and individual tree characteristic assessments. Jake Graham collected TLS data and provided initial analyses and results on tree growth. We thank two anonymous reviewers and the associate editor, whose comments greatly improved this manuscript. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research. Oak Ridge National Laboratory (ORNL) is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. SPRUCE is a cooperative venture between ORNL and the USDA Forest Service with interested university cooperators. We commit to making these data available to the public upon publication via the U.S. Department of Energy Oak Ridge National Laboratory SPRUCE project data repository. This manuscript has been authored in part by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). The authors would like to thank the following individuals for their participation in the collection of midwinter tree growth data: Kenneth A. Lowe, Zak T. Moore, W. Robert Nettles, Jennifer Peters, Donald E. Todd, Eric J. Wood, and Stan D. Wullschleger. We would also like to thank Deanne Brice and Kenneth A. Lowe for multiyear participation in the collection of the shrub‐layer vegetation assessments. Lucas Spaete deserves special recognition for the initial development of the TLS sampling design used for plot and individual tree characteristic assessments. Jake Graham collected TLS data and provided initial analyses and results on tree growth. We thank two anonymous reviewers and the associate editor, whose comments greatly improved this manuscript. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research. Oak Ridge National Laboratory (ORNL) is managed by UT‐Battelle, LLC, for the U.S. Department of Energy under contract DE‐AC05‐00OR22725. SPRUCE is a cooperative venture between ORNL and the USDA Forest Service with interested university cooperators. We commit to making these data available to the public upon publication via the U.S. Department of Energy Oak Ridge National Laboratory SPRUCE project data repository. This manuscript has been authored in part by UT‐Battelle, LLC under Contract No. DE‐AC05‐00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe‐public‐access‐plan ).