Tree ring evidence of rapid development of drunken forest induced by permafrost warming
Climate warming risks permafrost degradation causing "drunken" trees toppling along with thaw, but drunken forest also occurs with hummocky ground on continuous permafrost. However, no evidence has previously clarified whether tree leaning is activated by climate warming or is part of a na...
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| Format: | Dataset |
| Language: | unknown |
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2022
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| Online Access: | https://zenodo.org/record/4760439 https://doi.org/10.5061/dryad.dr7sqv9z5 |
| Summary: | Climate warming risks permafrost degradation causing "drunken" trees toppling along with thaw, but drunken forest also occurs with hummocky ground on continuous permafrost. However, no evidence has previously clarified whether tree leaning is activated by climate warming or is part of a natural hummock formation process. We test hypothesis that climate warming accelerates development of drunken forest. Results showed that trees' leaning synchronizes with development of soil hummocks and that tree leaning events are recorded in darkened lignin-rich tree rings. Cell morphology in tree rings shows that tree leaning is caused not by loosening of soil foundation in warming summer but by winter frost heaving. Activities of tree leaning and hummock formation increase with increasing air temperature. Reconstruction of drunken forest development using tree ring record suggests that hummock formation has shifted from periodic events until 1960 to continuous mound rising. Recent warming increases hummock development and soil potentials for carbon storage on continuous permafrost, but further warming risks permafrost degradation and hummock collapse with carbon loss. Field site. We investigated 50 mounds in the Mackenzie upland area between Inuvik and Tsiigehtchic, which are located in the Northwest Territories, Canada (N68°03', W133°30'; Tables S1, S2). The soil is underlain by continuous permafrost that has developed during ice ages with no coverage by Laurentide ice sheet. To reconstruct the development of soil hummocks and drunken trees, we analyzed the tree-ring records of black spruce (Picea mariana L.) and soil microrelief. Inuvik has a subarctic climate; the mean annual air temperature is –8.8ºC. The soil surface is covered by lichen (Cladonia mitis L. and Cladonia stellaris L.)-covered mounds and moss (Pleurozium schreberii L., Hylocomium splendens L., and Sphagnum fuscum L.)-covered depressions. Experimental design. We collected a total of 50 tree disks from 50 hummocks at two plots with contrasting permafrost ... |
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