Tree mortality from a global-change type drought coupled with a short-duration freezing event in a Southwestern piñon-juniper woodland, USA
- Subject Areas
- Climate Change Biology, Conservation Biology, Ecology, Environmental Sciences, Plant Science
- tree mortality, piñon-juniper woodlands, drought, global change, freeze-thaw cycles, Big Bend National Park
- © 2014 Poulos
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ PrePrints) and either DOI or URL of the article must be cited.
- Cite this article
- 2014. Tree mortality from a global-change type drought coupled with a short-duration freezing event in a Southwestern piñon-juniper woodland, USA. PeerJ PrePrints 2:e237v1 https://doi.org/10.7287/peerj.preprints.237v1
This study documents tree mortality in Big Bend National Park in Texas in response to the most acute one-year drought on record, which occurred in conjunction with a five-day winter freeze. I estimated changes in forest stand structure and species composition due to drought in the Chisos Mountains of Big Bend National Park using permanent monitoring plot data. Tree mortality was pervasive, and it occurred across the entire elevation gradient. Significant mortality occurred in trees up to 20 cm diameter (P < 0.05). Pinus cembroides Zucc. experienced the greatest seedling and tree mortality (P < 0.0001), and over five times as many standing dead pines were observed in 2012 than in 2009. Juniperus deppeana vonSteudal and Quercus emoryi Leibmann also experienced significant declines (P < 0.02). Trees probably died as a result of hydraulic failure, however the preferential mortality of P. cembroides relative to other species could also be tied to its adoption of an isohydric drought tolerance strategy. Subsequent droughts under climate change will likely cause even greater damage to trees that survived this record drought, especially if such events are coupled with freezes. The results from this study highlight the vulnerability of trees in the Southwest to climatic change and that future shifts in forest structure can have large-scale community consequences.
Tree abundance-elevation change
Changes in live tree abundances at low, middle, and high elevation in response to the 2011 freeze and drought event.
Climatic conditions from 2010-2012 in the Chisos Basin of Big Bend National Park, Texas (WRCC 2013) including A) monthly extreme low temperatures, B) mean monthly maximum temperatures, and C) mean monthly precipitation. The weather station is located within 0.25 km of the middle elevation sample sites in this study.
Stand structural data
Changes in forest stand structure due to drought and freezing in 2011 in the Chisos Mountains, Big Bend National Park, Texas. Mean values (+ S. E.) prior to the drought (2009) and after the drought (2011) are shown for A) seedlings by species, B) live trees (> 5 cm dbh) by species, C) live trees in 5 cm diameter classes, and D) standing dead trees. Significant changes between sampling intervals (P < 0.05) are indicated with an (*).
Tree size-mortality regression
Regression of tree dbh (cm) as a predictor of percentage tree mortality. Percentage mortality was significantly (P = 0.0016) correlated with tree size (y = 9.9538e-0.062x). Smaller trees suffered 2 to 5 times higher mortality than larger trees.
Trees by elevation
Changes in mean (+ SE) live tree density (ha-1) at low, middle, and high elevations of the Chisos Mountains, Texas. Significant changes between sampling intervals (P < 0.05) are indicated with an (*).