College of the Environment, Wesleyan University , Middletown, CT , United States.
PeerJ. 2014 Jun 10;2:e404. doi: 10.7717/peerj.404. eCollection 2014.
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 following a five-day winter freeze. I estimated changes in forest stand structure and species composition due to freezing and drought in the Chisos Mountains of Big Bend National Park using permanent monitoring plot data. The drought killed over half (63%) of the sampled trees over the entire elevation gradient. Significant mortality occurred in trees up to 20 cm diameter (P < 0.05). Pinus cembroides Zucc. experienced the highest seedling and tree mortality (P < 0.0001) (55% of piñon pines died), 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 in tree density (P < 0.02) (30.9% and 20.7%, respectively). Subsequent droughts under climate change will likely cause even greater damage to trees that survived this record drought, especially if such events follow 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.
本研究记录了德克萨斯州大本德国家公园因有记录以来最严重的一年干旱而导致的树木死亡情况，该干旱发生在为期五天的冬季冻结之后。我使用大本德国家公园奇索斯山脉的永久性监测样地数据，估算了因冰冻和干旱导致的森林林分结构和物种组成的变化。这场干旱导致了整个海拔梯度上超过一半（63%）的抽样树木死亡。在直径达 20 厘米的树木中，死亡率达到了显著水平（P<0.05）。胶柏（Pinus cembroides Zucc.）经历了最高的幼苗和树木死亡率（P<0.0001）（55%的柏树苗死亡），而在 2012 年，比 2009 年观察到的立枯柏木多了五倍以上。刺柏（Juniperus deppeana vonSteudal）和牧豆树（Quercus emoryi Leibmann）的树木密度也显著下降（P<0.02）（分别为 30.9%和 20.7%）。在气候变化下，未来的干旱很可能会对经历了这场创纪录干旱的树木造成更大的损害，尤其是如果此类事件发生在冰冻之后。本研究的结果突出了西南地区树木对气候变化的脆弱性，以及未来森林结构的变化可能会对大规模的群落产生影响。
