<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="article-header-container" style="box-sizing: border-box; color: rgb(62, 61, 64); font-family: MuseoSans, Georgia, "Times New Roman", Times, serif; font-size: 15px; font-variant-ligatures: normal; orphans: 2; widows: 2; text-decoration-thickness: initial; outline: 0px !important;"><div class="header-bar-three-container" style="box-sizing: border-box; display: flex; outline: 0px !important;"><div class="header-bar-three" style="box-sizing: border-box; padding-right: 24px; align-self: center; line-height: 1.25rem; font-size: 0.875rem; color: rgb(40, 40, 40); -webkit-box-flex: 0; min-width: 50%; outline: 0px !important;"><span style="background-color: rgb(255, 255, 255);" class="">Front. For. Glob. Change, 12 October 2023<br style="box-sizing: border-box; outline: 0px !important;" class="">Sec. Forest Management<br style="box-sizing: border-box; outline: 0px !important;" class=""><span class="volumeInfo" style="box-sizing: border-box; font-size: 0.75rem; line-height: 1.0625rem; outline: 0px !important;">Volume 6 - 2023 | </span><a href="https://doi.org/10.3389/ffgc.2023.1198156" style="box-sizing: border-box; color: rgb(40, 40, 40); text-decoration: none; outline: none; word-break: break-word; font-size: 0.75rem; line-height: 1.0625rem;" class="">https://doi.org/10.3389/ffgc.2023.1198156</a></span></div><div class="research-topic-container" style="box-sizing: border-box; padding-left: 24px; max-width: 60%; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(213, 213, 213); outline: 0px !important;"><a href="https://www.frontiersin.org/research-topics/47109#articles" data-test-id="relatedRT-link" style="box-sizing: border-box; color: rgb(40, 40, 40); text-decoration: none; outline: none; word-break: break-word; display: block;" class=""><div class="research-topic-data" style="box-sizing: border-box; outline: 0px !important;"><h5 class="topic-title" style="box-sizing: border-box; font-family: MuseoSans, "Lucida Grande", "Trebuchet MS", Arial, sans-serif; font-weight: 500; line-height: 1.25rem; margin: 0px 0px 4px; font-size: 0.875rem; border-top-left-radius: 8px; border-top-right-radius: 8px; border-bottom-right-radius: 8px; border-bottom-left-radius: 8px; outline: 0px !important;"><span style="box-sizing: border-box; outline: 0px !important; background-color: rgb(255, 255, 255);" class="">This article is part of the Research Topic</span></h5><div style="box-sizing: border-box; margin: 0px; font-size: 0.75rem; line-height: 1.0625rem; outline: 0px !important;" class=""><span style="background-color: rgb(255, 255, 255);" class="">The Potential Impacts of Climate Change on the Distribution of Tree Species</span></div><div class="topic-link-trim" data-event="rt-link-click" style="box-sizing: border-box; font-size: 0.75rem; line-height: 1.0625rem; color: rgb(29, 181, 195); margin-top: 6px; outline: 0px !important;"><span style="background-color: rgb(255, 255, 255);" class="">View all 9 Articles <span style="box-sizing: border-box; outline: 0px !important; position: relative; top: 1px;" class=""></span></span></div></div></a></div></div></div><div class="JournalAbstract" style="box-sizing: border-box; color: rgb(62, 61, 64); font-family: MuseoSans, Georgia, "Times New Roman", Times, serif; font-size: 15px; font-variant-ligatures: normal; orphans: 2; widows: 2; text-decoration-thickness: initial; outline: 0px !important;"><a id="h1" name="h1" class="reset-hash-position" style="box-sizing: border-box; color: inherit; outline: none; top: -50px; clear: both; display: block; position: relative; visibility: hidden; word-break: break-word;"></a><h1 style="box-sizing: border-box; margin: 32px 0px; font-size: 2rem; font-weight: 500; line-height: 2.75rem; color: rgb(40, 40, 40); outline: 0px !important;" class=""><span style="background-color: rgb(255, 255, 255);" class="">Mortality thresholds of juvenile trees to drought and heatwaves: implications for forest regeneration across a landscape gradient</span></h1><div class="authors" style="box-sizing: border-box; font-size: 0.875rem; line-height: 1.25rem; color: rgb(40, 40, 40); padding: 0px; outline: 0px !important;"><span style="background-color: rgb(255, 255, 255);" class=""><a href="https://www.frontiersin.org/people/u/2131287" class="user-id-2131287" style="box-sizing: border-box; color: rgb(40, 40, 40); text-decoration: none; outline: none; word-break: break-word; font-size: 0.875rem; line-height: 1.25rem; padding: 0px; display: inline-block; margin-bottom: 8px;"><img class="pr5" src="https://loop.frontiersin.org/images/profile/2131287/24" style="box-sizing: border-box; border: 0px; vertical-align: middle; outline: 0px !important; width: 32px; height: 32px; border-radius: 50%; overflow: hidden; margin-right: -4px; margin-left: 16px; transform: translateX(-12px);">Alexandra R. Lalor</a><span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">1</span><span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">*</span> <img class="pr5" src="https://f96a1a95aaa960e01625-a34624e694c43cdf8b40aa048a644ca4.ssl.cf2.rackcdn.com/Design/Images/newprofile_default_profileimage_new.jpg" style="box-sizing: border-box; border: 0px; vertical-align: middle; outline: 0px !important; width: 32px; height: 32px; border-radius: 50%; overflow: hidden; margin-right: -4px; margin-left: 16px; transform: translateX(-12px);">Darin J. Law<span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">1</span> <img class="pr5" src="https://f96a1a95aaa960e01625-a34624e694c43cdf8b40aa048a644ca4.ssl.cf2.rackcdn.com/Design/Images/newprofile_default_profileimage_new.jpg" style="box-sizing: border-box; border: 0px; vertical-align: middle; outline: 0px !important; width: 32px; height: 32px; border-radius: 50%; overflow: hidden; margin-right: -4px; margin-left: 16px; transform: translateX(-12px);">David D. Breshears<span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">1</span> <img class="pr5" src="https://f96a1a95aaa960e01625-a34624e694c43cdf8b40aa048a644ca4.ssl.cf2.rackcdn.com/Design/Images/newprofile_default_profileimage_new.jpg" style="box-sizing: border-box; border: 0px; vertical-align: middle; outline: 0px !important; width: 32px; height: 32px; border-radius: 50%; overflow: hidden; margin-right: -4px; margin-left: 16px; transform: translateX(-12px);">Donald A. Falk<span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">1</span> <img class="pr5" src="https://f96a1a95aaa960e01625-a34624e694c43cdf8b40aa048a644ca4.ssl.cf2.rackcdn.com/Design/Images/newprofile_default_profileimage_new.jpg" style="box-sizing: border-box; border: 0px; vertical-align: middle; outline: 0px !important; width: 32px; height: 32px; border-radius: 50%; overflow: hidden; margin-right: -4px; margin-left: 16px; transform: translateX(-12px);">Jason P. Field<span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">1</span> <a href="https://www.frontiersin.org/people/u/577174" class="user-id-577174" style="box-sizing: border-box; color: rgb(40, 40, 40); text-decoration: none; outline: none; word-break: break-word; font-size: 0.875rem; line-height: 1.25rem; padding: 0px; display: inline-block; margin-bottom: 8px;"><img class="pr5" src="https://loop.frontiersin.org/images/profile/577174/24" style="box-sizing: border-box; border: 0px; vertical-align: middle; outline: 0px !important; width: 32px; height: 32px; border-radius: 50%; overflow: hidden; margin-right: -4px; margin-left: 16px; transform: translateX(-12px);">Rachel A. Loehman</a><span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">2</span> <img class="pr5" src="https://f96a1a95aaa960e01625-a34624e694c43cdf8b40aa048a644ca4.ssl.cf2.rackcdn.com/Design/Images/newprofile_default_profileimage_new.jpg" style="box-sizing: border-box; border: 0px; vertical-align: middle; outline: 0px !important; width: 32px; height: 32px; border-radius: 50%; overflow: hidden; margin-right: -4px; margin-left: 16px; transform: translateX(-12px);">F. Jack Triepke<span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">3</span> <img class="pr5" src="https://f96a1a95aaa960e01625-a34624e694c43cdf8b40aa048a644ca4.ssl.cf2.rackcdn.com/Design/Images/newprofile_default_profileimage_new.jpg" style="box-sizing: border-box; border: 0px; vertical-align: middle; outline: 0px !important; width: 32px; height: 32px; border-radius: 50%; overflow: hidden; margin-right: -4px; margin-left: 16px; transform: translateX(-12px);">Greg A. Barron-Gafford<span style="box-sizing: border-box; position: relative; font-size: 10px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important;" class="">4</span></span></div><ul class="notes" style="box-sizing: border-box; margin: 16px 0px 24px; font-size: 0.75rem; line-height: 1.0625rem; color: rgb(107, 107, 107); padding: 0px; list-style-type: none; outline: 0px !important;"><li style="box-sizing: border-box; outline: 0px !important;" class=""><span style="background-color: rgb(255, 255, 255);" class=""><span style="box-sizing: border-box; outline: 0px !important;" class=""><span style="box-sizing: border-box; position: relative; font-size: 9px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important; margin-right: 4px;" class="">1</span></span>School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, United States</span></li><li style="box-sizing: border-box; outline: 0px !important;" class=""><span style="background-color: rgb(255, 255, 255);" class=""><span style="box-sizing: border-box; outline: 0px !important;" class=""><span style="box-sizing: border-box; position: relative; font-size: 9px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important; margin-right: 4px;" class="">2</span></span>United States Geological Survey, Alaska Science Center, Anchorage, AK, United States</span></li><li style="box-sizing: border-box; outline: 0px !important;" class=""><span style="background-color: rgb(255, 255, 255);" class=""><span style="box-sizing: border-box; outline: 0px !important;" class=""><span style="box-sizing: border-box; position: relative; font-size: 9px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important; margin-right: 4px;" class="">3</span></span>Southwestern Region, USDA Forest Service, Albuquerque, NM, United States</span></li><li style="box-sizing: border-box; outline: 0px !important;" class=""><span style="background-color: rgb(255, 255, 255);" class=""><span style="box-sizing: border-box; outline: 0px !important;" class=""><span style="box-sizing: border-box; position: relative; font-size: 9px; line-height: 0; vertical-align: baseline; top: -0.5em; outline: 0px !important; margin-right: 4px;" class="">4</span></span>School of Geography, Development and Environment, University of Arizona, Tucson, AZ, United States</span></li></ul><p style="box-sizing: border-box; margin: 0px 0px 8px; color: rgb(40, 40, 40); font-size: 1.125rem; line-height: 1.75rem; outline: 0px !important;" class=""><span style="background-color: rgb(255, 255, 255);" class="">Tree loss is increasing rapidly due to drought- and heat-related mortality and intensifying fire activity. Consequently, the fate of many forests depends on the ability of juvenile trees to withstand heightened climate and disturbance anomalies. Extreme climatic events, such as droughts and heatwaves, are increasing in frequency and severity, and trees in mountainous regions must contend with these landscape-level climate episodes.</span><span style="background-color: rgb(0, 253, 255);" class=""> Recent research focuses on how mortality of individual tree species may be driven by drought and heatwaves, but how juvenile mortality under these conditions would vary among species spanning an elevational gradient</span><span style="background-color: rgb(255, 255, 255);" class="">—given concurrent variation in climate, ecohydrology, and physiology–remains unclear. We address this knowledge gap by implementing a growth chamber study, imposing extreme drought with and without a compounding heatwave, for juveniles of five species that span a forested life zones in the Southwestern United States. </span><span style="background-color: rgb(0, 253, 255);" class="">Overall, the length of a progressive drought required to trigger mortality differed by up to 20 weeks among species. </span><span style="background-color: rgb(255, 255, 255);" class="">Inclusion of a heatwave hastened mean time to mortality for all species by about 1 week. Lower-elevation species that grow in warmer ambient conditions died earlier (<i style="box-sizing: border-box; outline: 0px !important;" class="">Pinus ponderosa</i> in 10 weeks, <i style="box-sizing: border-box; outline: 0px !important;" class="">Pinus edulis</i> in 14 weeks) than did higher-elevation species from cooler ambient conditions (<i style="box-sizing: border-box; outline: 0px !important;" class="">Picea engelmannii</i> and <i style="box-sizing: border-box; outline: 0px !important;" class="">Pseudotsuga menziesii</i> in 19 weeks, and <i style="box-sizing: border-box; outline: 0px !important;" class="">Pinus flexilis</i> in 30 weeks).</span><span style="background-color: rgb(0, 253, 255);" class=""> When exposed to a heatwave in conjunction with drought, mortality advanced significantly only for species from cooler ambient conditions </span><span style="background-color: rgb(255, 255, 255);" class="">(</span><i style="background-color: rgb(255, 255, 255); box-sizing: border-box; outline: 0px !important;" class="">Pinus flexilis</i><span style="background-color: rgb(255, 255, 255);" class="">: 2.7 weeks earlier; </span><i style="background-color: rgb(255, 255, 255); box-sizing: border-box; outline: 0px !important;" class="">Pseudotsuga menziesii</i><span style="background-color: rgb(255, 255, 255);" class="">: 2.0 weeks earlier). Cooler ambient temperatures may have buffered against moisture loss during drought, resulting in longer survival of higher-elevation species despite expected drought tolerance of lower-elevation species due to tree physiology. </span><span style="background-color: rgb(0, 253, 255);" class="">Our study suggests that droughts will play a leading role in juvenile tree mortality and will most directly impact species at warmer climate thresholds, with heatwaves in tandem with drought potentially exacerbating mortality especially of high elevation species. </span><span style="background-color: rgb(255, 255, 255);" class="">These responses are relevant for assessing the potential success of both natural and managed reforestation, as differential juvenile survival following episodic extreme events will determine future landscape-scale vegetation trajectories under changing climate.</span></p></div><div class="">
<meta charset="UTF-8" class=""><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Verdana; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;"><br class="Apple-interchange-newline"><br class=""></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Verdana; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;">~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<br class=""><br class="">A species or ecosystem's recovery from disturbances can be reversed, and fail; e.g., “ … recovery rates decrease as a catastrophic regime shift is approached, a phenomenon known in physics as 'critical slowing down.' …. In all the models we analyzed, critical slowing down becomes apparent quite far from a threshold point, suggesting that it may indeed be of practical use as an early warning signal” <br class=""><br class="">Egbert H. van Nes and Marten Scheffer. Slow Recovery from Perturbations as a Generic Indicator of a Nearby Catastrophic Shift<br class=""> American Naturalist, June 2007</div>
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