Climate warming and precipitation redistribution modify tree–grass interactions and tree species establishment in a warm‐temperate savanna. (13th December 2012)

• Record Type: Journal Article
• Authors: Volder, Astrid; Briske, David D.; Tjoelker, Mark G.
• Is Part Of: Global change biology. Volume 19:Number 3(2013:Mar.)
• Page Start: 843
• Page End: 857
• Publication Date: 2012-12-13
• Subjects: Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.12068
• Languages: English
• ISSNs: 1354-1013

Abstract

<abstract abstract-type="main" xml:lang="en" id="gcb12068-abs-0001"> <title>Abstract</title> <p>Savanna tree–grass interactions may be particularly sensitive to climate change. Establishment of two tree canopy dominants, post oak <italic>(Quercus stellata</italic>) and eastern redcedar (<italic>Juniperus virginiana), </italic> grown with the dominant C<sub>4</sub> perennial grass (<italic>Schizachyrium scoparium</italic>) in southern oak savanna of the United States were evaluated under four climatic scenarios for 6 years. Tree–grass interactions were examined with and without warming (+1.5 °C) in combination with a long‐term mean rainfall treatment and a modified rainfall regime that redistributed 40% of summer rainfall to spring and fall, intensifying summer drought. The aim was to determine: (1) the relative growth response of these species, (2) potential shifts in the balance of tree–grass interactions, and (3) the trajectory of juniper encroachment into savannas, under these anticipated climatic conditions. Precipitation redistribution reduced relative growth rate (RGR) of trees grown with grass. Warming increased growth of <italic>J. virginiana</italic> and strongly reduced <italic>Q. stellata</italic> survival. Tiller numbers of <italic>S. scoparium</italic> plants were unaffected by warming, but the number of reproductive tillers was increasingly suppressed by intensified drought each year. Growth rates of <italic>J. virginiana</italic> and <italic>Q. stellata</italic> were suppressed by grass presence early, but in subsequent years were higher when grown with grass. <italic>Quercus stellata</italic> had overall reduced RGR, but enhanced survival when grown with grass, while survival of <italic>J. virginiana</italic> remained near 100% in all treatments. Once trees surpassed a threshold height of 1.1 m, both tiller number and survival of <italic>S. scoparium</italic> plants were drastically reduced by the presence of <italic>J. virginiana, </italic> but not <italic>Q. stellata</italic>. <italic>Juniperus virginiana</italic> was the only savanna dominant in which neither survival nor final aboveground mass were adversely affected by the climate scenario of warming and intensified summer drought. These responses indicate that climate warming and altered precipitation patterns will further accelerate juniper encroachment and woody thickening in a warm‐temperate oak savanna.</p> </abstract>