Tree Circumference Changes and Species-Specific Growth Recovery After Extreme Dry Events in a Montane Rainforest in Southern Ecuador
Tree Circumference Changes and Species-Specific Growth Recovery After Extreme Dry Events in a Montane Rainforest in Southern Ecuador
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DOI：
10.3389/fpls.2019.00342
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发表时间：
2019-03
影响因子：
5.6
通讯作者：
Volker Raffelsbauer;Susanne Spannl;Kelly Peña;Darwin Pucha-Cofrep;K. Steppe;A. Bräuning
中科院分区：
文献类型：
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作者：
Volker Raffelsbauer;Susanne Spannl;Kelly Peña;Darwin Pucha-Cofrep;K. Steppe;A. Bräuning
在干旱条件下，即使是热带雨林也可能从碳汇转变为碳源，树种组成也可能因死亡率增加而改变。 2007年7月至2010年11月以及2015年3月至2017年12月，我们在厄瓜多尔南部的热带山地雨林中利用高分辨率树木测量仪监测了属于11个不同树属和3种树木生活型的40个树干直径超过10厘米的树个体的茎直径变化。厄瓜多尔南部是生物多样性热点地区，有300多种属于不同功能类型的不同树种。尽管我们的研究区域的年降雨量约为 2200 毫米，但在 10 月至 11 月所谓的“Veranillo del Niño”（VdN）期间经常出现干旱。在气候变化情景中，预计干旱的频率和强度将比现在更高。我们选择至少连续四天的干旱间隔来研究不同树种如何应对干旱胁迫，从而提出了一些树种是否能更好地适应可能更高的频率和增加干旱期持续时间的问题。我们分析了干旱期间和之后特定物种的平均茎干收缩率和恢复时间。连续10天干旱后，两种落叶阔叶树种Cedrela montana和Handroanthus chrysanthus的茎干缩最大，达2毫米。对连续 600 天的日周长变化的比较显示，在相同气候条件下，各科对茎干缩/增量天数百分比的干旱反应不同，范围从 Graffenrieda emarginata 的 27.5% 至 72.5% 到罗汉松的 45% 至 55%。此外，我们发现两种常绿阔叶树种 Vismia cavanillesiana 和 Tapirira guianensis 在长期（即八到十天）VdN 干旱事件后的恢复时间存在很大差异。 Vismia 仅在 5 天后就恢复到 VdN 之前的茎周长，而 Tapirira 平均需要 52 天才能恢复其周长。因此，干旱频率较高可能会增加物种间竞争和物种特异性死亡率，并可能最终改变生态系统的物种组成。
Under drought conditions, even tropical rainforests might turn from carbon sinks to sources, and tree species composition might be altered by increased mortality. We monitored stem diameter variations of 40 tree individuals with stem diameters above 10 cm belonging to eleven different tree genera and three tree life forms with high-resolution dendrometers from July 2007 to November 2010 and additionally March 2015 to December 2017 in a tropical mountain rainforest in South Ecuador, a biodiversity hotspot with more than 300 different tree species belonging to different functional types. Although our study area receives around 2200 mm of annual rainfall, dry spells occur regularly during so-called “Veranillo del Niño” (VdN) periods in October-November. In climate change scenarios, droughts are expected with higher frequency and intensity as today. We selected dry intervals with a minimum of four consecutive days to examine how different tree species respond to drought stress, raising the question if some species are better adapted to a possible higher frequency and increasing duration of dry periods. We analyzed the averaged species-specific stem shrinkage rates and recovery times during and after dry periods. The two deciduous broadleaved species Cedrela montana and Handroanthus chrysanthus showed the biggest stem shrinkage of up to 2 mm after 10 consecutive dry days. A comparison of daily circumference changes over 600 consecutive days revealed different drought responses between the families concerning the percentage of days with stem shrinkage/increment, ranging from 27.5 to 72.5% for Graffenrieda emarginata to 45–55% for Podocarpus oleifolius under same climate conditions. Moreover, we found great difference of recovery times after longer-lasting (i.e., eight to ten days) VdN drought events between the two evergreen broadleaved species Vismia cavanillesiana and Tapirira guianensis. While Vismia replenished to pre-VdN stem circumference after only 5 days, Tapirira needed 52 days on average to restore its circumference. Hence, a higher frequency of droughts might increase inter-species competition and species-specific mortality and might finally alter the species composition of the ecosystem.