Photosynthetic and Respiratory Acclimation of Understory Shrubs in Response to in situ Experimental Warming of a Wet Tropical Forest
Photosynthetic and Respiratory Acclimation of Understory Shrubs in Response to in situ Experimental Warming of a Wet Tropical Forest
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DOI：
10.3389/ffgc.2020.576320
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发表时间：
2020-09-30
影响因子：
3.2
通讯作者：
Cavaleri, Molly A.
中科院分区：
文献类型：
--
作者：
Carter, Kelsey R.;Wood, Tana E.;Cavaleri, Molly A.
尽管热带森林对全球碳平衡很重要，但我们对热带植物生理学如何应对气候变暖的理解是有限的。此外，热带森林林下植被对全球碳循环的贡献预计将随着气温的上升而增加，然而，迄今为止，对热带森林植物的原位变暖研究仅集中在上层树冠。我们目前的结果，在波多黎各（热带气候变化的反应实验; TRACE）的一个insitifield-scale +4摄氏度林下红外变暖实验。我们调查了两种常见的林下灌木，Psychotria brachiataandPiper glabrescens，暴露于4个月和8个月的变暖后的气体交换反应。我们以两种方式评估了生理适应：（1）通过比较加热处理与对照处理在升温之前和之后的地块水平生理响应，以及（2）通过检查个体植物对所有地块、季节和处理中的环境驱动因素变化的生理响应。光叶侧耳的光合作用参数在最适温度（A（opt））下没有显著增加，但在最适温度（A（opt））下光合作用速率下降，气孔导度降低。与预期相反的是，这两个物种都没有表现出强有力的呼吸适应证据。只有在干燥的冬季，当日气温升高时，Brachiatadown调节基础呼吸。P. glabrescens没有表现出呼吸适应的证据。出乎意料的是，土壤水分，是最强的环境驱动程序的日常生理温度响应，而不是植被温度。T（opt）增加，而光合作用和基础呼吸下降，土壤干燥，这表明干燥的条件下产生负面影响的碳吸收两个物种。总的来说，早演替灌木P. brachiata对每日温度变化表现出更高的适应潜力，可能减轻慢性变暖的负面影响。P. glabrescens是一种中期演替的灌木，这表明该物种可能无法成功地耐受未来更温暖的温度。这些结果强调了在评估气候变化时考虑物种的重要性，并在大规模变暖实验中说明了土壤水分对植物功能的重要性。
Despite the importance of tropical forests to global carbon balance, our understanding of how tropical plant physiology will respond to climate warming is limited. In addition, the contribution of tropical forest understories to global carbon cycling is predicted to increase with rising temperatures, however,in situwarming studies of tropical forest plants to date focus only on upper canopies. We present results of anin situfield-scale +4 degrees C understory infrared warming experiment in Puerto Rico (Tropical Responses to Altered Climate Experiment; TRACE). We investigated gas exchange responses of two common understory shrubs,Psychotria brachiataandPiper glabrescens, after exposure to 4 and 8 months warming. We assessed physiological acclimation in two ways: (1) by comparing plot-level physiological responses in heated versus control treatments before and after warming, and (2) by examining physiological responses of individual plants to variation in environmental drivers across all plots, seasons, and treatments.P. brachiatahas the capacity to up-regulate (i.e., acclimate) photosynthesis through broadened thermal niche and up-regulation of photosynthetic temperature optimum (T-opt) with warmer temperatures.P. glabrescens, however, did not upregulate any photosynthetic parameter, but rather experienced declines in the rate of photosynthesis at the optimum temperature (A(opt)), corresponding with lower stomatal conductance under warmer daily temperatures. Contrary to expectation, neither species showed strong evidence for respiratory acclimation.P. brachiatadown-regulated basal respiration with warmer daily temperatures during the drier winter months only.P. glabrescensshowed no evidence of respiratory acclimation. Unexpectedly, soil moisture, was the strongest environmental driver of daily physiological temperature responses, not vegetation temperature.T(opt)increased, while photosynthesis and basal respiration declined as soils dried, suggesting that drier conditions negatively affected carbon uptake for both species. Overall,P. brachiata, an early successional shrub, showed higher acclimation potential to daily temperature variations, potentially mitigating negative effects of chronic warming. The negative photosynthetic response to warming experienced byP. glabrescens, a mid-successional shrub, suggests that this species may not be able to as successfully tolerate future, warmer temperatures. These results highlight the importance of considering species when assessing climate change and relay the importance of soil moisture on plant function in large-scale warming experiments.