Experimental warming across a tropical forest canopy height gradient reveals minimal photosynthetic and respiratory acclimation
Experimental warming across a tropical forest canopy height gradient reveals minimal photosynthetic and respiratory acclimation
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DOI：
10.1111/pce.14134
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发表时间：
2021-07-06
影响因子：
7.3
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.
热带森林的冠层循环大量的碳，但我们仍然对这些关键的生态系统将如何应对气候变暖的了解有限。我们实施了原位叶级+ 3摄氏度的实验变暖从下层到上层的两个波多黎各热带树种，Guarea guidonia和Ocotea sintenisii。经过大约1个月的持续变暖，我们评估了光合作用，叶绿素荧光，气孔导度，叶片性状和叶片呼吸的调整。变暖并没有改变净光合温度的反应，无论是物种，然而，最适温度的Ocotea林下叶光合电子传递向上移动。没有Ocotea呼吸处理效应，而Guarea呼吸温度敏感性（Q（10））在加热叶片中下调。光合作用的最适温度（T-opt）从林下到冠层最高位置降低3-5 ℃，这可能是由于冠层上部气孔导度的限制。Guarea上部冠层T-opt与白天平均温度相似，而Ocotea冠层叶片通常在Topt以上操作。由于上层树冠对较高温度的适应性很小，进一步变暖可能使这些森林面临减少二氧化碳吸收的风险，这可能会削弱这一热带森林的整体碳汇强度。
Tropical forest canopies cycle vast amounts of carbon, yet we still have a limited understanding of how these critical ecosystems will respond to climate warming. We implemented in situ leaf-level + 3 degrees C experimental warming from the understory to the upper canopy of two Puerto Rican tropical tree species, Guarea guidonia and Ocotea sintenisii. After approximately 1 month of continuous warming, we assessed adjustments in photosynthesis, chlorophyll fluorescence, stomatal conductance, leaf traits and foliar respiration. Warming did not alter net photosynthetic temperature response for either species; however, the optimum temperature of Ocotea understory leaf photosynthetic electron transport shifted upward. There was no Ocotea respiratory treatment effect, while Guarea respiratory temperature sensitivity (Q(10)) was down-regulated in heated leaves. The optimum temperatures for photosynthesis (T-opt) decreased 3-5 degrees C from understory to the highest canopy position, perhaps due to upper canopy stomatal conductance limitations. Guarea upper canopy T-opt was similar to the mean daytime temperatures, while Ocotea canopy leaves often operated above Topt. With minimal acclimation to warmer temperatures in the upper canopy, further warming could put these forests at risk of reduced CO2 uptake, which could weaken the overall carbon sink strength of this tropical forest.