O. Vogado, Nara, Liddell, Michael J., Laurance, Susan G.W., Campbell, Mason J., Cheesman, Alexander W., Engert, Jayden E., Palma, Ana C., Ishida, Francoise Y., and Cernusak, Lucas A. (2020) The effects of an experimental drought on the ecophysiology and fruiting phenology of a tropical rainforest palm. Journal of Plant Ecology, 13 (6). pp. 744-753.

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Abstract

Aims: Anthropogenic climate change is predicted to increase mean temperatures and rainfall seasonality. How tropical rainforest species will respond to this climate change remains uncertain. Here, we analysed the effects of a 4-year experimental throughfall exclusion (TFE) on an Australian endemic palm (Normambya normanbyi) in the Daintree rainforest of North Queensland, Australia. We aimed to understand the impact of a simulated reduction in rainfall on the species' physiological processes and fruiting phenology.

Methods: We examined the fruiting phenology and ecophysiology of this locally abundant palm to determine the ecological responses of the species to drought. Soil water availability was reduced overall by similar to 30% under a TFE experiment, established in May 2015. We monitored monthly fruiting activity for 8 years in total (2009-2018), including 4 years prior to the onset of the TFE. In the most recent year of the study, we measured physiological parameters including photosynthetic rate, stomatal conductance and carbon stable isotopes (delta C-13, an integrated measure of water use efficiency) from young and mature leaves in both the dry and wet seasons.

Important Findings: We determined that the monthly fruiting activity of all palms was primarily driven by photoperiod, mean solar radiation and mean temperature. However, individuals exposed to lower soil moisture in the TFE decreased significantly in fruiting activity, photosynthetic rate and stomatal conductance. We found that these measures of physiological performance were affected by the TFE, season and the interaction of the two. Recovery of fruiting activity in the TFE palms was observed in 2018, when there was an increase in shallow soil moisture compared with previous years in the treatment. Our findings suggest that palms, such as the N. normanbyi, will be sensitive to future climate change with long-term monitoring recommended to determine population-scale impacts.

摘要 据预测，人为气候变化将季节性地增加平均温度和降雨。热带雨林物种将如何应对这种气候变化仍不确定。本研究分析了对澳大利亚昆士兰北部丹特里雨林的一种澳大利亚特有棕榈(Normambya normanbyi)进行4年降雨实验的影响，目的是了解模拟降雨减少对物种生理 过程和果实物候的影响。我们考察了这种本地丰富的棕榈的果实物候和生理生态学特性，以确定该物种对干旱的生态响应。2015年5月，通过排涝实验，降低了约30%的土壤水分有效性。我们总共监测了8年(2009–2018年)的月度果实活性，包括排涝实验开始之前的4年。在最近几年的研究中，我们测量了干、湿两季幼嫩和成熟叶片的光合速率、气孔导度和碳稳定同位素等生理参数。研究结果表明，所有棕榈树的月度果实活性主要受光周期、平均太阳辐射和平均温度的驱动。然而，暴露于较低土壤水分的植株，其果实活性、光合速率和气孔导度均显著下降。我们还发现这些生理表现受到排涝实验、季节以及两者的相互作用的影响。2018年观察到排涝实验的棕榈的果实活力有所恢复，土壤浅层水分也有所增加(与前几年相比)。我们的研究结果表明，像N. normanbyi 这样的棕榈树对未来的气候变化非常敏感，建议对其进行长期监测，以确定其对种群规模的影响。

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