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Vascular epiphytes show low physiological resistance and high recovery capacity to episodic, short‐term drought in Monteverde, Costa Rica
Functional Ecology ( IF 4.6 ) Pub Date : 2020-07-12 , DOI: 10.1111/1365-2435.13613 Cameron B. Williams 1 , Jessica G. Murray 2 , Andrew Glunk 1 , Todd E. Dawson 3 , Nalini M. Nadkarni 4 , Sybil G. Gotsch 1
中文翻译：
血管附生植物对哥斯达黎加蒙特维德的偶发性短期干旱表现出较低的生理抵抗力和较高的恢复能力
更新日期：2020-07-12
Functional Ecology ( IF 4.6 ) Pub Date : 2020-07-12 , DOI: 10.1111/1365-2435.13613 Cameron B. Williams 1 , Jessica G. Murray 2 , Andrew Glunk 1 , Todd E. Dawson 3 , Nalini M. Nadkarni 4 , Sybil G. Gotsch 1
Affiliation
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- Tropical montane cloud forests support abundant epiphytic vascular plant communities that serve important ecosystem functions, but their reliance on atmospheric inputs of water may make them susceptible to the drying effects of rising cloud bases and more frequent droughts.
- We conducted a common garden experiment to explore the combined effects of decreasing cloud influence—lower humidity, warmer temperature, brighter light—and meteorological drought (i.e. absence of rain) on the physiology and morphology of vascular epiphytes native to primary forests of Monteverde, Costa Rica. The epiphytes, which exhibited C3 photosynthesis, were sourced from a lower montane cloud forest (CF) or a rainforest (RF) below the current cloud base and transplanted into nearby shadehouses (CF or RF shadehouse respectively). Vapour pressure deficit (VPD) and light availability, measured as photosynthetically active radiation, were 2.5 and 3.1 times higher in the RF than the CF shadehouse. Half of the plants were subjected to a severe 4‐week drought followed by a recovery period, and the other half were watered controls.
- Plants subjected to low VPD/light conditions of the CF shadehouse were physiologically and morphologically resistant to the drought treatment. However, compared to control plants, both sources of plants subjected to high VPD/light conditions of the RF shadehouse experienced declines in maximum net photosynthesis (Amax), stomatal conductance (gs) and the proportion of healthy leaves (those not exhibiting chlorosis, desiccation or necrosis). At peak drought, leaves from the RF were 19% thinner than controls. Within 7–14 days after rewatering, Amax, gs and leaf health recovered to nearly the levels of controls. Growth rate, mortality and phenology were unaffected by the treatments.
- The divergent responses to drought in the CF versus RF shadehouses, combined with the recovery in the RF shadehouse, indicate that these epiphytes possess adaptive properties that confer low resistance, but high recovery capacity, to episodes of short‐term drought over a range of cloud influence. In addition, the reduction in Amax suggests stomatal regulation that favours water conservation over carbon acquisition, a strategy that may inform epiphyte responses to rising clouds and increasing drought frequency expected in the long term.
中文翻译：
血管附生植物对哥斯达黎加蒙特维德的偶发性短期干旱表现出较低的生理抵抗力和较高的恢复能力
- 热带山地云雾森林支撑着丰富的附生维管植物群落，这些群落具有重要的生态系统功能，但是它们对大气水的依赖可能会使它们易受云量上升和干旱频发的干旱影响。
- 我们进行了一项普通的花园实验，以探索减少云影响（湿度降低，温度升高，光线明亮）和气象干旱（即无雨）对原产于哥斯达黎加蒙特沃德的原始森林维管植物的生理学和形态的综合影响。丽卡 附生植物，表现出C 3光合作用来自当前云根下方的山地低层云雾森林（CF）或雨林（RF），并移植到附近的遮荫棚（分别为CF遮蔽棚或RF遮荫棚）中。以光合有效辐射测量，蒸汽压亏缺（VPD）和光利用率在CF中比CF遮棚高2.5到3.1倍。一半的植物遭受了严重的4周干旱，随后又恢复了一段时间，另一半则是浇水的对照。
- CF遮蔽棚的低VPD /光照条件下的植物在生理和形态上均抗干旱。但是，与对照植物相比，遭受高VPD /光照条件的RF遮荫植物的两种植物的最大净光合作用（A max），气孔导度（g s）和健康叶片的比例（不表现出绿化作用）均下降，干燥或坏死）。在干旱高峰时，来自RF的叶子比对照组薄19％。再浇水后7–14天内，A max，g s和叶片健康恢复到接近对照水平。增长率，死亡率和物候学不受治疗的影响。
- CF和RF遮蔽棚对干旱的不同响应，再加上RF遮蔽棚的恢复，表明这些附生植物具有适应性，可对一定范围的云层短期干旱产生低抵抗力，但具有较高的恢复能力影响。另外，A max的降低表明气孔调节有利于节水，而不是碳吸收，这种策略可能会告知附生植物对长期上升的云层和干旱频率增加的反应。
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