A catastrophic tropical drought kills hydraulically vulnerable tree species

Powers, Jennifer S.; Vargas, G German; Brodribb, Timothy J.; Schwartz, Naomi B.; Peréz‐Aviles, Daniel; Smith‐Martin, Chris M.; Becknell, Justin M.; Aureli, Filippo; Blanco, Roger; Calderón-Morales, Erick; Calvo–Alvarado, Julio; Calvo-Obando, Ana Julieta; Chavarría, María Marta; Carvajal-Vanegas, Dorian; Jiménez-Rodríguez, César; Chacon, Evin Murillo; Schaffner, Colleen M.; Werden, Leland K.; Xu, Xiangtao; Medvigy, D.

doi:10.1111/gcb.15037

Cited by 163 publications

(218 citation statements)

References 64 publications

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“…The estimated drought-driven SIF 757 changes across the ERs ( Figure 4B) may be indicators of the changes in GPP dynamics between different drought categories of the same ER. These may also be indicators of mortality [71] of hydraulically vulnerable species [26] that would lead to variations in GPP. Such GPP variations have been reported to have enormous impacts on the structure and function of the Amazonian forest ecosystems [72,73], as well as on their provisioning of ecosystem services [74,75].…”

Section: Sif 757 Response During the El Niño 2015-2016 Extreme Droughmentioning

confidence: 99%

“…Such GPP variations have been reported to have enormous impacts on the structure and function of the Amazonian forest ecosystems [72,73], as well as on their provisioning of ecosystem services [74,75]. However, it is difficult to tell when a plant that contributes with chlorophyll fluorescence radiance to a SIF retrieval is dead [76] and, as a consequence, its ecological niche has been occupied by better adapted species [24][25][26], or when physiological responses have taken place. This is because an OCO-2 SIF retrieval captures a unit of land with a diverse plant community under constant interaction.…”

Section: Sif 757 Response During the El Niño 2015-2016 Extreme Droughmentioning

confidence: 99%

“…A reduced CO 2 uptake limits photosynthetic activity and results in lower SIF values. Drought can also cause mortality via carbon starvation, hydraulic failure, and phloem transport failure [23], which alter the ecological balance by shifting the composition of vegetation communities [24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

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OCO-2 Solar-Induced Chlorophyll Fluorescence Variability across Ecoregions of the Amazon Basin and the Extreme Drought Effects of El Niño (2015–2016)

et al. 2020

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Amazonian ecosystems are major biodiversity hotspots and carbon sinks that may lose species to extinction and become carbon sources due to extreme dry or warm conditions. We investigated the seasonal patterns of high-resolution solar-induced chlorophyll fluorescence (SIF) measured by the satellite Orbiting Carbon Observatory-2 (OCO-2) across the Amazonian ecoregions to assess the area´s phenology and extreme drought vulnerability. SIF is an indicator of the photosynthetic activity of chlorophyll molecules and is assumed to be directly related to gross primary production (GPP). We analyzed SIF variability in the Amazon basin during the period between September 2014 and December 2018. In particular, we focused on the SIF drought response under the extreme drought period during the strong El Niño in 2015–2016, as well as the 6-month drought peak period. During the drought´s peak months, the SIF decreased and increased with different intensities across the ecoregions of the Amazonian moist broadleaf forest (MBF) biome. Under a high temperature, a high vapor pressure deficit, and extreme drought conditions, the SIF presented differences from −31.1% to +17.6%. Such chlorophyll activity variations have been observed in plant-level measurements of active fluorescence in plants undergoing physiological responses to water or heat stress. Thus, it is plausible that the SIF variations in the ecoregions’ ecosystems occurred as a result of water and heat stress, and arguably because of drought-driven vegetation mortality and collateral effects in their species composition and community structures. The SIF responses to drought at the ecoregional scale indicate that there are different levels of resilience to drought across MBF ecosystems that the currently used climate- and biome-region scales do not capture. Finally, we identified monthly SIF values of 32 ecoregions, including non-MBF biomes, which may give the first insights into the photosynthetic activity dynamics of Amazonian ecoregions.

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Section: Sif 757 Response During the El Niño 2015-2016 Extreme Droughmentioning

confidence: 99%

Section: Sif 757 Response During the El Niño 2015-2016 Extreme Droughmentioning

confidence: 99%

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OCO-2 Solar-Induced Chlorophyll Fluorescence Variability across Ecoregions of the Amazon Basin and the Extreme Drought Effects of El Niño (2015–2016)

et al. 2020

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“…Consequently, we would argue that cortical collapse and resistant xylem together provides the ideal mechanism for Selaginella plants to survive diurnal excursions in VPD, or even short periods of soil water deficit, with stomata that cannot close sufficiently. It is also tempting to speculate that the highly resistant xylem of Selaginella may have also evolved to protect species from rare episodes of drought, which can also occur in tropical forests (Powers et al, 2020).…”

Section: Researchmentioning

confidence: 99%

Drought‐induced lacuna formation in the stem causes hydraulic conductance to decline before xylem embolism in Selaginella

et al. 2020

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Summary Lycophytes are the earliest diverging extant lineage of vascular plants, sister to all other vascular plants. Given that most species are adapted to ever‐wet environments, it has been hypothesized that lycophytes, and by extension the common ancestor of all vascular plants, have few adaptations to drought. We investigated the responses to drought of key fitness‐related traits such as stomatal regulation, shoot hydraulic conductance (Kshoot) and stem xylem embolism resistance in Selaginella haematodes and S. pulcherrima, both native to tropical understory. During drought stomata in both species were found to close before declines in Kshoot, with a 50% loss of Kshoot occurring at −1.7 and −2.5 MPa in S. haematodes and S. pulcherrima, respectively. Direct observational methods revealed that the xylem of both species was resistant to embolism formation, with 50% of embolized xylem area occurring at −3.0 and −4.6 MPa in S. haematodes and S. pulcherrima, respectively. X‐ray microcomputed tomography images of stems revealed that the decline in Kshoot occurred with the formation of an air‐filled lacuna, disconnecting the central vascular cylinder from the cortex. We propose that embolism‐resistant xylem and large capacitance, provided by collapsing inner cortical cells, is essential for Selaginella survival during water deficit.

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“…The impacts of drought on diverse biomes across the globe are substantial, with prolonged drought resulting in forest dieback and plant mortality, changes in species distribution, local extinction and decline in ecosystem function and resilience (Allen et al, 2010;Goulden and Bales, 2019;Powers et al, 2020). Predicting the impacts of drought on biomes and plant lineages remains a challenging task for scientists, as most predictions relying on species distribution models (SDM) and climatic niche data lack the species physiological tolerance (Fitzpatrick et al, 2008;McDowell et al, 2008;Razgour et al, 2019;Urban, 2015).…”

Section: Introductionmentioning

confidence: 99%

Drought tolerance ofHakeaspecies (Proteaceae) from a range of biomes and life-histories predicted by climatic niche

Oyanoghafo

Brien

Choat

et al. 2020

Preprint

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Extreme drought conditions across the globe are impacting biodiversity with serious implications for the persistence of native species. However, quantitative data on drought tolerance is not available for diverse flora to inform conservation management. We quantified physiological drought tolerance in the diverse Hakea genus (Proteaceae) to test predictions based on climatic-origin, life history and functional traits. We sampled terminal branches of replicate plants of 16 species in a common garden. Xylem cavitation was induced in branches under varying water potential (tension) in a centrifuge and the tension generating 50% loss of conductivity (stem P50) was characterized as a metric for drought tolerance. The same branches were used to estimate plant functional traits, including wood density, specific leaf area, and Huber value (sap flow area to leaf area ratio). There was significant variation in stem P50 among species, which was negatively associated with the species climate-origin (rainfall and aridity). Drought tolerance did not differ among life histories; however, a drought avoidance strategy with terete leaf form and greater Huber value may be important for species to colonize and persist in the arid biome. Our findings will contribute to future prediction of species vulnerability to drought and adaptive management under climate change.

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A catastrophic tropical drought kills hydraulically vulnerable tree species

Cited by 163 publications

References 64 publications

OCO-2 Solar-Induced Chlorophyll Fluorescence Variability across Ecoregions of the Amazon Basin and the Extreme Drought Effects of El Niño (2015–2016)

OCO-2 Solar-Induced Chlorophyll Fluorescence Variability across Ecoregions of the Amazon Basin and the Extreme Drought Effects of El Niño (2015–2016)

Drought‐induced lacuna formation in the stem causes hydraulic conductance to decline before xylem embolism in Selaginella

Drought tolerance ofHakeaspecies (Proteaceae) from a range of biomes and life-histories predicted by climatic niche

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