The importance of hydraulic architecture to the distribution patterns of trees in a central Amazonian forest

Cosme, Luiza Helena Menezes; Schietti, Juliana; Costa, Flávia R. C.; Oliveira, Rafael S.

doi:10.1111/nph.14508

Cited by 96 publications

(129 citation statements)

References 111 publications

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“…We observed a lower P 88 in the HSF, which could be an evolutionary adjustment allowing these species to maintain xylem conductivity in highly seasonal environments where some embolism may be unavoidable, mainly for shallow‐rooted species in HSF (Brum et al ., ). Thus, we emphasize the importance of xylem embolism resistance (represented by the vulnerability curves) as one of key functional traits relevant for explaining the patterns of plant distribution in biodiverse tropical ecosystems, as proposed for other environments (Pockman & Sperry, ; Brodribb, ; Cosme et al ., ; Trueba et al ., ; Oliveira et al ., ).…”

Section: Discussionmentioning

confidence: 99%

Hydraulic traits explain differential responses of Amazonian forests to the 2015 El Niño‐induced drought

et al. 2019

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Summary Reducing uncertainties in the response of tropical forests to global change requires understanding how intra‐ and interannual climatic variability selects for different species, community functional composition and ecosystem functioning, so that the response to climatic events of differing frequency and severity can be predicted. Here we present an extensive dataset of hydraulic traits of dominant species in two tropical Amazon forests with contrasting precipitation regimes – low seasonality forest (LSF) and high seasonality forest (HSF) – and relate them to community and ecosystem response to the El Niño–Southern Oscillation (ENSO) of 2015. Hydraulic traits indicated higher drought tolerance in the HSF than in the LSF. Despite more intense drought and lower plant water potentials in HSF during the 2015‐ENSO, greater xylem embolism resistance maintained similar hydraulic safety margin as in LSF. This likely explains how ecosystem‐scale whole‐forest canopy conductance at HSF maintained a similar response to atmospheric drought as at LSF, despite their water transport systems operating at different water potentials. Our results indicate that contrasting precipitation regimes (at seasonal and interannual time scales) select for assemblies of hydraulic traits and taxa at the community level, which may have a significant role in modulating forest drought response at ecosystem scales.

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Section: Discussionmentioning

confidence: 99%

Hydraulic traits explain differential responses of Amazonian forests to the 2015 El Niño‐induced drought

et al. 2019

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“…Such anisohydric behaviour of the lower canopy is an important strategy to sustaining plant productivity, considering that drought‐induced mortality risk might be mitigated by some other compensatory mechanism such as xylem structural reinforcement or plasticity (Cosme et al., ; Fonti et al., ; Markesteijn, Poorter, Bongers, Paz, & Sack, ). In fact, our results help to explain the low mortality rates observed in small trees (DBH <20 cm) in throughfall exclusion experiments in the Amazon (Da Costa et al., ; Nepstad, Tohver, Ray, Moutinho, & Cardinot, ), and even the increased growth rates of small trees following the substantial mortality of larger trees during droughts at two Eastern Amazon forest sites (Brando et al., ; Rowland et al., ).…”

Section: Discussionmentioning

confidence: 99%

Hydrological niche segregation defines forest structure and drought tolerance strategies in a seasonal Amazon forest

et al. 2018

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The relationship between rooting depth and above‐ground hydraulic traits can potentially define drought resistance strategies that are important in determining species distribution and coexistence in seasonal tropical forests, and understanding this is important for predicting the effects of future climate change in these ecosystems. We assessed the rooting depth of 12 dominant tree species (representing c. 42% of the forest basal area) in a seasonal Amazon forest using the stable isotope ratios (δ18O and δ2H) of water collected from tree xylem and soils from a range of depths. We took advantage of a major ENSO‐related drought in 2015/2016 that caused substantial evaporative isotope enrichment in the soil and revealed water use strategies of each species under extreme conditions. We measured the minimum dry season leaf water potential both in a normal year (2014; Ψnon‐ENSO) and in an extreme drought year (2015; ΨENSO). Furthermore, we measured xylem hydraulic traits that indicate water potential thresholds trees tolerate without risking hydraulic failure (P50 and P88). We demonstrate that coexisting trees are largely segregated along a single hydrological niche axis defined by root depth differences, access to light and tolerance of low water potential. These differences in rooting depth were strongly related to tree size; diameter at breast height (DBH) explained 72% of the variation in the δ18Oxylem. Additionally, δ18Oxylem explained 49% of the variation in P50 and 70% of P88, with shallow‐rooted species more tolerant of low water potentials, while δ18O of xylem water explained 47% and 77% of the variation of minimum Ψnon‐ENSO and ΨENSO. We propose a new formulation to estimate an effective functional rooting depth, i.e. the likely soil depth from which roots can sustain water uptake for physiological functions, using DBH as predictor of root depth at this site. Based on these estimates, we conclude that rooting depth varies systematically across the most abundant families, genera and species at the Tapajós forest, and that understorey species in particular are limited to shallow rooting depths. Our results support the theory of hydrological niche segregation and its underlying trade‐off related to drought resistance, which also affect the dominance structure of trees in this seasonal eastern Amazon forest. Synthesis. Our results support the theory of hydrological niche segregation and demonstrate its underlying trade‐off related to drought resistance (access to deep water vs. tolerance of very low water potentials). We found that the single hydrological axis defining water use traits was strongly related to tree size, and infer that periodic extreme droughts influence community composition and the dominance structure of trees in this seasonal eastern Amazon forest.

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“…The NP species would benefit from relatively high hydraulic conductivity and resistance to drought but would have a disadvantage in harsher environments with high risks of winter embolism, contributing to an overall weaker frost resistance than Acer and Betula species, that is, two groups of species well‐known for tolerating extremely low temperatures (Sakai, ). The obvious divergences in xylem hydraulics observed here between these functional groups may provide an important basis for species niche differentiation and co‐existence in the heterogeneous environments (Hao et al ., , ; Taneda & Sperry, ; Christoffersen et al ., ; Cosme et al ., ; Zhang et al ., ).…”

Section: Discussionmentioning

confidence: 99%

Divergent hydraulic strategies to cope with freezing in co‐occurring temperate tree species with special reference to root and stem pressure generation

2018

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Some temperate tree species mitigate the negative impacts of frost-induced xylem cavitation by restoring impaired hydraulic function via positive pressures, and may therefore be more resistant to frost fatigue (the phenomenon that post-freezing xylem becomes more susceptible to hydraulic dysfunction) than nonpressure-generating species. We test this hypothesis and investigate underlying anatomical/physiological mechanisms. Using a common garden experiment, we studied key hydraulic traits and detailed xylem anatomical characteristics of 18 sympatric tree species. These species belong to three functional groups, that is, one generating both root and stem pressures (RSP), one generating only root pressure (RP), and one unable to generate such pressures (NP). The three functional groups diverged substantially in hydraulic efficiency, resistance to drought-induced cavitation, and frost fatigue resistance. Most notably, RSP and RP were more resistant to frost fatigue than NP, but this was at the cost of reduced hydraulic conductivity for RSP and reduced resistance to drought-induced cavitation for RP. Our results show that, in environments with strong frost stress: these groups diverge in hydraulic functioning following multiple trade-offs between hydraulic efficiency, resistance to drought and resistance to frost fatigue; and how differences in anatomical characteristics drive such divergence across species.

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The importance of hydraulic architecture to the distribution patterns of trees in a central Amazonian forest

Cited by 96 publications

References 111 publications

Hydraulic traits explain differential responses of Amazonian forests to the 2015 El Niño‐induced drought

Hydraulic traits explain differential responses of Amazonian forests to the 2015 El Niño‐induced drought

Hydrological niche segregation defines forest structure and drought tolerance strategies in a seasonal Amazon forest

Divergent hydraulic strategies to cope with freezing in co‐occurring temperate tree species with special reference to root and stem pressure generation

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