Coupled plant traits adapted to wetting/drying cycles of substrates co‐define niche multidimensionality

Rodríguez‐Robles, Ulises; Arredondo, J. T.; Huber­-Sannwald, Elisabeth; Yépez, Enrico A.; Ramos‐Leal, José Alfreso

doi:10.1111/pce.13837

Cited by 29 publications

(30 citation statements)

References 44 publications

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“…Zhao et al (2016) also observed intratree fractionation of deuterium between water pools. The trunk and leaves of the oaks at our study site shrink and swell diurnally, due, presumably, to short‐term water storage and release (Hahm et al, 2018), as also recently observed in oak trunks studied by Rodríguez‐Robles et al (2020). It is possible that the roots also similarly store and release water, perhaps to the surrounding materials in the subsurface; if this water is isotopically altered within the plant it could then impart a distinct isotopic signature on the soil and weathered bedrock adjacent to roots, as well as the plant transpiration stream.…”

Section: Discussionsupporting

confidence: 82%

Oak Transpiration Drawn From the Weathered Bedrock Vadose Zone in the Summer Dry Season

Hahm

Rempe

Dralle

et al. 2020

Water Resources Research

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The spatiotemporal dynamics of plant water sources are hidden and poorly understood. We document water source use of Quercus garryana growing in Northern California on a profile of approximately 50 cm of soil underlain by 2-4 m of weathered bedrock (sheared shale mélange) that completely saturates in winter, when the oaks lack leaves, and progressively dries over the summer. We determined oak water sources by combining observations of water stable isotope composition, vadose zone moisture and groundwater dynamics, and metrics of tree water status (potential) and use (sapflow). During the spring, oak xylem water is isotopically similar to the seasonal groundwater and shallow, evaporatively enriched soil moisture pools. However, as soils dry and the water table recedes to the permanently saturated, anoxic, low-conductivity fresh bedrock boundary, Q. garryana shifts to using a water source with a depleted isotopic composition that matches residual moisture in the deep soil and underlying weathered bedrock vadose zone. Sapflow rates remain high as late-summer predawn water potentials drop below −2.5 MPa. Neutron probe surveys reveal late-summer rock moisture declines under the oaks in contrast to constant rock moisture levels under grass-dominated areas. We therefore conclude that the oaks temporarily use seasonal groundwater when it occupies the weathered profile but otherwise use deep unsaturated zone moisture after seasonal groundwater recedes. The ample moisture, connected porosity, and oxygenated conditions of the weathered bedrock vadose zone make it a key tree water resource during the long summer dry season of the local Mediterranean climate. Plain Language Summary What are the water sources that allow oaks to transpire through extended dry periods? Oaks in California are thought to tap into groundwater to meet dry season water demand. Here, we show that oaks growing in a savanna woodland instead use tightly held moisture within deep soil and weathered bedrock above the saturated zone. We determined this by matching stable isotopes in the trees' water to these moisture pools. Deep soil and rock moisture were isotopically lighter than shallow soil moisture, which was affected by evaporative enrichment, and the groundwater, which looked more like average wet season rainfall. Monitored moisture declines within the weathered bedrock corroborate the isotopic interpretation that rock moisture sustained oak transpiration. Although the saturated zone was only a few meters below the ground surface in late summer, the trees did not use it due to its low oxygen content and residence in low permeability fresh bedrock. Our findings matter to forest management because of the need to determine when and where trees use groundwater, which regulates ecologically critical baseflow. Moisture extraction from the weathered bedrock unsaturated zone is likely important globally, as forests are widespread on hillslopes with thin soils overlying weathered bedrock.

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Section: Discussionsupporting

confidence: 82%

Oak Transpiration Drawn From the Weathered Bedrock Vadose Zone in the Summer Dry Season

Hahm

Rempe

Dralle

et al. 2020

Water Resources Research

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“…7a). This fits the concept of hydrological niche segregation (Araya et al ., 2011), where co‐existing plants occupy different temporal and spatial niches under moderate drought conditions and do not necessarily compete strongly for water resources so long as water reserves are sufficient (Rodríguez‐Robles et al ., 2020).…”

Section: Discussionmentioning

confidence: 99%

Nonlinear plant–plant interactions modulate impact of extreme drought and recovery on a Mediterranean ecosystem

et al. 2021

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 Interaction effects of different stressors, such as extreme drought and plant invasion, can have detrimental effects on ecosystem functioning and recovery after drought. With ongoing climate change and increasing plant invasion, there is an urgent need to predict the short-and long-term interaction impacts of these stressors on ecosystems.  We established a combined precipitation exclusion and shrub invasion (Cistus ladanifer) experiment in a Mediterranean cork oak (Quercus suber) ecosystem with four treatments: 1) Q. suber control, 2) Q. suber with rain exclusion, 3) Q. suber invaded by shrubs, 4) Q. suber with rain exclusion and shrub invasion. As key parameter, we continuously measured ecosystem water fluxes.  In an average precipitation year, the interaction effects of both stressors were neutral.However, the combination of imposed drought and shrub invasion led to amplifying interaction effects during an extreme drought by strongly reducing tree transpiration.Contrarily, the imposed drought reduced the competitiveness of the shrubs in the following recovery period, which buffered the negative effects of shrub invasion on Q. suber.  Our results demonstrate the highly dynamic and non-linear effects of interacting stressors on ecosystems and urges for further investigations on biotic interactions in a context of climate change pressures.

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“…This result is supported by prior evidence for phylogenetic signals in root traits that may carry implications for RWU (Comas & Eissenstat, 2009; McCormack et al., 2020; Valverde‐Barrantes et al., 2017). Some ecosystems show evidence of seasonal oscillations between niche segregation and direct competition driven by seasonal soil water limitation (Andrews et al., 2012; De Deurwaerder et al., 2018; Kulmatiski et al., 2020; McCormack et al., 2020; Rodríguez‐Robles et al., 2020), suggesting higher‐order interactions between the phylogenetic, niche, and locality hypotheses. In a mixed species forests, co‐occurring trees may rely on similar water sources during dry days, but exhibit divergent RWU depths in response to recent precipitation (Grossiord et al., 2017; Liu et al., 2019; Volkmann et al., 2016).…”

Section: Discussionmentioning

confidence: 99%

Phylogenetic Underpinning of Groundwater Use by Trees

Knighton

Fricke

Evaristo

et al. 2021

Geophysical Research Letters

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Transpiration mediates the transfer of water and energy between the land surface and the atmosphere (Fan et al., 2017;Good et al., 2015), impacting the regulation of climate and distribution of vegetation over land (Beerling & Berner, 2005). Trees play a particularly relevant role in water and energy transfer because they exhibit a wide range of maximum rooting depths (RD MAX ). This suggests that trees may be able to access groundwater that is not immediately available for evaporation. Root water uptake (RWU) of local soil moisture and groundwater by trees thereby influences the partitioning of precipitation between surface runoff (immediate streamflow), water infiltrating into forest soils (i.e., catchment stored water) and transpiration. Establishing a possible environmental and physiological basis for RD MAX and RWU patterns is specifically important because current ecohydrological models at catchment and continental scales tend to oversimplify RWU strategies (Warren et al., 2015). These simplifications in turn limit model veracity and utility for predicting future global change (

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Coupled plant traits adapted to wetting/drying cycles of substrates co‐define niche multidimensionality

Cited by 29 publications

References 44 publications

Oak Transpiration Drawn From the Weathered Bedrock Vadose Zone in the Summer Dry Season

Oak Transpiration Drawn From the Weathered Bedrock Vadose Zone in the Summer Dry Season

Nonlinear plant–plant interactions modulate impact of extreme drought and recovery on a Mediterranean ecosystem

Phylogenetic Underpinning of Groundwater Use by Trees

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