Examination of the ecohydrological separation hypothesis in a humid subtropical area: Comparison of three methods

Luo, Zidong; Guan, Huade; Zhang, Xinping; Xu, Xiang; Dai, Junjie; Mingquan, Hua

doi:10.1016/j.jhydrol.2019.02.019

Cited by 26 publications

(10 citation statements)

References 26 publications

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“…However, this hypothesis remains largely untested in ecosystems and climatic regimes where there is little evidence that there is true separation from interflow and water held back by soil matric potential ( 45 ). In some instances, where it has been investigated, it was either undetectable ( 46 ) or seasonally variable ( 47 , 48 ). During the growing season of this study, there is a consistently low sampling frequency, as expected, which suggests that the lysimeter volumes we reported reflect changes in ET.…”

Section: Methodsmentioning

confidence: 99%

Intensified vegetation water use under acid deposition

et al. 2019

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Despite the important role vegetation plays in the global water cycle, the exact controls of vegetation water use, especially the role of soil biogeochemistry, remain elusive. In this study, we reveal a new mechanism of soil biogeochemical control of large-scale vegetation water use. Nitrate and sulfate deposition from fossil fuel burning have caused substantial soil acidification, leading to the leaching of soil base cations. Of these, calcium has a unique role in plant cells by regulating stomatal aperture, thus affecting vegetation water use. We hypothesized that the leaching of the soil calcium supply, induced by acid deposition, would increase large-scale vegetation water use. We present evidence from a long-term whole watershed acidification experiment demonstrating that the alteration of the soil calcium supply by acid deposition can significantly intensify vegetation water use (~10% increase in evapotranspiration) and deplete available soil water. These results are critical to understanding future water availability, biogeochemical cycles, and surface energy flux and to help reduce uncertainties in terrestrial biosphere models.

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Section: Methodsmentioning

confidence: 99%

Intensified vegetation water use under acid deposition

et al. 2019

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“…Indistinctively of soil depth, extraction method, season or region, water extracted from soil samples exhibited a clear meteoric origin in line with rainfall isotope seasonality and with minimal enrichment. Remarkably, the coincidence of ground and soil water along the CR MWL ( Figure 10A), suggests no strong evaporative effect and that there is a single soil water pool, rather than two soil water pools as suggested by the ecohydrological separation hypothesis (mobile vs. immobile water) reported by other studies worldwide (e.g., Evaristo et al, 2015;Luo et al, 2019). These results are coincident with those from a recent article by Jiménez-Rodríguez et al 2019, who showed a lack of evaporation and coincidence with the LMWL of soil samples of a wet lowland forest of Costa Rica during the dry season.…”

Section: Groundwater and Surface Water Connectivitymentioning

confidence: 54%

Tracing Water Sources and Fluxes in a Dynamic Tropical Environment: From Observations to Modeling

et al. 2020

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Tropical regions cover approximately 36% of the Earth's landmass. These regions are home to 40% of the world's population, which is projected to increase to over 50% by 2030 under a remarkable climate variability scenario often exacerbated by El Niño Southern Oscillation (ENSO) and other climate teleconnections. In the tropics, ecohydrological conditions are typically under the influence of complex land-oceanatmosphere interactions that produce a dynamic cycling of mass and energy reflected in a clear partition of water fluxes. Here, we present a review of 7 years of a concerted and continuous water stable isotope monitoring across Costa Rica, including key insights learned, main methodological advances and limitations (both in experimental designs and data analysis), potential data gaps, and future research opportunities with a humid tropical perspective. The uniqueness of the geographic location of Costa Rica within the mountainous Central America Isthmus, receiving moisture inputs from the Caribbean Sea (windward) and the Pacific Ocean (complex leeward topography), and experiencing strong ENSO events, poses a clear advantage for the use of isotopic variations to underpin key drivers in ecohydrological responses. In a sequential approach, isotopic variations are analyzed from moisture transport, rainfall generation, and groundwater/surface connectivity to Bayesian and rainfall-runoff modeling. The overarching goal of this review is to provide a robust humid tropical example with a progressive escalation from common water isotope observations to more complex modeling outputs and applications to enhance water resource management in the tropics.

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“…The algorithms of uncertainty analysis for the two models can be found in the Supporting information. The first one, PIB‐A is illustrated in Equations and (3) (Luo et al, ).

δ_{normali + 1} = δ_{Th} \times β_{A} + δ_{i} \times ((), 1 - β_{A})

β_{A} = \frac{δ_{normali + 1} - δ_{i}}{δ_{Th} - δ_{i}} \times 100 %,

where β A is the estimated contribution of throughfall to root‐zone moisture at Time Step i. δ i + 1 is the root‐zone moisture isotopic composition, δ i is the antecedent root‐zone moisture isotopic composition, δ Th is the isotopic composition of rain‐replenishment part of root‐zone moisture between Time Steps i and i + 1.…”

Section: Methodsmentioning

confidence: 99%

Root‐zone moisture replenishment in a native vegetated catchment under Mediterranean climate

Guan

Skrzypek

et al. 2019

Hydrological Processes

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The root-zone moisture replenishment mechanisms are key unknowns required to understand soil hydrological processes and water sources used by plants. Temporal patterns of root-zone moisture replenishment reflect wetting events that contribute to plant growth and survival and to catchment water yield. In this study, stable oxygen and hydrogen isotopes of twigs and throughfall were continuously monitored to characterize the seasonal variations of the root-zone moisture replenishment in a native vegetated catchment under Mediterranean climate in South Australia.The two studied hillslopes (the north-facing slope [NFS] and the south-facing slope [SFS]) had different environmental conditions with opposite aspects. The twig and throughfall samples were collected every~20 days over 1 year on both hillslopes.The root-zone moisture replenishment, defined as percentage of newly replenished root-zone moisture as a complement to antecedent moisture for plant use, calculated by an isotope balance model, was about zero (±25% for the NFS and ± 15% for the SFS) at the end of the wet season (October), increased to almost 100% (±26% for the NFS and ± 29% for the SFS) after the dry season (April and May), then decreased close to zero (±24% for the NFS and ± 28% for the SFS) in the middle of the following wet season (August). This seasonal pattern of root-zone moisture replenishment suggests that the very first rainfall events of the wet season were significant for soil moisture replenishment and supported the plants over wet and subsequent dry seasons, and that NFS completed replenishment over a longer time than SFS in the wet season and depleted the root zone moisture quicker in the dry season. The stable oxygen isotope composition of the intraevent samples and twigs further confirms that rain water in the late wet season contributed little to root-zone moisture. This study highlights the significant role of the very first rain events in the early wet season for ecosystem and provides insights to understanding ecohydrological separation, catchment water yield, and vegetation response to climate changes.

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Examination of the ecohydrological separation hypothesis in a humid subtropical area: Comparison of three methods

Cited by 26 publications

References 26 publications

Intensified vegetation water use under acid deposition

Intensified vegetation water use under acid deposition

Tracing Water Sources and Fluxes in a Dynamic Tropical Environment: From Observations to Modeling

Root‐zone moisture replenishment in a native vegetated catchment under Mediterranean climate

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