Persistence and memory timescales in root‐zone soil moisture dynamics

Ghannam, Khaled; Nakai, T.; Paschalis, Alec; Oishi, Christopher A.; Kotani, Ayumi; Igarashi, Yasunori; Kumagai, Tomo’omi; Katul, Gabriel G.

doi:10.1002/2015wr017983

Cited by 79 publications

(92 citation statements)

References 60 publications

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“…In an alternative scenario, trees conserve their reliance on winter precipitation, which we refer to as the persistence scenario, and seems to be consistent with the ubiquitous use of winter precipitation as described by Allen et al (). To study these dynamics, decadal length datasets of plant water use are needed because many of the relevant subsurface processes such as residence time of deep water pools (Ghannam et al, ) and the turnover time of fine roots (Matamala et al, ) have multi‐annual timescales. Therefore, the ecohydrological response time and/or adjustment to change may lag the forcing and persist for years after the stressor has been removed.…”

Section: Introductionmentioning

confidence: 99%

Persistence and Plasticity in Conifer Water‐Use Strategies

et al. 2020

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The selective use of seasonal precipitation by vegetation is critical to understanding the residence time and flow path of water in watersheds, yet there are limited datasets to test how climate alters these dynamics. Here, we use measurements of the seasonal cycle of tree ring δ18O for two widespread conifer species in the Rocky Mountains of North America to provide a multi‐decadal depiction of the seasonal origins of forest water use. The results show that while the conifer tree stands had a dominant preference for use of snowmelt, there were multi‐annual periods over the last four decades when use of summer precipitation was preferential. Utilization of summer rain emerged during years with increased snowfall and tree growth, suggesting that summer rain enhanced the transpiration stream only during the periods of highest water use. We hypothesize this could be explained through shallowing of the root profile during wetter periods and/or through the influence of changing water table depths on the residence time of summer precipitation in the root zone. We suggest the tree ring proxy approach used here could be applied in other watersheds to provide critical insight into the temporal dynamics of plant water use that could not be inferred from short measurement campaigns. These data on the seasonal origins of forest water are critical for understanding forest vulnerability to drought, the processes that affect precipitation pathways and residence time in watersheds and the interpretation of tree ring proxy data.

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Section: Introductionmentioning

confidence: 99%

Persistence and Plasticity in Conifer Water‐Use Strategies

et al. 2020

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“…In a planar homogeneous soil volume, its dynamics are governed by the vertically integrated water budget:

Δz \frac{normald θ}{normald t} = P (t) - L (θ, t) = P (t) - (D (θ, t) + ET (θ, t) + Q (θ, t)),

where θ is volumetric soil moisture (−), t is time (T), Δ z is the depth of the soil volume below the surface (L), P ( t ) is the precipitation rate (L T −1 ), and L ( t ) is the rate at which water is lost from the volume due to runoff ( Q ( θ , t )), drainage ( D ( θ , t )), and evapotranspiration ( E T ( θ , t )) (L T −1 ). It is natural to combine these fluxes into the single function L since they are quasi‐deterministic characteristics of the land surface [ Delworth and Manabe , ; Ghannam et al , ], compared to precipitation, which is an exogenous forcing and often modeled stochastically.…”

Section: Introductionmentioning

confidence: 99%

Global characterization of surface soil moisture drydowns

McColl

Wang

Peng

et al. 2017

Geophysical Research Letters

122

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Loss terms in the land water budget (including drainage, runoff, and evapotranspiration) are encoded in the shape of soil moisture “drydowns”: the soil moisture time series directly following a precipitation event, during which the infiltration input is zero. The rate at which drydowns occur—here characterized by the exponential decay time scale τ—is directly related to the shape of the loss function and is a key characteristic of global weather and climate models. In this study, we use 1 year of surface soil moisture observations from NASA's Soil Moisture Active Passive mission to characterize τ globally. Consistent with physical reasoning, the observations show that τ is lower in regions with sandier soils, and in regions that are more arid. To our knowledge, these are the first global estimates of τ—based on observations alone—at scales relevant to weather and climate models.

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“…In addition to the effects of global warming, loss in vegetation cover in some regions produces changes that affect the partition of energy and water fluxes at the surface. Such alterations affect the capacity to assimilate atmospheric CO 2 and the capacity to intercept and store moisture in land surface reservoirs, leading to decreases in availability of water for human and ecosystem uses (Acharya, Halihan, Zou, & Will, ; Ghannam et al, ; Kim & Jackson, ; McColl et al, ; Winter, Harvey, Franke, & Alley, ). This phenomenon can be particularly dramatic in tropical ecosystems and has been documented to occur in a variety of locations worldwide (Allen et al, ; Chazdon, Brenes, & Alvarado, ; Condit, Hubbell, & Foster, ; Khan, Rodgers, Johnsingh, & Mathur, ; Laurance et al, ; Leigh, Windsor, Rand, & Foster, ; Lwanga, ; Phillips et al, ; Rolim, Jesus, Nascimento, do Couto, & Chambers, ; Williamson et al, ).…”

Section: Introductionmentioning

confidence: 99%

On the ecohydrology of the Yucatan Peninsula: Evapotranspiration and carbon intake dynamics across an eco‐climatic gradient

Uuh-Sonda

Gutiérrez-Jurado

Figueroa-Espinoza

et al. 2018

Hydrological Processes

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The hydrology and productivity of the ecosystems of the Yucatan Peninsula (YP) are highly constrained by two factors: (a) the lack of surface drainage networks due to the existence of a highly permeable and connected karstic aquifer roughly the size of the peninsula and (b) a climatic gradient that leads to a transition from seasonally dry deciduous and sub‐deciduous tropical forests, in the north‐western and central parts of the Peninsula, to evergreen forests, in the southern and eastern parts. As a result, surface water fluxes of the YP are restricted to evapotranspiration (ET) that are tightly coupled to ecosystems health and gross primary productivity (GPP). The magnitude and seasonal variation of these fluxes are sensitive to climatic variability and perturbations caused by extreme events such as droughts and tropical storms that are frequent in the YP. In this study, we assess the spatio‐temporal dynamics of ET and GPP above average dry and wet conditions through time series analyses of 15 years of remotely sensed data from both Moderate Resolution Imaging Spectroradiometer and Tropical Rainfall Measuring Mission satellite products. Our results show that ET and GPP follow a regional moisture and temperature gradient that highly controls the distribution of ecosystems within the peninsula. We observe that ET and GPP are in phase with the rainy season in the deciduous forests, but for the evergreen forests, only the GPP is in phase. Additionally, and with the exception of droughts on deciduous ecosystems of the northern part of the YP, the productivity of these ecosystems shows a legacy effect, responding more to a defined trajectory (wetting or drying on the previous years), rather than to punctual extreme climatic events. This has implications on the resilience of these ecosystems to natural perturbations of climate. Comparisons between deciduous and evergreen forest indicate that both types of ecosystems have different plant water use strategies in response to hydrologic variability.

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Persistence and memory timescales in root‐zone soil moisture dynamics

Abstract: Abstract.The memory timescale that characterizes root-zone soil mois-

Cited by 79 publications

References 60 publications

Persistence and Plasticity in Conifer Water‐Use Strategies

Persistence and Plasticity in Conifer Water‐Use Strategies

Global characterization of surface soil moisture drydowns

On the ecohydrology of the Yucatan Peninsula: Evapotranspiration and carbon intake dynamics across an eco‐climatic gradient

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