Modeling Climate Impacts on Tree Growth to Assess Tree Vulnerability to Drought During Forest Dieback

Forest dieback because of drought is a global phenomenon threatening particular tree populations. Particularly vulnerable stands are usually located in climatically stressing locations such as xeric sites subjected to seasonal drought. These tree populations show a pronounced loss of vitality, growth decline, and high mortality in response to extreme climate events such as heat waves and droughts. However, dieback events do not uniformly affect stands, with some trees showing higher symptoms of drought vulnerability than other neighboring conspecifics. In this study, we investigated if trees showing different vulnerabilities to dieback showed lower growth rates (Grs) and higher sensitivities to the climate in the past using dendroecology and the Vaganov-Shashkin (VS) process-based growth model. We studied two Pinus pinaster stands with contrasting Grs showing recent dieback in the Iberian System, north-eastern Spain. We compared coexisting declining (D) and non-declining (ND) trees with crown defoliation values above and below the 50% threshold, respectively. The mean growth rate was lower in D than in ND trees in the two stands. The two vigor classes showed a growth divergence prior to the dieback onset and different responsiveness to climate. The ND trees were more responsive to changes in spring water balance and soil moisture than D trees, indicating a loss of growth responsiveness to the climate in stressed trees. Such an interaction between water availability and vigor was reflected by the VS-model simulations, which provided evidence for the observation that growth was mainly limited by low soil moisture in both sites. Such an interaction between water availability and vigor was reflected by the VS-model simulations, which provided evidence for the observation that growth was mainly limited by low soil moisture in both sites. The presented comparisons indicated different stand vulnerabilities to drought contingent on-site conditions. Further research should investigate the role played by environmental conditions and individual features such as access to soil water or hydraulic traits and implement them in process-based growth models to better forecast dieback.

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Shifts in Growth Responses to Climate and Exceeded Drought-Vulnerability Thresholds Characterize Dieback in Two Mediterranean Deciduous Oaks

Forests ◽

10.3390/f11070714 ◽

2020 ◽

Vol 11 (7) ◽

pp. 714 ◽

Cited By ~ 1

Author(s):

Raúl Sánchez-Salguero ◽

Michele Colangelo ◽

Luis Matías ◽

Francesco Ripullone ◽

J. Julio Camarero

Keyword(s):

Soil Moisture ◽

Growth Models ◽

Summer Drought ◽

Growth Responses ◽

Drought Vulnerability ◽

Growth Variability ◽

Crown Defoliation ◽

Dry Conditions ◽

Quercus Canariensis ◽

Water Limitations

Drought stress has induced dieback episodes affecting many forest types and tree species worldwide. However, there is scarce information regarding drought-triggered growth decline and canopy dieback in Mediterranean deciduous oaks. These species face summer drought but have to form new foliage every spring which can make them vulnerable to hotter and drier conditions during that season. Here, we investigated two stands dominated by Quercus frainetto Ten. and Quercus canariensis Willd. and situated in southern Italy and Spain, respectively, showing drought-induced dieback since the 2000s. We analyzed how radial growth and its responses to climate differed between non-declining (ND) and declining (D) trees, showing different crown defoliation and coexisting in each stand by: (i) characterizing growth variability and its responsiveness to climate and drought through time, and (ii) simulating growth responses to soil moisture and temperature thresholds using the Vaganov–Shashkin VS-lite model. Our results show how growth responsiveness to climate and drought was higher in D trees for both oak species. Growth has become increasingly limited by warmer-drier climate and decreasing soil moisture availability since the 1990s. These conditions preceded growth drops in D trees indicating they were more vulnerable to warming and aridification trends. Extremely warm and dry conditions during the early growing season trigger dieback. Changes in the seasonal timing of water limitations caused contrasting effects on long-term growth trends of D trees after the 1980s in Q. frainetto and during the 1990s in Q. canariensis. Using growth models allows identifying early-warning signals of vulnerability, which can be compared with shifts in the growth responses to warmer and drier conditions. Our approach facilitates establishing drought-vulnerability thresholds by combining growth models with field records of dieback.

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Soil Moisture Dynamics in Response to Precipitation and Thinning in a Semi-Dry Forest in Northern Mexico

Water ◽

10.3390/w13010105 ◽

2021 ◽

Vol 13 (1) ◽

pp. 105

Author(s):

Argelia E. Rascón-Ramos ◽

Martín Martínez-Salvador ◽

Gabriel Sosa-Pérez ◽

Federico Villarreal-Guerrero ◽

Alfredo Pinedo-Alvarez ◽

...

Keyword(s):

Soil Moisture ◽

Forest Management ◽

Water Availability ◽

Dry Forest ◽

Rainfall Events ◽

Rainfall Characteristics ◽

Northern Mexico ◽

The Difference ◽

The Impact ◽

Moisture Dynamics

Understanding soil moisture behavior in semi-dry forests is essential for evaluating the impact of forest management on water availability. The objective of the study was to analyze soil moisture based in storm observations in three micro-catchments (0.19, 0.20, and 0.27 ha) with similar tree densities, and subject to different thinning intensities in a semi-dry forest in Chihuahua, Mexico. Vegetation, soil characteristics, precipitation, and volumetric water content were measured before thinning (2018), and after 0%, 40%, and 80% thinning for each micro-catchment (2019). Soil moisture was low and relatively similar among the three micro-catchments in 2018 (mean = 8.5%), and only large rainfall events (>30 mm) increased soil moisture significantly (29–52%). After thinning, soil moisture was higher and significantly different among the micro-catchments only during small rainfall events (<10 mm), while a difference was not noted during large events. The difference before–after during small rainfall events was not significant for the control (0% thinning); whereas 40% and 80% thinning increased soil moisture significantly by 40% and 53%, respectively. Knowledge of the response of soil moisture as a result of thinning and rainfall characteristics has important implications, especially for evaluating the impact of forest management on water availability.

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Publisher Correction: Soil moisture–atmosphere feedbacks mitigate declining water availability in drylands

Nature Climate Change ◽

10.1038/s41558-021-00988-w ◽

2021 ◽

Author(s):

Sha Zhou ◽

A. Park Williams ◽

Benjamin R. Lintner ◽

Alexis M. Berg ◽

Yao Zhang ◽

...

Keyword(s):

Soil Moisture ◽

Water Availability

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Summer temperature response to extreme soil water conditions in the Mediterranean transitional climate regime

Climate Dynamics ◽

10.1007/s00382-021-05815-8 ◽

2021 ◽

Author(s):

Stefano Materia ◽

Constantin Ardilouze ◽

Chloé Prodhomme ◽

Markus G. Donat ◽

Marianna Benassi ◽

...

Keyword(s):

Boundary Layer ◽

Soil Moisture ◽

Soil Water ◽

Land Surface ◽

Heat Waves ◽

Climate Regime ◽

Seasonal Forecasts ◽

Near Surface ◽

Surface Temperatures ◽

The Mediterranean

AbstractLand surface and atmosphere are interlocked by the hydrological and energy cycles and the effects of soil water-air coupling can modulate near-surface temperatures. In this work, three paired experiments were designed to evaluate impacts of different soil moisture initial and boundary conditions on summer temperatures in the Mediterranean transitional climate regime region. In this area, evapotranspiration is not limited by solar radiation, rather by soil moisture, which therefore controls the boundary layer variability. Extremely dry, extremely wet and averagely humid ground conditions are imposed to two global climate models at the beginning of the warm and dry season. Then, sensitivity experiments, where atmosphere is alternatively interactive with and forced by land surface, are launched. The initial soil state largely affects summer near-surface temperatures: dry soils contribute to warm the lower atmosphere and exacerbate heat extremes, while wet terrains suppress thermal peaks, and both effects last for several months. Land-atmosphere coupling proves to be a fundamental ingredient to modulate the boundary layer state, through the partition between latent and sensible heat fluxes. In the coupled runs, early season heat waves are sustained by interactive dry soils, which respond to hot weather conditions with increased evaporative demand, resulting in longer-lasting extreme temperatures. On the other hand, when wet conditions are prescribed across the season, the occurrence of hot days is suppressed. The land surface prescribed by climatological precipitation forcing causes a temperature drop throughout the months, due to sustained evaporation of surface soil water. Results have implications for seasonal forecasts on both rain-fed and irrigated continental regions in transitional climate zones.

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Sensitivity of stomatal conductance to soil moisture: implications for tropospheric ozone

10.5194/acp-2017-1057 ◽

2017 ◽

Author(s):

Alessandro Anav ◽

Chiara Proietti ◽

Laurent Menut ◽

Stefano Carnicelli ◽

Alessandra De Marco ◽

...

Keyword(s):

Soil Moisture ◽

Stomatal Conductance ◽

Soil Water ◽

Water Uptake ◽

Atmospheric Chemistry ◽

Water Availability ◽

Dry Deposition ◽

Lower Troposphere ◽

Lower Atmosphere ◽

Water Limitation

Abstract. Soil moisture and water stress play a pivotal role in regulating stomatal behaviour of plants; however, in the last decade, the role of water availability was often neglected in atmospheric chemistry modelling studies as well as in integrated risk assessments, despite through stomata plants remove a large amount of atmospheric compounds from the lower troposphere. The main aim of this study is to evaluate the effect of soil water limitation on stomatal conductance and assess the resulting changes in atmospheric chemistry testing various hypotheses of water uptake by plants in the rooting zone; following the main assumption that roots maximize water uptake, i.e. they adsorb water at different soil depths depending on the water availability, we improve the dry deposition scheme within the chemistry transport model CHIMERE. Results highlight how dry deposition significantly declines when soil moisture is used to regulate the stomatal opening, mainly in the semi-arid environments: in particular, over Europe the amount of ozone removed by dry deposition in one year without considering any soil water limitation to stomatal conductance is about 8.5 Tg O3, while using a dynamic layer that ensures plants to maximize the water uptake from soil, we found a reduction of about 10 % in the amount of ozone removed by dry deposition (~ 7.7 Tg O3). Despite dry deposition occurs from top of canopy to ground level, it affects the concentration of gases remaining into the lower atmosphere with a significant impact on ozone concentration (up to 4 ppb) extending from the surface to the upper troposphere (up to 650 hPa). Our results shed light on the importance of improving the parameterizations of processes occurring at plant level (i.e. from the soil to the canopy) as they have significant implications on concentration of gases in the lower troposphere.

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Does Altering Local Water Availability for an Invasive Plant (Raphanus raphanistrum) Affect Floral Morphology and Reproductive Potential?

American Journal of Undergraduate Research ◽

10.33697/ajur.2015.008 ◽

2015 ◽

Vol 12 (2) ◽

Cited By ~ 2

Author(s):

Natalia Pirimova ◽

Alison Parker ◽

Lesley Campbell

Keyword(s):

Soil Moisture ◽

Foraging Behavior ◽

Water Availability ◽

Community Dynamics ◽

Invasive Plant ◽

Floral Morphology ◽

Insect Community ◽

Raphanus Raphanistrum ◽

Anther Length ◽

Corolla Diameter

Abiotic environmental variation can have dramatic effects on plant floral morphology and nectar or pollen rewards. In response, pollinators may change their foraging behavior and distribution and if pollinators change their foraging behavior or distribution, this could have dramatic effects on the reproductive success of plant populations. To start tackling this problem, we measured the response of floral morphology (corolla diameter, stamen length, and ovule number) of Raphanus raphanistrum to experimental manipulations of field soil moisture. As soil moisture increased, corolla diameter and anther length grew. We expect these changes to provide more visitation rewards for insects in moist conditions. Therefore, water availability influences growth and development of flowers, and may have dramatic effects on insect community dynamics. KEYWORDS: Floral Rewards, Climate, Rain-out Shelters, Flower Morphology, Raphanus raphanistrum, Brassicaceae

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Hydrological Control of Vegetation Greenness Dynamics in Africa: A Multivariate Analysis Using Satellite Observed Soil Moisture, Terrestrial Water Storage and Precipitation

Land ◽

10.3390/land9010015 ◽

2020 ◽

Vol 9 (1) ◽

pp. 15 ◽

Cited By ~ 4

Author(s):

Sabastine Ugbaje ◽

Thomas Bishop

Keyword(s):

Soil Moisture ◽

Water Availability ◽

Water Storage ◽

Important Variable ◽

Delayed Response ◽

Terrestrial Water Storage ◽

Vegetation Greenness ◽

Vegetation Activity ◽

Terrestrial Water ◽

Hydrological Variables

Vegetation activity in many parts of Africa is constrained by dynamics in the hydrologic cycle. Using satellite products, the relative importance of soil moisture, rainfall, and terrestrial water storage (TWS) on vegetation greenness seasonality and anomaly over Africa were assessed for the period between 2003 and 2015. The possible delayed response of vegetation to water availability was considered by including 0–6 and 12 months of the hydrological variables lagged in time prior to the vegetation greenness observations. Except in the drylands, the relationship between vegetation greenness seasonality and the hydrological measures was generally strong across Africa. Contrarily, anomalies in vegetation greenness were generally less coupled to anomalies in water availability, except in some parts of eastern and southern Africa where a moderate relationship was evident. Soil moisture was the most important variable driving vegetation greenness in more than 50% of the areas studied, followed by rainfall when seasonality was considered, and by TWS when the monthly anomalies were used. Soil moisture and TWS were generally concurrent or lagged vegetation by 1 month, whereas precipitation lagged vegetation by 1–2 months. Overall, the results underscore the pre-eminence of soil moisture as an indicator of vegetation greenness among satellite measured hydrological variables.

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A conceptual dynamic vegetation-soil model for arid and semiarid zones

Hydrology and Earth System Sciences ◽

10.5194/hess-12-1175-2008 ◽

2008 ◽

Vol 12 (5) ◽

pp. 1175-1187 ◽

Cited By ~ 17

Author(s):

D. I. Quevedo ◽

F. Francés

Keyword(s):

Soil Moisture ◽

Water Stress ◽

Water Balance ◽

Water Availability ◽

Leaf Biomass ◽

Soil Conditions ◽

Model Parameters ◽

Arid Zones ◽

Soil Model ◽

Arid And Semiarid

Abstract. Plant ecosystems in arid and semiarid climates show high complexity, since they depend on water availability to carry out their vital processes. In these climates, water stress is the main factor controlling vegetation development and its dynamic evolution. The available water-soil content results from the water balance in the system, where the key issues are the soil, the vegetation and the atmosphere. However, it is the vegetation, which modulates, to a great extent, the water fluxes and the feedback mechanisms between soil and atmosphere. Thus, soil moisture content is most relevant for plant growth maintenance and final water balance assessment. A conceptual dynamic vegetation-soil model (called HORAS) for arid and semi-arid zones has been developed. This conceptual model, based on a series of connected tanks, represents in a way suitable for a Mediterranean climate, the vegetation response to soil moisture fluctuations and the actual leaf biomass influence on soil water availability and evapotranspiration. Two tanks were considered using at each of them the water balance and the appropriate dynamic equation for all considered fluxes. The first one corresponds to the interception process, whereas the second one models the evolution of moisture by the upper soil. The model parameters were based on soil and vegetation properties, but reduced their numbers. Simulations for dominant species, Quercus coccifera L., were carried out to calibrate and validate the model. Our results show that HORAS succeeded in representing the vegetation dynamics and, on the one hand, reflects how following a fire this monoculture stabilizes after 9 years. On the other hand, the model shows the adaptation of the vegetation to the variability of climatic and soil conditions, demonstrating that in the presence or shortage of water, the vegetation regulates its leaf biomass as well as its rate of transpiration in an attempt to minimize total water stress.

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On the scaling characteristics of observed and simulated spatial soil moisture fields

Nonlinear Processes in Geophysics ◽

10.5194/npg-16-141-2009 ◽

2009 ◽

Vol 16 (1) ◽

pp. 141-150 ◽

Cited By ~ 20

Author(s):

M. Gebremichael ◽

R. Rigon ◽

G. Bertoldi ◽

T. M. Over

Keyword(s):

Soil Moisture ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Spatial Correlation ◽

Hydrologic Model ◽

Invariance Property ◽

Spatial Average ◽

Hydrologic Models ◽

Model Simulations

Abstract. By providing continuous high-resolution simulations of soil moisture fields, distributed hydrologic models could be powerful tools to advance the scientific community's understanding of the space-time variability and scaling characteristics of soil moisture fields. However, in order to use the soil moisture simulations from hydrologic models with confidence, it is important to understand whether the models are able to represent in a reliable way the processes regulating soil moisture variability. In this study, a comparison of the scaling characteristics of spatial soil moisture fields derived from a set of microwave radiometer observations from the Southern Great Plains 1997 experiment and corresponding simulations using the distributed hydrologic model GEOtop is performed through the use of generalized variograms. Microwave observations and model simulations are in agreement with respect to suggesting the existence of a scale-invariance property in the variograms of spatial soil moisture fields, and indicating that the scaling characteristics vary with changes in the spatial average soil water content. However, observations and simulations give contradictory results regarding the relationship between the scaling parameters (i.e. spatial organization) and average soil water content. The drying process increased the spatial correlation of the microwave observations at both short and long separation distances while increasing the rate of decay of correlation with distance. The effect of drying on the spatial correlation of the model simulations was more complex, depending on the storm and the simulation examined, but for the largest storm in the simulation most similar to the observations, drying increased the long-range correlation but decreased the short-range. This is an indication that model simulations, while reproducing correctly the total streamflow at the outlet of the watershed, may not accurately reproduce the runoff production mechanisms. Consideration of the scaling characteristics of spatial soil moisture fields can therefore serve as a more intensive means for validating distributed hydrologic models, compared to the traditional approach of only comparing the streamflow hydrographs.

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