ORCID Profile
0000-0002-6339-5981
Current Organisation
Luxembourg Institute of Science and Technology
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Publisher: Authorea, Inc.
Date: 18-09-2023
Publisher: Copernicus GmbH
Date: 28-01-2022
DOI: 10.5194/BG-2021-311
Abstract: Abstract. Forest transpiration is controlled by the atmospheric water demand, potentially constrained by soil moisture availability, and regulated by plant physiological properties. During summer periods, soil moisture availability at sites with thin soils can be limited, forcing the plants to access moisture stored in the weathered bedrock. Land surface models (LSMs) have considerably evolved in the description of the physical processes related to vegetation water use but the effects of bedrock position and water uptake from fractured bedrock has not received much attention. In this study, the Community Land Model version 5.0 (CLM 5) is implemented at four forested sites with relatively shallow bedrock and located across an environmental gradient in Europe. Three different bedrock configurations (i.e., default, deeper, and fractured) are applied to evaluate if the omission of water uptake from weathered bedrock could explain some model deficiencies with respect to the simulation of seasonal transpiration patterns. Sap flow measurements are used to benchmark the response of these three bedrock configurations. It was found that the simulated transpiration response of the default model configuration is strongly limited by soil moisture availability at sites with extended dry seasons. Under these climate conditions, the implementation of an alternative (i.e., deeper and fractured) bedrock configuration resulted in a better agreement between modeled and measured transpiration. At the site with a continental climate, the default model configuration accurately reproduced the magnitude and temporal patterns of the measured transpiration. The implementation of the alternative bedrock configurations at this site provided more realistic water potentials in plant tissues but negatively affects the modeled transpiration during the summer period. Finally, all three bedrock configurations did not show differences in terms of water potentials, fluxes, and performances on the more northern and colder site exhibiting a transition between oceanic and continental climate. Model performances at this site are low, with a clear overestimation of transpiration compared to sap flow data. The results of this study call for increased efforts into better representing lithological controls on plant water uptake in LSMs.
Publisher: Wiley
Date: 02-11-2022
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-7199
Abstract: & & The drought resilience of forest ecosystems depends on the water use strategies and the degree of vulnerability to hydraulic failure of in idual tree species. The coordination between hydraulic and allocation traits along with stomatal control determines the tree water-use strategy, ranging from acquisitive to conservative tree species. This work explores the role of different plant hydraulic traits (& #936 & sub& P50& /sub& , & em& c& /em& & sub& k& /sub& , and & em& k& /em& & sub& max& /sub& in the Community Land Model 5.0) on the simulated plant water use dynamics. We selected two broadleaved tree species (& em& Quercus ilex& /em& L. and & em& Fagus sylvatica& /em& L.) at four SAPFLUXNET experimental sites having contrasting climate conditions. From the range of plant hydraulic traits reported for each species in the Xylem Functional Traits (XFT) database and other literature, the most vulnerable and most resistant parameter combination was chosen as extreme cases. Four sets of experiments were carried out that include modification of the shape of the plant vulnerability curve changing only & #936 & sub& P50& /sub& and & em& c& /em& & sub& k& /sub& (CS-experiment), changing only & em& k& /em& & sub& max& /sub& (k-experiment), changing the three parameters of the vulnerability equation (FC-experiment), and changing gradually & em& k& /em& & sub& max& /sub& (KS-experiment) to test the model sensitivity to & em& k& /em& & sub& max& /sub& . The stand transpiration obtained from SAPFLUXNET was used as a benchmark for the model comparisons. The CS-experiment revealed that a vulnerable configuration increases the modeled transpiration during conditions with le water supply, and causes severe water stress and reduced transpiration during dry periods as compared to a resistant configuration. This indicates that transpiration is hydraulically limited even at le water supply in the model so that the more negative & #936 & sub& P50& /sub& enables increased transpiration. Although a more negative & #936 & sub& P50& /sub& allows the vegetation to access more soil water than would be the case for vulnerable configurations, the difference in actual plant available water is small at this dry end of the water retention curve, and hence the dry period water stress is mainly determined by early-season transpiration. The K- and KS- experiments illustrate the role of & em& k& /em& & sub& max& /sub& to effectively scale up/down the transpiration response. Finally, the FC-experiments revealed the potential of plant hydraulic traits to mimic either conservative or acquisitive water-use strategies, allowing the vegetation to manage more efficiently the soil water resources. This work underlines the importance of selecting a suitable plant hydraulic parametrization contemplating the ersity of plant water use strategies.& &
Publisher: Copernicus GmbH
Date: 20-07-2022
Abstract: Abstract. Forest transpiration is controlled by the atmospheric water demand, potentially constrained by soil moisture availability, and regulated by plant physiological properties. During summer periods, soil moisture availability at sites with thin soils can be limited, forcing the plants to access moisture stored in the weathered bedrock. Land surface models (LSMs) have considerably evolved in the description of the physical processes related to vegetation water use, but the effects of bedrock position and water uptake from fractured bedrock have not received much attention. In this study, the Community Land Model version 5.0 (CLM 5) is implemented at four forested sites with relatively shallow bedrock and located across an environmental gradient in Europe. Three different bedrock configurations (i.e., default, deeper, and fractured) are applied to evaluate if the omission of water uptake from weathered bedrock could explain some model deficiencies with respect to the simulation of seasonal transpiration patterns. Sap flow measurements are used to benchmark the response of these three bedrock configurations. It was found that the simulated transpiration response of the default model configuration is strongly limited by soil moisture availability at sites with extended dry seasons. Under these climate conditions, the implementation of an alternative (i.e., deeper and fractured) bedrock configuration resulted in a better agreement between modeled and measured transpiration. At the site with a continental climate, the default model configuration accurately reproduced the magnitude and temporal patterns of the measured transpiration. The implementation of the alternative bedrock configurations at this site provided more realistic water potentials in plant tissues but negatively affected the modeled transpiration during the summer period. Finally, all three bedrock configurations did not show differences in terms of water potentials, fluxes, and performances on the more northern and colder site exhibiting a transition between oceanic and continental climate. Model performances at this site are low, with a clear overestimation of transpiration compared to sap flow data. The results of this study call for increased efforts into better representing lithological controls on plant water uptake in LSMs.
Location: Costa Rica
No related grants have been discovered for César Dionisio Jiménez-Rodríguez.