César Dionisio Jiménez-Rodríguez | Luxembourg Institute of Science and Technology (original) (raw)

Papers by César Dionisio Jiménez-Rodríguez

Forest transpiration is controlled by the atmospheric water demand, potentially constrained by so... more 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.

Interactive comment on "Contribution of understory evaporation in a tropical wet forest" by C. D.... more Interactive comment on "Contribution of understory evaporation in a tropical wet forest" by C. D. Jiménez-Rodríguez et al. C. D. Jiménez-Rodríguez et al.

Tropical dry forests (TDF) in Mesoamerica are highly endangered by the expansion of human activit... more Tropical dry forests (TDF) in Mesoamerica are highly endangered by the expansion of human activities (e.g., agriculture and cattle ranching). In contrast, TDF in Costa Rica have experienced outstanding restoration due to changes in economic and conservation policies. Currently TDF landscapes in Costa Rica are a mosaic of different successional stages. Tree breeding systems and pollination and dispersal syndromes are key elements for understanding restoration processes in TDFs. In this study we describe and compare tree species composition and diversity in three TDF successional stages (early, intermediate and late) in Guanacaste, Costa Rica. We describe for the first time tree species breeding systems and pollination and dispersal syndromes for the largest and most significant TDF remnant in Mesoamerica. We set up nine plots, three per successional stage, and we measured and identified 1,072 trees from 96 species. Species richness and diversity indices were higher for the intermediate stage. Monoecy was the most common breeding system, as in other tropical life zones. Insects were the dominant pollinators, facilitated by the trees’ small inflorescences. Wind was found to be not only the next most influential pollinator, mainly in open and disturbed early forests, but also it was also a good seed dispersal agent. As TDF age increases so does the relevancy of birds and mammals as dispersers; the late stage therefore has more tree species with adaptations to these dispersers

Water

Seasonal wetlands in the tropics are important habitats for local and migratory bird species. In ... more Seasonal wetlands in the tropics are important habitats for local and migratory bird species. In the northwestern Pacific of Costa Rica, Palo Verde National Park has one of the most important seasonal wetlands of Central America. The management history of this wetland has shown the impact of invasive plant species such as Parkinsonia aculeata L. whose cover extension and canopy structure impact not only the ecological niches of bird species, but also the wetland hydrology. A 300 m2 plot was established in a P. aculeata stand to evaluate the role of P. aculeata on the partitioning and redistribution of precipitation. Gross precipitation (PGr), throughfall (PTF) and stemflow (PSF) were measured on a daily basis to determine the interception of precipitation (PI) and net precipitation (PNet). A total of 43 precipitation events were sampled during the wet season of 2003. We measured 530.5 mm of PGr and 458 mm of PTF, with an average sampling error of 0.7 mm or 6.1%. Canopy storage capac...

. Forest transpiration is controlled by the atmospheric water demand, potentially constrained by ... more . 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.

These videos are also on YouTube for easier viewing.</stron... more These videos are also on YouTube for easier viewing. Vertical temperature profiles of the air temperature (red) and the wet-bulb temperature (blue) are animated through time. The measurement tower and an example tree is shown on the right. The time shown is in UTC+1 Different radiation shielding above canopy was available (or absent), which is shown on the right hand side of the video. From 2017/08/03 onwards, a coiled fiber measures the temperature profile in the bottom 1.0 meters. The measurement method is described in doi.org/10.5194/hess-22-819-2018 Part of the raw data (2016) is available on doi.org/10.4121/uuid:5c81f10a-1249-4b85-8dec-2b029dd88b99

Precipitation Partitioning by Vegetation

While evaporation is the largest water consumer of terrestrial water, its importance is often (li... more While evaporation is the largest water consumer of terrestrial water, its importance is often (limitedly) linked to increasing crop productivities. As a consequence, our knowledge of the evaporation process is highly biased by agricultural settings, and results in erroneous estimates of evaporation for other land surfaces and especially for forest systems. The reason why crop and forest systems differ has to do with the vegetation height and what is happening in the space between the plant top and surface. Forests are multi-layered systems, where under the tallest tree species, lower vegetation layers are present. These lower vegetation layers transpire, but at a different rate then the main vegetation, since the atmospheric conditions are different under the canopy. Additionally, the sub-vegetation layers, and also the forest floor, intercept water. Next to different atmospheric conditions per layer, the interception process is highly complex due to differences in interception capacity and a time delay caused by the cascade of water when water flows from the top canopy down to the forest floor. Lastly, forests also have the capacity to store heat and vapor in the air column, biomass, and soil. While this energy storage can be up to 110 W/m2 it is often neglected in evaporation models. To get a better understanding of what is happening inside a forest, for the purpose of evaporation modeling, we should make use of new sensing techniques that allow identifying the rainfall, energy, and evaporation partitioning. This will help to improve evaporation estimates for tall vegetation, like forest, and allow spatial up scaling.

Se establecio un ensayo para evaluar el efecto de cinco sustratos en el crecimiento, contenido fo... more Se establecio un ensayo para evaluar el efecto de cinco sustratos en el crecimiento, contenido foliar de nutrientes y clorofila (valores SPAD-502) de tres especies forestales. Los sustratos fueron: tres tipos de suelos (Ultisol, Andisol, Inceptisol) y de dos suelos odificados; Ultisol mejorado con CaCO3+NPK y Andisol con NPK. Las especies seleccionadas fueron Gmelina arborea (L.) Roxb (melina), Tectona grandis L.f. (teca) y Swietenia macrophylla King (caoba). Se incluyo en los ensayos clones de teca y de melina. Se concluye que el sustrato de Ultisol mejorado tiene tasas de crecimientos comparables o mejores que los otros sustratos, lo que corrobora que este tipo de suelo se puede mejorar para proyectos de reforestacion. Las interacciones entre especies y los niveles de fertilidadson distintas, pero en general el nivel de fertilidad, el pH, la saturacion intercambiable de acidez en porcentaje (SA%) y el nivel de K son factores importantes que controlan el buen crecimiento y se relac...

Fine roots biomass and density distribution in a succesional gradient in the Costa Rican northen ... more Fine roots biomass and density distribution in a succesional gradient in the Costa Rican northen region. This study evaluated root biomass distribution, root area index (RAI) and longitudinal density (RLD) of fine roots (< 5 mm) in a succesional gradient of tropical rain forest in Florencia de San Carlos, Costa Rica. The variation of these parameters was evaluated as a function of soil depth and succesional stage. Root biomass as well as RAI and RLD, decreases as soil profile increases and correlates with changes in the evaluated physical properties of soil. Biomass

We would like to thank the reviewer for his/her valuable comments on our manuscript. We appreciat... more We would like to thank the reviewer for his/her valuable comments on our manuscript. We appreciate that the reviewer acknowledges the interest and relevance of our study. Nonetheless, the reviewer indicated some issues which we will clarify point-by-point: In my opinion, the two main important aspects not justified are: 1) The isotopic differences between the lab air sampled directly, and lab air sampled with the bags are significant. Table 1 presents larger differences between the lab air directly sampled (Laboratory) and sampled with the bags (sample D), than differences

The rainfall interception was determined by evaluating gross rainfall, canopy throughfall and ste... more The rainfall interception was determined by evaluating gross rainfall, canopy throughfall and stemflow in three secondary stages of Tropical wet Forest in the Guanacaste National Park, Costa Rica. Species composition, tree diameter and tree total height were measured in three temporal plots. The Vegetal Area Index (VAI) and the Holdridge Complexity Index (HCI) were estimated to describe the forest structure. The trial was carried out from July to October 2007; measured total rainfall during the sampling period was of 491,2 mm for the Intermediate stage and 706,1 mm in the Early and Late stages. The rainfall interception shows a pattern of increment with the maturity of the three stages of forest succession maturity.

Forest plantation valuation and quality: application in five plantations of Vochysia guatemalensi... more Forest plantation valuation and quality: application in five plantations of Vochysia guatemalensis Donn. Sm. in the North and Caribbean Regions of Costa Rica. A forest plantation quality valuation was conducted in five Vochysia guatemalensis Donn. Sm. plantations in the North and Caribbean Regions of Costa Rica. An evaluation of tree diameter, tree height, stem and logs quality, crown position and phytosanitary state was conducted in each plantation following the methods described by Murillo (2000) and Murillo and Camacho (1998). Most of the plantations were graded as 2 or 3 quality. Acceptable phytosanitary state but unacceptable plantation quality with respect to steam straightness and degree of bifurcation was found for all plantations. The proposed indexes are very practical in assessing heterogeneous forest plantations quality with regards age and management.

Este estudio evaluo la incorporacion de nutrientes de la precipitacion bruta (Pb) y el lavado de ... more Este estudio evaluo la incorporacion de nutrientes de la precipitacion bruta (Pb) y el lavado de copas de un bosque secundario y de plantaciones forestales de Vochysia guatemalensis Donn. Sm. y Vochysia ferruginea Mart. en la Estacion Biologica La Selva, Sarapiqui, Costa Rica. Se analizaron las concentraciones en mg/l de los nutrientes NH4 +, NO3-, K+, Ca2+ y Mg2+, el pH y la conductividad electrica (μS/cm). Los valores de pH y conductividad electrica del agua de lluvia, se incrementaron en su paso a traves de las hojas y ramas de los arboles, debiendose principalmente al aumento de bases, en donde el pH y la CE de la precipitacion bruta fueron los valores mas bajos. El bosque secundario mostro una remocion del 23.8% del NH4 + incorporado por la Pb mientras que Vochysia ferruginea removio el 21% del NO3 - presente en la Pb; ambas retensiones se pueden originar por los requerimientos fisiologicos en la epoca de fructificacion de los arboles dominantes en ambos ecosistemas y la posibl...

Water

Precipitation Partitioning by Vegetation