Study of the interactions between snowpack and forest cover in the Aragonese Pyrenees and their eco-hydrological implications

En las montañas de latitudes medias los bosques y la nieve constituyen recursos naturales prioritarios, tanto desde el punto de vista medioambiental como del económico. Los Pirineos no son una excepción, dado que en esta cordillera ambos elementos coexisten e interaccionan complejamente en el rango altitudinal comprendido entre los 1600 y los 2300–2500 m s.n.m., ocupado en su mayor parte por el piso bioclimático subalpino. Sin embargo, las interacciones que tienen lugar entre los bosques de montaña y el manto de nieve en esta región no habían sido estudiadas en profundidad hasta el momento. Y menos aún se sabía acerca de la respuesta de las interacciones bosque–nieve al proceso de calentamiento que está aconteciendo en esta cordillera y que seespera se vea acelerado en las próximas décadas. De manera que, el principal objetivo de la presente Tesis Doctoral es avanzar en el conocimiento existente sobre las interacciones que se producen entre los bosques de montaña y el manto de nieve en los Pirineos, desde una perspectiva eco–hidrológica. La misma, se presenta como un compendio de cuatro publicaciones científicas, en las que diferentes objetivos específicos son evaluados.La mayor parte de este estudio interdisciplinar tuvo lugar en un valle de montaña (Baños de Panticosa) localizado en el Pirineo central. El diseño experimental incluyó cuatro bosques de Pinus uncinata de diversas características ambientales, entre las cuales cabe mencionar su diferente elevación (desde 1674 a 2104 m s.n.m.), exposición, estructura forestal y microclimatología debido a la compleja topografía de este enclave montañoso. En estos bosques se monitorizó intensivamente, entre 2015 y 2020, la evolución del manto de nieve, las condiciones climáticas y del suelo, la fenología de los pinos, su xylogénesis, la variación intra–anual del radio de su tronco y la concentración de carbohidratos no estructurales presentes en su albura y acículas jóvenes. En este marco se contextualizó la primera publicación científica que compone esta Tesis, la cual informó con detalle sobre los efectos que la cubierta forestal produce en la dinámica del manto de nieve en esta región, destacando las similitudes y diferencias que existen entre áreas cercanas y entre distintas temporadas de invierno. La segunda publicación científica, identificó por primera vez una señal nival en el crecimiento radial inter–anual de P. uncinata. Esta investigación se contextualizó en un contexto espacio–temporal más amplio, analizando dendrocronológicamente 36 bosques de P. uncinata localizados en las principales cordilleras montañosas del NE Peninsular y las condiciones nivales acontecidas en los mismos en las últimas décadas. La tercera publicación científica, describió cómo la dinámica estacional del manto de nieve es capaz de modificar ciertas condiciones microclimáticas de los bosques estudiados en el valle de Baños de Panticosa, y demostró cómo esta influencia nival determina en buena parte el crecimiento radial intra–anual de P. uncinata. La cuarta publicación científica, exploró cómo los futuros cambios del clima pirenaico podrían afectar a las actuales interacciones bosque–nieve que tienen lugar en el valle de Baños de Panticosa. Para ello, se simularon los cambios que experimenta la dinámica nival en los bosques estudiados bajo varios grados de forzamiento climático.Los resultados obtenidos en esta Tesis demuestran, por tanto, que el manto de nieve y los bosques de P. uncinata interactúan en ambos sentidos en las áreas de montaña analizadas, si bien, tales interacciones están sujetas a importantes fuentes de variabilidad espacial y temporal. Por una parte, la cubierta forestal, principalmente debido a la intercepción que producen las copas de los pinos y a la alteración que produce en el balance de energía, determina la distribución del manto de nieve, su magnitud y su temporalidad. Por otra parte, el manto de nieve, principalmente mediante las modificaciones que produce en el régimen de temperaturas del suelo, influye en el crecimiento radial intra e inter–anual de P. uncinata, independientemente del ampliamente conocido efecto que tiene la temperatura del aire durante la temporada de crecimiento en la formación de sus anillos. Además, esta Tesis sugiere que la cubierta forestal puede tener un importante rol en la sensibilidad del manto de nieve ante los futuros cambios que se esperan en el clima de los Pirineos.Las cuestiones abordadas en esta Tesis, titulada "Estudio de las interacciones entre el manto de nieve y la cubierta forestal en el Pirineo Aragonés y sus implicaciones eco–hidrológicas", son de gran interés científico, pero también proporcionan una valiosa información de gran aplicabilidad en la presente y futura gestión de los recursos hídricos y forestales del Pirineo.<br /

Comparando procesos nivales sobre diferentes cordilleras ibéricas

13 páginas.- Presentación elaborada para las Jornadas IPErinas 2016, celebradas en Zaragoza, el 15 de diciembre de 2016Peer reviewe

Snow dynamics influence tree growth by controlling soil temperature in mountain pine forests

Snow dynamics are key to understanding tree growth in mountain forests and future response to climate change. However, precise monitoring of microclimate conditions and variables related to tree growth and functioning are lacking. To advance on those issues, snow cover and microclimate conditions, tree phenology, xylogenesis, intraannual radial growth and the concentration of sapwood and needle non-structural carbohydrates were intensively monitored in four Pinus uncinata forests along an altitudinal gradient over three years in a Pyrenean valley (NE Spain). Snow dynamics exerted strong influence on soil temperature and moisture, particularly before and during the early growing season. Soil temperature was the most relevant microclimate variable during the overall xylogenesis, mainly influencing the production of mature tracheids. Large snow accumulation resulted in later snow depletion and a consequent delay in soil warming onset. Low soil temperatures in the spring, related to prolonged snow persistence, retarded cambial reactivation and led to lower growth rate. Despite strong spatial variability among plots, wood production was determined by snow dynamics in three out of the four studied plots. This study highlights the major role played by early and late growing season soil temperatures on radial growth of mountain conifers. The results of this study suggest that a future shallower and more transitory snowpack in the studied forests, together with warmer soil and air temperatures, may increase radial growth and productivity of similar mid-latitude, young mountain forests

Daily gridded datasets of snow depth and snow water equivalent for the Iberian Peninsula from 1980 to 2014

We present snow observations and a validated daily gridded snowpack dataset that was simulated from downscaled reanalysis of data for the Iberian Peninsula. The Iberian Peninsula has long-lasting seasonal snowpacks in its different mountain ranges, and winter snowfall occurs in most of its area. However, there are only limited direct observations of snow depth (SD) and snow water equivalent (SWE), making it difficult to analyze snow dynamics and the spatiotemporal patterns of snowfall. We used meteorological data from downscaled reanalyses as input of a physically based snow energy balance model to simulate SWE and SD over the Iberian Peninsula from 1980 to 2014. More specifically, the ERA-Interim reanalysis was downscaled to 10 km 10 km resolution using the Weather Research and Forecasting (WRF) model. The WRF outputs were used directly, or as input to other submodels, to obtain data needed to drive the Factorial Snow Model (FSM). We used lapse rate coefficients and hygrobarometric adjustments to simulate snow series at 100m elevations bands for each 10 km 10 km grid cell in the Iberian Peninsula. The snow series were validated using data from MODIS satellite sensor and ground observations. The overall simulated snow series accurately reproduced the interannual variability of snowpack and the spatial variability of snow accumulation and melting, even in very complex topographic terrains. Thus, the presented dataset may be useful for many applications, including land management, hydrometeorological studies, phenology of flora and fauna, winter tourism, and risk management. The data presented here are freely available for download from Zenodo (https://doi.org/10.5281/zenodo.854618). This paper fully describes the work flow, data validation, uncertainty assessment, and possible applications and limitations of the database.Esteban Alonso-González is supported by the Spanish Ministry of Economy and Competitiveness (BES- 2015-071466). This study was funded by the Spanish Ministry of Economy and Competitiveness projects CGL2014-52599-P 10 (Estudio del manto de nieve en la montaña española y su respuesta a la variabilidad y cambio climatico) and CGL2017- 82216-R (HIDROIBERNIEVE) and (with additional support from the European Community funds, FEDER) CGL2013-48539-R (Impactos del cambio climático en los recursos hídricos de la cuenca del Duero a alta resolución). Also, the Regional Government of Andalusia has funded this research with the project P11-RNM-7941 (Impactos del Cambio Climático en la cuenca del Guadalquivir, LICUA)

Efecto de los factores abióticos en los parámetros estructurales de una comunidad de sotobosque de un pinar de repoblación y un robledal

Comparamos la diversidad y composición de especies del sotobosque en un pinar de repoblación (Pinus sylvestris) y un robledal o melojar de Quercus pyrenaica. Nuestro principal objetivo fue conocer el efecto de la especie arbórea dominante sobre las características estructurales dentro de nuestra comunidad. La prueba de disimilaridad y posterior clasificación determinó que ambos sotobosques constituyen una única comunidad, sabiendo que el robledal alberga mayor riqueza de especies; esto último guarda relación con la cantidad de radiación solar que llega al sotobosqu

Effect of snow on mountain river regimes: an example from the Pyrenees

16 páginas.- Ilustraciones.- 3 apéndices al final del documento.- © Higher Education Press and Springer-Verlag Berlin Heidelberg 2017.The purpose of this study was to characterize mountain river regimes in the Spanish Pyrenees and to assess the importance of snow accumulation and snowmelt on the timing of river flows. Daily streamflow data from 9 gauging stations in the Pyrenees were used to characterize river regimes. These data were analyzed by hydrological indices, with a focus on periods when snow accumulation and snowmelt occurred. These results were combined with data on Snow Water Equivalent (SWE) (from measurements of depth and density of snow in the main river basins and also simulated by a process-based hydrological model), snowmelting (simulated by a process-based hydrological model), precipitation (from observations), and temperature (from observations). Longitude and elevation gradients in the Pyrenees explain the transition of river regimes from those that mostly had low nival signals (in the west and at low elevations) to those that mostly had high nival signals (low winter runoff and late spring peakflow, in the east and at high elevations). Although trend analyses indicated no statistically significant changes, there was a trend of decreased nival signal over time in most of the analyzed rivers. Our results also demonstrated that snow processes cannot explain all of the interannual variability of river regimes, because the temporal distribution of liquid precipitation and temperature play key roles in hydrography.This study was funded by the research project CGL2014-52599-P, "Estudio del manto de nieve en la montana espanola y su respuesta a la variabilidad y cambio climatico" from the Spanish Ministry of Economy and Competitiveness. The authors thank the ERHIN program for providing the snow data used in this study.Peer reviewe

Small-Scale Effect of Pine Stand Pruning on Snowpack Distribution in the Pyrenees Observed with a Terrestrial Laser Scanner

Forests in snow-dominated areas have substantial effects on the snowpack and its evolution over time. Such interactions have significant consequences for the hydrological response of mountain rivers. Thus, the impact of forest management actions on the snow distribution, and hence the storage of water in the form of snow during winter and spring, is a major concern. The results of this study provide the first detailed comparison of the small-scale effect of forest characteristics on the snowpack distribution, assessed prior to and following major modification of the structure of the canopy by pruning of the lower branches of the trees to 3 m above the ground. This is a common management practice aimed at reducing the spread of forest fires. The snowpack distribution was determined using terrestrial laser scanning (LiDAR technology) at a high spatial resolution (0.25 m) over a 1000 m2 study area during 23 survey dates over three snow seasons in a small study area in the central Pyrenees. The pruning was conducted during summer following the snow season in the second year of the study (i.e., the study duration encompassed two seasons prior to canopy pruning and one following). Principal component analysis (PCA) was used to identify recurring spatial patterns of snow distribution. The results showed that pruning reduced the average radius of the canopy of trees by 1.2 m, and increased the clearance around the trunks, as all the branches that formerly contacted the ground were removed. However, the impact on the snowpack was moderate. The PCA revealed that the spatial configuration of the snowpack did not change significantly, as the principal components included survey days from different periods of the snow season, and did not discriminate days surveyed prior to and following pruning. Nevertheless, removal of the lower branches reduced the area beneath the canopy by 36%, and led to an average increase in total snow depth of approximately 14%

Performance Assessment of Optical Satellite-Based Operational Snow Cover Monitoring Algorithms in Forested Landscapes

International audienceForest cover is a crucial factor that influences the performance of optical satellite-based snow cover monitoring algorithms. However, evaluation of such algorithms in forested landscapes is rare due to lack of reliable in situ data in such regions. In this investigation, we assessed the performance of the operational snow detection (SCA) and fractional snow cover estimation (FSC) algorithms employed by the Copernicus Land Monitoring Service for High-Resolution Snow & Ice Monitoring (HRSI) with a combination of Sentinel-2 and Landsat-7/8 satellite scenes, lidar-based, and in situ datasets. These algorithms were evaluated over test sites located in the forested mountainous landscape of the Pyrenees in Spain and the Sierra Nevada in the USA. Over the Pyrenees site, the effectiveness of snow cover detection was evaluated with respect to a time-series of in situ snow depth measurements logged over test plots with different aspects, canopy cover, and solar irradiance. Over the Sierra Nevada site, the impact of ground vegetation was assessed over the under canopy fractional snow cover retrievals using airborne lidar-derived fractional vegetation cover information. The analyses over the Pyrenees indicated a good accuracy of snow detection with the exception of plots with eithe

Sensitivity of forest–snow interactions to climate forcing: Local variability in a Pyrenean valley

© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Mountain forests affect spatial and temporal variability of snow processes through snow interception and by modifying the energy balance of snowpack. The high sensitivity of snow cover to seasonal temperatures in mid–latitude mountains is well known and is of particular interest with regard to a future warmer climate. The snowpack in the Pyrenees is expected to be the most impacted by climate change in the Mediterranean mountains, where future climate trends project rising temperatures and decreasing precipitation. This study analyzes how changes in temperature and precipitation can affect current forest–snow interactions in four forests, located near each other but under contrasting topographic settings, in the Spanish Pyrenees. This understanding will allow us to anticipate the future hydrological responses of Pyrenean forested mountain basins. The research was accomplished by performing a sensitivity analysis using simulations from the Cold Regions Hydrological Model (CRHM) and by comparing forest canopy sites (F) vs. openings (O). The CRHM platform focuses on the incorporation of physically based descriptions of snow–dominated regions hydrological processes. It was found that forest cover induced different snowpack sensibility to climatic change conditions in the studied forests. Delayed onset of snow accumulation (F: 13 days·°C−1; O: 5 days·°C−1) and reduced snowpack duration (F: 28 %·°C−1; O: 23 %·°C−1) under warmer temperatures were more intense in areas beneath the forest canopy compared to openings. A lower annual peak of snow water equivalent (SWE) (F: 81 mm·°C−1; O: 129 mm·°C−1), earlier melt-out date (F: 8 days·°C−1; O: 10 days·°C−1) and slower melting rates (F: 0.4 mm·day−1·°C−1; O: 0.5 mm·day−1·°C−1) with increasing temperatures were more intense in forest openings. The forest–driven reduction in snowpack duration (40%) was significantly enhanced with warming (10% per °C). Lower precipitation (20% precipitation reduction) could increase the response of this forest effect to warming (32%), while higher precipitation (20% precipitation increment) could reduce it (−26%). There was relevant topographic variability in the forest−snow interactions in response to climate change among the study stands, despite their proximity.This study was supported by the projects: “Bosque, nieve y recursos hídricos en el Pirineo ante el cambio global” funded by Fundación Iberdrola, CGL2014-52599-P (IBERNIEVE) and CGL2017-82216-R (HIDROIBERNIEVE) funded by the Spanish Ministry of Economy and Competitiveness. ASV was supported by a pre–doctoral University Professor Training grant [FPU16/00902] funded by the Spanish Ministry of Education, Culture and Sports. JJC acknowledges funding by project RTI2018-096884-B-C31 (Spanish Ministry of Economy and Competitiveness).Peer reviewe