Open Access
CO2 fertilization plays a minor role in long-term carbon accumulation patterns in temperate pine forests in the southwestern Pyrenees
(Elsevier, 2019) Lo, Yueh-Hsin; Blanco Vaca, Juan Antonio; González de Andrés, Ester; Imbert Rodríguez, Bosco; Castillo Martínez, Federico; Institute for Multidisciplinary Research in Applied Biology - IMAB
Isolating the long-term fertilization effect of CO 2 from other climate- and site-related effects on tree growth has been proven a challenging task. To isolate long-term effects of [CO2] on water use efficiency at ecosystem level, we used the FORECAST Climate forest model, calibrated for Scots pine (Pinus sylvestris L.) forests in the southwestern Pyrenees, growing at a Mediterranean montane site and at a continental subalpine site. Future climate scenarios (RCP 4.5 and RCP 8.5) were generated using a battery of six climate models to estimate daily values of temperature and precipitation in a 90-year series. A factorial experiment was designed to disentangle the importance on C pools of three growing limiting factors (nitrogen limitation, climate (temperature + precipitation) limitation and atmospheric CO 2 concentration). The relative importance of each factor was quantified by comparing the scenario with the limitation of each individual factor turned on with the non-limitation scenario. Positive CO 2 fertilization due to improvement in water use efficiency was detected by the model, but its quantitative impact improving tree growth was minimum: its average increase in ecosystem C pools ranged from 0.3 to 0.9%. At the site with cooler climate conditions (continental), the main limitation for tree growth was climate. Such limitation will be reduced under climate change and the ecosystem will store more carbon. At the site with milder climate conditions (Mediterranean), N availability was the main limiting factor albeit modulated by water availability. Such limitation could be reduced under climate change as N cycling could accelerate (higher litterfall production and decomposition rates) but also increase if droughts become more frequent and severe. In addition, the magnitude of the uncertainty related to climate model selection was much more important than CO 2 fertilization, indicating that atmospheric processes are more important than tree physiological processes when defining how much carbon could be gained (or lost) in forests under climate change. In conclusion, due to the small changes in forest C pools caused by variation of atmospheric CO 2 concentrations compared to changes caused by other growth limiting factors (nutrients, climate), reducing uncertainty related to climate projections seems a more efficient way to reduce uncertainty in tree growth projections than increasing forest model complexity.
Open Access
Pinus sylvestris L. and Fagus sylvatica L. effects on soil and root properties and their interactions in a mixed forest on the Southwestern Pyrenees
(Elsevier, 2021) Yeste Yeste, Antonio; Blanco Vaca, Juan Antonio; Imbert Rodríguez, Bosco; Zozaya Vela, Helena; Elizalde Arbilla, Martín; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Ciencias
Tree species alter soil properties, potentially modifying forest nutrients cycling. In the current management context in which mixed species forests are favoured over monocultures due to their biodiversity and productivity-related advantages, the assessment of species effects on soils, as well as their interactions with other species, gains increasing relevance. In this study, the effects of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) on soil properties were evaluated. Fine roots were paid special attention, measuring their biomass, functional traits (specific root length, root tissue density) and vertical distribution in order to discern the direction of these species interaction, either complementary or competitive. The research was carried out in the Southwestern Pyrenees (northern Spain), in an originally Scots pine stand transformed nowadays into a mixed forest by European beech natural regeneration. Soil and root samples were taken close to pine trees surrounded by other pines in areas that remain similar to pine monospecific stands, and close to pine and beech trees surrounded by both species in mixed areas. A lower C/N ratio was found in the soil close to beech stems. This suggests better quality in mixed litter in comparison to pine litter, leading to higher decomposition rates. Higher fine root biomass was found in the mixed areas mainly due to beech fine roots great abundance, which correlated positively with microbial biomass. Fine roots functional traits such as specific root length and diameter did not vary depending on their proximity to different tree species, though Scots pine fine root biomass decreased sharply when close to beech trees. This reduction, together with the already more abundant fine root biomass of beech, with higher specific root length and root tissue density than pine, lead to a competitive interaction in which European beech tends to dominate the soil at all depths. In this case, no complementarity effect at belowground level, strong enough to allow Scots pines to cope with beech soil colonization, was found under natural conditions.
Open Access
Drought-induced changes in wood density are not prevented by thinning in Scots pine stands
(MDPI, 2018) Candel Pérez, David; Lo, Yueh-Hsin; Blanco Vaca, Juan Antonio; Chiu, Chih-Ming; Camarero, Jesús Julio; González de Andrés, Ester; Imbert Rodríguez, Bosco; Castillo Martínez, Federico; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Density is an important wood mechanical property and an indicator of xylem architecture and hydraulic conductivity. It can be influenced by forest management and climate. We studied the impact of thinning and climate variables on annual stem radial growth (ring width and ring density, and their earlywood and latewood components) in two contrasting Scots pine (Pinus sylvestris L.) stands in northern Spain (one continental, one Mediterranean). At each site, three thinning regimes (control or T0, removing 20% basal area or T20, and removing 30% or T30) were randomly applied to nine plots per site (three plots per treatment) in 1999. Thinning was repeated at the Mediterranean site in 2009 (increasing thinning intensity in T30 to 40%). Eight trees per plot were cored in spring 2014. Second thinning at the Mediterranean site and first thinning at the continental site generally caused significantly wider ring (RW), earlywood (EW) and latewood (LW) widths, although no differences between T20 and T30/40 were found, supporting in part the common observation that radial growth is enhanced following thinning as competition for water and nutrients is reduced. At the Mediterranean site, values of latewood density (LD) and maximum density (Dmax) relative to pre-thinning conditions were significantly lower in T0 than in T30. However, at the continental site, relative changes of ring density (RD) and LD were significantly higher in T0 than in T20 and T30. Climate significantly affected not only RWbut also RD, with significant RD drops during or right after unusually warm-dry years (e.g., 2003, 2011), which were characterized by LD reductions between 5.4 and 8.0%. Such RD decreases were quickly followed by recovery of pre-drought density values. These results indicate trees temporarily reduce LD as a way to enhance hydraulic conductivity during dry summers. However, climate effects on wood density were site-dependent. We also detected that the thinning effect was not intense enough to prevent drought-induced changes in wood density by altering water availability, but it could help to reduce wood properties fluctuations and therefore maintain more homogeneous wood mechanic features.
Open Access
Invertebrate community of Scots pine coarse woody debris in the Southwestern Pyrenees under different thinning intensities and tree species
(MDPI, 2021) Herrera Álvarez, Ximena; Blanco Vaca, Juan Antonio; Imbert Rodríguez, Bosco; Álvarez, Willin; Rivadeneira Barba, Gabriela; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB; Ciencias
Background and Objectives: The forest in the Southwestern Pyrenees Mountains (Northern Spain) is mainly composed of pure Pinus sylvestris L. or a mix of P. sylvestris and Fagus sylvatica L. The most common forest management technique to harvest pine is the application of forest thinning with different intensities. It promotes a change in the forest composition and structure. Taking into consideration this region as a site specific research about this topic, we aimed to understand the CWD invertebrate composition response to different thinning intensities and canopy type of these tree species. Materials and Methods: CWD samples were collected belonging to intermediate and advanced decay classes, approximately 10 cm long and 5 cm in diameter. Using a design of three thinning intensities (0%, 20%, and 40% of basal area removed), with three replications per treatment (nine plots in total), four samples were taken per plot (two per canopy type) to reach 36 samples in total. Meso- and macrofauna were extracted from CWD samples with Berlese– Tullgren funnels, and individuals were counted and identified. Results: Most of the taxonomic groups belonged to mesofauna, mainly to Acari and Collembola orders. On the other hand, the macrofauna represented a minimum percentage of the community composition. Our results indicated that although thinning intensities did not significantly affect the invertebrate community, canopy type and CWD water content influenced significantly. It is imperative to consider in forest management the responses of canopy type and thinning intensities in CWD water content, this disturbance could also slow down the organic matter decomposition process in the soil, thus affecting in the long term the natural cycle of nutrients.
Open Access
Simulando la interacción entre la densidad inicial y los flujos de agua y nutrientes para comprender el desarrollo de rodales mixtos de Pinus sylvestris y Fagus sylvatica bajo cambio climático
(Asociación Española de Ecología Terrestre, 2017) Candel Pérez, David; Blanco Vaca, Juan Antonio; González de Andrés, Ester; Lo, Yueh-Hsin; Imbert Rodríguez, Bosco; Castillo Martínez, Federico; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
La gestión de bosques mixtos se ha convertido en una estrategia de adaptación para reducir los riesgos relacionados con el cambio climático. A su vez, los modelos ecológicos pueden ser una herramienta útil para el estudio del crecimiento y la productividad de dichas masas. En este trabajo se presenta una evaluación de la capacidad del modelo híbrido “FORECAST Climate” de simular el estrés hídrico y la productividad en bosques mixtos de pino silvestre y haya en Navarra (norte de España) y su interacción con distintos niveles de densidad de regenerado. En el estudio se incluyeron tres escenarios climáticos para comprobar la capacidad del modelo para simular los flujos de agua bajo condiciones de cambio climático. Las estimaciones del modelo tanto de estrés hídrico como de acumulación de biomasa se mostraron sensibles a la reducción en la densidad de regeneración inicial. Los resultados indicaron que el modelo muestra la suficiente capacidad para simular los efectos de la competencia entre especies en la mortalidad de árboles en bosques mixtos y estimar variables relacionadas con los flujos hídricos. Por un lado, los efectos más significativos de la densidad del rodal sobre la disponibilidad hídrica aparecen durante la primera etapa de desarrollo, mientras que, por otro, el estrés hídrico es mayor en el caso del haya, aunque la reducción de la competencia podría compensar dicho aumento. Las implicaciones de este trabajo para la gestión adaptativa de bosques mixtos sugieren el actual control de la densidad para que los efectos acumulativos sean significativos en próximas décadas.
Open Access
Drought limits tree growth more than greenness and reproduction: insights from five case studies in Spain
(KeAi Communications, 2025-08-01) Camarero, Jesús Julio; Rubio-Cuadrado, Álvaro; González de Andrés, Ester; Valeriano, Cristina; Pizarro, Manuel; Imbert Rodríguez, Bosco; Lo, Yueh-Hsin; Blanco Vaca, Juan Antonio; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB
Droughts impact forests by influencing various processes such as canopy greenness, tree growth, and reproduction, but most studies have only examined a few of these processes. More comprehensive assessments of forest responses to climate variability and water shortages are needed to improve forecasts of post-drought dynamics. Iberian forests are well-suited for evaluating these effects because they experience diverse climatic conditions and are dominated by various conifer and broadleaf species, many of which exhibit masting. We assessed how greenness, evaluated using the normalized difference vegetation index (NDVI), tree radial growth, and seed or cone production responded to drought in five tree species (three conifers: silver fir (Abies alba), Scots pine (Pinus sylvestris), and stone pine (Pinus pinea); two broadleaves: European beech (Fagus sylvatica) and holm oak (Quercus ilex) inhabiting sites with different aridity. We correlated these data with the standardized precipitation evapotranspiration index (SPEI) using the climate window analysis (climwin) package, which identifies the most relevant climate window. Drought constrained growth more than greenness and seed or cone production. Dry conditions led to high seed or cone production in species found in cool, moist sites (silver fir, beech, and Scots pine). We also found negative associations of cone production with summer SPEI in the drought-tolerant stone pine, which showed lagged growth−cone negative correlations. However, in the seasonally dry holm oak forests, severe droughts constrained both growth and acorn production, leading to a positive correlation between these variables. Drought impacts on greenness, growth, seed, and cone production depended on species phenology and site aridity. A negative correlation between growth and reproduction does not necessarily indicate trade-offs, as both may be influenced by similar climatic factors.
Open Access
8ª Edición de la Escuela de verano de Ecología de Navarra: ecólogas/os por un día
(Asociación Española de Ecología Terrestre, AEET, 2022) Imbert Rodríguez, Bosco; Blanco Vaca, Juan Antonio; Ciencias; Zientziak; Institute for Multidisciplinary Research in Applied Biology - IMAB
Durante los pasados 23 y 24 de junio tuvo lugar la 8ª edición de la Escuela de Verano de Ecología de Navarra de la Universidad Pública de Navarra (UPNA) con el título ‘Ecólogas/os por un día’. En la jornada se impartieron cuatro ponencias por parte de los miembros del grupo de investigación de Ecología y Medio Ambiente de la Universidad Pública de Navarra, pero la mayor parte del tiempo se dedicó al trabajo de campo en el parque. En dicho trabajo de campo los asistentes pudieron trabajar tres temas diferentes: el estudio de las comunidades vegetales en pastos, el estudio de la estructura de una comunidad arbórea y la observación y estimación de censos de aves. Los trabajos incluyeron la demostración y familiarización de los estudiantes con las distintas técnicas y aparatos para medir variables ambientales como luz ambiental, temperatura del suelo, humedad del suelo, diámetro y altura de árboles, así como las técnicas para realizar inventarios florísticos o de fauna.
Open Access
Changes in long-term light properties of a mixed conifer–broadleaf forest in Southwestern Europe
(MDPI, 2021) Ruiz de la Cuesta Vela, Ignacio; Blanco Vaca, Juan Antonio; Imbert Rodríguez, Bosco; Peralta de Andrés, Francisco Javier; Rodríguez Pérez, Javier; Ciencias; Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Natural and anthropogenic factors affect forest structure worldwide, primarily affecting forest canopy and its light properties. However, not only stand-replacing events modify canopy structure, but disturbances of lower intensity can also have important ecological implications. To study such effects, we analyzed long-term changes in light properties of a conifer–broadleaf mixed forest in the Southwestern Pyrenees, placed in the fringe between the Mediterranean and Eurosi- berian biogeographical regions. At this site, a thinning trial with different intensities (0%, 20%, and 30–40% basal area removed) took place in 1999 and 2009, windstorms affected some plots in 2009 and droughts were recurrent during the sampling period (2003, 2005, 2011). We monitored light properties during 14 years (2005–2019) with hemispherical photographs. We applied partial autocorrelation functions to determine if changes between years could be attributed to internal canopy changes or to external disturbances. In addition, we mapped the broadleaf canopy in 2003, 2008, and 2016 to calculate broadleaf canopy cover and richness at the sampling points with different buffer areas of in- creasing surface. We applied generalized linear mixed models to evaluate the effects of light variables on canopy richness and cover. We found that light variables had the most important changes during the period 2008 to 2010, reacting to the changes caused that year by the combined effects of wind and forest management. In addition, we found that an area of 4.0 m radius around the sampling points was the best to explain the relationship between light properties and species richness, whereas a radius of 1.0 m was enough to estimate the relationship between light and canopy cover. In addition, light-related variables such as diffuse light and leaf area index were related to species richness, whereas structural variables such as canopy openness were related to canopy cover. In summary, our study demonstrates that non stand-replacing disturbances such as windstorms, thinning, or droughts can have an important role in modifying structural and light-related canopy properties, which in turn may inﬂuence natural processes of stand development and ecological succession.
Open Access
Increased complementarity in water-limited environments in Scots pine and European beech mixtures under climate change
(Wiley, 2017) González de Andrés, Ester; Seely, Brad; Blanco Vaca, Juan Antonio; Imbert Rodríguez, Bosco; Lo, Yueh-Hsin; Castillo Martínez, Federico; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Management of mixedwoods is advocated as an effective adaptation strategy to increase ecosystem resiliency in the context of climate change. While mixedwoods have been shown to have greater resource use efficiency relative to pure stands, considerable uncertainty remains with respect to the underlying ecological processes. We explored species interactions in Scots pine / European beech mixedwoods with the process-based model FORECAST Climate. The model was calibrated for two contrasting forests in the southwestern Pyrenees (northern Spain): a wet Mediterranean site at 625 m.a.s.l. and a subalpine site at 1335 m.a.s.l. Predicted mixedwood yield was higher than that for beech stands but lower than pine stands. When simulating climate change, mixedwood yield was reduced at the Mediterranean site (-33%) but increased at the subalpine site (+11%). Interaction effects were enhanced as stands developed. Complementarity dominated the Mediterranean stand but neutral or net competition dominated the subalpine stand, which had higher stand density and water availability. Reduced water demand and consumption, increased canopy interception, and improved water-use efficiency in mixtures compared to beech stands suggest a release of beech intra-specific competition. Beech also facilitated pine growth through better litter quality, non-symbiotic nitrogen fixation and above- and belowground stratification, leading to higher foliar nitrogen content and deeper canopies in pines. In conclusion, mixtures may improve water availability and use efficiency for beech and light interception for pine, the main limiting factors for each species, respectively. Encouraging pine-beech mixtures could be an effective adaptation to climate change in drought-prone sites in the Mediterranean region.
Open Access
¿Están los bosques mixtos pirenaicos de pino silvestre y haya en el camino hacia la saturación por nitrógeno?
(Asociación Española de Ecología Terrestre, 2017) Blanco Vaca, Juan Antonio; San Emeterio Garciandía, Leticia; González de Andrés, Ester; Imbert Rodríguez, Bosco; Larrainzar Rodríguez, Estíbaliz; Peralta de Andrés, Francisco Javier; Lo, Yueh-Hsin; Castillo Martínez, Federico; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Las actividades humanas causan altos niveles de deposición atmosférica crónica de N que pueden estar trastornando el ciclo del N en los bosques de los Pirineos occidentales. Para probar esta hipótesis, se han investigado los efectos de la deposición de N atmosférico en el ciclo de N en dos bosques mixtos de pino silvestre y haya en Navarra. Un bosque está situado a 1350 m de altitud y tiene un clima continental, mientras que el otro está situado a 650 m y tiene un clima mediterráneo húmedo. Pruebas preliminares indicaron una fijación biológica de N 2 atmosférico indetectable, así como la casi nula presencia de plantas con simbiontes fijadores como en la actividad de fijadores libres. Por lo tanto se asumió que la principal entrada de N en estos bosques es la deposición atmosférica. Se estimó la dependencia de la productividad de estos ecosistemas de la deposición por medio del modelo ecológico FORECAST, calibrado para estos sitios. Se simularon seis escenarios con tasas de deposición en un rango de 5 a 30 kg ha -1 año -1 . Los resultados indicaron que la productividad de estos bosques es dependiente de la deposición de N, pero indicios de saturación por N (aumento de lixiviación y carencia de aumento de productividad) indican que pueden saturarse a partir de 20-25 kg N ha -1 año -1 , unos 5-10 kg N ha -1 año -1 por encima de los niveles observados actualmente.