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
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
Calculadora de sostenibilidad FIRST-Heat Navarra: generando energía sostenible al reducir el riesgo de incendios forestales en comunidades rurales
(Sociedad Española de Ciencias Forestales, 2020) Candel Pérez, David; Blanco Vaca, Juan Antonio; Lo, Yueh-Hsin; Montero, Eduardo; Barrena Figueroa, Ramo; Castillo Martínez, Federico; Ciencias; Zientziak; Gestión de Empresas; Enpresen Kudeaketa
El cambio climático, la expansión urbanística o el aumento del uso recreativo en zonas forestales están aumentando la probabilidad de ocurrencia de incendios forestales. Las comunidades rurales pueden afrontar la oportunidad de combinar actividades silvícolas para reducir el riesgo de incendios con el desarrollo energético basado en el aprovechamiento de la biomasa forestal generada. Para demostrar la viabilidad de este tipo de gestión, se ha creado una herramienta informática demostrativa de apoyo a la toma de decisiones. Mediante la modificación y calibración del modelo ecológico FORECAST, se simularon las condiciones de diferentes localidades y especies forestales de Navarra. Sobre dichas simulaciones, se ha desarrollado la interfaz de usuario de esta calculadora (Fire Interface Rural Screening Tool for Heating: FIRST-Heat Navarra), que pretende estimar la sostenibilidad ecológica y socio-económica del uso de la biomasa forestal a nivel local. Esta herramienta se muestra capaz de simular los efectos del cambio en las condiciones de crecimiento del bosque mediante un modelo ecológico dinámico. También presenta la capacidad de integrar, resumir y comunicar de forma efectiva el último conocimiento científico sobre ecología forestal, y el conocimiento técnico, económico y social sobre la tecnología de calefacción de distrito a partir de biomasa.
Open Access
Resilience assessment of lowland plantations using an ecosystem modeling approach
(MDPI, 2015) Wu, Chia-Hsin; Lo, Yueh-Hsin; Blanco Vaca, Juan Antonio; Chang, Shih-Chieh; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
As afforestation programs of former farmlands take hold in Taiwan to achieve a variety of ecological and socio-economic values, it is becoming necessary to define best forest management. Hence, we simulated mixed stands of Cinnamomum camphora and Fraxinus griffithii planted through a gradient of soil fertility and varying camphor/ash density ratios, but maintaining a fixed total stand density of 1500 trees ha −1 . Total stand productivity was slightly lower in mixed stands than the combination of both monocultures in rich and poor sites. Maximum negative yield surpluses for 50-year old stands were 7 Mg ha −1 and 6 Mg ha −1 for rich and poor sites with a 1:1 camphor laurel/ash ratios. Maximum stand woody biomass in rich sites was reached in camphor laurel monocultures (120 Mg ha −1 ) and in poor sites for Himalayan ash monocultures (58 Mg ha −1 ). However, for medium-quality sites, a small yield surplus (11 Mg ha −1 ) was estimated coinciding with a maximum stand woody biomass of 95 Mg ha −1 for a 1:1 camphor laurel/ash density ratio. From an ecological resilience point of view, rotation length was more important than stand composition. Long rotations (100 years) could improve soil conditions in poor sites. In rich sites, short rotations (50 years) should be avoided to reduce risks or fertility loss.
Open Access
Highlighting complex long-term succession pathways in mixed forests of the Paciﬁc Northwest: a Markov chain modelling approach
(MDPI, 2021) Blanco Vaca, Juan Antonio; Lo, Yueh-Hsin; Kimmins, J.P. (Hamish); Weber, Adrian; Ciencias; Zientziak
Forest succession is an ecological phenomenon that can span centuries. Although the concept of succession was originally formulated as a deterministic sequence of different plant communities by F. Clements more than a century ago, nowadays it is recognized that stochastic events and disturbances play a pivotal role in forest succession. In spite of that, forest maps and management plans around the world are developed and focused on a unique “climax” community, likely due to the difﬁculty of quantifying alternative succession pathways. In this research, we explored the possibility of developing a Markov Chain model to study multiple pathway succession scenarios in mixed forests of western red cedar, hemlock and Paciﬁc silver ﬁr on northern Vancouver Island (western Canada). We created a transition matrix using the probabilities of change between alternative ecological stages as well as red cedar regeneration. Each ecological state was deﬁned by the dominant tree species and ages. Our results indicate that, compared to the traditional Clementsian, deterministic one-pathway succession model, which is unable to replicate current stand distribution of these forests in the region, a three-pathway stochastic succession model, calibrated by a panel of experts, can mimic the observed landscape distribution among different stand types before commercial logging started in the region. We conclude that, while knowing the difﬁculty of parameterizing this type of models, their use is needed to recognize that for a given site, there may be multiple “climax” communities and hence forest management should account for them.
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.
Open Access
Survival and growth as measures of shade tolerance of planted western redcedar, western hemlock and amabilis fir seedlings in hemlock-fir forests of northern Vancouver Island
(Elsevier, 2017) Weber, Adrian; Leckie, Sara; Kimmins, J.P. (Hamish); Gilbert, Benjamin; Blanco Vaca, Juan Antonio; Lo, Yueh-Hsin; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
We examined two measures of shade tolerance (survival and growth) of planted 1-year-old seedlings of western redcedar (Thuja plicata (Donn ex D. Don)), western hemlock (Tsuga heterophylla ([Raf.] Sarg.)) and amabilis fir (Abies amabilis ([Dougl. ex Loud] Dougl. ex Forbes)). Seedlings were planted at two different sites (forest interior: 4.5% mean above canopy photosynthetically active radiation [ACPAR], and forest edge: 41.5% mean ACPAR), in a 90-year-old, windthrow origin, unmanaged mesic western hemlock-amabilis fir stand. Seedlings were planted in 1997, and re-measured in 1998 and 2001 (after five growing seasons). To assess the effects of deer browsing on redcedar survival and growth, additional seedlings of this species were planted and protected with Vexar© tubes. To examine for nutrient-light interactions, half of these seedlings were fertilized with N-P-K and micronutrients at planting. Western redcedar had high levels of survival after 4 years (98% in edge plots and 93% in interior plots). Redcedar seedlings in edge plots were more vigorous but were browsed more heavily than in the interior plots. At edge sites, the negative effects of the Vexar© tubes may have been lower than their positive effects. Hemlock survival was about 50% in the stand interior but 80% in the edge plots. Amabilis fir in the interior plots had the lowest survival of the three species, with only 40% of initial seedlings surviving over the next four years, but had high survival in edge plots (95%). Height, biomass, and root collar diameter growth were significantly higher in edge plots for fir and hemlock. However, for redcedar, only biomass was significantly higher and no differences were detected for height and diameter. Our results show that shade tolerance cannot be assessed by simple measures of leaf/light relationships alone, but also requires consideration of light, nutrition, growth and browsing.
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
Multiple pathway succession in coastal Tsuga heterophylla, Thuja plicata and Abies amabilis forests on northeastern Vancouver Island, British Columbia
(NRC Research Press, 2014) Weber, Adrian; Kimmins, J.P. (Hamish); Gilbert, Benjamin; Lo, Yueh-Hsin; Blanco Vaca, Juan Antonio; Ciencias del Medio Natural; Natura Ingurunearen Zientziak
Sustainable forest practices are often designed to mimic natural disturbance and successional processes, yet succession is poorly understood in many ecosystems. On northeastern Vancouver Island, the ‘disturbance hypothesis’ is a widely-assumed succession model that asserts shade tolerant western redcedar (Thuja plicata) and the ericaceous shrub salal (Gaultheria shallon) invade and colonize highly productive western hemlock (Tsuga heterophylla) – Pacific silver fir (Abies amabilis) stands (HA) on zonal sites in the absence of stand-replacing wind disturbance. This leads to the development of low productivity, low density, uneven-aged, open-crowned redcedar-hemlock-salal stands (CH). In conflict with this model, old, apparently stable HA stands lacking redcedar can be found on such sites as well. We sought evidence for the predicted transition to CH stands by examining stand composition, crown closure, tree size class frequency distributions, salal cover, and redcedar establishment on young HA (~90 years old), old HA (>160 years), and CH (>160 years) stands. When adjacent to a redcedar stand, young HA stands had fewer redcedar seedlings but more redcedar adult trees than old HA stands. However, redcedar abundance did not differ between young and old HA stands at distances further than 10 m from adjacent redcedar stands. This could indicate that redcedar recruits into HA stands at stand establishment, and that redcedar seedling establishment is low under the thick canopy of young HA stands. The chronosequence data also suggest that both old HA and CH stands are self-replacing stand types in these forests, contrary to the disturbance hypothesis. We develop a new, multi-pathway model for this ecosystem that is based on the chronosequence data and life-history traits of the focal tree species, and suggest that disturbance plays a role opposite to the equilibrium model.