1,721,062 research outputs found
XLA Petiole Index: A Novel Hydraulic Function Metric for Interpreting Drought-Induced Dieback in Mediterranean Ring-Porous Oak Forests
Full text linkClimate-induced forest mortality is an increasing global phenomenon occurring at both regional and local scales, with implications for ecosystem functioning and the provision of essential ecosystem services. In recent years, the Italian peninsula has experienced widespread oak forest decline, with forests showing increased susceptibility to severe heat waves and prolonged droughts. Our study examined a drought-induced tree mortality episode in the Mediterranea region (Pollino National Park, Southern Italy) focusing on deciduous oak forest stands (Quercus frainetto Ten.). We employed a comprehensive approach, combining ecophysiological and dendro-ecological analyses to compare non-decaying (ND) and decaying (D) coexisting trees. Recent advancements in understanding the relationship between petiole xylem anatomy and leaf form and function have revealed a positive correlation between petiole vessel diameter and leaf size, both within and across species. Leaf petioles, serving as the singular entry point for water into the leaf venation system, offer a standardized basis for comparing xylem investment with downstream transpirational demands. To quantify this relationship, we employed a novel index derived from quantitative wood anatomy of petioles. This integrative trait characterizes leaf water transport function by measuring the ratio of cross-sectional xylem area (XA) at the petiole to the downstream leaf area, termed the XLA petiole Index. Our assessment of XLA petiole variation can provide evidence supporting a safety-efficiency trade-off in oak leaves, a crucial aspect of plant hydraulic strategy
Climatic drivers of cork growth depend on site aridity
Full text linkCork is one of the main non-timber forest products in the world. Most of its production is concentrated in the Iberian Peninsula, a climate change hotspot. Climate warming may lead to increased aridification and reduce cork production in that region. However, we still lack assessments of climate-cork relationships across ample geographical and climatic gradients explicitly considering site aridity. We quantified cork growth by measuring cork ring width and related it to climate variables and a drought index using dendrochronology. Four cork oak (Quercus suber L.) forests located from north eastern Spain to south western Morocco and subjected to different aridity levels were sampled. Our results showed that warm conditions in spring to early summer, when cork is formed, reduced cork width, whereas high precipitation in winter and spring enhanced it. The response of cork to increased water availability in summer peaked in the most arid and continental site considering 14-month long droughts. A severe drought caused a disproportionate loss of cork production in this site, where for every five-fold decrease in the drought index, the cork-width index declined by a factor of thirteen. Therefore, site aridity determines the responses of cork growth to the soil water availability resulting from accumulated precipitation during winter and spring previous to cork growth and until summer. In general, this cumulative water balance, which is very dependent on temperature and evapotranspiration rate, is critical for cork production, especially in continental, dry sites. The precipitation during the hydrological year can be used as a proxy of cork production in similar sites. Assessments of climate-cork relationships in the western Mediterranean basin could be used as analogues to forecast the impacts of aridification on future cork production
La variación intraespecífica en el uso del agua del suelo explica el decaimiento de bosques causado por sequía en especies de robles en el sur de Italia
Full text linkEl decaimiento de los bosques debido al cambio climático es un fenómeno global que afecta a
muchas especies de árboles, principalmente en áreas propensas a sequías, como la región
mediterránea. En el sur de Italia varias especies de robles muestran fenómenos de decaimiento
desde principios de siglo debido al estrés inducido por sequía. Si bien el fenómeno se extiende a
rodales enteros, el daño (desecación a nivel del follaje, reducción del crecimiento, etc.) no afecta por
igual a todos los individuos. Por lo tanto, existen mecanismos intraespecíficos que explican la
variabilidad de la vulnerabilidad a la sequía y que aún no se comprenden completamente. El objetivo
general del estudio fue verificar si la variabilidad en dicha vulnerabilidad puede estar relacionada
con diferencias en el acceso al agua entre individuos de la misma especie. El estudio se realizó en
dos sitios en decaimiento (Gorgoglione y San Paolo Albanese), durante la sequía estival más
extrema de la última década (2017), comparando las respuestas de tres robles mediterráneos que
presentaban diferentes necesidades ecológicas con respecto a la disponibilidad hídrica: Quercus
pubescens, Quercus cerris y Quercus frainetto. Para cada especie comparamos pares de individuos
dominantes mostrando mucha (decaídos) o poca (no decaídos) defoliación. Sobre estas categorías
se analizó la señal isotópica de oxígeno (δ18O) e hidrógeno (δ2H) del agua contenida en el xilema de
las ramas y en el suelo. También caracterizamos el crecimiento radial para detectar divergencias a
largo plazo entre árboles decaídos y no decaídos. Finalmente, se midió la concentración de
carbohidratos no estructurales (NSC) en la albura para evaluar las diferencias entre árboles. Al
comparar los isótopos estables del agua en el suelo y en el xilema, encontramos diferencias
significativas entre individuos decaídos y no decaídos en Q. cerris y Q. pubescens, pero no en Q.
frainetto. Los árboles no decaídos utilizaron agua menos enriquecida, derivada de fuentes de agua
más profundas, lo que sugiere que disponen de un sistema de raíces más profundo capaz de
asegurar un suministro de agua en caso de sequía extrema. La tasa de crecimiento radial promedio
de los árboles decaídos, que eran en general menos altos, fue un 44% menor que la de los no
decaídos. Encontramos concentraciones más bajas de NSC en árboles decaídos de Q. pubescens, la
especie que forma un sistema radical menos profundo. Estos resultados no apoyan la idea de que el
decaimiento está relacionado con la escasez de reservas de carbono. La vulnerabilidad a la sequía
entre individuos de una misma especie depende, entre otros factores, del acceso a los recursos
hídricos disponible a distintas profundidades del suelo
Climatic drivers of cork growth depend on site aridity
Full text linkCork is one of the main non-timber forest products in the world. Most of its production is concentrated in the Iberian Peninsula, a climate change hotspot. Climate warming may lead to increased aridification and reduce cork production in that region. However, we still lack assessments of climate-cork relationships across ample geographical and climatic gradients explicitly considering site aridity. We quantified cork growth by measuring cork ring width and related it to climate variables and a drought index using dendrochronology. Four cork oak (Quercus suber) forests located from north eastern Spain to south western Morocco (31.5–41.5° N) and subjected to different aridity levels were sampled. Warm conditions in spring to early summer, when cork is formed, reduced cork width, whereas high precipitation in winter and spring enhanced it. The response of cork to increased water availability in summer peaked (r = 0.89, p = 0.00002) in the most arid and continental site considering 14-month long droughts. A severe drought caused a disproportionate loss of cork production in this site, where for every five-fold decrease in the drought index, the cork-width index declined by a factor of thirteen. Therefore, site aridity determines the responses of cork growth to the soil water availability resulting from accumulated precipitation during winter and spring previous to cork growth and until summer. In general, this cumulative water balance, which is very dependent on temperature and evapotranspiration rate, is critical for cork production, especially in continental, dry sites. The precipitation during the hydrological year can be used as a proxy of cork production in similar sites. Assessments of climate-cork relationships in the western Mediterranean basin could be used as analogues to forecast the impacts of aridification on future cork production
Using wood rings to determine age and climate constraints of grapevine (Vitis vinifera) radial growth
Full text linkGrapevine (Vitis vinifera) is the most widely cultivated and economically relevant crop in the world, but its productivity is menaced by aridification in some wine-growing regions such as the Mediterranean Basin. The impacts of climate on vines depend on regional conditions, cultivar, and vine age, among other factors. Hence, a better understanding of vine radial-growth responses to climate in different regions is sorely needed. First, we related climate data and drought severity with a long-term series of vine leaf unfolding from NE Spain to test if climate warming is advancing the onset of the growing season. Second, we used growth rings to estimate age and quantify climate-growth relationships of vines using dendrochronology. Three sites from different designations of origin and vine varieties were studied: Logroño in northern Spain (La Rioja, Tempranillo), San Martín del Río in northeast Spain (Calatayud, Garnacha) and Anzi in southern Italy (Aglianico, Aleatico). Vine leaf unfolding occurred earlier as winter-spring conditions were warmer and drier. Vine ages ranged between 16 (Logroño, Anzi) and 56 years (S. Martín del Río), and growth rates declined in the two youngest grapevines. Ring widths varied between 1.19 (S. Martín del Río) and 1.80 mm (Logroño), with Anzi showing intermediate values (1.37 mm). February precipitation enhanced vine growth in San Martín del Río (r = 0.64) and Anzi (r = 0.49), whereas the correlation with soil moisture peaked in March in San Martín del Río (r=0.83). Vine growth rates positively responded to September minimum temperatures in San Martín del Río (r=0.51) and Logroño (r=0.50). Garnacha cultivar in San Martín del Río showed the highest responsiveness to water availability. Therefore, similar old grapevines from continental, seasonally dry areas could be the most negatively affected by future warmer and drier climate conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
High responsiveness of wood anatomy to water availability and drought near the equatorial rear-edge of Douglas fir
Full text linkIn trees, wood anatomy is a more precise and informative measure of hydraulic responses to drought than radial growth. Tree populations located near the equatorial-range edge of their distribution (rear edge) are used to monitor responses to changes in hydroclimate; however, few studies have assessed the wood anatomy of these populations. We measured tracheid lumen diameter (LD) and cell wall thickness (CWT) in a rear-edge Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) population. We also evaluated the formation of intra-annual density fluctuations (IADFs), characterized by earlywood (EW) tracheids with narrow lumens. We expected that EW LD would be particularly sensitive to hydroclimate variability. We found that EW LD was directly related to precipitation during the previous year’s late winter and the current year’s spring. Wet conditions were associated with wider EW tracheids and improved growth. These correlations peaked when considering cumulative precipitation from January to May. EW IADFs were formed in response to dry conditions during March and April, suggesting that dry spring conditions limit tracheid expansion. The described associations in a rear-edge Douglas-fir population confirm that wood anatomy is highly responsive to drought. We conclude that EW LD is a valuable proxy for hydroclimate reconstruction in Douglas-fir.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Mixed Pine Forests in a Hotter and Drier World: The Great Resilience to Drought of Aleppo Pine Benefits It Over Other Coexisting Pine Species
Full text link© 2022 Gazol, Oliva, Valeriano, Colangelo and Camarero. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.Drought is an important driver of forest dynamics in the Mediterranean region. The forecasted increase in drought frequency and severity can notably influence tree growth, forest structure, composition and productivity. Understanding how coexisting tree species respond to drought is thus crucial to understand which are less vulnerable and will perform better in a warmer and drier world. To assess drought vulnerability, we used dendrochronology to study the radial growth trends and responses to a drought index of four pine species (Pinus halepensis, Pinus pinea, Pinus nigra, and Pinus sylvestris) coexisting in North-eastern Spain. We reconstructed the growth of each species and evaluated their short- and long-term growth response to drought for the common period 1980–2017. The growth of the four pine species depended on water availability and high early spring temperatures impacted the growth of P. nigra and P. sylvestris negatively. The occurrence of a severe drought between 2005 and 2007 lead to marked growth reductions in the four species, but it was greater in magnitude in P. pinea and P. halepensis in 2005, and in P. nigra in 2007. The results of basal area increment models at the individual tree level suggested that P. halepensis trees grow more than the rest of species. After accounting for age and drought effects, P. nigra and P. sylvestris displayed negative growth trends in the 2008–2017 period while P. pinea and P. halepensis displayed positive growth trends. P. sylvestris was the most resistant species and P. pinea the less resistant. Conversely, P. halepensis and P. pinea were slightly more resilient than P. sylvestris. Moreover, P. sylvestris was the species displaying the highest autocorrelation and the lowest coefficient of variation in ring-width indices. A marked drop in the autocorrelation of P. pinea ring-width index was observed in response to the 2005 drought. These results indicate that all study species are vulnerable to drought but in different degrees. The strong resilience capacity of P. halepensis suggests that it will better thrive in a drier future, but mixed pine forests, such as the one here studied, may contract or become rare due to the strong sensitivity of P. pinea to drought and the lower post-drought performance of P. nigra and P. sylvestris.We acknowledge funding from the Barcelona Provincial Council (Diputació de Barcelona), by project RTI2018-096884-B-C31 and by FPI grant (ref. PRE2019-089800) to CV (Spanish Ministry of Science). AG and JO were also supported by the Ramon y Cajal Program of the Spanish MICINN under Grants RyC2020-030647-I and RYC-2015-17459, respectively. This research has received funding from PIE-20223AT003 of CSIC.Peer reviewe
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