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Rubielos de Mora, Spain

Voltas J.,University of Lleida | Camarero J.J.,CSIC - Pyrenean Institute of Ecology | Carulla D.,University of Lleida | Aguilera M.,University of Lleida | And 2 more authors.
Plant, Cell and Environment

Winter-drought induced forest diebacks in the low-latitude margins of species' distribution ranges can provide new insights into the mechanisms (carbon starvation, hydraulic failure) underlying contrasting tree reactions. We analysed a winter-drought induced dieback at the Scots pine's southern edge through a dual-isotope approach (Δ13C and δ18O in tree-ring cellulose). We hypothesized that a differential long-term performance, mediated by the interaction between CO2 and climate, determined the fates of individuals during dieback. Declining trees showed a stronger coupling between climate, growth and intrinsic water-use efficiency (WUEi) than non-declining individuals that was noticeable for 25 years prior to dieback. The rising stomatal control of water losses with time in declining trees, indicated by negative Δ13C-δ18O relationships, was likely associated with their native aptitude to grow more and take up more water (suggested by larger tracheid lumen widths) than non-declining trees and, therefore, to exhibit a greater cavitation risk. Freeze-thaw episodes occurring in winter 2001 unveiled such physiological differences by triggering dieback in those trees more vulnerable to hydraulic failure. Thus, WUEi tightly modulated growth responses to long-term warming in declining trees, indicating that co-occurring individuals were differentially predisposed to winter-drought mortality. These different performances were unconnected to the depletion of stored carbohydrates. © 2013 John Wiley & Sons Ltd. Source

Palacio S.,CSIC - Pyrenean Institute of Ecology | Hernandez R.,Laboratorio Of Sanidad Forestal | Maestro-Martinez M.,CSIC - Pyrenean Institute of Ecology | Camarero J.J.,CSIC - Pyrenean Institute of Ecology
Trees - Structure and Function

Defoliation by herbivores may alter the source:sink balance of trees leading to transient decreases in carbon (C) stores. When C stores are replenished concurrently with re-growth both processes may compete, store formation proceeding at the expenses of growth. However, the interactions between both processes are not fully understood. We investigated the effects of defoliation by the pine processionary moth (PPM, Thaumetopoea pityocampa Dennis and Schiff.) on the non-structural carbohydrate (NSC) and nitrogen (N) stores and the growth of Pinus nigra Arnold trees. Short-term effects were evaluated immediately after a PPM outbreak and at the end of the first growing season in trees suffering a range of defoliation damage. Long-term effects were explored by a 17-year-long PPM defoliation experiment, with 11 years of repeated defoliation treatments followed by 6 years of recovery. Defoliation by PPM was followed by transient NSC decreases, but trees were able to exceed initial NSC pools and compensate growth in just one growing season. Such recovery was linked to increased foliage N. Repeated severe defoliations decreased growth and survival of trees in the long-term, but trees increased starch allocation to stems. Defoliation led to an accumulation of C storage compounds in P. nigra trees irrespective of their ability to re-grow. In trees included in the short-term experiment, the accumulation of stores proceeded concurrently with re-growth. However, the repeated severe defoliations included in our long-term experiment impaired the growth of trees, surplus C being accumulated as stores. These results indicate that, growth declines in pines defoliated by PPM are not due to C (source) limitation but may respond to the reduced sink strength of growing meristems due to defoliation, and thus, a decrease in C allocation to growth. © 2012 Springer-Verlag. Source

Cayuela L.,Rey Juan Carlos University | Hernandez R.,Laboratorio Of Sanidad Forestal | Hodar J.A.,University of Granada | Sanchez G.,Servicio de Sanidad Forestal y Equilibrios Biologicos | Zamora R.,University of Granada
Forest Ecology and Management

The pine processionary moth (Thaumetopoea pityocampa, PPM) is one of the most destructive pests in Mediterranean woodlands. Assessment of PPM impact involves the quantification of pest damage at the stand level from visual evaluations by forestry technicians, using different infestation indices. One such index, widely used in national and regional forest monitoring programmes, is an ordinal index that ranges from no infestation (0) to massive defoliation (5). This index now offers an outstanding opportunity to investigate patterns and processes in PPM population dynamics. Its use as a proxy for insect population density requires, however, knowledge on the relationship between stand defoliation and population density-related measures, which is something that has not been explored to date. In this study, we investigated the relationship between the infestation index, quantifying damage at the stand level by the PPM, and fined-grained measures of PPM population size (number of egg batches, number of hatched caterpillars, number of winter tents) within and between generations. We used data from a long-term monitoring programme conducted in three pine woodland stands at Mora de Rubielos, Spain, for a 19-year period. Generalized linear models (GLM) were fitted in order to test the following hypotheses: (1) high values of population density-related variables, on a log basis, will cause high defoliation in the coming winter (within generation); and (2) high defoliation rates will be associated with high stocks of population size at the next generation of PPM (between generations). Our results indicate that, within the same generation, there was a poor relationship between the infestation index and all three fine-grained measures of population size (maximum R2=0.442), possibly as a result of post-sampling larval survival over winter due to climatic factors. Goodness of fit was higher for PPM population density-related measures in the next generation and the infestation index (maximum R2=0.735). Overall, the results suggest that visual evaluation of pest damage by PPM at the stand level provides an accurate proxy for population size at the next generation, and therefore opens the potential to the use of this index to investigate PPM population dynamics where no direct measures of population size exist. © 2014 Elsevier B.V. Source

Sanguesa-Barreda G.,CSIC - Pyrenean Institute of Ecology | Camarero J.J.,University of Barcelona | Camarero J.J.,CSIC - Pyrenean Institute of Ecology | Garcia-Martin A.,Centro Universitario Of La Defensa Of Zaragoza | And 3 more authors.
Forest Ecology and Management

Outbreak insects are among the major biotic disturbances affecting Mediterranean forests by reducing their growth and vitality through severe defoliations. Despite their relevance for the management of these drought-prone areas, we lack information on the relationships between growth, canopy cover and insect defoliations at ample spatial and temporal scales. Here, we combine remote sensing (vegetation indexes) and dendrochronological information (basal area increment, BAI) to assess the effects of pine processionary moth (Thaumetopoea pityocampa, PPM) defoliations on growth and cover changes of several pine species, mainly focusing on Pinus nigra. We compared both datasets with a long-term field survey of PPM stand defoliations carried out in eastern Spain during the period 1970-2012. Lastly, we fitted linear-mixed models of BAI using as predictors climatic variables and a multi-scalar drought index to distinguish drought-related growth reductions from those attributed to PPM outbreaks. PPM severe defoliations mainly affected edge or low-density stands. Several vegetation indices (Moisture Stress Index, Normalized Burn Ratio and Normalized Difference Infrared Index) reflected the cover decrease corresponding to severe PPM defoliations. We found that trees affected by various severe PPM defoliations took at least 2. years to recover BAI values similar to those observed before the outbreak. The combined use of remote sensing and dendrochronology allows monitoring the impact of PPM defoliations from stands to trees, and these are valuable approaches to forecast outbreaks and their effects on Mediterranean forest. We consider both powerful tools to further assess the interacting effects of climate warming and PPM dynamics on drought-prone forests. © 2014 Elsevier B.V. Source

Martin-Santafe M.,CSIC - Centro de Investigacion y Tecnologia Agroalimentaria | Martin-Santafe M.,Research Center perimentacion En Truficultura Of La Diputacioan Of Huesca | Perez-Fortea V.,Laboratorio Of Sanidad Forestal | Zuriaga P.,Laboratorio Of Sanidad Forestal | Barriuso J.,CSIC - Centro de Investigacion y Tecnologia Agroalimentaria
Forest Systems

Aim of study: In black truffle plantations, many factors are driving the emergence of new pests and diseases which in forestry areas go unnoticed. Usually, the incidence of most of them is low. Nevertheless, in specific cases, some of them are capable of causing irreversible damage that could endanger the harvest or even tree survival. Area of study: This paper presents an in-depth study of the pests and diseases more frequently associated with truffle plantations in the region of Aragón (Spain). Damages have been arranged into the main production stages: nursery, plantations and fruiting bodies. Material and methods: The data used in this work come from the technical enquiries from truffle growers to researchers and technical staff, as well as from field visits undertaken by those work teams. Sampling methodology has been carried out following standard procedures. Insects were collected with the traps commonly used in entomology works. Main result: More than 50 damages have been described in this paper. Some of them are capable of weakening the plants and other can even kill them. Mycorrhizal competitor fungi have also been considered in this paper. These organisms do not cause real phytosanitary problems, but they can lead to important economic losses. Research highlights: Researches, truffle hunters and managers must be alert in the face of the possible occurrence of potentially dangerous organisms. The final aim: being able to take action in an efficient way in the case of a pest outbreak. Source

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