Modelo interregional de selvicultura para Pinus pinea L. : aproximación mediante funciones con componentes aleatorios

Se presenta un modelo general integrado para el crecimiento y producción de madera y piña para Pinus pinea L. El modelo propuesto es de tipo estocástico, empírico, árbol individual, independiente de la distancia, y está definido para cuatro de las regiones españolas con mayor presencia de la especie: Andalucía Occidental, Meseta Norte, Sistema Central y Cataluña. El modelo desarrollado constituye una herramienta de gestión selvícola, al permitir simular la evolución y producción de las masas regulares de Pinus pinea L. bajo diferrentes supuestos de gestión El modelo general permite inferir el valor de variables selvícolas de interés a partir de un número reducido de variables de entrada (diámetro individual, altura dominante y edad de la masa). Para un instante determinado el modelo estima la altura de cada árbol, la forma del fuste, el volumen individual de madera con clasificación de productos y la producción de pinal. El modelo incluye además una función para el crecimiento en altura dominante de la masa y una función para el crecimiento en diámetro del árbol individual, que permiten definir y caracterizar la evolución futura de la masa. Para evitar los problemas de inferencia estadística derivados de la falta de independencia entre las observaciones, las funciones que componene el modelo general quedan formuladas como modelos mixtos. La inclusión de componentes aleatorios permite dotar al modelo de carácter estocástico y facilita la calibración del modelo para su aplicación en nuevos rodales

Modelling seed germination in forest tree species through survival analysis. The Pinus pinea L. case study

The direct application of existing models for seed germination may often be inadequate in the context of ecology and forestry germination experiments. This is because basic model assumptions are violated and variables available to forest managers are rarely used. In this paper, we present a method which addresses the aforementioned shortcomings. The approach is illustrated through a case study of Pinus pinea L. Our findings will also shed light on the role of germination in the general failure of natural regeneration in managed forests of this species. The presented technique consists of a mixed regression model based on survival analysis. Climate and stand covariates were tested. Data for fitting the model were gathered from a 5-year germination experiment in a mature, managed P. pinea stand in the Northern Plateau of Spain in which two different stand densities can be found. The model predictions proved to be unbiased and highly accurate when compared with the training data. Germination in P. pinea was controlled through thermal variables at stand level. At microsite level, low densities negatively affected the probability of germination. A time-lag in the response was also detected. Overall, the proposed technique provides a reliable alternative to germination modelling in ecology/forestry studies by using accessible/ suitable variables. The P. pinea case study highlights the importance of producing unbiased predictions. In this species, the occurrence and timing of germination suggest a very different regeneration strategy from that understood by forest managers until now, which may explain the high failure rate of natural regeneration in managed stands. In addition, these findings provide valuable information for the management of P. pinea under climate-change conditions

Decline in commercial pine nut and kernel yield in mediterranean stone pine (Pinus pinea L.) in Spain

10 Pág.Cones of the Mediterranean stone pine (Pinus pinea L.) constitute one of the most relevant non-wood forest products collected in the Mediterranean forests, providing high value edible kernels. In the last years it has been observed a severe decline in the kernel-per-cone yield (kg of kernels obtained from a kg of fresh cones) through the whole area of the species. This decline has been associated with both ongoing climate change and the recent expansion over the Mediterranean Basin of the Western Conifer Seed Bug, Leptoglossus occi-dentalis Heideman, an exotic pest which predates seeds of conifer species. In the present work we aimed to confirm and quantify the impact of this recent decline on pine nut and kernel production, identify the main factors provoking this reduction, and give evidence over causality by a potential biotic agent. We analysed recent and historical series of pine nut and kernel production obtained in the four main regions where Pinus pinea occurs in Spain. Our results showed a significant drop in the final kernel-per-cone yield on three of the four regions analysed, reaching reductions over 50% in the most affected areas. We observed that this reduction is mainly associated with a significant and generalised drop in the kernel-per-nut yield (kg of kernels per kg of pine nuts in shell), triggered by an increment in the rate of damaged pine nuts and, to a lesser extent, a reduction in the number of pine nuts per cone. The prevalence of this reduction on kernel-per-cone yield over different years and provenances with contrasting climate reinforces the hypothesis of the implica-tion of a biotic factor which can be aggravated on extreme drought years.This work has been carried out under the financial and functional framework of the PROPINEA agreement CC-16-095, between INIA, ITACYL and Deputation of Valladolid; EG-17-042-C2.2 agreement between INIA and MAPA; National Projects RTA-2013-00011.C2.1 and AGL-2017-83828-C2.1; and the H2020_CSA project 774632-INCREdible. Authors wish to thank personnel from the Forest Services of Valladolid, Ávila, Junta de Andalucía and CTFC for their permanent support with the inventory, cone collection and maintenance of the experimental trials.Peer reviewe

Growth and yield models in Spain Historical overview, contemporary examples and perspectives

In this paper we present a review of forest models developed in Spain in recent years for both timber and non timber production and forest dynamics (regeneration, mortality). Models developed are whole stand, size (diameter) class and individual-tree. The models developed to date have been developed using data from permanent plots, experimental sites and the National Forest Inventory. In this paper we show the different sub-models developed so far and the friendly use software. Main perspectives of forest modeling in Spain are presented

Interregional nonlinear height-diameter model with random coefficients for stone pine in Spain

An individual-tree height-diameter model was developed for stone pine (Pinus pinea L.) in fSpain. Five biparametric nonlinear equations were fitted and evaluated based on a data set consisting of 8614 trees from 455 plots located in the four most important regions where the species occurs in Spain. Because of the problem of high correlation among observations taken from the same sampling unit, a mixed-model approach, including random coefficients, is proposed. Several stand variables, such as density, dominant height, or diametric distribution percentiles, were included in the model as covariates to explain among plot variability. To determine interregional variability among the regions studied, regional effects were included in the model using fixed dummy variables. Two models, one for inland regions and one for coastal regions, were found to be sufficient to explain regional variability in the height-diameter relationship for the species in Spain. Mixed models allow predictive role in two ways a typical response, including only fixed effects, and a calibrated response, where random effects are predicted and included in the model from the prior measurement of the height in a subsample of trees. Different alternatives were tested to determine optimum subsample size. Measurement of the height of the 20% largest trees in the plot has been shown to be a useful approach

Adaptive Strategies of Seedlings of Four Mediterranean Co-Occurring Tree Species in Response to Light and Moderate Drought: A Nursery Approach

17 Pág.This research was funded by Ministerio de Ciencia e Innovación, grant number AGL2017-83828-C2-1-R.Peer reviewe

Cone and seed production from stone pine (Pinus pinea L.) stands in Central Range (Spain)

Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be difficult to attain. The success of this regeneration is affected by factors such as the total amount of seed available, the short dispersal ability of the pinyon, the conditions required for germination, specific problems associated with the establishment, early survival of the seedlings due to severe summer heat and drought, competition for water and mineral resources and grazing damage. This study focuses on seed availability. The amount of available seeds depends on the number and size of the cones and the number of viable pinyons within the cones. In stone pine stands, both variables show great year to year variability. Both cone and seed production, for a given year, are also conditioned by the vigour and health of the tree, its size, the condition and attributes of the stand and the loss of seed through pests or predation. In this study, the main factors which influence cone and pinyon production are identified and a multivariate model to predict annual cone and viable seed production is developed. To consider the correlation among observations coming from the same tree, stand or year, random components are included in the model. The multivariate random structure allows for future calibration of the model for a given year from a small additional sample of observations. It is important to know the total amount of viable seed produced in a stand for a given year since regeneration cuttings for Stone pine should be concentrated in high crop years. © 2005 Springer-Verlag

Responses of Pinus pinea seedlings to moderate drought and shade is the provenance a differential factor?

The widespread Mediterranean Pinus pinea showed exceptionally low genetic diversity and low differentiation between traits in the adult phase. We explored the adaptation potential of seedlings from four main Iberian provenances during their regeneration phase. We assessed the variability of shoot growth, allometry, physiological traits, and phenotypic plasticity to the interactive effect of light and water environments during 8-month moderate water-stress cycle and after one-week heat wave. The effect of shade and drought was mainly orthogonal whatever the provenance. The inland La Mancha provenance showed higher shoot growth and biomass compared to the southern coastal Depresión-del-Guadalquivir provenance. Following the heat wave, La Mancha presented higher net photosynthetic rates, a lower decrease in maximal quantum efficiency of PSII, and a higher accumulated relative height growth, thus, showing an adaptive advantage. The observed differences corroborated the ecological grouping of the provenances along latitudinal and inland–coastal gradients. We confirmed the high adaptive plasticity of Pinus pinea to the unpredictable Mediterranean environment

Hybrid estimation based on mixed-effects models in forest inventories

In forest inventories, there are many variables of interest that are difficult to measure. Practitioners have to rely on auxiliary variables and models to obtain predictions of these variables. In such contexts, design-based or model-dependent inferences are often ineffective and hybrid estimators are required. Because most models now contain mixed effects, we investigated how the random effects and residual errors affected the inferences in a context of hybrid estimation. We first developed hybrid estimators for the different mixed models. We then tested these estimators through a simulation study. Finally, the estimators were applied to a real-world case study stone pine (Pinus pinea L.) cone production in central Spain. It turned out that the contributions of the random effects and the residual errors to the variance were constant regardless of the sample size. In our case study, these contributions were rather small when compared with those of the sampling and parameter estimates. The greatest impact came from the underestimation of the variance of the parameter estimates when random effects were not taken into account in the model. As the variance estimators make it possible to distinguish different variance components, they can be useful for identifying the greatest sources of uncertainty. © 2016, Canadian Science Publishing. All rights reserved

Climatic factors control rodent seed predation in Pinus pinea L. stands in Central Spain

• Context Pinus pinea L. presents serious problems of natural regeneration in managed forest of Central Spain. The species exhibits specific traits linked to frugivore activity. Therefore, information on plant–animal interactions may be crucial to understand regeneration failure. • Aims Determining the spatio-temporal pattern of P. pinea seed predation by Apodemus sylvaticus L.;the factors involved. Exploring the importance of A. sylvaticus L. as a disperser of P. pinea. Identifying other frugivores and their seasonal patterns. • Methods An intensive 24-month seed predation trial was carried out. The probability of seeds escaping predation was modelled through a zero-inflated binomial mixed model. Experiments on seed dispersal by A. sylvaticus were conducted. Cameras were set up to identify other potential frugivores. • Results Decreasing rodent population in summer and masting enhances seed survival. Seeds were exploited more rapidly nearby parent trees and shelters. A. sylvaticus dispersal activity was found to be scarce. Corvids marginally preyed upon P. pinea seeds. • Conclusions Survival of P. pinea seeds is climate-controlled through the timing of the dry period together with masting occurrence. Should germination not take place during the survival period, establishment may be limited. A. sylvaticus-mediated dispersal does not modify the seed shadow. Seasonality of corvid activity points to a role of corvids in dispersal. © 2014, INRA and Springer-Verlag France