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Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Regional assessment of natural regeneration occurrence in Mediterranean forests. • Regeneration occurrence depends on climatic and stand variables. • According climate predictions suitable conditions for regeneration will decreases. • Regeneration benefited from the presence of mixture in the overstory. The generation of projections under different climate scenarios and stand conditions provides a useful tool to explore the consequences of climate change on ecosystem dynamics and to define possible interventions to ensure their persistence over time. Over recent decades, climate change has been particularly severe in the Mediterranean basin, where a lack of natural regeneration is one of the main limitations threatening Mediterranean forests. In this context, in order to define the main drivers affecting this process, we evaluated the occurrence of regeneration in P. pinea and P. pinaster forests, taking into account the stand-structure as well as climate conditions. The regeneration data is taken from a network of 1703 plots located on the Northern Plateau of Spain and monitored over 15 years. Through survival analysis we modeled the probability of regeneration occurrence after a time t (years since regeneration fellings were carried out) at regional level. The model was then used to simulate regeneration success under two climatic scenarios. According to the modeling results, the ability of P. pinaster to regenerate was always lower than that of P. pinea , regardless of the scenario and stand conditions. The relationship between regeneration success and presence of adult trees varies depending on the species composition. Higher probabilities of regeneration occurrence were positively associated with mixed species composition in adult trees for both species, while P. pinaster exhibited significantly lower regeneration under monospecific P. pinea adult trees. Regeneration probability was negatively associated with increasing levels of grass cover on soils. The results also pointed to the existence of climate-mediated annual regeneration occurrence, reflecting the complex interaction which exists between environmental factors and the optimum conditions for natural regeneration. The findings obtained in the present study could help us to identify problematic areas with regard to natural regeneration so that appropriate management can be defined to favor the different species in future stands. [ABSTRACT FROM AUTHOR]

Generally, the effects of climate change on tree growth focus on changes in one dimension of a tree. However, diameter increment along the main stem reacts differently to climatic variables, which in turn influences tree form. These differences can thus have important implications on stem volume, which could induce biases in future forest biomass estimation. A stem taper model including climatic variables was fitted to stem analysis data of five different species ( Abies balsamea , Betula papyrifera , Picea glauca , Picea mariana , Populus tremuloides ) distributed along a gradient from the temperate to the boreal forest of Eastern Canada. The effects of shifts in stem form on tree volume between different climatic scenarios were then estimated and related to different functional traits. Changes in stem form with climatic variables were observed for four of the five species, with up to 5% differences in stem volume between different climatic situations. Changes in stem volume were found to decrease with increasing waterlogging and shade tolerance. The most important differences in stem volume can induce changes of 3–4% in the biomass of a single tree. Not taking into account shifts in stem form could have implications in forest biomass estimations. [ABSTRACT FROM AUTHOR]

Insect predation on seeds of forests species during the predispersal phase is a special case of plant-pest interaction in which, while plant survival and growth is not threatened, natural regeneration can be negatively affected. In the case of seeds with a high economic value, as is the case of nuts from the Mediterranean stone pine ( Pinus pinea L.), predispersal predation can also result in severe economic losses. The insect-seed relationship shows complex spatiotemporal dynamics, including patterns of dependency between fruit availability and fluctuations in insect population, occurrence of insect outbreaks, spatial contagion and masting habit. In the present study, we focus on the damage caused by a native pest, the Dioryctria mendacella Stgr. moth, to cones and seeds of P. pinea , a forest species showing a marked masting habit. We firstly identified those environmental and stand-level factors controlling the spatiotemporal pattern of damage by D. mendacella , as well as the self-regulatory effect that interannual variability in seed production could have on the population dynamics of the moth. In a second phase, we constructed a predictive phenomenological model to forecast the probability of cone damage in a given location, as well as the expected patterns of spatiotemporal spread and dispersion. Our results revealed a strong correlation between the probability of damage and crop size in a given year, pointing to a dependency between feeding resources and predator population. Additionally, the probability of damage is affected by the number of damaged cones observed in the previous year, indicating temporal contagion. Cone and seed damage is also affected by the temperature during different phases of the complex life-cycle of D. mendacella , which suggests that breakout processes are synchronized within the territory and linked to the occurrence of bumper crops and favorable climatic conditions. We detected that the level of infestation at a given location is related to site and environmental conditions, with no significant pattern of contagion/spreading from stands with high resource availability to those with low availability. Damage prediction under warmer climate scenarios reveals a counterbalance among favorable/unfavorable conditions for insect expansion and expected decline in cone production, resulting in only slight changes. [ABSTRACT FROM AUTHOR]

Extreme climatic events, such as windstorms and drought, and competition are some of the main factors underlying tree mortality in Atlantic and Central European forest stands. However, current empirical tree mortality models are not adapted to separately consider the different causes of mortality. In addition, these approaches do not distinguish between intra- and inter-specific competition. In this study, we present a comprehensive empirical single-tree mortality model that incorporates all of the aforementioned features. On the one hand, extreme events can enter the model via fixed effects and random effects. The latter allows taking the stochasticity of the process into consideration. The distribution of these random effects can be seen as an extreme event severity distribution, which is of great interest for carrying out stochastic simulations on tree mortality. On the other hand, intra- and inter-specific competition is taken into account through linear interactions of species-specific competition indexes and species factors. In order to test this approach, we selected the beech–oak mixture in France as a case study. Beech–oak mixed forests are a common type in France which provides owners with significant economic benefits. Our findings confirm that drought and, especially, windstorm occurrence are major causes of tree mortality in these forests. The model was able to capture the stochasticity of windstorm events by means of random effects. In terms of competition, the probability of mortality in beech understories was expected to decrease in the presence of oak overstories with respect to pure beech stands. This result reveals the importance of complementarity processes in tree mortality. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights: [•] Differences between reported and modelled C emission values were compared. [•] Accounting method selected by countries best explained differences. [•] For some selected countries specific factors were identified to cause differences. [•] At the root of these differences are differences in input data. [•] These input differences are calling for better sharing of data. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: In 1999, the major windstorm, Lothar, damaged many beech stands on the French Lorraine limestone plateau. Some of them were coppices with standards (CWS) while others were high forest (HF) stands. The use of statistical models to compare the wind firmness of different stand structures is often limited by poor estimates of the individual wind loading. Available knowledge about the mechanics of windthrow processes such as wind loading could improve statistical modeling. Our aim was to identify the main trees and site risk factors for beech and to compare wind firmness of both stand structures by fitting such a model. We developed a windthrow model with mixed effects, which is based on a simplified mechanical analysis of the wind-induced stresses and Weibull’s theory of fracture. This analysis revealed the relevancy of including the product of the crown diameter and the square of the tree height, known as the bending moment coefficient, in the model. The Weibull-based model was compared with multiple logistic regressions. Both models were fitted using tree and site factors on 384 dominant beeches (196 in CWS and 188 in HF) from 51 plots with comparable site conditions between the two stand structures. Damage mainly increased with tree height, although it also slightly increased with crown width. The bending moment coefficient used in the Weibull-based model more effectively accounted for tree size and tree shape effects than the logistic regressions. Stand structure showed an interesting second-order effect since the increase of risk with the increase of the bending moment coefficient was higher for HF. Including a random plot effect significantly improved the model likelihood and, therefore, took partly wind-induced spatial variability into account. To apply Weibull’s theory to windthrow, many assumptions that require further investigation must be made regarding the brittle behavior and the distribution of stresses in the root-soil plate. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: For Quercus petraea (sessile oak), the origin of forks is either traumatic or related to crown base formation (“metamorphosis”). The objectives of this study were to quantify forking, distinguish the two origins and test the effect of initial stocking density and tree attributes on the number of forks and height to the lowest one. The experiment took place in a 23-year-old sessile oak plantation in Normandy, France, where three initial planting densities were compared (1333, 2667 and 5333seedlings per ha). The forks were observed every 3years after the plantation. Fork number was modelled with a system of simultaneous linear equations that respectively predicted tree girth, height and the log-transformed fork frequency, with age and initial stocking density as explanatory variables. This model 1 was fitted as a seemingly unrelated regression with random effects to account for the tree and plot clustering. For trees having at least one fork, lowest fork height was quantified using a linear mixed model including predictors compatible with the response variables of model 1, age and stocking. The results showed that the number of forks can be predicted using the expected explanatory variables and it is significantly correlated with height and girth as well. Traumatic and metamorphosis-related origins were not clearly distinguished, but significant differences between the initial seedling densities were found, with the lowest density showing the highest number of forks. Lowest fork height depended on response variables of model 1, age and stocking. The stocking effect was significant but small. This study presents the first statistical quantification of tree forking ever made. From this quantification, it seemed obvious that the initial density of 2667 seedlings per ha could be a relevant initial density to avoid the emergence of too many forks and the insertion of the lowest forks too low down. [Copyright &y& Elsevier]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Forest dynamics following a partial cut conducted in the early 1950s in the Lac Édouard Experimental Forest in the Mauricie National Park, Quebec, Canada, were studied. Changes in vegetation were analyzed for the period between 1946 and 2001 in 109 mesic stands of the sugar maple — yellow birch bioclimatic domain. Three cutting intensities were considered: 1) low intensity, 15-30% of the basal area; 2) moderate intensity, 30-45% of the basal area; and 3) uncut. More than fifty years following cutting, the original relative proportion of the deciduous and softwood species was maintained. The relative proportion of basal area occupied by softwood species relative to the total basal area varied only from 2.0% to 7.4%. Red spruce (Picea rubens Sarg.) basal area increased in forest types Cornus (Co) and Oxalis-Comus (O-Co) whereas balsam fir basal area decreased. In the Viburnum-Oxalis (Vi-O) forest type, sugar maple (Acer saccharum Marsh.) basal area increased and yellow birch (Betula alleghaniensis Britt.) decreased. Cutting areas were not invaded by competition species such as mountain maple (Acer spicatum Lamb.). In the Co and O-Co forest types, the regeneration density is probably sufficient to maintain the current cover type. In the Vi-O forest type, where moderate partial cutting was conducted, the deciduous component could substantially increase. Stands reacted positively to partial cutting. The increased growth of residual stems and the arrival of new stems resulted in 2001 total basal areas that were equal to or larger than those observed before cutting (1946). [ABSTRACT FROM AUTHOR]