A conversion method of young hornbeam coppices and its possible impact on future stand structural attributes

Tulbure C., Duduman G., 2012. A conversion method of young hornbeam coppices and its possible impact on future stand structural attributes. Ann. For. Res. 55(2): 281-296, 2012. Abstract. The paper analyse the substitution of hornbeam coppice stands and conversion into high forest stands, formed by species that better valorise the site conditions. An improved alternative for the method of substitution in corridors is presented. The main goal of this new substitution-conversion alternative is to gradually conduct the actual structure of the coppice stands towards the target structure imposed by the forest management objectives, without a total elimination of the species that will be substituted. Two plot areas were selected in order to put into practice the proposed method. Bands were created for reducing the effective costs of the substitution process. 450 respectively 468, small seedlings (of beech, pedunculate oak and sessile oak) per hectare were planted in the created bands. The planting scheme took into account the shadow tolerance of the species from the target composition. Based on the field data and using the yield tables, the evolution of the stands in the two selected plots was simulated. In this respect, the forest treatments were parameterized according to the Romanian forest rules regarding the application of thinning and regeneration cuttings. The substitution-conversion process started from an almost pure hornbeam coppice and, simulating the application of the proposed method for 120 years, it was predicted that the method allows directing the actual stand structure to the target structure. The dynamics of species and structural diversity were assessed and the results of 120 years simulation indicate an important increase of both the species (the Shannon species index increases from 0.203 to 1.073) and structural diversity (the Gini structural index increases from 0.032 to 0.200)

Climate modulates the effects of tree diversity on forest productivity

Despite growing evidence that, on average, diverse forests tend to be more productive than species‐poor ones, individual studies often report strongly contrasting relationships between tree species richness and above‐ground wood production (AWP). In the attempt to reconcile these apparently inconsistent results, we explored whether the strength and shape of AWP–diversity relationships shifts along spatial and temporal environmental gradients in forests across Europe. We used tree ring data from a network of permanent forest plots distributed at six sites across Europe to estimate annual AWP over a 15‐year period (1997–2011). We then tested whether the relationship between tree species richness and AWP changes (i) across sites as a function of large‐scale gradients in climatic productivity and tree packing density and (ii) among years within each sites as a result of fluctuating climatic conditions. AWP–species richness relationships varied markedly among sites. As predicted by theory, the relationship shifted from strongly positive at sites where climate imposed a strong limitation on wood production and tree packing densities were low, to weakly negative at sites where climatic conditions for growth were most suitable. In contrast, we found no consistent effect of interannual fluctuations in climate on the strength of AWP–species richness relationships within sites. Synthesis. Our results indicate that the shape and strength of the relationship between tree diversity and forest productivity depends critically on environmental context. Across Europe, tree diversity shows the greatest potential to positively influence forest productivity at either end of the latitudinal gradient, where adverse climatic conditions limit productivity and lead to the development of less densely packed stands.The research leading to these results received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 265171.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/1365-2745.1252

Can School Children Support Ecological Research? Lessons from the Oak Bodyguard Citizen Science Project

Peer reviewe

Herbivory on the pedunculate oak along an urbanization gradient in Europe : Effects of impervious surface, local tree cover, and insect feeding guild

Urbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intraurban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that – just like in non-urban areas – plant-herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactions.Agence Nationale de la Recherche, Grant/Award Number: ANR-10--LABX-45; Fondation BNP Paribas.info:eu-repo/semantics/publishedVersio

Herbivory on the pedunculate oak along an urbanization gradient in Europe : Effects of impervious surface, local tree cover, and insect feeding guild

Urbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intra-urban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that-just like in non-urban areas-plant-herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactions.Peer reviewe

Herbivory on the pedunculate oak along an urbanization gradient in Europe: Effects of impervious surface, local tree cover, and insect feeding guild

Urbanization is an important driver of the diversity and abundance of tree-associated insect herbivores, but its consequences for insect herbivory are poorly understood. A likely source of variability among studies is the insufficient consideration of intra-urban variability in forest cover. With the help of citizen scientists, we investigated the independent and interactive effects of local canopy cover and percentage of impervious surface on insect herbivory in the pedunculate oak (Quercus robur L.) throughout most of its geographic range in Europe. We found that the damage caused by chewing insect herbivores as well as the incidence of leaf-mining and gall-inducing herbivores consistently decreased with increasing impervious surface around focal oaks. Herbivory by chewing herbivores increased with increasing forest cover, regardless of impervious surface. In contrast, an increase in local canopy cover buffered the negative effect of impervious surface on leaf miners and strengthened its effect on gall inducers. These results show that-just like in non-urban areas-plant-herbivore interactions in cities are structured by a complex set of interacting factors. This highlights that local habitat characteristics within cities have the potential to attenuate or modify the effect of impervious surfaces on biotic interactions

Aplicarea metodei claselor de vârstă la fonduri de producție puternic excedentare în arborete exploatabile: un studiu de caz [ Age class method applied in growing stoks highly exceding in overaged-exploitable stands: A case study]

This paper aims to find optimal planning solutions for the management of high forests, designed to produce regular wood assortments and facing with a significant surplus of exploitable stands. In production unit III Șoimu from Tazlău Forest District, the surplus of exploitable stands, determined in relation to forest area, evolved during 1994-2014 from 78.2% to 107.6% of the size of the normal periodic area although, in the same period, the allowable cutting volume increased by 41% (from 13100 to 18500 m3 an-1). Given the difficulties of leading the real growing stock structure to the structure of the normal growing stock, 10 different normalization scenarios have been proposed. Their comparison permitted determining the pattern of normal structure that allows the fastest diminishing of exploitable stands excess and a substantial diminution of exploitability sacrifices in the next 60 years. It has been found that the best scenario corresponds to a rotation of 100 years, divided into four periods, as follows: two periods of 30 and two periods of 20 years. Thus, compared to the solutions provided by current management plan, in the identified scenario, after the first 20 years the growing stock already reaches a small deficit of exploitable stands and, after about 60 years, it reaches a structure very similar to the normal one. In contrast, according to the solutions provided by the current forest management plan, it is estimated that normalization of the growing stock will be achieved in at least 120 years and the exploitability sacrifices will be significantly higher. In addition, periods characterized by high excess of exploitable stands will alternate with highly deficitary periods in exploitable stands and, over about 90 years, the allowable cutting volume will be about 65% lower than the normal one

Vârste ale exploatabilității tehnice pentru principalele specii forestiere din România [Technical harvesting ages of the main forest species in Romania]

Technical harvesting ages were calculated for the main wood species in Romania: Norway spruce, silver fir, Austrian pine, European larch, European beech, sessile oak, pedunculated oak, Turkey oak, Hungarian oak, European hornbeam, silver birch, silver linden, willow, black locust, silver poplar and black poplar. Target wood assortments considered in the study were established based on dimensional assortments presented in the Romanian sorting tables. The actuality and the relevance of this study is given by several factors, such as the diversification of ownership structure over the forest lands in Romania and the necessity of technical harvesting ages established for a wider range of wood assortments than those presented in the Romanian technical norms for forest management planning. Since the current technical harvesting ages are based on the old Romanian yield tables and taking into account the numerous changes of the Romanian forest laws, an upgrade of harvesting ages was necessary

Competition for light and water play contrasting roles in driving diversity-productivity relationships in Iberian forests

Mixed‐species forests generally sequester and store more carbon in above‐ground woody biomass compared to species‐poor systems. However, the mechanisms driving the positive relationship between diversity and above‐ground wood production (AWP) remain unclear. We investigate the role of competition for light and water as possible sources of complementarity among Iberian pine and oak species. Using tree core data from permanent plots, we test the hypotheses that (i) contrasting abilities of pines and oaks to tolerate shade will promote AWP in mixtures, while (ii) drought stress results in less room for complementarity. We found that pine species receive more light, develop larger crowns and grow 138–155% faster when in mixture with oaks. However, this positive effect of species mixing on growth was severely reduced under drought conditions due to increased competition for water with neighbouring oaks. In contrast to pines, oak trees were less responsive to mixing, primarily as a result of their ability to tolerate shade and water shortage. Mixed pine‐oak forests produce an average 48% more above‐ground woody biomass compared to monocultures each year. However, the magnitude of the diversity effect on AWP fluctuates with time, decreasing noticeably in strength during drought years. Synthesis. Complementary light use strategies among neighbouring trees are critical in explaining why above‐ground wood production (AWP) increases in mixed‐species stands. In contrast, drought causes trees in mixture to compete more fiercely for below‐ground resources, leaving less room for complementarity and causing positive diversity effects to lessen in strength. Together, these two mechanisms provide much needed context for AWP–diversity relationships in Mediterranean forests. Whether or not managing for mixed pine‐oak forests proves to be beneficial for AWP is likely to depend on how climate changes in the Iberian Peninsula.European Union Seventh Framework Programme. Grant Numbers: FP7/2007-2013, 265171This is the accepted manuscript version of the following article: Jucker, T., Bouriaud, O., Avacaritei, D., Dănilă, I., Duduman, G., Valladares, F., Coomes, D. A. (2014), Competition for light and water play contrasting roles in driving diversity–productivity relationships in Iberian forests. Journal of Ecology. doi: 10.1111/1365-2745.12276, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/1365-2745.12276/abstract