Growth and yield of mixed versus pure stands of Scots pine (Pinus sylvestris L. ) and European beech (Fagus sylvatica L.) analysed along a productivity gradient through Europe

Mixing of complementary tree species may increase stand productivity, mitigate the effects of drought and other risks, and pave the way to forest production systems which may be more resource-use efficient and stable in the face of climate change. However, systematic empirical studies on mixing effects are still missing for many commercially important and widespread species combinations. Here we studied the growth of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in mixed versus pure stands on 32 triplets located along a productivity gradient through Europe, reaching from Sweden to Bulgaria and from Spain to the Ukraine. Stand inventory and taking increment cores on the mainly 60-80 year-old trees and 0.02-1.55 ha sized, fully stocked plots provided insight how species mixing modifies the structure, dynamics and productivity compared with neighbouring pure stands. In mixture standing volume (+12 %), stand density (+20 %), basal area growth (+12 %), and stand volume growth (+8 %) were higher than the weighted mean of the neighbouring pure stands. Scots pine and European beech contributed rather equally to the overyielding and overdensity. In mixed stands mean diameter (+20 %) and height (+6 %) of Scots pine was ahead, while both diameter and height growth of European beech were behind (−8 %). The overyielding and overdensity were independent of the site index, the stand growth and yield, and climatic variables despite the wide variation in precipitation (520-1175 mm year−1), mean annual temperature (6-10.5 °C), and the drought index by de Martonne (28-61 mm °C−1) on the sites. Therefore, this species combination is potentially useful for increasing productivity across a wide range of site and climatic conditions. Given the significant overyielding of stand basal area growth but the absence of any relationship with site index and climatic variables, we hypothesize that the overyielding and overdensity results from several different types of interactions (light-, water-, and nutrient-related) that are all important in different circumstances. We discuss the relevance of the results for ecological theory and for the ongoing silvicultural transition from pure to mixed stands and their adaptation to climate change.The networking in this study has been sup-ported by COST Action FP1206 EuMIXFOR. All contributors thanktheir national funding institutions to establish, measure, and analysedata from the triplets. The first author also thanks the BayerischenStaatsforsten (BaySF) for supporting the establishment of the plots,the Bavarian State Ministry for Nutrition, Agriculture, and Forestryfor permanent support of the project W 07 ‘‘Long-term experimentalplots for forest growth and yield research’’ (# 7831-22209-2013) andthe German Science Foundation for providing the funds for the pro-jects PR 292/12-1 ‘‘Tree and stand-level growth reactions on droughtin mixed versus pure forests of Norway spruce and European beech’’.Thanks are also due to Ulrich Kern for the graphical artwork, and totwo anonymous reviewers for their constructive criticism

Impact of thinning on the growth and yield of Scots pine stands – a case study from Kazlu Ruda (Lithuania)

One of the main tasks for the forest managers is to form the highly productive stands, and it is mainly performed by applying intermediate cuttings during the stand development. As the impact of thinning on the premature Scots pine, commercially most important species in Lithuania, has not been sufficiently investigated yet, our objective was to evaluate the impact of such treatments on the growth and yield of the pine stands by using data from the long term experimental plots. The described thinning experiment was established in 1983 in Kazlu˛ Ru−da (54.760395°N, 23.517736°E), in the 30−years−old Scots pine forest, growing in oligotrophic site conditions. Four square plots with the size of 0.25 ha each were set. The first one (5) was left as a control variant with no thinning, while the others were subjected to the treatments of different intensity. In variant 5A (slightly thinned) 15% of the basal area compared to the control plot was removed. Accordingly, in variant 5B (moderate thinning) 25% and in variant 5C (heavy thinning) 40% of basal area was subtracted. No additional thinning was implemented further during the experiment. Plots were re−measured at least 4 times with the last measurement in 2016, when the stand was 63 years old. The main result of this study was that after the 33 years no evident effect of various intensity of silvicultural treatments can be seen as the growth and yield of the un−thinned forest stand was the highest compared to the thinned ones. Growth and yield in the most intensely thinned stand reached 86 and 85% compared to the control variant, respectively. The best productive results were found for moderate thinning (92 and 89% of growth and yield of the un−thinned stand), while the worst – in the slightly thinned 5A variant (77 and 83% of values for the control stand). Further on, the number of trees and competition level in all plots were very different when the experiment was established. Yet after 33 years, these differences were remarkably reduced. Accordingly, the diameter distributions, being very different at the beginning of the experiment, eventually became very similar in all experimental plots. Finally, the results showed that in un− −thinned forest stand, natural mortality (self−thinning) of trees adjusted its density just in time. Thus this stand managed to keep its growing energy in later periods, avoiding degradation or destruction predicted by some theories

The greater resilience of mixed forests to drought mainly depends on their composition: Analysis along a climate gradient across Europe

Despite growing evidence that diverse forests play an important role in ecosystem functioning, ensuring the provision of different ecosystem services, whether such diversity improves their response to drought events remains unclear. In this study, we use a large tree-ring database from thirty case studies across nine European countries and eleven species, covering from Mediterranean to hemiboreal forests, to test if the growth response to site specific drought events that occurred between 1975 and 2015 varied between mixed and monospecific stands. In particular, we quantify how stands resist those specific drought events and recover after them, thus analyzing their resilience. For each drought event and forest stand we calculated resistance, recovery, resilience and relative resilience and we related the variation in these indices between monospecific and mixed stands with type of admixture, tree species identity, site aridity gradient, stand basal area and stand age. We found a large variability among case studies, even for those that share similar species composition and have similar climates. On average, mixed stands showed higher resistance, resilience and relative resilience to drought events than monospecific stands. However, the beneficial effect of mixtures could not be generalized, being greatly modulated by the type of admixture and tree species identity, and depending on site water supply and stand characteristics, such as basal area and age. The increase in resilience in mixtures compared with monocultures was greater on the conifer-broadleaved admixtures, and to a lesser extent in the broadleaved-broadleaved combinations. The observed response patterns to drought largely varied among the eleven studied species, thus revealing the importance of functional traits for understanding a species’ response to drought across its distribution range. Along the site aridity gradient, resilience and relative resilience to drought increased in drier sites for both monospecific and mixed stands, with an observed trend towards higher resilience in mixed stands in the drier and hotter sites. Our results confirm the complexity of the relationships found of resistance, recovery, resilience and relative resilience with drought when comparing pure vs mixed stands

The greater resilience of mixed forests to drought mainly depends on their composition: Analysis along a climate gradient across Europe

Despite growing evidence that diverse forests play an important role in ecosystem functioning, ensuring the provision of different ecosystem services, whether such diversity improves their response to drought events remains unclear. In this study, we use a large tree-ring database from thirty case studies across nine European countries and eleven species, covering from Mediterranean to hemiboreal forests, to test if the growth response to site specific drought events that occurred between 1975 and 2015 varied between mixed and monospecific stands. In particular, we quantify how stands resist those specific drought events and recover after them, thus analyzing their resilience. For each drought event and forest stand we calculated resistance, recovery, resilience and relative resilience and we related the variation in these indices between monospecific and mixed stands with type of admixture, tree species identity, site aridity gradient, stand basal area and stand age. We found a large variability among case studies, even for those that share similar species composition and have similar climates. On average, mixed stands showed higher resistance, resilience and relative resilience to drought events than monospecific stands. However, the beneficial effect of mixtures could not be generalized, being greatly modulated by the type of admixture and tree species identity, and depending on site water supply and stand characteristics, such as basal area and age. The increase in resilience in mixtures compared with monocultures was greater on the conifer-broadleaved admixtures, and to a lesser extent in the broadleaved-broadleaved combinations. The observed response patterns to drought largely varied among the eleven studied species, thus revealing the importance of functional traits for understanding a species’ response to drought across its distribution range. Along the site aridity gradient, resilience and relative resilience to drought increased in drier[...]Miškų ir ekologijos fakultetasVytauto Didžiojo universiteta

Croissance et structure des peuplements mixtes et monospécifiques de pin sylvestre (Pinus sylvestris L.) et de chêne sessile (Quercus petraea (Matt.) Liebl.). Analyses le long d'un gradient de productivité en Europe

International audiencePast failures of monocultures, caused by wind-throw or insect damages, and ongoing climate change currently strongly stimulate research into mixed-species stands. So far, the focus has mainly been on combinations of species with obvious complementary functional traits. However, for any generalization, a broad overview of the mixing reactions of functionally different tree species in different mixing proportions, patterns and under different site conditions is needed, including assemblages of species with rather similar demands on resources such as light. Here, we studied the growth of Scots pine and oak in mixed versus monospecific stands on 36 triplets located along a productivity gradient across Europe, reaching from Sweden to Spain and from France to Georgia. The set-up represents a wide variation in precipitation (456-1250 mm year-1), mean annual temperature (6.7-11.5 °C) and drought index by de Martonne (21-63 mm °C-1). Stand inventories and increment cores of trees stemming from 40- to 132-year-old, fully stocked stands on 0.04-0.94-ha-sized plots provided insight into how species mixing modifies stand growth and structure compared with neighbouring monospecific stands. On average, the standing stem volume was 436 and 360 m3 ha-1 in the monocultures of Scots pine and oak, respectively, and 418 m3 ha-1 in the mixed stands. The corresponding periodical annual volume increment amounted to 10.5 and 9.1 m3 ha-1 year-1 in the monocultures and 10.5 m3 ha-1 year-1 in the mixed stands. Scots pine showed a 10% larger quadratic mean diameter (p is smaller than 0.05), a 7% larger dominant diameter (p is smaller than 0.01) and a 9% higher growth of basal area and volume in mixed stands compared with neighbouring monocultures. For Scots pine, the productivity advantages of growing in mixture increased with site index (p is smaller than 0.01) and water supply (p is smaller than 0.01), while for oak they decreased with site index (p is smaller than 0.01). In total, the superior productivity of mixed stands compared to monocultures increased with water supply (p is smaller than 0.10). Based on 7843 measured crowns, we found that in mixture both species, but especially oak, had significantly wider crowns (p is smaller than 0.001) than in monocultures. On average, we found relatively small effects of species mixing on stand growth and structure. Scots pine benefiting on rich, and oak on poor sites, allows for a mixture that is productive and most likely climate resistant all along a wide ecological gradient. We discuss the potential of this mixture in view of climate change

Produktivität von Kiefer und Buche in Mischung im Vergleich zu benachbarten Reinbeständen. Untersuchung entlang eines Produktivitätsgradienten durch Europa

Leidinyje tik 1-ajam autoriui nurodyta prieskyraVytauto Didžiojo universitetasŽemės ūkio akademij

Cuadernos de pedagogía

A través de relatos biográficos, el grupo de investigación Esbrina se propone reconstruir, conjuntamente con sus protagonistas, el paso de dieciocho jóvenes por la Educación Secundaria Obligatoria. Estas investigaciones sitúan el foco de la investigación en el sujeto y en las relaciones que construye. Forma parte de un dossier titulado “Las relaciones de los jóvenes con el saber”.Madrid (Comunidad Autónoma). Subdirección General de Formación del Profesorado. CRIF Las Acacias; Calle General Ricardos 179; 28025 Madrid; Tel. +34915250893; Fax +34914660991; [email protected]

Growth and yield of mixed versus pure stands of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) analysed along a productivity gradient through Europe

Mixing of complementary tree species may increase stand productivity, mitigate the effects of drought and other risks, and pave the way to forest production systems which may be more resource-use efficient and stable in the face of climate change. However, systematic empirical studies on mixing effects are still missing for many commercially important and widespread species combinations. Here we studied the growth of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in mixed versus pure stands on 32 triplets located along a productivity gradient through Europe, reaching from Sweden to Bulgaria and from Spain to the Ukraine. Stand inventory and taking increment cores on the mainly 60-80 year-old trees and 0.02-1.55 ha sized, fully stocked plots provided insight how species mixing modifies the structure, dynamics and productivity compared with neighbouring pure stands. In mixture standing volume (+12 %), stand density (+20 %), basal area growth (+12 %), and stand volume growth (+8 %) were higher than the weighted mean of the neighbouring pure stands. Scots pine and European beech contributed rather equally to the overyielding and overdensity. In mixed stands mean diameter (+20 %) and height (+6 %) of Scots pine was ahead, while both diameter and height growth of European beech were behind (-8 %). The overyielding and overdensity were independent of the site index, the stand growth and yield, and climatic variables despite the wide variation in precipitation (520-1175 mm year(-1)), mean annual temperature (6-10.5 A degrees C), and the drought index by de Martonne (28-61 mm A degrees C-1) on the sitesVytauto Didžiojo universitetasŽemės ūkio akademij