Effects of initial planting density on branch development in 4-year-old plantation grown Eucalyptus pilularis and Eucalyptus cloeziana trees

The effect of planting density on branch development was examined in 4-year-old Eucalyptus pilularis Sm. and Eucalyptus cloeziana F. Muell. plantations located near the coast of north-eastern NSW. Branch diameter, angle and status (live or dead) were measured along the entire stem of trees established at 1250, 1667 and 3333 stems per hectare (sph). Measurements of tree height and stem diameter at breast height over bark (DBH) were also recorded. Results showed that with an increase in initial planting density from 1250 to 1667 sph, branch size decreased, branch mortality on the lower stem increased, branch angle became more acute and DBH decreased in trees of both E. pilularis and E. cloeziana. A further increase in initial planting density from 1667 to 3333 sph did not significantly reduce branch size or branch angle but did result in increased branch mortality and decreased DBH in both species. These results suggest that increasing initial planting density from 1250 to 1667 sph will improve early branch control. However, there is no advantage in establishing trees at 3333 sph rather than 1667 sph to reduce branch size or increase branch mortality in either species. Clearwood production on the lower stem in all stocking treatments of both species was negligible at age 4

On the knowns and unknowns of natural regeneration of silviculturally managed sessile oak (Quercus petraea (Matt.) Liebl.) forests—a literature review

Key message This literature review identified the main factors for the success of different silvicultural approaches to regenerate sessile oak naturally and unveiled at the same time important knowledge gaps. Most previous studies were only short-term and restricted to a few factors and single locations. Hence, the findings of these studies are of limited explanatory power and do not allow to develop general, widely applicable management recommendations. Context Successful natural regeneration of sessile oak (Quercus petraea (Matt.) Liebl.) through silvicultural actions depends on a number of biotic, abiotic and management factors and their interactions. However, owing to a limited understanding about the influence of these critical factors, there is great uncertainty about suitable silvicultural approaches for natural oak regeneration, in particular regarding the size of canopy openings and speed of canopy removal. Aims This study aimed at critically evaluating documented information on natural regeneration of sessile oak. Specifically, we identified (i) the factors that determine the success of approaches for natural regeneration and (ii) evaluated the evidence base associated with different silvicultural approaches. Methods A comprehensive literature search was done considering relevant peer-reviewed publications of ISI-listed journals as well as non-ISI listed published papers and reports by practitioners. Out of more than 260 collected references, a set of 53 silvicultural ‘core publications’ was identified and analyzed using a catalogue of numeric and categorical evaluation criteria. Results The most important factors determining regeneration success extracted from the literature were light availability, presence of competing vegetation, initial oak seedling density, browsing of seedlings and intensity of stand tending measures. However, the review revealed also great uncertainty regarding the interactions between these factors and the magnitude of their influence. Most studies were of short duration and restricted to single locations. In only 20% of the experimental studies, the observation period exceeded five years. Total costs of regeneration efforts were quantified and reported in only two studies. This lack of data on the expenses of different approaches to natural oak regeneration appears to be one of the most crucial knowledge deficits revealed in this literature review. Conclusion Natural regeneration of sessile oak may be achieved under a wide range of canopy openings, if competing vegetation and browsing is negligible, seedling density is high and tending to remove competing vegetation is carried out consistently. However, since the silvicultural regeneration success depends on the interactions among these factors, which have often not been adequately considered, we caution against general recommendations for silvicultural systems developed from case studies and call for new long-term studies with comprehensive experimental designs.publishedVersio

Tree microhabitat abundance and richness in Central European montane forests as indicators for future old growth elements

The continued provision of old-growth elements in forest landscapes has been identified as a critical factor for biodiversity conservation in Central Europe. A well-established method of estimating the potential of forests to maintain biodiversity is to quantify tree microhabitat structures. Our aim is to predict the microhabitat abundance and richness for collectives of potential habitat trees (15 largest trees per plot).  Microhabitats were inventoried on 2085 trees across 139 plots (each 1 ha) and assessed based on a detailed catalogue comprising 64 different microhabitat structures in montane forests of the Black Forest, southwest Germany. We tested the influence of forest management, forest cover in surrounding landscape, forest type, structural complexity (number of standing dead trees), altitude and average tree size on the abundance and richness of microhabitats on living trees. Generalized linear models (GLM) were used to identify the significant drivers of abundance and richness of microhabitats. The results indicate that the abundance of microhabitats of the respective 15 trees is greater on plots located in higher altitudes. Increasing average tree diameter leads to significantly higher abundances and richness of microhabitats. The collectives of inventoried trees located in monospecific coniferous forests have the highest abundance but those in mixed-coniferous-broadleaved forests have the greatest richness of tree microhabitats. Additionally we explored to which degree specific microhabitat types are influenced by the forest variables. The occurrences of 11 out of 64 specific microhabitat structures show a relation to forest management, forest type, altitude or average tree diameter. Specific microhabitats are increasing in mixed-coniferous-broadleaved and in relation to average tree size. The altitude influences especially abundances of epiphytes on potential habitat trees.This study demonstrates that based on the selected forest attributes the average abundance and richness of microhabitats can be reasonably well predicted and the occurrence of specific microhabitats can be identified.peerReviewe

Growth of wild service tree in the formerly coppiced nahebergland forests

L’Alisier torminal [Sorbus torminalis L. (Crantz)] quoique rare est relativement présent dans les taillis de chênes d’Europe centrale. Les connaissances sur sa régénération et sa croissance sont peu nombreuses malgré un bois de haute valeur. Le taillis étant actuellement en forte régression, des interrogations se posent vis-à-vis de la persistance de la population de S. torminalis en tant que couvert forestier continu ou de la nécessité du taillis pour préserver l’espèce. Sur trois parcelles expérimentales d’un hectare de taillis de chênes situées en Allemagne, la présence de l’espèce a été quantifiée. L’âge de 62 arbres a été déterminé. La croissance en diamètre et hauteur a été reconstruite par analyses des cernes de croissance sur 20 arbres. Les résultats suggèrent que le taillis favorise l’établissement de S. torminalis et que l’Alisier est extrêmement tolérant à l’ombre et à la compétition. Lors des 80 dernières années, une régénération apparaît continuellement. L’arrêt du taillis ne serait donc pas une menace pour S. torminalis.Although the wild service tree [Sorbus torminalis L. (Crantz)] is generally rare, it is fairly common in the oak coppices of central Europe. There is little knowledge about its regeneration and growth in spite of the high value of the wood. Since coppicing is less and less popular, questions arise as to the survival of S. torminalis populations by way of continuous forest cover or whether there is a need to maintain coppicing to preserve this species. Three one-hectare experimental plots of oak coppices in Germany were studied to quantify the presence of this species. The age of 62 trees was determined. Girth growth and height were reconstructed by analysing growth rings on 20 trees. The results suggest that coppicing encourages the establishment of S. torminalis and that service trees are extremely tolerant to shade and to competition. Regenerations appear continuously over the last 80 years. It is therefore expected that discontinuing coppicing would not threaten S. torminalis

Predictors of Microhabitat Frequency and Diversity in Mixed Mountain Forests in South-Western Germany

Tree-related microhabitats are an important determinant of forest biodiversity. Habitat trees, which typically provide many microhabitats such as hollows, crown dead wood, etc., are therefore selected to maintain those structural attributes within managed forests. To what extent the occurrence of microhabitats on potential habitat trees may be predicted from common tree attributes is a question of high practical relevance. Until now, most studies have attempted to predict the quantity of microhabitats at the tree or forest stand level. In our study, we aimed at explaining microhabitat occurrence from a qualitative perspective by considering their diversity. Tree diameter at breast height (dbh), tree species, and canopy class were useful predictors of microhabitat diversity. Microhabitat diversity on broadleaved trees was on average higher than in conifers of the same diameter. In contrast to microhabitat quantity, microhabitat diversity saturated towards higher dbh levels. Microhabitat diversity in beech trees of lower tree canopy classes was found to be surprisingly high. Habitat trees support not only more, but also more diverse, microhabitats in comparison to crop trees. Considering these findings on microhabitat distribution, the selection of habitat trees within Central European mixed mountain forests can be significantly improved

Impacts of climate change on the establishment, distribution, growth and mortality of Swiss stone pine (Pinus cembra L.)

Anticipated future climate changes are expected to significantly influence forest ecosystems, particularly in treeline ecotones. Climate change will have both direct and indirect effects on the future distribution of alpine tree species, some of which will be positive and others negative. Although increased temperatures are on the whole likely to have a positive impact on growth and distribution of Swiss stone pine (Pinus cembra L.), indirect effects that influence seed dispersal may threaten the population viability of species. The complexity of the interrelations between climatic and non-climatic factors demands further research, which should include long-term monitoring

On the knowns and unknowns of natural regeneration of silviculturally managed sessile oak (Quercus petraea (Matt.) Liebl.) forests—a literature review

Key message This literature review identified the main factors for the success of different silvicultural approaches to regenerate sessile oak naturally and unveiled at the same time important knowledge gaps. Most previous studies were only short-term and restricted to a few factors and single locations. Hence, the findings of these studies are of limited explanatory power and do not allow to develop general, widely applicable management recommendations. Context Successful natural regeneration of sessile oak (Quercus petraea (Matt.) Liebl.) through silvicultural actions depends on a number of biotic, abiotic and management factors and their interactions. However, owing to a limited understanding about the influence of these critical factors, there is great uncertainty about suitable silvicultural approaches for natural oak regeneration, in particular regarding the size of canopy openings and speed of canopy removal. Aims This study aimed at critically evaluating documented information on natural regeneration of sessile oak. Specifically, we identified (i) the factors that determine the success of approaches for natural regeneration and (ii) evaluated the evidence base associated with different silvicultural approaches. Methods A comprehensive literature search was done considering relevant peer-reviewed publications of ISI-listed journals as well as non-ISI listed published papers and reports by practitioners. Out of more than 260 collected references, a set of 53 silvicultural ‘core publications’ was identified and analyzed using a catalogue of numeric and categorical evaluation criteria. Results The most important factors determining regeneration success extracted from the literature were light availability, presence of competing vegetation, initial oak seedling density, browsing of seedlings and intensity of stand tending measures. However, the review revealed also great uncertainty regarding the interactions between these factors and the magnitude of their influence. Most studies were of short duration and restricted to single locations. In only 20% of the experimental studies, the observation period exceeded five years. Total costs of regeneration efforts were quantified and reported in only two studies. This lack of data on the expenses of different approaches to natural oak regeneration appears to be one of the most crucial knowledge deficits revealed in this literature review. Conclusion Natural regeneration of sessile oak may be achieved under a wide range of canopy openings, if competing vegetation and browsing is negligible, seedling density is high and tending to remove competing vegetation is carried out consistently. However, since the silvicultural regeneration success depends on the interactions among these factors, which have often not been adequately considered, we caution against general recommendations for silvicultural systems developed from case studies and call for new long-term studies with comprehensive experimental designs

The history of introduced tree species in a nuttshell

status: publishe