Udo Hans Sauter

Land availability and potential biomass production with poplar and willow short rotation coppices in Germany

Several factors influence land availability for the growth of short rotation coppices (SRC) with fast‐growing tree species, including the nationwide availability of agricultural land, economic efficiency, ecological impacts, political boundaries and environmental protection regulations. In this study, we analysed the growing potential of poplar and willow SRC for bioenergy purposes in Germany without negative ecological impacts or land use conflicts. The potential biomass production using SRC on agricultural land in Germany was assessed taking into account ecological, ethical, political and technical restrictions. Using a geographic information system (GIS), digital site maps, climate data and a digital terrain model, the SRC biomass production potential on cropland and grassland was estimated using water supply and mean temperature during the growing season as parameters. From this analysis, a yield model for SRC was developed based on the analysed growth data and site information of 62 short rotation plantations in Germany and France. To assess the technical, ethical and ecological potential of SRC, restrictions in protected areas, technical constraints and competition with food and feed production were investigated. Our results revealed that approximately 18% (2.12 Mio. ha) of cropland and 54% (2.5 Mio. ha) of grassland in Germany were highly suitable for SRC plantations, providing favourable water supplies and mean temperatures during the growing season. These identified sites produced an average yield of more than 14 tons of dry matter per hectare per year. Due to local climate and soil conditions, the federal states in northern and eastern Germany had the highest theoretical SRC potential for agricultural land. After considering all ecological, ethical, political and technical restrictions, as well as future climate predictions, 5.7% (680 000 ha) of cropland and 33% (1.5 Mio. ha) of grassland in Germany were classified as suitable for biomass production with fast‐growing tree species in SRC.

Towards assessing the sustainability of European logging operations

The forest-based sector has been at the forefront in operationally implementing the sustainability concept, its associated principles and indicators for sustainable forest management. Several methods have been developed to study environmental impacts of forestry activities, but none of the existing tools address all the dimensions of sustainability along the whole forest wood chain (FWC) in a balanced way. Consequently, the decision was made to develop a tool for sustainability impact assessment (ToSIA), the modelling framework for sustainability impact assessment of FWCs. The objective of the EU Project Eforwood was to develop ToSIA, a decision support tool. Within ToSIA, a FWC is modelled as a number of interconnected processes. For each process, a range of economic, environmental and social indicators and their respective values are calculated, thus representing the three pillars of sustainability. By this method, the multifunctionality of forests can be assessed and supply chains can be compared with respect to sustainability. Sensitivity analysis and scenario techniques can be applied to learn about the effect of expected changes to the structure of the chain, the material flows and the indicator values. In order to provide the tool with information about forest and logging operations, data were collected at two fundamental levels: (1) a regional level with case studies in Scandinavia, Iberia and Baden-Württemberg and (2) a European level with a case study that reflects conditions in the 27 countries of the European Union. This paper describes and details the harvesting and logging processes for the European countries. The results are displayed for each of the three regional case studies as well as aggregated to five principal areas in Europe: Eastern, Northern, Western, Central and Southwest Europe.

Alley coppice—a new system with ancient roots

ContextCurrent production from natural forests will not satisfy future world demand for timber and fuel wood, and new land management options are required.AimsWe explore an innovative production system that combines the production of short rotation coppice in wide alleys with the production of high-value trees on narrow strips of land; it is an alternative form of alley cropping which we propose to call ‘alley coppice’. The aim is to describe this alley coppice system and to illustrate its potential for producing two diverse products, namely high-value timber and energy wood on the same land unit.MethodsBased on a comprehensive literature review, we compare the advantages and disadvantages of the alley coppice system and contrast the features with well-known existing or past systems of biomass and wood production.ResultsWe describe and discuss the basic aspects of alley coppice, its design and dynamics, the processes of competition and facilitation, issues of ecology, and areas that are open for future research.ConclusionBased on existing knowledge, a solid foundation for the implementation of alley coppice on suitable land is presented, and the high potential of this system could be shown.

Effect of Knot Detection Errors When Using a Computed Tomography Log Scanner for Sawing Control

Abstract Roundwood scanners utilizing X-ray computed tomography (CT) provide the information required for individual log-sawing optimization. However, errors in the automated detection of quality-r...

Crack Detection in Computer Tomographic Scans of Softwood Tree Discs

Abstract Cracks in softwood are an important defect that reduces the quality of sawn timber for construction purposes. As with all other quality reducing features in wood, it is of significant interest to know about their number and position in a log before sawing. On one hand, cracks are relatively easy to distinguish from wood by means of computer tomographic (CT) scanning owing to the large differences in density. The fact that they tend to be irregular and very thin, however, complicates detection. This study describes a method for automated crack detection in single CT slices and evaluates its precision in terms of both detection rate and length measurement. Twenty tree discs were sampled from spruce (Picea abies) and silver fir (Abies alba) logs and scanned with a computer tomograph. The results of the automated detection are compared with data from manual reference measurements on the physical discs and with data from visual inspection of the CT images. Under optimal conditions, the detection rate ...

Comparison of models for estimating bark thickness of Picea abies in southwest Germany: the role of tree, stand, and environmental factors

Key messageBark thickness was shown to vary between regions, stands, and trees. Bark thickness prediction equations of different model complexity can be suggested depending on the purpose of application. Site and stand conditions, which influence variation of growth rate to a large extent, seem to have a strong influence on bark thickness, with better site quality leading to smaller relative bark thickness.ContextFor many applications in forestry and forest science, local or regional species-specific bark thickness equations are used to estimate inside-bark diameters with outside-bark diameter measurements.AimsThe objectives of this study were (1) to assess variation in bark thickness due to tree and stand factors in two Norway spruce (Picea abies (L.) Karst) datasets from different time periods, (2) to compare and evaluate alternative established model forms for estimating bark thickness, and (3) to assess spatial variation in bark thickness to estimate the effects of environmental factors on bark thickness.MethodsDifferent bark thickness models were chosen from the literature and compared for their predictive quality for new measurements and a dataset from the 1970s. Mixed-effect modelling was applied to account for the hierarchical data structure, and generalized additive mixed models were used to analyse spatial effects and the influence of climatic factors, such as precipitation and temperature.ResultsA strong positional autocorrelation of bark thickness within trees and within plots could be shown. Bark thickness was smaller in the new data compared to the measurements from the 1970s. The variation between stands could not be explained by the tested environmental factors, but tree age had a strong positive effect on bark thickness.ConclusionIn the study region, the variation of site productivity and individual growth rate seem to have a strong influence on bark thickness, whereas no significant effect of large scale climatic factors could be found.

Tests of reception of the combination of GPS and GLONASS signals under and above forest canopy in the Black Forest, Germany, using choke ring antennas

Mobilizing timber resources from the smallest private forest ownership should be possible by ensuring straight information management along the logistics chain, including precise localization of trees and their ownership. Precise navigation during harvest operations by heavy forest machines is necessary to keep them on established skid trails to avoid additional soil compaction. Furthermore, the construction of a skid trail network itself as a contribution to soil protection requires precise positional information. Therefore, the main purpose of this study was to find an easy-to-apply and high-precision solution for real-time navigation within forest stands. Static measurements with two choke ring antennas, which are touted to highly reduce multipath effects, were conducted in two heights on 19 test sites in the Black Forest Mountain region, South Western Germany, to investigate Global Navigation Satellite System (GNSS) signal reception below and above forest canopy. All sites showed a significantly lower precision under the canopy, far away from sub-meter level. Since our aim for dynamic navigation is a trueness of 0.35 m, the conclusion is that the application of high precision GNSS-antennas, as a single means of optimization, does not meet the requirements for real-time navigation within forest stands and further research and improvement is needed. The combination of GPS and GLONASS satellite systems was investigated, which delivers a slightly higher precision than GPS only and is therefore recommended. The precision of GLONASS only is much lower and therefore unsuitable. The causes for low precision under canopy were investigated. Our data clearly shows a correlation between canopy density and decreasing precision. Under small opened canopy, we identified a dominating influence of scattering effects on the precision. Leaf type of trees, slopes and direction have an influence on the precision, but much smaller than the sky openness.

Successional changes of phytodiversity on a short rotation coppice plantation in Oberschwaben, Germany

To allow for information on successional changes in phytodiversity over time and space, as well as information on differences between clones and treatments, phytodiversity was monitored on a poplar short rotation coppice plantation in Oberschwaben, Southwest Germany, in four consecutive years. The investigated plantation was divided into two core areas, one planted with poplar clone Max4, the other with Monviso; each core area was divided into two blocks with alternating treatments: (i) irrigation and fertilization; (ii) irrigation; and (iii) no treatment. All vascular plant species of the ground vegetation were recorded in 72 permanent sampling plots of 25 m2 each during vegetation periods using the Braun-Blanquet scale. Results showed that total number of species increased in first 2 years and declined after harvest of the SRC-trees. Total vegetation cover decreased during the 4 years of study. Especially for the two clones there was an opposed trend: grass layer had a high cover on Monviso plots, but low cover on Max4 plots; herb layer the very reverse. However, there was no significant difference between the three treatments compared within each year. Perennial species were dominating over all years, as well as light-demanding species, but their proportion decreased steadily. Our results confirm the conclusion of previous studies which indicate that plant community succession takes place in ground vegetation of SRC and imply that species composition is age-dependent. The selection of clones for SRC can influence ground vegetation; some floristic changes for example caused by different treatments may be visible only when monitored over a longer period of time.

Improved models of harvest-induced bark damage

Key messageWe provided a precise quantitative analysis of the factors at the origin of bark damage during harvesting operations and developed a model able to predict them accurately. The major factors were the distance of trees to skid trails, the intensity of removals, the harvesting system as well as the interactions between the distance of trees to skid trails with harvesting systems, the average skidding distance, the tree species and tree height.• ContextDuring timber harvesting, trees in the remaining stand may suffer bark damage resulting from tree-felling or log manipulation. Although a multitude of case studies and empirical observations provide qualitative and quantitative information with respect to the potential causal factors, the basic quantitative relationship between major factors of influence and the resulting degree of bark damage remains largely unclear.• AimsThe objective was to provide a precise quantitative analysis of impact factors explaining the occurrence of bark damage during harvesting operations.• MethodsThree different modelling approaches were tested: boosted regression tree (BRT), a generalised linear mixed effects model (GLMM) and Bayesian Markov chain Monte Carlo generalised linear mixed models (MCMCglmm).• ResultsThe major factors with a significant impact on the occurrence of bark damage were the distance of trees to skid trails, the intensity of removals, the harvesting system and the interaction term between the distance of trees to skid trails with harvesting systems, average skidding distance, tree species and tree height.• ConclusionThe final model includes the relevant major factors impacting on the infliction of bark damage during practical harvesting operations. Furthermore, it discriminates well with respect to the occurrence of bark damage, and it provides managers with a rational and conclusive tool for optimising harvesting operations.

Klassifikation und Vermessung von Rissen in Nadelrund- und Nadelschnittholz

Classification and measurement of visible cracks in softwood logs and sawn timber Cracks as an attribute of logs are an important quality factor for the production of sawn timber. They can develop in the standing tree due to growth stresses or external influences, but also in felled trees due to tension releases or drying. The definitions for different types of cracks that can be found in standards and in literature lack consistancy and are not sufficient for scientific use. This paper proposes a classification scheme for cracks in logs and sawn timber that is based on existing definitions in literature but also includes newly drafted definitions. A method for the estimation of crack damaged volume in wood is presented, which is based on manual measurement of the crack features for scientific use. The results give detailed and, depending on the dimensions of the sawn timber, also precise information about type, size and position of cracks as well as the expected volume of reject.