Jens Nitzsche

Mit einem neu entwickelten Internet-Tool können Vorkommen von Zukunftsbaumarten einfach dokumentiert werden. Alle Waldfachleute sind eingeladen, ihre Erfahrungen über bestehende oder neu entstandene Bestände beizutragen. Je mehr mitmachen, desto besser.

Estimating growing stock is one of the main objectives of forest inventories. It refers to the stem volume of individual trees which is typically derived by models as it cannot be easily measured directly. These models are thus based on measurable tree dimensions and their parameterization depends on the available empirical data. Historically, such data were collected by measurements of tree stem sizes, which is very time- and cost-intensive. Here, we present an exceptionally large dataset with section-wise stem measurements on 40'349 felled individual trees collected on plots of the Experimental Forest Management project. It is a revised and expanded version of previously unpublished data and contains the empirically derived coarse (diameter ≥7 cm) and fine branch volume of 27'297 and 18'980, respectively, individual trees. The data were collected between 1888 and 1974 across Switzerland covering a large topographic gradient and a diverse species range and can thus support estimations and verification of volume functions also outside Switzerland including the derivation of whole tree volume in a consistent manner.

Wurden Erfahrungen mit Atlaszedern auf Kalkböden gemacht, gedeihen sie da? Hat bereits jemand Zerreichen im Zürcher Oberland gepflanzt, und wie haben die sich entwickelt? Lohnt es sich die seltenen, natürlich aufkommenden, jungen Nussbäume in der Buchenverjüngung zu fördern oder ist der Aufwand zu gross? Wer etwas wagt und neue Baumarten einbringt, oder seltene Baumarten in der Naturverjüngung fördert, würde gerne am Erfahrungsschatz von anderen teilhaben. Viele sind bereit, ihre Erfahrungen zu teilen. Oft ist es schwierig, den Kontakt und den Austausch zu ermöglichen. Das neue DokuTool Zukunftsbaumarten bietet sich als Plattform für diesen Erfahrungsaustausch an.

Most strategic and operational forest management decisions are taken based on stand-level information, and quantitative models of forest dynamics are key for developing sustainable management strategies. However, data on forest stands for the initialisation of such models that are representative at large spatial scales, e.g., countries or ecoregions, are often lacking. National Forest Inventories (NFIs) provide forest data from small sample plots at large spatial scales, yet deriving full stand information based on such data is challenging. Here, we evaluate seven methods of varying complexity for deriving quantitative stand descriptions based on sample data as provided by the Swiss NFI. We selected 271 extensively measured Swiss forests stands with unimodal diameter distributions, classified them as beech- vs. spruce-dominated in five development stages and randomly placed a small sized sample plot in each stand using the Swiss NFI sampling design (i.e., a circular plot of 500 m²). Seven modelling approaches were used to derive diameter distributions and species-specific stem numbers (i.e., tree species composition) from the sample data that are representative for a particular stand (local scale) and for stand types in general (generalised scale). The prediction performance of the modelling approaches was evaluated using 100 random samples per stand to calculate prediction errors. Generalised even-aged diameter distributions were best predicted by the simultaneous parameter prediction method (PPM), i.e. a combined three-step regression approach, with on average 1.3 to 2.5 times lower prediction errors compared to the simple pooling of diameter samples. However, uneven-aged diameter distributions were best predicted by pooling. At the local scale, the simultaneous PPM performed best for data from sample plots with fewer than 17 to 19 trees across all development stages. Prediction performance of the PPMs increased for structurally and spatially diverse local stands with positively skewed diameter distributions. A Random Forest approach was most suitable for predicting species composition at both the generalised and the local scale. Our study evaluates the strengths and weaknesses of methods to model stands based on data from small sample plots. We emphasise terminological pitfalls by consequently distinguishing local accuracy and generalised representativity of the stand descriptions. We demonstrate the feasibility of deriving locally accurate stands using data from small forest sample plots and evaluate the derivation of generalised stands representative at large regions. At both scales, our developments contribute to an improved initialisation of forest models and thus to a more realistic modelling of forest development under future boundary conditions.

Long-term changes in growth, physiology and stand structure, as well as differences due to species composition, were examined in six types of Swiss plenter forests: (1) Picea abies dominated, (2) mixtures of P. abies and Abies alba, (3) mixtures of P. abies, A. alba and Fagus sylvatica, (4) mixtures of Larix decidua, Pinus cembra/sylvatica and P. abies, (5) F. sylvatica dominated and (6) species diverse stands. Long-term changes were examined using 19 plots measured for an average of 94 years. These data were then combined with the literature plenter forest data to compare the growth and structure of 15 species compositions from Europe, North America and Australia. Over the past 100 years, common trends included increases in growth, maximum tree sizes, species diversity, and increasingly convex diameter distributions with fewer medium sized trees and more very large trees. Differences in growth between species compositions were generally consistent with their light-use efficiency, transpiration and water-use efficiency, which were calculated using a process-based model. Stand volume of each forest type was negatively correlated with the shade tolerance (but not crown architectures) of the species it contained, but no such correlations existed for stand basal area. This reflects the high structural variability of these forests (through time and between sites) as well as the high tree neighbourhood variability within plots, which appear to buffer the effects of stand density on regeneration and recruitment. This study shows that despite significant temporal and spatial variability in structure, the negative exponentially shaped diameter distributions were maintained in the long term by applying simple silvicultural principles rather than requiring a very specific stand structure, i.e. a certain stand density, or that all diameter classes strictly lie on the curve of a negative exponentially shaped diameter distribution. The values of stand structural characteristics reported in this study could be used as a guide for the conversion of relatively simply structured forests into plenter forests.

The development of our forests under climate change and the influence of today’s actions on future ecosystem services in forests have become important silvicultural issues. There-fore, model-based tools are needed for forest planning and the optimization of interventions. In this article the new, scientifically based forest growth model SwissStandSim is presented, which shall become part of a future decision support system for the Swiss forestry. SwissStandSim is based on the data of the long-term experimental growth and yield plots in Switzerland. These data are used to create a climate sensitive single-tree based forest growth model. The tree data were combined with many environmental variables to model the demographic processes of management, growth, mortality and ingrowth. The climate variables showed ecologically in-teresting interactions, especially between precipitation and temperature, both for growth and mortality. A further inter-action was found between the intensity of forest management and mortality. The stronger the management, the higher the mortality in the following years. This allows inter-pretations regarding the vulnerability of stands after major interventions. Simulations with SwissStandSim for three exemplary growth and yield plots show a good agreement between data and model, with the frequency and intensity of natural disturbances playing a key role. The calibration of SwissStandSim was based on a mean disturbance regime, which can lead to an over-or underestimation of mortality depending on the local situation. With SwissStandSim the management of forest stands can be simulated flexibly. Thus, SwissStandSim is very suitable to become part of a practical tool for decision support in silvicultural questions at the stand level developed in the WSL project SessFor (NFP73).

One of the longest running scientific projects in Switzerland is the Experimental Forest Management project (EFM), which has been collecting growth and yield data for more than a century. Thus, a strength of the EFM data is the very long‐term monitoring (Hanewinkel et al., 2013). Remarkably, some of the plots have been measured regularly for > 100 years, making them some of the oldest scientific experiments in the world. These data often play a central role when examining the long‐term effects of management, climate and other environmental drivers on forest growth and functioning in Switzerland. These data have not only proven valuable for multiple groups within WSL and Swiss foresters (about 70% of Swiss forests are managed), but also internationally. [...]

Forests dominated by European beech (Fagus sylvatica L.) are among both the most widespread in Europe and the most intensely exploited globally. One of the largest remnants of unmanaged beech forests in Europe is the Uholka‐Shyrokyi Luh forest in Transcarpathia, Ukraine, covering 8,800 ha of primeval forest. In 2000, a permanent forest plot of 10 ha has been established in the Uholka massif. All living and dead trees with a diameter at breast height (DBH) ≥ 60 mm were identified to species, DBH measured, stems tagged and mapped. Since then, the plot has been remeasured in 2005, 2010, and 2015. In total, 4,820 individual trees were measured with 14,116 individual measurements throughout all four inventories. In spring 2018, an Airborne Laser Scan was carried out, covering the Uholka‐Shyrokyi Luh forest. This data set allows us to derive a high‐resolution digital elevation model (DEM) of the plot area. European beech covers a share of ≈ 95% of the basal area (BA) of all living stems. While BA was relatively stable throughout all inventories (≈ 38 m²/ha), the number of stems increased considerably between 2010 and 2015 from 290 to 430 stems/ha. Additionally, the proportion of beech stems decreased from 95% in 2010 to 86% in 2015. The continuity of the share of beech on BA and the decrease in number of stems can be traced back to disturbance events, which led to an increase of more light demanding species in the recruitment but did not alter the distribution of BA as these small trees contribute very little to BA. The data set allows for important insights into the development and the spatial and temporal dynamics of primeval beech forests. It can be used to quantify the demographic processes growth, mortality, and recruitment, and to study inter‐ and intraspecific effects on demographic rates, stand structure, and species composition. No copyright or proprietary restrictions are associated with the use of this data set other than citation of this Data Paper.