Central European Conditions Research Articles

Calibration of the process-based model 3-PG for major central European tree species

Process-based forest models are important tools for predicting forest growth and their vulnerability to factors such as climate change or responses to management. One of the most widely used stand-level process-based models is the 3-PG model (Physiological Processes Predicting Growth), which is used for applications including estimating wood production, carbon budgets, water balance and susceptibility to climate change. Few 3-PG parameter sets are available for central European species and even fewer are appropriate for mixed-species forests. Here we estimated 3-PG parameters for twelve major central European tree species using 1418 long-term permanent forest monitoring plots from managed forests, 297 from un-managed forest reserves and 784 Swiss National Forest Inventory plots. A literature review of tree physiological characteristics, as well as regression analyses and Bayesian inference, were used to calculate the 3-PG parameters.The Swiss-wide calibration, based on monospecific plots, showed a robust performance in predicting forest stocks such as stem, foliage and root biomass. The plots used to inform the Bayesian calibration resulted in posterior ranges of the calibrated parameters that were, on average, 69% of the prior range. The bias of stem, foliage and root biomass predictions was generally less than 20%, and less than 10% for several species. The parameter sets also provided reliable predictions of biomass and mean tree sizes in mixed-species forests. Given that the information sources used to develop the parameters included a wide range of climatic, edaphic and management conditions and long time spans (from 1930 to present), these species parameters for 3-PG are likely to be appropriate for most central European forests and conditions.

Persistence of Xanthomonas campestris pv. campestris in Field Soil in Central Europe.

Xanthomonas campestris pv. campestris (Xcc) is a bacterium that causes black rot of crucifers. The greatest losses of brassica crop production usually result from seed-borne infection, but carry-over of inoculum in field soil may also be possible. The aim of this study was to monitor persistence of Xcc in field soil in central Europe using a conventional PCR assay with hrpF primers and a two-step nested real-time PCR assay using Zur primers. The work has demonstrated that nested real-time PCR can be used to improve the analytical sensitivity for detection of Xcc in soil compared to conventional PCR, and that Xcc may persist in soil for up to two years following an infected brassica crop in central European climatic conditions.

A study of Phytophthora spp. in declining highbush blueberry in Germany reveals that P. cinnamomi can thrive under Central European outdoor conditions

Phytophthora cinnamomi and P. cactorum were detected in soil samples from a Vaccinium corymbosum stand in southern Germany. Both species were virulent in an underbark inoculation assay and have not been reported from highbush blueberry in Germany before. While P. cactorum is a widely distributed species in nurseries and (semi)natural habitats like forests, field reports of P. cinnamomi in Germany are rare due to its sensitivity to frost. Its occurrence in an outdoor blueberry stand indicates its potential to survive Central European winter periods that tend to be increasingly mild. Phytophthora cinnamomi was also found in the substrate of young V. corymbosum nursery plants, suggesting a high degree of contamination in commercial blueberry production and demonstrating the risk of spreading exotic invasive plant pathogens via planting of infested nursery stock.

Cup plant, an alternative to conventional silage from a LCA perspective

The growing awareness of the importance of biodiversity in agroecosystems in increasing and ensuring the supply of biomass has led to heightened interest from governments and farmers in alternative crops. This article assesses one such alternative crop, cup plant (Silphium perfoliatum L.), in terms of the environmental aspects of cultivation for forage production. Many studies have previously focused on cup plant, but so far, this plant has not been assessed using the life cycle assessment (LCA) method. This study compares the environmental load of cup plant with the most commonly grown silage crops in Central European conditions—maize—and with another common forage crop—lucerne using LCA. The system boundaries include all the processes from cradle to farm gate and both mass-based (1 ton of dry matter) and area-based (1 ha of monoculture) functional units were chosen for the purposes of this study. The results cover the impact categories related to the agricultural LCAs, and the ReCiPe Midpoint (H) characterization model was used for the data expression, by using SimaPro 9.0.0.40 software. This study compares the cultivation of cup plant with the most commonly grown silage crop in Central European conditions—maize—and with another common forage crop—lucerne. The paper shows the potential of cup plant to replace conventional silage (maize and lucerne silage mix) with certain environmental savings in selected impact categories, and importantly, while still maintaining the same performance levels in dairy farming as with conventional silage, as already reported in previous publications. For the Czech Republic alone, this would, in practice, mean replacing up to 50,000 ha of silage maize and reducing the environmental load by about tens of percent or more within the various impact categories and years of cultivation. Cup plant can replace the yield and quality of silage maize, represents a lower environmental load per unit of production and unit of area and generally carries many other benefits. Thus, cup plant is a recommendable option for dairy farming. Given the recent experience and knowledge of the issue, the cup plant can be considered an effective alternative to conventional silage.

Performance of 13 crop simulation models and their ensemble for simulating four field crops in Central Europe

AbstractThe main aim of the current study was to present the abilities of widely used crop models to simulate four different field crops (winter wheat, spring barley, silage maize and winter oilseed rape). The 13 models were tested under Central European conditions represented by three locations in the Czech Republic, selected using temperature and precipitation gradients for the target crops in this region. Based on observed crop phenology and yield from 1991 to 2010, performances of individual models and their ensemble were analyzed. Modelling of anthesis and maturity was generally best simulated by the ensemble median (EnsMED) compared to the ensemble mean and individual models. The yield was better simulated by the best models than estimated by an ensemble. Higher accuracy was achieved for spring crops, with the best results for silage maize, while the lowest accuracy was for winter oilseed rape according to the index of agreement (IA). Based on EnsMED, the root mean square errors (RMSEs) for yield was 1365 kg/ha for winter wheat, 1105 kg/ha for spring barley, 1861 kg/ha for silage maize and 969 kg/ha for winter oilseed rape. The AQUACROP and EPIC models performed best in terms of spread around the line of best fit (RMSE, IA). In some cases, the individual models failed. For crop rotation simulations, only models with reasonable accuracy (i.e. without failures) across all included crops within the target environment should be selected. Application crop models ensemble is one way to increase the accuracy of predictions, but lower variability of ensemble outputs was confirmed.

HeProMo: A decision support tool to estimate wood harvesting productivities.

In the field of forestry, one of the most economically important ecosystem service is the provision of timber. The need to calculate the economic effects of forest management in the short, medium, and long term is increasing. Forest operations or timber harvesting, which comprises felling, processing, and transport of trees or timber, are responsible for a large part of the costs and environmental impacts associated to forest management or enterprises. From a decision maker's perspective, it is essential to estimate working productivity and production costs under given operating conditions before any operation is conducted. This work addresses the lack of a valid collection of models that allows estimating time, productivities, and costs of labor and machinery for the most important forest operations in forest stands under Central European conditions. To create such models, we used data from forest enterprises, manual time studies, and the literature. This work presents a decision support tool that estimates the wood harvesting productivities of 12 different kinds of forest operations under Central European conditions. It includes forest operations using chainsaws, harvesters, skidders, forwarders, chippers, cable and tower yarders, and helicopters. In addition, the tool covers three models for wood volume estimation. The tool is written in Java and available open-source under the Apache License. This work shows how the tool can be used by describing its graphical user interface (GUI) and its application programming interface (API) that facilitates bulk processing of scientific data. Carefully selected default values allow estimations without knowing all input variables in detail. Each model is accompanied by an in-depth documentation where the forest operation, input variables, formulas, and statistical background are given. We conclude that HeProMo is a very useful tool for applications in forest practice, research, and teaching.

Solar elevation impact on the heat stress mitigation of pedestrians on tree-lined sidewalks of E-W street canyons – Analysis under Central European heat wave conditions

For both tree-lined sidewalks of a shallow and deep E-W street canyon located in the city of Freiburg (Southwest Germany), the solar elevation impact on the magnitude of the daytime human heat stress mitigation (hhsm) is analysed in dependence of different tree scenarios. Identic ENVI-met simulations are carried out on the summer solstice day 21 June 2003 and heat wave day 4 August 2003. All simulation scenarios indicate an almost negligible solar elevation impact on hhsm in terms of spatiotemporal averaged air temperature. The results achieved on both simulation days for the spatiotemporal averaged mean radiation temperature (Tmrt) and physiologically equivalent temperature (PET) as well as spatially high-resolution PET reflect that the north-facing sidewalk in both street canyons is entirely shaded by the south-bounding building. Secondarily it is influenced by lower radiant flux densities from the trees near the curb edges of both sidewalks. On both simulation days, the south-facing sidewalk in the shallow street canyon is only shaded by the tree crowns. In the deep street canyon, however, the south-facing sidewalk is completely shaded on 4 August by the south-bounding building, while on 21 June this shade is limited to its southern half, i.e. its northern half is directly influenced by the shade of trees. Due to these shading conditions, the results focused on pedestrians on both sidewalks show different patterns of the solar elevation impact on Tmrt and PET as well as hhsm in terms of Tmrt and PET. While increasing tree crown projection areas lead to a lower solar elevation impact on Tmrt and PET, they cause a more distinct hhsm in terms of Tmrt and PET for higher solar elevations. The non-negligible magnitude of the solar elevation impact in all scenarios leads to the recommendation to carry out ensemble simulations in order to achieve Tmrt, PET, hhsm-Tmrt and hhsm-PET results, which are reliable for planning applications.

The Impacts of Tracking System Inaccuracy on CPV Module Power

The accuracy and reliability of solar tracking greatly impacts the performance of concentrator photovoltaic modules (CPV). Thus, it is of utmost significance to know how deviations in tracking influence CPV module power. In this work, the positioning characteristics of CPV modules compared to the focus points were investigated. The performance of CPV modules mounted on a dual-axis tracking system was analysed as a function of their orientation and inclination. The actual experiment was carried out with CPV cells of 3 mm in diameter. By using a dual tracking system under real weather conditions, the module’s position was gradually modified until the inclination differed by 5° relative to the optimal position of the focus point of the CPV module. The difference in inclination was established by the perfect perpendicularity to the Sun’s rays. The results obtained specifically for CPV technology help determine the level of accuracy that solar tracking photovoltaic systems are required to have to keep the loss in power yield under a certain level. Moreover, this power yield loss also demonstrated that the performance insensitivity thresholds of the CPV modules did not depend on the directions of the alterations in azimuthal alignment. The novelty of the research lies in the fact that earlier, no information had been found regarding the tracking insensitivity point in CPV technologies. A further analysis was carried out to compare the yield of CPV to other, conventional photovoltaic technologies under real Central European climate conditions. It was shown that CPV needs a sun tracking accuracy of at least 0.5° in order to surpass the yield of other PV technologies. Besides providing an insight into the tracking error values of solar tracking sensors, it is believed that the results might facilitate the planning of solar tracking sensor investments as well as the economic calculations related to 3 mm cell diameter CPV system investments.

Presence of Bradyrhizobium sp. under Continental Conditions in Central Europe

Soil samples from different locations with varied soybean cultivation histories were taken from arable fields in 2018 in East Germany and Poland (Lower Silesia) to evaluate the specific microsymbionts of the soybean, Bradyrhizobium japonicum, one to seven years after inoculation. Soybeans were grown in the selected farms between 2011 and 2017. The aim of the experiment was to investigate whether there is a difference in rhizobia contents in soils in which soybeans have been recultivated after one to seven years break, and whether this could lead to differences in soybean plant growth. The obtained soil samples were directly transferred into containers, then sterilized soybean seeds were sown into pots in the greenhouse. After 94 days of growth, the plants were harvested and various parameters such as the nodular mass, number of nodules, and dry matter in the individual plant parts were determined. In addition, the relative abundances of Bradyrhizobium sp. in soil samples were identified by sequencing. No major decline in Bradyrhizobium sp. concentration could be observed due to a longer interruption of soybean cultivation. Soil properties such as pH, P, and Mg contents did not show a significant influence on the nodule mass or number, but seem to have an influence on the relative abundance of Bradyrhizobium sp. The investigations have shown that Bradyrhizobium japonicum persists in arable soils even under Central European site conditions and enters into an effective symbiosis with soybeans for up to seven years.

Long-Term Statistics of Riming in Nonconvective Clouds Derived from Ground-Based Doppler Cloud Radar Observations

AbstractRiming is an efficient process of converting liquid cloud water into ice and plays an important role in the formation of precipitation in cold clouds. Due to the rapid increase in ice particle mass, riming enhances the particle’s terminal velocity, which can be detected by ground-based vertically pointing cloud radars if the effect of vertical air motions can be sufficiently mitigated. In our study, we first revisit a previously published approach to relate the radar mean Doppler velocity (MDV) to rime mass fraction (FR) using a large ground-based in situ dataset. This relation is then applied to multiyear datasets of cloud radar observations collected at four European sites covering polluted central European, clean maritime, and Arctic climatic conditions. We find that riming occurs in 1%–8% of the nonconvective ice containing clouds with median FR between 0.5 and 0.6. Both the frequency of riming and FR reveal relatively small variations for different seasons. In contrast to previous studies, which suggested enhanced riming for clean environments, our statistics indicate the opposite; however, the differences between the locations are overall small. We find a very strong relation between the frequency of riming and temperature. While riming is rare at temperatures lower than −12°C, it strongly increases toward 0°C. Previous studies found a very similar temperature dependence for the amount and droplet size of supercooled liquid water, which might be closely connected to the riming signature found in this study. In contrast to riming frequency, we find almost no temperature dependence for FR.

Verifying the Utility of Black Locust (Robinia pseudoacacia L.) in the Reclamation of a Lignite Combustion Waste Disposal Site in Central European Conditions

N-fixing tree species, such as black locust, have achieved very promising results in the reclamation of technosols, especially those at combustion waste disposal sites, which have extremely poor nutrients and adverse physicochemical parameters. This paper presents an assessment of the survival rates, growth parameters, and quality and vitality of and nutrient supply (NPK) to black locust (Robinia pseudoacacia L.) specimens that were experimentally planted on a lignite combustion waste disposal site. The black locust seedlings were introduced directly into the combustion waste using two variants of NPK (7% N, 5.5% P2O5, and 9% K2O) fertilisation, at doses of 250 and 500 kg ha−1, and in control plots with no mineral fertilisation. No significant impacts of the applied mineral fertilisation were found on the soil properties, growth parameters, or nutrient supplies to the trees. Black locust introduced to the landfill after three years of revegetation was characterised by a very high survival rate of 95%–100%, as well as good growth parameters (height and diameter at the root collar). Nutrient supply was determined on the basis of the chemical composition of the leaves, which indicated an adequate supply of nitrogen, similar to levels found under natural conditions. In the case of K and P, the supply levels were lower than optimal when compared with data from the literature. However, at this initial stage of tree development on the combustion waste disposal site, nutrient supply is similar on all variants and is not a critical factor for successful black locust introduction. We suggest using growth parameters, survival, and vitality of trees as decisive factors for the reclamation of combustion waste landfill sites strategy. All these factors confirmed the usefulness of black locust to the reclamation of combustion waste disposal sites.

Influence of photovoltaic installation on energy performance of a nursery building in Warsaw (Central European conditions)

Nowadays, high energy efficiency and low environmental impact of buildings are required, regardless of external climate conditions. This demand is essential in the case of nursery buildings, due to strict requirements concerning indoor temperature. The following study investigates the effects of various solutions applied for energy supply to nursery buildings in reference to their energy performance indicators in the cold climate of Central Europe by analyzing various heat source and PV installation setups. A gas boiler and two heat pumps types were tested as the heat source, together with varying PV installation configurations. Nursery building computation model was diversified in terms of ventilation. Both natural ventilation and mechanical ventilation system with heat recovery were tested. A total of 24 variants were suggested and analysed by computation of monthly and annual energy demands. The study was intended to determine the importance of PV installation in nursery buildings for Central European conditions. The analysis of the results indicated that for buildings where power is mostly supplied by electricity, application of PV installations exerts most significant impact on their energy performance indicators. The contribution of clean renewable energy was greatest for the building model with cascade of air-source heat pumps and 60 kWp PV installation. Apart from no PV installation variants, the lowest impact of PV installation was observed in the naturally ventilated building model with gas condensing boiler as the heat source and with 10 kWp PV installation. The present research is applicable for designing energy supply solutions for early education buildings.

Data analysis of a monitored building using machine learning and optimization of integrated photovoltaic panel, battery and electric vehicles in a Central European climatic condition

Climate change is the biggest challenge of the present era. Buildings being one of the largest consumers of energy can help address this issue in various ways. The objective of the present study is to simulate and optimize a photovoltaic-based energy system integrated with onsite battery and electric vehicles for a demo site in Belgium in the Central European climatic conditions. The energy system of the demo site consists of photovoltaic-thermal panels, providing electricity and heat to the building, a battery as well as several long- and short-term thermal storages to reduce electricity curtailment and import. In the present study, the focus is on the optimization of the electric vehicle and battery charging and the import from the electrical network. Monitored data from the demo site is processed using a machine learning method to identify overproduction curtailment and electric vehicle charging events and to generate profiles of the photovoltaic (PV) energy production, feasible time windows and energy requirements for electric vehicle charging and building’s energy demand. These profiles and data are then used in an optimization method using linear and mixed integer programming to minimize the annual cost of the purchased electricity. Different case studies in terms of PV capacity, battery capacity and electric vehicle charging scenarios are investigated to compare against the performance of the real system. Various criteria, such as the curtailment of the PV production, imported energy cost, onsite energy fraction and matching indicators and lastly the net-zero energy balance of the building are considered to compare the results of the case studies. The study shows that machine learning can be used for the investigation of the monitored data, which can be later used for simulating and optimizing the case studies. The results shows that PV panels with 20 kWp (PV generation to demand ratio of 97%) and battery capacity of 16.1 kWh can result in annual energy cost saving of up to 807€ (31% reduction) with PV curtailment ratio of 34%, compared with the installed real demo building that has 10 kWp PV panels (PV generation to demand ratio of 49%) and battery capacity of 32.2 kWh. This would lead to an increase in the onsite-energy fraction indicator from 45% to 68%. Moreover, this combination can bring the building closer to the net-zero energy balance if the surplus electricity is exported rather than being curtailed. The optimization of the energy system in terms of equipment sizing and operation control is needed to increase the techno-economic performance of the whole system.

Population and Stand-Level Inference in Forest Inventory with Penalized Splines

AbstractPenalized splines have potential to decrease estimates of variance in forest inventories with a design-based population-level inference, and a model-based domain-level inference by decreasing the likelihood of a model misspecification. We provide examples with second-order (B2) B-splines and radial basis (RB) functions as extensions to a linear working model (WM). Bias was not prominent, yet greater with B2 and in particular with RB than with WM, and decreased with sample size. Important reductions in the variance of a population mean were achieved with both B2 and RB, but at the domain-level only with RB. The proposed regression estimator of variance generated estimates of variance being slightly smaller than the observed variance. A consistent and larger underestimation was seen with the popular difference estimator of variance.Study Implications: Forest inventories supported by light detection and range (LiDAR) data require—in the estimation phase—a model for linking LiDAR metrics to attributes of interest. Formulating a parametric model can be a challenge and unsatisfactory if the goodness of fit varies across the range of the attribute of interest. A semiparametric model provides more flexibility and lessens the chance of a model misspecification, albeit with the potential of overfitting. A penalty directed at reducing overfitting is required. A flexible semiparametric model is potentially also better suited for applications to small areas like stands than a parametric model. We demonstrate that important reductions in variance are indeed possible, but also that they depend on the form of the nonparametric part of the chosen model and the level of inference (population versus domains). With regard to practical application, reliable estimates of forest attributes at stand-level are of special interest within the scope of forest-management planning, as silvicultural treatments are always stand-oriented, at least with small-scale forestry under Central European conditions, and stand-related volume (basal area, tree density) belongs to the set of relevant parameters for management decisions regarding harvest and regeneration measures.

Long-term experience with conservation tillage practices in Austria: Impacts on soil erosion processes

In 1994 a field study started at three sites in eastern Austria to investigate the impacts of mulch till and no-till on soil erosion, surface runoff, nutrient and pesticide losses. The aim of this paper is to show long-term impacts of reduced tillage on runoff, erosion and related processes.The experiments were carried out on fields of agricultural schools in Lower Austria about 100 km north and west of Vienna. Soil textures range from silt loam to silty clay loam. Average annual rainfall at the sites ranges from 621 to 916 mm with average annual air temperatures between 9.4 and 10.4 °C. The following soil tillage treatments were investigated: (1) conventional tillage system with ploughing in fall (CT), (2) mulch tillage with cover crops during winter (MT) and (3) no-till with cover crops during winter (NT).Throughout growing season event based measurements of soil erosion, surface runoff, and nutrient and carbon losses were conducted for all sites and tillage systems. Data on losses of pesticide residues are only available for a few years. The crop rotation at the sites was mainly small grains-root crop but included also other field crops.On a long-term basis reduced tillage practices decreased surface runoff from silt loam by 25–55 % (MT) and 49–60 % (NT). For the not well drained silty clay loam soil an increase by 12–21 % was observed which is related to significantly higher soil bulk densities of MT and NT in the 0−20 cm depth. Mean long-term annual erosion rates for CT ranged between 8.6 and 33.2 t ha−1, for MT between 3.6 and 5.3 t ha−1and for NT between 1.9 and 3.0 t ha−1. Compared to conventional tillage MT and NT reduced soil loss from a silty clay loam by 38 and 65 %, and from silt loam by 70–88 % and 84–93 %, respectively. 10−30% fewer erosion events occurred from MT plots and about 20 % fewer events from NT plots. Higher aggregate stabilities of MT and NT due to higher soil organic carbon contents in the 0−10 cm soil depth, higher soil cover as well as lower flow velocities are responsible for this reduction in soil loss from reduced tillage treatments.Low erosion rates from the reduced tilled plots correlated with low runoff losses of nitrogen and phosphorus. Total nitrogen losses ranged from 13.3–48.1 kg ha−1 for CT, from 4.5–18.7 kg ha−1 for MT and from 1.6–9.4 for NT. Total nitrogen losses ranged from 13.3–48.1 kg ha−1 for CT, from 4.5–18.7 kg ha−1 for MT and from 1.6–9.4 for NT. Corresponding total P losses ranged from 6.7–29.4 kg ha−1 for CT, 2.1 to 3.7 kg ha−1 for MT and from 0.7 to 2.4 kg ha−1 for NT. Low erosion rates from the reduced tilled plots correlated with low runoff losses of nitrogen and phosphorus even though N and P concentrations in runoff were greater than from CT and sediments were enriched severalfold in N and P. Conservation tillage methods reduced the SOC losses by 34–86 % for MT and by 58–89 % for NT. Other studies show that these results are not only obtained in central Europe but also in other regions worldwide.The long-term results of this study show that the use of mulch and no tillage in well-drained soils is beneficial for the farmers under central European conditions by improving soil´s aggregate stability and soil water contents and for the environment by reducing soil and nutrient losses.

Special issue in honour of Prof. Reto J. Strasser - Seasonal monitoring of PSII functionality and relative chlorophyll content on a field site in two consecutive years: A case study of different oak species

In search for practical silvicultural management tools to identify alternative tree species for predicted Central European climate conditions, a cross-species survey with five evergreen, semi-evergreen, and deciduous Quercus taxa with contrasting morphological leaf traits was performed. Fast chlorophyll fluorescence induction of PSII and relative leaf chlorophyll contents were performed to assess the overall plant vitality at any point in time during two complete vegetation periods in consecutive years (2012 and 2013). Maximum photochemical efficiency of PSII and the performance index on absorption base showed a very conservative relationship to each other and a similar intra-annual progress in all deciduous species, but with a different speed of increase and decrease during leaf development and senescence and thus a different length of vegetation period. The intra-annual variability of OJIP and chlorophyll content parameters is considered with respect to the practicability of measurements in the field for management purposes.

Analysis of freezable water content by DSC for apple dormant bud cryopreservation

Dormant bud cryopreservation is a valuable tool for the germplasm of temperate trees preservation. Freezable water content, as an important cryopreservation characteristic, was analysed by DSC. Scions of modern apple tree varieties (Malus domestica) were collected during the winter season from orchards, freeze-dehydrated to 26–32% of water content at –5°C and cryopreserved by the two-step procedure. Samples were rehydrated in moist peat after 4 months of cryopreservation and grafted on rootstocks in a field. Regeneration by sprouting buds on rootstocks was evaluated. The varieties were divided into three groups according to their water content and percentage of crystallized water. The regeneration in the three groups decreased with decreasing bud water content. Regeneration was higher than 80% in most of the varieties and reached 100% in almost 1/3 of the tested varieties. In only one variety, was regeneration lower than 40%, which is still a high regeneration rate for considering apple genotypes as successfully cryopreserved. According to this study, the two-step cryoprotocol was successfully optimized for Central European conditions.

Impact of the spacing between tree crowns on the mitigation of daytime heat stress for pedestrians inside E-W urban street canyons under Central European conditions

Concerning Central European conditions the mitigation of daytime heat stress for pedestrians by evenly positioned plane trees on both sidewalks of a shallow and a deep E-W street canyon is quantified by scenario simulations. Using the ENVI-met model v4.0 BETA, they were performed for a previous heat wave day in Freiburg (Southwest Germany). Related to both sidewalks, the simulations are focused on the impact of the spacing between two adjacent tree crowns, which in turn depends on the size and number of trees. It determines the coverage of both sidewalks by tree crowns. The simulation results each averaged over 10–16 CET also refer to (i) the aspect ratios (H/W) of both street canyons and (ii) two values of the inflow speed (v) into the simulation domain. Human thermal comfort is determined by the mean radiant temperature (Tmrt) and physiologically equivalent temperature (PET). Due to the maximum solar elevation (59.3°) on the simulation day, spatially high-resolution PET results as well as spatiotemporal averaged Tmrt and PET results clearly show the dominant shading effect of the S-bordering building for pedestrians on the N-facing sidewalk. It masks the mitigation of their daytime heat stress only due to the trees. On the S-facing sidewalk, however, the spatiotemporal averaged Tmrt and PET results are distinctly lowered by the tree shading as compared to tree-free conditions. The reduction of the Tmrt and PET values increases as the spacing between their crowns decreases, i.e. the crown coverage gets larger. This human-biometeorological heat stress mitigation is more pronounced inside the shallow street canyon (H/W = 0.5) than inside the deep one (H/W = 2.0). Regardless of crown coverage, orientation of the sidewalks, H/W ratio and v, the reduction of the spatiotemporal averaged air temperature due to tree shading is almost marginal.

In-stand debarking with the use of modified harvesting heads: a potential solution for key challenges in European forestry

Modern forestry is increasingly confronted with challenges that appear with intensive forest management and the progression of the effects of climate change. The forestry sector is able to react to the changing conditions by adapting management plans, forest structure or planting tree species with a higher stress resistance. However, during stand management activities, silvicultural treatments and harvesting operations can have an impact on the further development of the remaining forest ecosystem. In Germany, the most widely used harvesting system for thinning operations is a single-grip harvester used for felling and processing trees followed by a forwarder for timber extraction from the machine operating trails to roadside. In this research project, debarking rollers and other modifications designed for Eucalyptus harvesting heads were tested on conventional harvesting heads for the first time to assess the possibility of adding debarking to mechanized forest operations under Central European conditions. Seven field tests with varying tree species, diameters and age classes, were established within German state forests in Lower Saxony and in Bavaria. These tests were repeated in both summer and winter seasons to evaluate the influence of associated tree sap flows on debarking quality. Three different harvesting heads were modified to assess the altered mechanical characteristics and setups. To assess debarking ability originating from head modifications, a photo-optical measurement system developed within the scope of the project was used. The results demonstrate that especially for summertime operations, simple modifications to currently used harvesting heads are able to provide an average debarking efficiency up to 90% depending on the modifications. Another key finding is that a negatively affected sap flow, experienced during wintertime operations, resulted in 46% lower debarking efficiency, while spruce bark beetle infestations only resulted in a wider spread of the variation. Additionally, the vertical position of the log within the tree proved to have an influence on debarking efficiency, resulting in 15% lower average debarking for butt logs and 9% for top logs as compared to middle logs. Since a debarking process requires the stem to be fed through the harvesting head on multiple occasions to remove bark, average harvesting productivity might be reduced by approx. 10% compared to productivity measured with conventional harvesting heads. Considering the results and the extent of the modifications, the system proved to be a potential addition to existing harvesting methods facing changing challenges in future forestry.

Uncertainty of Carbon Economy Using the Faustmann Model

Forest growth predictions are used to build expectations about the future economic performance of management decisions. Faustmann land expectation value (LEV) is a widely used criterion in forestry to evaluate a diversity of decision parameters, such as rotation age and thinning regimes. Most of the predictions and, consequently, expectations are based on emperical knowledge, assuming a steady state in climate and a deterministic forest growth approach. However, the climate may change to potentially different degrees in the coming decades, causing a dynamic and uncertain forest growth and carbon budget. Moreover, carbon economy in forestry, defined as opportunity cost of in situ carbon sequestration, can hardly be analysed using empirical models and calls for process-based forest biomass production models. Process-based models include numerous parameters and processes that embody some degree of uncertainty. The uncertainty of these parameters and climate state propagates over time to the final decision about carbon economy and optimal management solutions. Here we quantify this uncertainty using Bayesian inference and apply twelve different climate change scenarios to evaluate the forecasts of the process-based forest model 3-PG, to predict the growth of European beech (Fagus Sylvatica) in central european conditions as an example. The results show a strong influence of the model’s parameters uncertainty on the final decisions about timber based and carbon economy. The uncertainty triples if different climate change scenarios are applied as a source of deep uncertainty where no probability can be assigned to any scenario. To deal with deep uncertainty, a robust decision-making approach has been applied to find solutions with minimum regret or maximum value at risk regarding all scenarios. We conclude that communicating uncertainty is a fundamental issue for forestry economics under changing climate conditions, especially if carbon sequestration is an asset. The key message for designing global forest governance policy in the uncertain times of climate change will be the necessity to take into account both the uncertainty on the demand side, that is, socio-economic developments and regional population needs for forest ecosystem services such as wood, but also the uncertainty of the supply side and the inherent ecological uncertainties in predicting the forests’ growth, resources, and climatic conditions.