Favourable Site Conditions Research Articles

Farmers' preferences for the design of a slurry hosing support scheme to combat soil compaction: Insights from a discrete choice experiment in Germany

CONTEXTFollowing that 60% of the EU's soils are in unhealthy condition, the German government has identified soil protection as a key area of action within the framework of the Agricultural Strategy 2035 as a part of the development of a sustainable agricultural and food system. In particular, harmful compaction of topsoil and subsoil has a negative impact on yield, nitrogen efficiency and greenhouse gas emissions. Slurry hosing is an effective technique to reduce the risk of soil compaction by simultaneously minimising both the number of field passes and the weight of the machinery during slurry spreading. OBJECTIVEThis article assesses farmers' preferences for a stylised slurry hosing support scheme and ascertains the personal and farm characteristics that are likely to affect scheme uptake. METHODSIn a discrete choice survey of 100 German farmers, the respondents were asked to choose among different support schemes and the status quo. The support schemes on offer varied the subsidy rate, the spatial coverage of the scheme, the minimum proportion of a farm's manure to be applied via slurry hosing, the time window for slurry spreading, the commitment period, and the type of compliance monitoring. Since the participants' decision for or against participation in the support programme is binomial, the survey data was analysed by logistic regression in the form of a mixed logit model and a latent-class model. CONCLUSIONA mixed logit results suggest that the majority of respondents valued an extension of the time window for slurry spreading, whereas tighter programme requirements were mostly rejected. The latent-class model revealed three preference classes with different perceptions of the scheme's attributes. Younger farmers with larger farms and suitable site conditions for the hosing technique were identified as a potential target group for the scheme. SIGNIFICANCEOverall uptake rates are likely to remain low should such a scheme be launched. Furthermore, the recommendations for scheme design are not universal. They rather apply only to the group of farmers surveyed, i.e. larger farms with largely favourable site conditions. Since smaller farms may have self-selected themselves out of the survey, it is not permissible to tailor the programme to these very farms on the basis of the results.

Exploring the influence of tree species richness on vertical structure variability in young plantations using terrestrial laser scanning

Forest structure spatially varies at the landscape-scale (between-plot) but also local-scale (within-plot). Both scales of structural variability have significant impacts on forest ecosystem functioning and stability. However, we still have a limited understanding of how tree species richness affects the spatial structural variability. In this study, we disentangled within- and between-plot variability in stand structural variables depending on tree species richness level. Terrestrial laser scanning (TLS) technology, capable of developing forest vertical structure in 3D detail, was applied in the FORBIO tree diversity experiment at three sites in Belgium. One site was 9-year old (Hechtel-Eksel) and other two sites were 11-year old (Zedelgem and Gedinne). Each site included five different sets of one, two, three, and four tree species mixtures with one replica. At each plot, four single scan locations were used. Six stand structural variables were quantified based on TLS vertical plant profiles. We hypothesized that within-plot structural variability would increase with species richness, but that the between-plot structural variability would decrease with species richness. Our study revealed notable differences in structural variability between monocultures and mixtures across all sites examined. However, the relationship between tree species richness and structural variability patterns is site-dependent. Specifically, at the Zedelgem site, we observed increased within-plot variability and decreased between-plot variability with species richness, supporting the hypothesis that species richness drives stand structural variability. However, the hypothesized pattern was not as strong at the Hechtel-Eksel and Gedinne sites. Moreover, the various structural variables displayed contrasting responses to changes in species richness. These findings indicated the potential influence of tree species richness on within- and between-plot structural variability in young plantations, particularly in favorable site conditions with well-adapted species pools. Hence, afforestation measures would benefit from planting multiple tree species to initiate structurally complex stands by considering species richness level.

Direct Seeding for Conifer Regeneration in the Pacific Northwest: A Past, Present, and Future of Operational Practices

Abstract United States Pacific Northwest (PNW) forests are important ecological, cultural, and recreational landscapes. Direct seeding to aid forest regeneration in the PNW region was developed to reduce reforestation costs and timelines. These practices were largely discontinued in the 1970s due to poor establishment resulting from issues of seed predation, a lack of targeting favorable site conditions, seed distribution issues, and improvements to nursery seedling production. A recent renewed interest in direct seeding research has resulted from the growing geographic extent of postdisturbance areas requiring reforestation. This interest is also supported by the increasing recognition of the logistical impossibility of satisfying reforestation demand via planted seedlings. This historical review highlights the timeline of direct seeding research and practice in the PNW. It describes the main obstacles to its widespread use and opportunities for improvement. These opportunities include upscaling seed collection efforts, increasing distribution precision of seeding methods, upgrading seed quality evaluations, and mitigating seed predation and desiccation. Study Implications: The availability of seedlings is increasingly limited due to the rising demand for reforestation as a result of more frequent and severe wildfires. Further research into direct seeding as an artificial regeneration strategy for trees is necessary to operationally increase reforestation abilities and thus supplement natural regeneration and seedling planting. This study summarizes findings from prior direct seeding studies in the Pacific Northwest region and identifies (1) improving seed collection efforts, (2) refining seed quality assessments, (3) standardizing seed dispersal methods, and (4) improving seedling establishment by targeting favorable site conditions and predation mitigation as key future research priorities.

Disentangling interspecific and intraspecific variability in height–diameter allometry of dominant tree species in the Rocky Mountains across broad spatial scales

Abstract Height–diameter (H-D) allometric relationships provide us with insights into tree growth strategies and resource utilization. Yet, we have a poor understanding about the underlying drivers that limit or alter tree H-D allometries at large scales. Based on 569 502 pairs of height versus diameter from 53 808 plots of 20 species in the Rocky Mountains, USA, we used a mixed-effects approach to model the variability in H-D allometry across species (interspecific variation) and within-species (intraspecific variation) along gradients of site condition, climate, and competition. The allometric theories derived from physics or biological laws provide a fundamental framework for tree growth and performance, but our findings also show that physiological and environmental factors further shape the interspecific and intraspecific patterns in tree allometry with the intraspecific variation being smaller than the interspecific variation along all the gradients we considered. In general, trees growing in favorable site conditions and highly competitive environments tend to comparatively invest more in height growth, while trees may preferentially invest in diameter growth when constrained by water stress or other unfavorable climatic condition. Trees will choose the most appropriate growth strategies with corresponding allometric patterns to adapt to environmental changes. Our study is expected to provide applied value for estimating biomass and carbon stocks at broad environmental scales.

Site properties, species identity, and species mixture affect fine root production, mortality, and turnover rate in pure and mixed forests of European Beech, Norway spruce, and Douglas-fir

It is already well known that the effects of tree diversity on aboveground wood productivity depend on tree species identity and site conditions and thus can vary among different tree mixtures and forest sites. The effects of species diversity, specifically on belowground productivity and dynamics, have rarely been studied, so potential interactions with species identity and/or site conditions are largely unknown.Sequential soil coring was applied in mature pure and mixed stands of European beech, Norway spruce, and Douglas-fir in two regions of northern Germany to investigate the potential site, species, and mixing effects on fine root productivity, mortality, and turnover rates. In these ecologically and economically important species mixtures, a strong effect of site conditions on all fine root variables was found. In particular, more fine root growth was observed at the less favorable site conditions than at the more favorable ones. Species identity and interaction between site conditions and species identity were additional explanatory factors, whereat beech showed the strongest effect by site conditions. No overyielding was observed when fine root productivity was plotted against area potentially available (APA), nor were mortality or turnover. However, at specific soil depths, a mixing effect, caused mainly by beech, was observed for all variables and for both species mixtures.This study suggests that site conditions and species identity rather than species mixture are essential in explaining fine root dynamics and that increasing tree species diversity may not guarantee higher belowground productivity. However, in the face of climate change and the demand for wood as a natural and renewable resource, an admixture of Douglas-fir to pure European beech stands seems to be a reasonable alternative to an admixture of spruce, a species that is already seriously suffering by drought and bark beetle attacks.

Plant species diversity and composition in limestone forests of the Vietnamese Cat Ba National Park

Plant species diversity and composition play crucial roles in many ecosystem services and are largely influenced by environmental conditions, as well as natural and/or anthropogenic disturbances. However, our knowledge of the drivers of plant species diversity and composition in the limestone forests of Vietnam, a hotspot of biodiversity, is limited. To fill this knowledge gap, we surveyed plant species in the Cat Ba National Park (CBNP), located on a limestone archipelago. We hypothesised that: (1) topography, accessibility and spatial isolation drive the diversity and composition of plant communities in the CBNP and that (2) isolated areas contribute to high floristic regional diversity by supporting unique species assemblages. We expected high tree species diversity within the tropical limestone forests of the CBNP, but also that: (3) the abundance of non-tree species negatively affects tree regeneration diversity and abundance. Data were obtained from 90 random sample plots (500 m2) and 450 sub-sample plots (25 m2) in three areas of the CBNP. We differentiated four different plant species communities and found a total of 302 species belonging to 112 families. Tree species contributed 50% to total species richness. The distribution of different plant communities in the CBNP was driven mainly by topography; that is, the percentage of rock surface and slope and concomitant differences in soil depth. Contrary to our expectations, isolated areas did not contribute greatly to the CBNP’s plant species diversity. It seems that isolated areas and, as in our case, rough topography, may act as natural barriers to seed dispersal, creating an environmental filter for tree species. Across the CBNP, there was no effect of non-tree species on tree species regeneration, but regeneration patterns differed between communities. In species-rich communities growing under favourable site conditions (e.g. low rock surface and slope), greater coverage by non-tree species had an increasingly negative effect on tree species richness and abundance in the regeneration layer. The opposite was observed in communities growing under harsh site conditions. We conclude that plant species diversity in the CBNP is high, particularly in easily accessible lowland areas where tree species contribute greatly to biodiversity. However, here, non-tree species can even restrict tree regeneration.

Annual and spatial variabilities in the acorn production of Quercus mongolica

BackgroundGenus Quercus is a successful group that has occupied the largest area of forest around the world including South Korea. The acorns are an important food source for both wild animals and humans. Although the reproductive characteristics of this genus are highly variable, it had been rarely studied in South Korea. Therefore, in Seoraksan and Odaesan National Parks (i) we measured the acorn production of Quercus mongolica, an overwhelmingly dominant species in South Korea, for 3 years (2017–2019), (ii) evaluated the spatial-temporal variation of acorn production, and (iii) analyzed the effects of oak- and site-related variables on the acorn production.ResultsThe annual acorn production of Q. mongolica increased 36 times from 1.2 g m−2 in 2017 to 43.2 g m−2 in 2018, and decreased to 16.7 g m−2 in 2019, resulting in an annual coefficient of variation of 104%. The coefficient of spatial variation was high and reached a maximum of 142%, and the tree size was the greatest influencing factor. That is, with an increase in tree size, acorn production increased significantly (2018 F = 16.3, p < 0.001; 2019 F = 8.2, p < 0.01). Elevation and slope also significantly affected the production in 2019. However, since elevation and tree size showed a positive correlation (r = 0.517, p < 0.001), the increase in acorn production with increasing elevation was possibly due to the effect of tree size. The acorn production of Odaesan for 3 years was 2.2 times greater than that of Seoraksan. This was presumed that there are more distribution of thick oak trees and more favorable site conditions such as deep soil A-layer depth, high organic matter, and slower slopes.ConclusionAs reported for other species of the genus Quercus, the acorn production of Q. mongolica showed large spatial and annual variations. The temporal variability was presumed to be a weather-influenced masting, while the spatial variability was mainly caused by oak tree size.

Using Machine Learning to Assess Site Suitability for Afforestation with Particular Species

Judging and predicting tree suitability is of great significance in the cultivation and management of forests. Background and Objectives: Due to the diversity of tree species for afforestation in China and the lack of experts or the limitations of expert knowledge, the site rules of tree species in some regions are lacking or incomplete, so that a small number of tree suitability empirical site rules are difficult to adapt to the afforestation expert system’s diverse needs. Research Highlights: This paper explores an intelligent method to automatically extract rules for selecting favorable site conditions (tree suitability site rules) from a large amount of data to solve the problem of knowledge acquisition, updating and maintenance of suitable forest site rules in the expert system. Materials and Methods: Based on the method of site quality evaluation and the theory of the decision tree in knowledge discovery and machine learning, the dominant species of Chinese fir and Masson pine in the forest resources subcompartment data (FRSD) of Jinping County, Guizhou Province were taken as examples to select the important site factors affecting the forest quality and based on the site quality of potential productivity. Assessment methodology was proposed to determine the afforestation of a stand site by nonlinear quantile regression, the decision tree was constructed from the ID3, C5.0 and CART algorithms. Results: Finally, the best-performing CART algorithm was selected to construct the model, and the extractor of the afforestation rules was constructed. After validating the rules for selecting favorable site conditions of Chinese fir and Masson pine, the production representation method was used to construct the relationship model of the knowledge base. Conclusions: Intelligent extraction of suitable tree rules for afforestation design in an expert system was realized, which provided the theoretical basis and technical support for afforestation land planning and design.

Understorey phylogenetic diversity in thermophilous deciduous forests: overstorey species identity can matter more than species richness

BackgroundUnderstorey vegetation is a key biodiversity component of forest ecosystems. Previous studies examined its relations with the overstorey mainly in terms of taxonomic diversity, composition or productivity. So far, none focused on the phylogenetic aspect, which represents the deepest component of diversity in a community. Here, we explored the relations between overstorey species richness and identity and the phylogenetic structure of the understorey vegetation. As a model system we used a network of 36 plots in thermophilous deciduous forests of central Italy that are part of a European project on forest biodiversity and functions. The plots, characterized by similar site conditions, represent a gradient of overstorey richness from 1 to 4-species mixtures, with variable composition. After surveying the understorey in each plot, measures of phylogenetic diversity and structure (Phylogenetic Diversity, PD; Net Relatedness Index, NRI; and Nearest Taxon Index, NTI) were calculated from a fully resolved seed-plant phylogeny obtained from a ITS-5.8S nrDNA dataset including original sequences from local plant material.ResultsThe resulting understorey phylogenetic tree allowed reliable estimation of PD, NRTI and NTI. Phylogenetic diversity was dependent on species richness and the strength of this relationship did not change along the gradient of overstorey tree species richness. Net Relatedness and Nearest Taxon indices were both mostly positive but non-significant, indicating random phylogenetic structure of the understorey. The presence of Quercus petraea, usually found in more favorable site conditions, was associated with a significant phylogenetic clustering at the species level.ConclusionsOverstorey species richness was not related to understorey phylogenetic structure, while species identity (Q. petraea) was associated with an increase in evolutionary relatedness in this forest layer, possibly due to competitive exclusion in favorable site conditions. Further studies should examine whether and how understory phylogenetic structure is affected by variables such as small scale variations in site conditions and presence of a shrub layer, both present but not accounted for in our model system. A better understanding of the role of these variables and their interaction may contribute to fill the current gap between the theoretical field of phylogenetic ecology and forest management.

STRUKTUR TEGAKANTANAMAN MERANTI TEMBAGA (Shorea leprosula MIQ.) DI HUTAN PENELITIAN HAURBENTES, JASINGA

Natural regeneration of Dipterocarpaceae depends on the availability of the mother trees, flowering cycle, and favorable site conditions. Potential seed of Shorea leprosula in Haurbentes Forest Research, Jasinga District, Bogor, should be supported with sufficient regeneration ability. This research aims to identify the condition of regeneration of Shorea leprosula, environmental conditions and soil conditions that support for the sustainability of the S. leprosula regeneration in Haurbentes Forest Research, Jasinga, Bogor district. The results of the vegetation analysis showed that condition of the forest regeneration S. leprosula in KHDTK Haurbentes quite sufficient for seedling which are found quite a lot and dominating on every block of observations. However, seedlings are experiencing obstacles in resuming its growth to the level of sapling and poles. This can be seen by the existence of another species that dominates at the level of the sapling and the least amount of poles found. The existence of competition with other species and lack of space grows to regeneration due to the dominance of mature trees suspected that caused the regeneration S. leprosula on blocks of thisplant disturbed. Environmental conditions and soil conditions sufficiently support growth of S. leprosula. However, the lack of light intensity that goes into the stands is suspected to be one of the barriers to regeneration of S. leprosula .

Species indicators for naturally-regenerating and old calcareous grassland in southern England

Habitat restoration requires realistic goals. To naturally regenerate European lowland calcareous grassland, whose extent has severely declined, over a century may be required for vegetation to become indistinguishable from that of old calcareous grassland. Progress of natural regeneration can be characterized using member species of the reference vegetation as indicators of favourable site condition. Chronosequence studies have suggested that calcareous-grassland species differ predictably in their ability to colonize ex-arable land, with some usually colonizing early on, and others in later stages. If such patterns are affected by gradually-attenuating establishment limitation, this would have important implications for restoration practice and indication of progress. Particularly, late-colonizing species might be better indicators of favourable site conditions than early colonizers.To explore these aspects, we have reanalysed chronosequence data previously used to investigate causal mechanisms affecting calcareous-grassland restoration progress. We carried out an indicator species analysis to determine which species are indicative of particular stages of natural regeneration. Using correlation analyses, we tested whether species colonization patterns matched those found by previous chronosequence studies that were geographically more limited or relied on more informal approaches to determine species order of colonization. Correlation analyses were also used to test whether order of colonization could be explained by establishment limitation or by dispersal limitation, or by established plant strategies that underlie such limitations.We identified 30 species as indicative of particular stages of natural regeneration, including nine that specifically indicate old calcareous grassland. Correlation results confirmed high congruence with species order of colonization in previous chronosequence studies, and indicated that establishment limitation plays a role in shaping species order of colonization, potentially mediated through differential stress tolerance. We failed to demonstrate a role of dispersal limitation in shaping order of colonization. Based on our results, we derived three categories of indicator species for passively-restored calcareous grassland, mirroring the regeneration stage during which these species usually colonize. This includes a category labelled by us as ‘old-grassland indicators’ that achieve notable abundance only in old grassland. We conclude by discussing how such a categorization can benefit the measurement of restoration progress, the tentative identification of old grassland and its conservation, e.g. through linking agri-environment payments to the occurrence of old-grassland indicators, thus fostering positive change in farmer attitudes towards old grassland.

Very large trees in a lowland old-growth beech (Fagus sylvatica L.) forest: Density, size, growth and spatial patterns in comparison to reference sites in Europe

Abstract The frequent occurrence of very large trees (diameter at breast height DBH ≥ 80 cm) is a typical element of both primary and secondary old-growth forests. We analyzed the characteristics of very large trees in one of the few stands of lowland old-growth beech forest in Northwestern Europe, regenerated around 1775 and left unmanaged since 1986. We examined their density, diameter range, increment, mortality rate and spatial distribution, based on repeated full dendrometric surveys. In order to evaluate the results, we compared them to original datasets from primary and secondary old-growth beech forests in Europe, and an extensive reference table, compiled from inventories and literature. In our study site, the density of very large trees increased from 31.5 to 34.3 trees ha−1 over the last 25 years, reaching a median DBH of 97 cm (mean 98.9), with the largest tree attaining a DBH of 159 cm. Although the trees were over 240 years old, they still showed an average DBH increment of 4.75 mm year−1 and a low mortality rate (0.89% year−1), indicating that they were still vital. These figures are remarkably high compared to other old-growth beech forest reference sites, where the density of very large trees generally varies between 5 and 20 trees ha−1 (median value 13.1), with a median diameter of 85–90 cm and maximum DBH for beech trees rarely exceeding 100–130 cm. The regular spatial distribution pattern of the very large trees in the studied stand clearly differed from a typical old-growth stand, in which very large trees are randomly distributed. Over the last 25 years though, because of random mortality and ingrowth, the spatial distribution gradually became more random. The extraordinary densities and sizes of the very large trees in our study site can be explained by the favorable climate and site conditions that promote high increments, in combination with the former management interventions of tending and thinning that resulted in continuous non-suppressed growth. Although derived from a very specific case with particular conditions, our observations may be relevant to other beech forests, as they tend to reset certain baseline assumptions for tree size and longevity potential of beech in Northwestern Europe.

PRODUCTIVITY OF EUROPEAN BEECH COPPICE STANDS IN THE FOREST MANAGEMENT AREA “DONJEVRBASKO”, BOSNIAHERZEGOVINA

The object of this study were three coppice beech stands located in the forest management area“Donjevrbasko” close to Banja Luka in the Republic of Srpska, north-western part of Bosnia andHerzegovina. These coppice stands grow in different conditions. According to available eco-vegetationmaps, first beech coppice stand develops in favorable site conditions with high wood productionpotential for beech. Thereby, we chose such stand which on the first look had fairly goodquality of stools. The second coppice stand also grows in good site conditions where high productionpotential can be expected for beech, but in this case we selected for measurement such standwhich has poor technical quality of trees and poor health state. On the contrary, the third coppicestand grows in very poor site conditions where low production potential can be expected forbeech. The major goal of the study was to examine the effects of lengthening the rotation periodson wood production, quality and health status of trees in studied coppices.

Africa\u2019s highest mountain harbours Africa\u2019s tallest trees

While world records of tree heights were set by American, Australian and Asian tree species, Africa seemed to play no role here. In our study we show that Entandrophragma excelsum (Meliaceae) found in a remote valley at Kilimanjaro has to be included in the list of the world’s superlative trees. Estimating tree age from growth rates monitored by high resolution dendrometry indicates that tall individuals may reach more than 470 years of age. A unique combination of anatomical peculiarities and favorable site conditions might explain their enormous size. The late date of this discovery of Africa’s tallest trees may be due to the comparably low study efforts at Kilimanjaro compared with other biodiversity hotspots. Since only a few square kilometers of this habitat of Entandrophragma are left, Kilimanjaro (and Africa) is about to lose not only a unique biogeographical archive with highly diverse vegetation, but also its tallest trees. The inclusion of these valleys into the immediately neighboring Kilimanjaro National Park would be an excellent and urgent possibility of protection.

Effects of black locust and black pine on extremely degraded sites 60 years after afforestation - a case study of the Grdelica Gorge (southeastern Serbia)

Abstract: The selection of tree species can affect the success of afforestation in the rehabilitation of degraded forest sites and forest restoration. In general, black locust (Robinia pseudoacacia L.) and black pine (Pinus nigra Arnold.) represent the most commonly used species in the afforestation of soils that have been degraded by erosion. As far as the extent of the ameliorative effects of black locust and black pine are concerned, it was found that they may play an important role in the selection of species for the afforestation of extremely degraded sites. This study is aimed at determining the potential of black locust and black pine to affect several soil properties, erosion control and C stock, thus creating favourable site conditions for the restoration of previous forest vegetation. This research was conducted in the Grdelica Gorge in south east Serbia, where eight sample plots with an average size of 0.47 ha were established 60 years ago on terrain afforested with black locust and black pine. In each sample plot, we measured the diameter at breast height of all black locust and black pine trees, and the height of 10 black locust and 10 black pine trees in each diameter class. In addition, samples of mineral soil (from depths of 0-5, 5-10 and 10-20 cm) were taken at 4 randomly selected soil profiles in each sample plot, and 8 samples of litter (30 × 30 cm) were also collected. Additionally, laboratory analyses of the physical and chemical properties of the soil and litter were performed in 2 replicates. The obtained results showed that: (1) at the 0-5 cm depth, there was no statistically significant difference in the reaction of the soil solution, although a significant difference in the reaction of the soil solution between the soils under the two species was observed at soil depths greater than 5 cm; (2) there was a significantly higher N content under black locust in the 0-5 cm soil layer; (3) the reduction of soil loss under black locust is statistically significant in all observation periods; (4) black pine is more efficient in C storage. Our results demonstrate that black locust has the potential to improve soil properties and reduce soil loss caused by erosion, while its favourable impact does not decrease over time, making it more suitable for afforestation on degraded land in the examined area.

Effect of soil scarification on natural regeneration of mature scots pine (Pinus sylvestris) stands in Greece

&lt;div&gt; &lt;p&gt;The natural regeneration of Scots pine stands at the Sarakatsana location in the Pieria Mountains improved considerably after the removal of the dense ground vegetation followed mechanical soil scarification. The experimental design consisted of replications on scarified and non-scarified soil. The results four years after the experiment was set up showed that regeneration reached 59 seedlings m-2 in scarified and 7 seedlings m-2 in non-scarified soil. Soil scarification seems to have had a positive effect on the emergence and survival of naturally regenerated Scots pine. The negligible number of dead seedlings in the first two measurements could be due to the favourable site and/or good climatic conditions. Although the mother stand appears to be in a critical condition due to age and increased necrosis as a result of fungal attacks, there is still considerable potential for regeneration in terms of fructification and seed production. The study findings indicate that there can be new growth of Scots pine forest with the shelterwood method of natural regeneration in combination with soil scarification.&lt;/p&gt; &lt;/div&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Nutrient limitation and site-related growth potential of Norway spruce (Picea abies [L.] Karst) in the Bavarian Alps

The hypothesis that soil chemistry is a main constraint for the vigour of Norway spruce trees on calcareous soils is scrutinised based on data from 60 existing and new intensive study sites in the Bavarian Alps, where comprehensive information on soils, climate, foliar nutrient concentration, ground vegetation, and tree growth is available. We characterised ecological gradients of the response variables site index (SI), foliar nutrient level and needle weight by constrained ordination, identified nutrient limitations based on regression trees and modelled SI based on vegetation-based mean Ellenberg indicator values. Our study confirms the assumption that soil development and concurrent acidification are key determinants for the vitality and growth of spruce in the Bavarian Alps, which surpass the importance of climate on nutrition and growth. Pools and availability of P and N are limiting nutrition and growth of spruce in this region. We hypothesize that N-limitation persists despite considerable deposition inputs because N tends to be locked up in organic horizons with low biological activity. K and trace elements, especially Fe, can also be deficient in some cases but do not appear as major limiting factors. High foliar Mn concentrations are a reliable indicator of mature soils and favourable site conditions in the Bavarian Alps, but Mn itself is usually not limiting. P must be regarded as the most critical macronutrient in the Bavarian Alps, particularly in the face of biomass harvesting. Consequently, at sites with shallow soils forest, management should focus on sustaining or restoring humus stocks. SI of spruce can be predicted from composition of ground vegetation and Ellenberg indicator values with remarkable precision (R 2 = 0.75).

Wirtschaftlichkeit von kleinen Windenergieanlagen

Small wind turbines can contribute to the supply of electricity from renewable resources. They have attracted great interest, especially in the agricultural sector. On the one hand, the target can be an economical one: producing an as large as possible share of the electricity consumed on the farm and thus becoming more independent of electricity price developments. On the other hand, such a move offers a contribution to climate protection. Following a short overview on site selection, electricity yields and the legal framework this article discusses the profitability of small wind turbines taking into account various exemplary site conditions. It becomes clear that small wind turbines may be profitable through their production of electricity that otherwise would have to be purchased. Preconditions for this are favourable site conditions and a strong temporal correlation of electricity production and consumption.

Performance Assessment of On-Grade Horizontal Directional Drilling

Although horizontal directional drilling (HDD) has been widely accepted and used for installing gas lines, waterlines, and telecommunication cables, its applications to gravity-flow sewer lines have been limited. One primary reason is the difficulty with maintaining critical grades essential for gravity-flow sewer systems when using the conventional HDD tracking methods. Recently, advancements made in tracking systems, electronics, and operational techniques have made this HDD technology a technically feasible and an economically attractive method for installing on-grade underground pipes in many situations. This paper presents a newly developed HDD technology in terms of its technical capabilities and economic feasibilities compared with the traditional open-cut method on the basis of two real-scale case studies. Installation errors are quantitatively analyzed and discussed, and a general set of boundary site conditions for the application of this new technology is also discussed. The detailed analysis of the two case studies demonstrates that the on-grade HDD method could be a very attractive alternative construction method for gravity-flow sewer pipelines when some favorable site conditions are available.

Geomorphic Controls of Spatial Pattern and Process at Alpine Treeline*

This study examines the role of surface geomorphic features in tree establishment at the alpine treeline in Glacier National Park, Montana, through the presentation of a multiscale, conceptual model of biogeomorphic relationships at alpine treeline. Empirical observations gathered through a multiscale field methodology over three summers serve as a base for the model. The model highlights the importance of surface geomorphic features, specifically boulders and terrace risers, in creating favorable local site conditions, largely by protecting seedlings from wind. The sheltering effect of surface features enables initial seedling establishment, and in some cases survival, above current treeline locations, thereby initiating a positive feedback effect that encourages subsequent tree establishment. Geomorphic features are therefore important in linking scales of pattern and process at the alpine treeline ecotone.