Reinhard F. Hüttl

European forest ecosystems : building the future on the legacy of the past

Abstract The viability of the many civilisations of Europe has depended, to a very large extent, on an adequate supply of wood. In the Ancient World, this supply was secured through the exploitation of forest reserves, the conquest of new territories and, when these opportunities no longer presented themselves, through the conservation of diminishing resources. Ultimately, civilisations collapsed because of the shortage of wood. Although some silvicultural techniques were known in the pre-Christian era, the scientific management of forests was not widely practised until the late 18th century. It is argued that the controlled exploitation of ‘nature’, on sustained yield principles, only became possible when men came to view the forest, not as a nuisance, an Arcadia or a pagan horror, but as a centre of wood production, a biological factory. The emergence of scientific forestry, however, did not put an end to the exploitation of forest resources. Unregulated felling and traditional practices such as litter raking exerted an insidious, negative influence on the fertility of the soil. The impact of human exploitation has often been underestimated by scientists, in recent decades, in particular, in the context of forest decline. While sustainable management, seen as sustained yield of wood supply, has been practised in forestry for centuries modern ideas of sustainability are broader in scope, embracing all the goods and services of the forest. Increasingly, forests are being managed as multifunctional ecosystems, often for amenity purposes. Forest ecosystem research, which developed from a range of traditional, highly focused disciplines, requires, if it is to make a meaningful contribution to forest management, long-term interdisciplinary studies. It provides the basis for ecologically intelligent management decisions and as such, is central to the development of sustainable forestry management. Central to the successful implementation of research findings is their efficient transfer from the researcher to the manager. If the research community identifies such an interchange as an important part of their duties, it will be a decisive step towards the better use of forests in Europe. It is only by deepening our knowledge of the past, accepting the challenge of the present and acknowledging that, as researchers, we have also a responsibility to communicate with users, that we can foster the growth in wisdom which is fundamental to the wise use of Europe’s forests in the next millennium.

Types and chemical composition of organic matter in reforested lignite-rich mine soils

Abstract In the post-mining landscapes of Lusatia, forest soils develop from extremely acid, lignite-rich open cast mine spoils. The sites have been ameliorated with ash from lignite-fired power stations prior to afforestation. During stand development, incorporation of plant-derived organic matter leads to an intimate mixture with the substrate-derived lignite in the first centimetres of the soil (Ai horizon). The objective of the study was to characterise and to compare the composition of organic matter of mine soils under forest which contain substantial amounts of lignite. Therefore, the forest floor and the mineral soil (Ai and Cv horizon) under a 20-year-old pine and a 36-year-old red oak site were analysed for elemental composition, magnetic susceptibility, chemical structure by cross-polarisation magic angle spinning (CPMAS) 13 C and 15 N nuclear magnetic resonance (NMR) spectroscopy and lignite content by radiocarbon dating. The 13 C CPMAS NMR spectra of the forest floor and Ai horizon reveal signals at 56, 72, 105, 119, 130 and 150 ppm, indicating the presence of carbohydrates and lignin originating from plant material. Additionally, structures characteristic for lignite material (aromatic and aliphatic carbon) could be observed in the Oh and Ai horizons. Using radiocarbon dating, 25 to 83% of the total carbon in these horizons can be assigned to lignite. Lignite carbon may also indicate carbonaceous particles derived from amelioration ash as well as from lignite-derived airborne contamination, which are possible carbon sources of the forest floor and the surface soil. 13 C NMR and radiocarbon dating show that the subsoil (Cv horizon) is dominated by carbon derived from lignite. From these results it is concluded that mine soils, rich in lignite contain up to four organic matter types, namely lignite inherent to the parent substrate, organic matter derived from decomposition of plant residues, carbonaceous particles in amelioration ash and carbonaceous particles from airborne lignite-derived contamination. 15 N NMR spectroscopy revealed that most of the nitrogen of these soils is of recent biogenic origin.

Water repellency in sandy luvisols under different forest transformation stages in northeast Germany

Soil water repellency can adversely affect soil hydrological properties, reduce infiltration capacity and induce preferential flow, surface runoff and erosion. Although primarily described from semiarid and Mediterranean climates, it is also a concern in forest sites under the humid climatic conditions of central Europe. The objective of this study was to characterize the water repellency on geologically comparable forest sites with different stand ages and tree species in terms of the effects of forest transformation upon soil physical properties. The investigated forest site called “Kahlenberg” (50 km northeast of Berlin) contains populations of Pinus sylvestris and Fagus sylvatica of different ages and proportions of single tree species. For the characterization of water repellency, the water drop penetration time (WDPT) test, for determining the persistence of water repellency, and the ethanol percentage (EP) test, which measures the severity or degree of water repellency, were carried out using soil samples from four forest plots and different soil depths (0–160 cm). “Potential” water repellencies were determined after 3-day oven-drying at 45 °C. For two plots, the “actual” water repellency with field moist soil samples was also measured using the WDPT test. The WDPT test revealed a significant proportion of severely and extremely hydrophobic samples in the upper 10 cm of the soil profile for all plots, whereas the persistence of repellency decreased with increasing soil depth. Soil organic matter contents and measured WDPT gave a positive linear correlation with r=0.73. Maximum measured ethanol percentages were 30% and restricted to the upper 5 cm of the soil profiles. The correlation of the organic matter content with EP was r=0.83. For all plots, the EP exhibited a shallower depth distribution than the WDPT. The two plots with pure pine and beech stands exhibited relatively low water repellencies, compared to the plots with mixed tree populations. This corresponds to a higher proportion of mor-type humus and a greater thickness of the humose topsoil at mixed stands compared to the pure pine and beech sites.

Spatial variability of potential water repellency in a lignitic mine soil afforested with Pinus nigra

Reclaimed mine soils in Lusatia/Germany are heterogeneous sandy sediment mixtures, which often contain significant portions of lignite (brown coal). Water-repellent aliphatic organic compounds may cause preferential finger-type flow in mine soils. The objective of this study was to analyse the significance, spatial scales, and spatial variability of potential water repellency in a lignitic mine soil. The mine site was located northeast of the city of Cottbus, Germany. A soil block of 2.5-m length, 1.25-m width, and 1.5-m depth was divided into squares of 0.25-m edge length from where 25 soil cores of 636 cm3 were sampled at each 0.1-m depth increment. After drying the samples at 60°C for 4 days, the Water Drop Penetration Time (WDPT) test was carried out using 30 water drops per sample. The frequency distributions of the classified potential water repellency were analyzed (i) locally, within a sample, (ii) horizontally, within a layer, and (iii) vertically, within the soil block. The WDPT values of most samples were either smaller than 5–10 s or larger than 10 min. Such ‘bipolar’ distribution occurred for the whole block, as well as locally, i.e., the WDPT varied between repellent and not repellent from drop to drop at distances of about 1 cm. The persistence of potential water repellency seems somewhat larger in the subsoil (0.5–1.5-m depth) than in the ameliorated topsoil (0–40-m depth). However, hardly any spatial structures are obvious since severely repellent, as well as not repellent, soil material occurs throughout the soil profile and intra- was as large as inter-sample variability. To a large degree, the spatial variability of water repellency seems to reflect a situation that resulted from partially mixing of different overburden sediments. The small-scale variability of the potential water repellency may probably be correlated with the spatial distribution of lignite, minerals, and more-or-less lignite-coated sand particles. These spatial patterns of repellency may, in particular, affect water and solute movement in mine soils.

Organic matter composition and degree of humification in lignite-rich mine soils under a chronosequence of pine

In the Lusatian mining district, in the eastern part of the Federal Republic of Germany, organic matter of reclaimed mine soils consists of a mixture of lignite and recently formed soil organic matter (recent carbon). The aim of the study was to investigate the recent carbon accumulation and the degree of humification of a chronosequence of young mine soils under forest. The lignite content of the forest floor, Ai (0–5 cm) and Cv horizons (1 m depth) was determined by 14CU activity measurements and the structural composition of the organic matter was characterised by 13C CPMAS NMR spectroscopy. To obtain a characterisation of the degree of humification, the soil samples were analysed for the content of polysaccharides, proteins, lignin and lipids by wet chemical methods. 14C activity measurements indicate that at the oldest site, comparable amounts of carbon accumulated in the first few centimetres of the soil profile than in natural forest soils. 13C CPMAS NMR spectra of the organic matter in the Ai horizons of the three soil profiles were dominated by aromatic and alkyl carbon species characteristic for lignite, but indicated as well an increasing contribution of carbon species from decomposing plant litter with soil age. When the results from wet chemical analyses were normalised to the total carbon content no changes with age could be noticed. After normalisation of the amount of litter compounds to the recent carbon content, the carbon identified by plant litter compound analysis decreased with increasing depth and increasing age of the soils. After 32 years the values are comparable to those of natural forest soils. These observations were confirmed by increasing degree of lignin alteration with stand age and soil depth. The data of wet chemical analyses complement data obtained by 14C activity measurements and 13C CPMAS NMR spectroscopy and lead to the conclusion that 32 years after reforestation the degree of humification of the soil organic matter is in the same range as those of natural sites.

Ex ante impact assessment of land use changes in European regions: the SENSOR approach

Land use includes those human activities that exhibit a spatial dimension and that change the bio-geophysical conditions of land. Land use policy making at European level aims at fostering sustainability pathways of natural resource use and rural development through the decoupling of economic growth from environmental degradation while supporting social cohesion in rural areas. Targeted policy making requires tools for the ex ante assessment of impacts of policy driven land use changes on sustainable development opportunities in European regions. These tools have to cover all relevant land use sectors and impact issues including their interrelations. They have to be spatially explicit, allow scenario analysis of possible future developments, be based on reproducible analyses, and be transparent and easy to use. The European Commission funded Integrated Project SENSOR is dedicated to develop such ex-ante Sustainability Impact Assessment Tools (SIAT) for land use in European regions. SIAT is designed as a meta modelling toolkit, in which global economic trend and policy scenarios are translated into land use changes at 1km2 grid resolution for the area of Europe. Based on qualitative and quantitative indicator analyses, impacts of simulated land use changes on social, environmental and economic sustainability issues are assessed at regional (NUTS2/3) scale. Valuation of these impacts is based on the concept of multifunctionality of land use. It is conducted through expert and stakeholder valuations leading to the determination of sustainability choice spaces for European regions. This paper presents the analytical approach in SENSOR and describes the impact assessment framework.

Nutrient supply of forest soils in relation to management and site history

Internal and external factors like forest management practices and atmospheric deposition may have large influences on the nutrient supply of forest soils. Examples are given for the effects of tree species, harvesting, site history, changes of species and specific soil conditions, nitrogen deposition, and forest growth dynamics. It is concluded from these examples that all of these factors may contribute to soil acidification in forest ecosystems under humid temperate climatic conditions.

Magnesium deficiency in forest ecosystems.

1. Introduction R.F. Huttl, W. Schaaf. 2. Visual Mg-Deficiency Symptoms (Coniferous, Deciduous Trees) and Threshold Values (Foliar, Soil) P. Ende, F.H. Evers. 3. Temporal and Spatial Development of Mg Deficiency in Forest Stands in Europe, North America, New Zealand G. Landmann, et al. 4.1 Biogeochemistry of Mg in Forest Ecosystems K.H. Feger. 4.2. Tree Physiology S. Slovik. 4.3. Influence of Magnesium Supply on Tree Growth K. Makkonen-Spieker, H. Spiecker. 5. Causes of Magnesium Deficiency in Forest Ecosystems K. Katzensteiner, G. Glatzel. 6.1 Soil Chemistry S. Augustin, et al. 6.2. Tree Nutrition M. Kaupenjohann. 6.3. Structural Aspects of Mg-Deficiency S. Fink. 6.4. Fine Root Development S. Raspe. 7. Evaluation of Different Mg Fertilization Strategies W. Schaaf. 8. Concluding Remarks R.F. Huttl.

Forest ecosystem research - priorities for Europe.

Abstract European Forest Ecosystem Research Network (EFERN), was set up in 1996 as one result of the Ministerial Conferences on the Protection of European Forests in Strasbourg 1990 and Helsinki 1993 with the aim of promoting ecological research for sustainable forest management. Three plenary meetings were held, each with a specific theme. The results of these meetings have been documented in 10 chapters in a volume with the title ‘Pathways to the wise use of forests in Europe’. The intention was also to give priorities for future forest ecosystem research. In accepting the idea that sustainability includes a multifunctional view of forests, there is a need to find ways of integrating classical forest ecosystem research with biodiversity, water quality and socio-economics. The balancing of the different interests in the forests can be done through planning. From this results also a choice of adequate management methods of the forest resources. The classical stand level in forestry requires now an additional scale — the landscape level. The aim with this paper is to present a concept which attempts to integrate the disciplines involved — ecosystem and landscape ecology and its components. Areas where research efforts are central are also mentioned.

Microbial degradation of geogenic organic C and N in mine spoils

Many mine spoils present at the surface of reclamation sites in the Lower Lusatian mining district are carboniferous substrates, i.e. contain geogenic organic matter. Depending on its susceptibility to microbial degradation, geogenic organic matter might influence the establishment of a carbon requiring microflora in mine spoils. As geogenic organic matter contains substantial amounts of organic nitrogen it is also a potential source for plant available N. The objective of the present study was to quantify C and N mineralisation and microbial biomass in geogenic organic matter present at reclamation sites in Lower Lusatia. We also studied, whether these properties can be influenced by raising the originally low pH to near neutral conditions. In laboratory incubation studies, the rates of CO2 evolution and net N mineralisation were determined in geogenic organic matter and carboniferous mine spoil with and without addition of lime. At the same time, microbial biomass carbon was estimated. As a reference, soil organic matter originating from the humus layer of a 60-year-old Pinus sylvestris stand was used. As indicated by the initial rates of C mineralisation, geogenic carbon was microbially available but to a lower extent than soil organic carbon. During incubation, C mineralisation remained constant or tended to increase with time, depending on the origin of the sample, while it decreased in soil organic matter. Unlike in soil organic matter, in geogenic organic matter and carboniferous mine spoil, C mineralisation was not consistently promoted by lime addition. Prior to incubation, microbial biomass in geogenic organic matter and carboniferous mine spoil was about 10-fold lower than in soil organic matter and tended to increase with incubation time while it decreased in soil organic matter. Similar to C mineralisation, microbial biomass in geogenic organic matter increased after liming, while it declined in carboniferous mine spoil immediately after lime addition. Rates of net N mineralisation were very low in geogenic organic matter and carboniferous mine spoil regardless of the length of incubation and could not be enhanced by raising the pH. It was concluded, that in mine spoils where accumulation of soil organic matter has not yet occurred, geogenic organic matter can be favourable for the establishment of a heterotrophic microflora. However, in the short term, geogenic matter is no source for plant available N in mine spoils.