Showing papers by "Ernst Detlef Schulze published in 2005"

Europe-wide reduction in primary productivity caused by the heat and drought in 2003

Abstract: Future climate warming is expected to enhance plant growth in temperate ecosystems and to increase carbon sequestration. But although severe regional heatwaves may become more frequent in a changing climate their impact on terrestrial carbon cycling is unclear. Here we report measurements of ecosystem carbon dioxide fluxes, remotely sensed radiation absorbed by plants, and country-level crop yields taken during the European heatwave in 2003.We use a terrestrial biosphere simulation model to assess continental-scale changes in primary productivity during 2003, and their consequences for the net carbon balance. We estimate a 30 per cent reduction in gross primary productivity over Europe, which resulted in a strong anomalous net source of carbon dioxide (0.5 Pg Cyr21) to the atmosphere and reversed the effect of four years of net ecosystem carbon sequestration. Our results suggest that productivity reduction in eastern and western Europe can be explained by rainfall deficit and extreme summer heat, respectively. We also find that ecosystem respiration decreased together with gross primary productivity, rather than accelerating with the temperature rise. Model results, corroborated by historical records of crop yields, suggest that such a reduction in Europe's primary productivity is unprecedented during the last century. An increase in future drought events could turn temperate ecosystems into carbon sources, contributing to positive carbon-climate feedbacks already anticipated in the tropics and at high latitudes.

Ecosystem effects of biodiversity manipulations in european grasslands

Abstract: We present a multisite analysis of the relationship between plant diversity and ecosystem functioning within the European BIODEPTH network of plant-diversity manipulation experiments. We report results of the analysis of 11 variables addressing several aspects of key ecosystem processes like biomass production, resource use (space, light, and nitrogen), and decomposition, measured across three years in plots of varying plant species richness at eight different European grassland field sites. Differences among sites explained substantial and significant amounts of the variation of most of the ecosystem processes examined. However, against this background of geographic variation, all the aspects of plant diversity and composition we examined (i.e., both numbers and types of species and functional groups) produced significant, mostly positive impacts on ecosystem processes. Analyses using the additive partitioning method revealed that complementarity effects (greater net yields than predicted from monocultures due to resource partitioning, positive interactions, etc.) were stronger and more consistent than selection effects (the covariance between monoculture yield and change in yield in mixtures) caused by dominance of species with particular traits. In general, communities with a higher diversity of species and functional groups were more productive and utilized resources more completely by intercepting more light, taking up more nitrogen, and occupying more of the available space. Diversity had significant effects through both increased vegetation cover and greater nitrogen retention by plants when this resource was more abundant through N2 fixation by legumes. However, additional positive diversity effects remained even after controlling for differences in vegetation cover and for the presence of legumes in communities. Diversity effects were stronger on above- than belowground processes. In particular, clear diversity effects on decomposition were only observed at one of the eight sites. The ecosystem effects of plant diversity also varied between sites and years. In general, diversity effects were lowest in the first year and stronger later in the experiment, indicating that they were not transitional due to community establishment. These analyses of our complete ecosystem process data set largely reinforce our previous results, and those from comparable biodiversity experiments, and extend the generality of diversity–ecosystem functioning relationships to multiple sites, years, and processes.

Overyielding in experimental grassland communities - irrespective of species pool or spatial scale

Abstract: In a large integrated biodiversity project (The Jena Experiment in Germany) we established two experiments, one with a pool of 60 plant species that ranged broadly from dominant to subordinate competitors on large 20 · 20 m and small 3.5 · 3.5 m plots (¼ main experiment), and one with a pool of nine potentially dominant species on small 3.5 · 3.5 m plots (¼ dominance experiment). We found identical positive species richness–aboveground productivity relationships in the main experiment at both scales. This result suggests that scaling up, at least over the short term, is appropriate in interpreting the implications of such experiments for larger-scale patterns. The species richness–productivity relationship was more pronounced in the experiment with dominant species (46.7 and 82.6% yield increase compared to mean monoculture, respectively). Additionally, transgressive overyielding occurred more frequently in the dominance experiment (67.7% of cases) than in the main experiment (23.4% of cases). Additive partitioning and relative yield total analyses showed that both complementarity and selection effects contributed to the positive net biodiversity effect.

Forest diversity and function: temperate and boreal systems

Abstract: Table of Contents Section A: Introduction 1 The functional significance of forest diversity: the starting point Scherer-Lorenzen, M., Korner, Ch., Schulze, E.-D. 2 An introduction to the functional diversity of temperate forest trees Korner, Ch. Section B: Productivity and growth 3 Diversity and productivity in forests: evidence from long-term experimental plots Pretzsch, H. 4 Confounding factors of the observational productivity-diversity relationship in forests Vila, M., Inchausti, P., Vayreda, J., Barrantes, O., Gracia, C., Ibanez, J. J., Mata, T. 5 Genetic diversity parameters associated with viability selection, reproductive efficiency and growth in forest tree species G. Muller-Starck, G., Ziehe, M., Schubert, R. Section C: Biogeochemical cycles 6 Functioning of mixed-species stands: evidence from a long-term forest experiment Jones, H. E., McNamara, N. Mason, W.L. 7 The role of biodiversity on the evaporation of forests Baldocchi D. D. 8 Effects of tree species diversity on litter quality and decomposition Hattenschwiler, S. 9 The effect of biodiversity on carbon storage in soils G. Gleixner, C. Kramer, V. Hahn and D. Sachse 10 Silviculture and its interaction with biodiversity and the carbon balance of forest soils Mund, M., E.-D. Schulze Section D: Animals, Pests and Disturbances 11 Linkages between tree diversity, soil fauna and ecosystem processes Scheu, S. 12 A test of the biodiversity-stability theory: meta-analysis of tree species diversity effects on insect pest infestations, and re-examination of responsible factors Jactel, H., Brockerhoff, E., Duelli, P. 13 Susceptibility to fungal pathogens of forests differing in tree diversity Pautasso, M., Holdenrieder, O., Stenlid, J. 14 Implication of forest diversity for theresistance to strong winds 15 Fire regime and tree diversity in boreal forests: implications for the carbon cycle Wirth, C. Section E: Perspectives 16 The design of experimental tree plantations for functional biodiversity research Scherer-Lorenzen, M., Potvin, C., Koricheva, J., Schmid, B., Hector, A., Bornik, Z., Reynolds, G. Schulze, E.-D. 17 The functional significance of forest diversity: a synthesis Scherer-Lorenzen, M., Korner, Ch., Schulze, E.-D. Subject Index

Biological control of the terrestrial carbon sink

Abstract: . This lecture reviews the past (since 1964 when the International Biological Program began) and the future of our understanding of terrestrial carbon fluxes with focus on photosynthesis, respiration, primary-, ecosystem-, and biome-productivity. Photosynthetic capacity is related to the nitrogen concentration of leaves, but the capacity is only rarely reached under field conditions. Average rates of photosynthesis and stomatal conductance are closely correlated and operate near 50% of their maximal rate, with light being the limiting factor in humid regions and air humidity and soil water the limiting factor in arid climates. Leaf area is the main factor to extrapolate from leaves to canopies, with maximum surface conductance being dependent on leaf level stomatal conductance. Additionally, gas exchange depends also on rooting depth which determines the water and nutrient availability and on mycorrhizae which regulate the nutrient status. An important anthropogenic disturbance is the nitrogen uptake from air pollutants, which is not balanced by cation uptake from roots and this may lead to damage and breakdown of the plant cover. Photosynthesis is the main carbon input into ecosystems, but it alone does not represent the ecosystem carbon balance, which is determined by respiration of various kinds. Plant respiration and photosynthesis determine growth (net primary production) and microbial respiration balances the net ecosystem flux. In a spruce forest, 30% of the assimilatory carbon gain is used for respiration of needles, 20% is used for respiration in stems. Soil respiration is about 50% the carbon gain, half of which is root respiration, half is microbial respiration. In addition, disturbances lead to carbon losses, where fire, harvest and grazing bypass the chain of respiration. In total, the carbon balance at the biome level is only about 1% of the photosynthetic carbon input, or may indeed become negative. The recent observed increase in plant growth has different reasons depending on the region of the world: anthropogenic nitrogen deposition is the controlling factor in Europe, increasing global temperatures is the main factor in Siberia, and maybe rising CO2 the factor controlling the carbon fluxes in Amazonia. However, this has not lead to increases in net biome productivity, due to associated losses. Also important is the interaction between biodiversity and biogeochemical processes. It is shown that net primary productivity increases with plant species diversity (50% species loss equals 20% loss in productivity). However, in this extrapolation the action of soil biota is poorly understood although soils contribute the largest number of species and of taxonomic groups to an ecosystem. The global terrestrial carbon budget strongly depends on areas with pristine old growth forests which are carbon sinks. The management options are very limited, mostly short term, and usually associated with high uncertainty. Unmanaged grasslands appear to be a carbon sink of similar magnitude as forest, but generally these ecosystems lost their C with grazing and agricultural use. Extrapolation to the future of Earth climate shows that the biota will not be able to balance fossil fuel emissions, and that it will be essential to develop a carbon free energy system in order to maintain the living conditions on earth.

A proteomic fingerprint of dissolved organic carbon and of soil particles

Abstract: Mass spectrometry-based proteomics was applied to analyze proteins isolated from dissolved organic matter (DOM). The focal question was to identify the type and biological origin of proteins in DOM, and to describe diversity of protein origin at the level of higher taxonomic units, as well as to detect extracellular enzymes possibly important in the carbon cycle. Identified proteins were classified according to their phylogenetic origin and metabolic function using the National Center for Biotechnology Information (NCBI) protein and taxonomy database. Seventy-eight percent of the proteins in DOM from the lake but less than 50% in forest soil DOM originated from bacteria. In a deciduous forest, the number of identified proteins decreased from 75 to 28 with increasing soil depth and decreasing total soil organic carbon content. The number of identified proteins and taxonomic groups was 50% higher in winter than in summer. In spruce forest, number of proteins and taxonomic groups decreased by 50% on a plot where trees had been girdled a year before and carbohydrate transport to roots was terminated. After girdling, proteins from four taxonomic groups remained as compared to nine taxonomic groups in healthy forest. Enzymes involved in degradation of organic matter were not identified in free soil DOM. However, cellulases and laccases were found among proteins extracted from soil particles, indicating that degradation of soil organic matter takes place in biofilms on particle surfaces. These results demonstrate a novel application of proteomics to obtain a “proteomic fingerprint” of presence and activity of organisms in an ecosystem.

Carbon dioxide and methane exchange of a north‐east Siberian tussock tundra

Abstract: Carbon dioxide, energy flux measurements and methane chamber measurements were carried out in an arctic wet tussock grassland located on a flood plane of the Kolyma river in NE Siberia over a summer period of 155 days in 2002 and early 2003. Respiration was also measured in April 2004. The study region is characterized by late thaw of the top soil (mid of June) and periodic spring floods. A stagnant water table below the grass canopy is fed by thawing of the active layer of permafrost and by flood water. The climate is continental with average daily temperature in the warmest months of 131C (maximum temperature at midday: 281C by the end of July), dry air (maximum vapour pressure deficit at midday: 28hPa) and low rainfall of 50mm during summer (July‐ September). Summer evaporation (July‐September: 103mm) exceeded rainfall by a factor of 2. The daily average Bowen ratio (H/LE) was 0.62 during the growing season. Net ecosystem CO2 uptake reached 10lmolm � 2 s � 1 and was related to photon flux density (PFD) and vapour pressure deficit (VPD). The cumulative annual net carbon flux from the atmosphere to the terrestrial surface was estimated to be about � 38gCm � 2 yr � 1 (negative flux depicts net carbon sink). Winter respiration was extrapolated using the Lloyd and Taylor function. The net carbon balance is composed of a high rate of assimilation in a short summer and a fairly large but uncertain respiration mainly during autumn and spring. Methane flux (about 12gCm � 2 measured over 60 days) was 25% of C uptake during the same period of time (end of July to end of September). Assuming that CH4 was emitted only in summer, and taking the greenhouse gas warming potential of CH4 vs. CO2 into account (factor 23), the study site was a greenhouse gas source (at least 200gCequivalentm � 2 yr � 1 ). Comparing different studies in wetlands and tundra ecosystems as related to latitude, we expect that global warming would rather increase than decrease the CO2-C sink.

Effects of increasing fire frequency on black carbon and organic matter in Podzols of Siberian Scots pine forests

Abstract: European Journal of Soil Science, June 2005, 56, 417–428 doi: 10.1111/j.1365-2389.2004.00665.x Effects of increasing fire frequency on black carbon and organic matter in Podzols of Siberian Scots pine forests C. I. C ZIMCZIK a , M. W. I. S CHMIDT b & E.-D. S CHULZE a a Max-Planck-Institut fu¨r Biogeochemie, Hans-Kno¨ll-Strasse 10, 07745 Jena, Germany, and b University of Zu¨rich, Department of Geography, Winterthurerstrasse 190, 8057 Zu¨rich, Switzerland Summary Fires in boreal forests frequently convert organic matter in the organic layer to black carbon, but we know little of how changing fire frequency alters the amount, composition and distribution of black carbon and organic matter within soils, or affects podzolization. We compared black carbon and organic matter (organic carbon and nitrogen) in soils of three Siberian Scots pine forests with frequent, moder- ately frequent and infrequent fires. Black carbon did not significantly contribute to the storage of organic matter, most likely because it is consumed by intense fires. We found 99% of black carbon in the organic layer; maximum stocks were 72 g m 2 . Less intense fires consumed only parts of the organic layer and converted some organic matter to black carbon (> 5 g m 2 ), whereas more intense fires consumed almost the entire organic layer. In the upper 0.25 m of the mineral soil, black carbon stocks were 0.1 g m 2 in the infrequent fire regime. After fire, organic carbon and nitrogen in the organic layer accumulated with an estimated rate of 14.4 g C m 2 year 1 or 0.241 g N m 2 year 1 . Maximum stocks 140 years after fire were 2190 g organic C m 2 and 40 g N m 2 , with no differences among fire regimes. With increasing fire frequency, stocks of organic carbon increased from 600 to 1100 g m 2 (0–0.25 m). Stocks of nitrogen in the mineral soil were similar among the regimes (0.04 g m 2 ). We found that greater intensities of fire reduce amounts of organic matter in the organic layer but that the greater frequencies may slightly increase amounts in the mineral soil. Introduction Boreal forests cover 9% (13.7 10 6 km 2 ) of the land between 45 and 70 north. Fire, windthrow and outbreaks of insects and pathogens are frequent in them. We know little of how much such disturbances affect the stocks of organic matter beneath them, and we should because the soil contains roughly 22% (338–471 Pg C) of global soil carbon (IPCC, 2001). Fire is the most important disturbance in boreal regions, and is caused by lightning during summer droughts. This is espe- cially true for Siberian Scots pine (Pinus sylvestris) and larch (Larix gmelinii and L. cajanderi) forests (Conard & Ivanova, 1997) and the western boreal, subarctic, and mountain regions of Canada (Kurz & Apps, 1999). There are some indications that fires will be more frequent in the future (Flannigan et al., 2001), partly as a result of global warming, and partly caused by an increasing anthropogenic activity in the boreal region. Correspondence: C. Czimczik, Department of Earth System Science, University of California, 2103 Croul Hall, Irvine, CA 92697-3100, USA. E-mail: czimczik@uci.edu Received 6 January 2003; revised version accepted 19 May 2004 # 2004 British Society of Soil Science In the last 20 years, the area of boreal forest burned in northern America doubled, and a similar trend is thought to apply for Russia (Chapin et al., 2000). Fire reduces the amount of organic matter in the soil and alters its composition. In Russian Scots pine and larch forests, surface fires are the most frequent; they affect mainly the organic layer, and kill seedlings and trees in lower canopies (Wirth et al., 1999). Vegetation and soil organic matter can be distilled, oxidized, or charred. Most of the products are instan- taneously released. Organic carbon is converted to CO 2 , CO, and CH 4 , nitrogen to NO x and N 2 , and sulphur to SO 2 , all of which are lost into the atmosphere. Auclair & Carter (1993) estimated losses of carbon to be 0.13 Pg C year 1 between 1977 and 1990 for the northern hemisphere. Harden et al. (2000) reckon that 25% of the annual net primary production of Canadian jack pine (Pinus banksiana) forests is lost in this way, and Wirth et al. (2002a) estimate that 35% of net primary production of Siberian Scots pine forests is lost. However, during burning, a small fraction of carbon (0.7–8%, Czimczik et al., 2003) is converted to black carbon. The term black

Succession after stand replacing disturbances by fire, wind throw, and insects in the dark Taiga of Central Siberia

Abstract: The dark taiga of Siberia is a boreal vegetation dominated by Picea obovata, Abies sibirica, and Pinus sibirica during the late succession. This paper investigates the population and age structure of 18 stands representing different stages after fire, wind throw, and insect damage. To our knowledge, this is the first time that the forest dynamics of the Siberian dark taiga is described quantitatively in terms of succession, and age after disturbance, stand density, and basal area. The basis for the curve–linear age/diameter relation of trees is being analyzed. (1) After a stand-replacing fire Betula dominates (4,000 trees) for about 70 years. Although tree density of Betula decreases rapidly, basal area (BA) reached >30 m2/ha after 40 years. (2) After fire, Abies, Picea, and Pinus establish at the same time as Betula, but grow slower, continue to gain height and eventually replace Betula. Abies has the highest seedling number (about 1,000 trees/ha) and the highest mortality. Picea establishes with 100–400 trees/ha, it has less mortality, but reached the highest age (>350 years, DBH 51 cm). Picea is the most important indicator for successional age after disturbance. Pinus sibirica is an accompanying species. The widely distributed “mixed boreal forest” is a stage about 120 years after fire reaching a BA of >40 m2/ha. (3) Wind throw and insect damage occur in old conifer stands. Betula does not establish. Abies initially dominates (2,000–6,000 trees/ha), but Picea becomes dominant after 150–200 years since Abies is shorter lived. (4) Without disturbance the forest develops into a pure coniferous canopy (BA 40–50 m2/ha) with a self-regenerating density of 1,000 coniferous canopy trees/ha. There is no collapse of old-growth stands. The dark taiga may serve as an example in which a limited set to tree species may gain dominance under certain disturbance conditions without ever getting monotypic.

Partitioning direct and indirect human-induced effects on carbon sequestration of managed coniferous forests using model simulations and forest inventories

Abstract: Temperate forest ecosystems have recently been identified as an important net sink in the global carbon budget. The factors responsible for the strength of the sinks and their permanence, however, are less evident. In this paper, we quantify the present carbon sequestration in Thuringian managed coniferous forests. We quantify the effects of indirect human-induced environmental changes (increasing temperature, increasing atmospheric CO2 concentration and nitrogen fertilization), during the last century using BIOME-BGC, as well as the legacy effect of the current age-class distribution (forest inventories and BIOME-BGC). We focused on coniferous forests because these forests represent a large area of central European forests and detailed forest inventories were available. The model indicates that environmental changes induced an increase in biomass C accumulation for all age classes during the last 20 years (1982‐2001). Young and old stands had the highest changes in the biomass C accumulation during this period. During the last century mature stands (older than 80 years) turned from being almost carbon neutral to carbon sinks. In high elevations nitrogen deposition explained most of the increase of net ecosystem production (NEP) of forests. CO2 fertilization was the main factor increasing NEP of forests in the middle and low elevations. According to the model, at present, total biomass C accumulation in coniferous forests of Thuringia was estimated at 1.51tCha � 1 yr � 1 with an averaged annual NEP of 1.42tCha � 1 yr � 1 and total net biome production of 1.03tCha � 1 yr � 1 (accounting for harvest). The annual averaged biomass carbon balance (BCB: biomass accumulation rateharvest) was 1.12tCha � 1 yr � 1 (not including soil respiration), and was close to BCB from forest inventories (1.15tCha � 1 yr � 1 ). Indirect human impact resulted in 33% increase in modeled biomass carbon accumulation in coniferous forests in Thuringia during the last century. From the forest inventory data we estimated the legacy effect of the age-class distribution to account for 17% of the inventory-based sink. Isolating the environmental change effects showed that these effects can be large in a long-term, managed conifer forest.

Radiation, temperature, and leaf area explain ecosystem carbon fluxes in boreal and temperate European forests

Abstract: [1] We analyzed measurements of net ecosystem exchange of CO2 (NEE) over 15 European forests (the EuroFlux data set) to investigate which climate and forest characteristics explain temporal and intersite variations in NEE and its components, gross primary production (GPP) and respiration (R). Informed stepwise regression was used to derive a parameter-efficient, empirical model that was consistent with process knowledge. The resulting model required seven site-specific parameters to describe flux behavior at different temporal scales as a function of radiation, temperature, and air humidity. The interpretation appeared robust despite method and data uncertainties, although the data set was probably biased toward well-watered boreal and temperate European forests. Radiation, temperature, and leaf area (through forest assimilation capacity) appear to be the main drivers of the observed temporal and intersite variation in gross primary production, ecosystem respiration, and net ecosystem exchange.

The Functional Significance of Forest Diversity: A Synthesis

Abstract: Despite of the tremendous increase in knowledge about the relationship between biodiversity and ecosystem functioning during the last decade (Scherer-Lorenzen et al., Chap. 1, this Vol.), it should be noted that most of the studies were conducted with model systems, which – for very practical reasons – were small-statured, short-lived and even-aged, mainly herbaceous assemblages or microbial microcosms (e.g., Tilman et al. 1997b; Hector et al. 1999; Petchey et al. 2002; for an overview, see Schlapfer and Schmid 1999; Schmid et al. 2002). Experiments in forest ecosystems have been almost absent, with the exception of studies manipulating diversity of consumers or decomposers in the soil (e.g., Mikola and Setala 1998; Laakso and Setala 1999; see Scheu, Chap. 11, this Vol.). A manipulation of the producer level, i.e., trees, is obviously a difficult and long-lasting task and only recently attempts in this direction have been made (Scherer-Lorenzen et al., Chap. 16, this Vol.). The experiment by Ewel and colleagues in the tropics of Costa Rica (Berish and Ewel 1988; Ewel et al. 1991) has often been mentioned as the first manipulative diversity experiment indicating diversity effects on biogeochemistry (Vitousek and Hooper 1993). However, this experiment was designed to explore the possibilities of developing sustainable agroecosystems for the humid tropics, mimicking structural diversity of successional communities, and not to study the interaction of species richness and ecosystem functioning per se. Clear effects on soil chemistry were detectable between maize monocultures and highly-diverse (>100 species) treatments consisting of herbaceous and woody plants. Low and intermediate levels of diversity were lacking, which should be the part of the gradient where most effects are expected to occur, according to local deterministic processes involving species interactions (see below). Positive effects at such intermediate levels of tree species richness have been reported from afforestation experiments in Costa Rica, for example (Byard et al. 1996; Montagnini 2000). In contrast, mixture experiments from forestry

Effects of reforestation, deforestation, and afforestation on carbon storage in soils.

Abstract: This study reviews the effects of changes in land use and land management on SOC pools in forest soils. In the 1990s, deforestation remained the most important land-use change in tropical regions (-142 x 10(6) ha per year). In non-tropical regions the forested area increased in developed countries as a result of natural reforestation (+26 x 10(6) ha per year). Deforestation also continued in under-developed countries in temperate regions. Without intensive site preparation, harvest followed by natural regeneration or reforestation has little impact on SOC pools in the mineral topsoil (0-0.3 m). Intensive site preparation results in losses of 6-13% of the initial SOC from the topsoil in the first decades. On average, deforestation followed by conversion to cropland results in SOC losses of 42% (or 0.1-1500 g (C) m(-2)) from the mineral topsoil, whereas conversion to pasture results in gains of 8%. The largest changes in SOC storage occur within the first two decades. After reforestation, SOC accumulation depends on the kind of managed forest established. Under productive deciduous reforestation (excluding eucalypts), SOC in the mineral topsoil accumulates at a rate of 20-50 g (C) m(-2) per year, and SOC pools could recover from cultivation-induced losses within 40 years. Under coniferous reforestation, the rate of accumulation of carbon is highest (95 g (C) m(-2) per year) in the organic layer, which is very susceptible to site preparation practices. In the mineral topsoil, the rate of accumulation is much lower (4 g (C) m(-2) per year), and recovery of the initial SOC pools might take several hundred years. The resulting land-use 'memory effect' has introduced large variation of the SOC pools in contemporary carbon budget studies. Thus, there seems to be a large temporal asymmetry between the period of time over which depletion of SOC occurs and the time needed for recovery of the SOC pools in the mineral soil. This should be taken into account when considering land-use and land-management activities to decrease atmospheric CO2 concentrations over this century.

Silviculture and Its Interactions with Biodiversity and the Carbon Balance of Forest Soils

Abstract: It is well known that intensive forest management practices can have significant effects on the biogeochemistry and biodiversity of forest ecosystems. For example, planting and thinning affects the structural biodiversity. Planting of nursery trees also determines the species (including mycorrhizae) and genetic diversity. Fertilization changes the nutrient balance, and thus competitive interactions. Clear-cutting combined with intensive soil preparation causes soil erosion, soil compaction, and losses of soil organic carbon and cations, which in turn affects biodiversity (e.g., Heinsdorf and Krauß 1974; Bormann and Likens 1979; Covington 1981; Heinsdorf 1986; Black and Harden 1995; Apps and Price 1996; Nyland 1996; Jurgensen et al. 1997; Rollinger et al. 1998; Worrell and Hampson 1997; Prescott et al. 2000b; Quesnel and Curran 2000; Johnson and Curtis 2001; Block et al. 2002). However, our knowledge about the interactions of biodiversity with silviculture and site-specific factors and the role of biodiversity in biogeochemical cycles is still very limited. The Kyoto-Protocol (UN 1997) and the “Bonn agreement” (UN 2001), in particular, raised the question if and which forest management practices influence the carbon balance of forest ecosystems. It is evident that increased decomposition of dead organic matter after clear-cutting results in a net loss or a zero carbon balance of the forest ecosystem over about 5–6 years afterwards, even when successful regeneration occurs (Pypker and Fredeen 2002; Rannik et al. 2002). The time period of net carbon release can be prolonged to 14–20 years if growth of the regenerating stands is reduced or if large amounts of dead wood remain on site (e. g., Cohen et al. 1996; Schulze et al. 1999). Nevertheless, the relative contribution of decomposing dead wood, organic-layer material or soil organic matter (SOM) to the net ecosystem carbon balance is still unclear. Also, the mechanisms that could cause the large discrepancies observed between different case studies investigating the

The functional significance of forest diversity: the starting point

Abstract: The dramatic and accelerating changes the earth’s biota has undergone over the last decades have led to considerable research effort toward understanding the nature of biotic control over the processes within ecosystems. Predicting the consequences to the ecosystem of changes in species numbers, in distribution patterns of taxa, and in shifts of dominance that result in altered trophic interactions between organisms, has become a major challenge for community and ecosystem ecology. Does biodiversity matter for ecosystem integrity, functioning, and the provision of goods and services? This was the original question posed in a volume in Ecological Studies published in 1993 that started this field of research (Schulze and Mooney 1993). However, this question remained basically unanswered with respect to forests. It is the aim of the present book to summarize the state of knowledge with respect to forests, focusing on the temperate and boreal regions.