The soil fauna community in pure and mixed stands of beech and spruce of different age: trophic structure and structuring forces

This study investigates the response of the soil fauna community to replacement of beech by spruce or by mixed stands of beech and spruce. Stands of different age were investigated in a factorial design with the factors tree species (beech and spruce) and stand age (30 and 120 yr). The input of leaf/needle litter did not differ significantly between the study sites. By contrast, the amount of organic matter in upper soil layers (L/F, H/Ah) of spruce forests strongly exceeded that of beech forests particularly in mature stands. The increase in organic matter in spruce stands was not associated by an increase in the amount of microbial biomass. Biomass of eight (bacterivorous, fungivorous and omnivorous nematodes, enchytraeids, earthworms, isopodes, mycetophilid and cecidomyiid Diptera) of the twelve microbi‐detritivorous soil animal groups studied was significantly increased in beech forests; only that of one group (elaterid beetles) was increased in spruce forests and three groups did not respond significantly (collembolans, oribatid mites, sciarid Diptera). This indicates that in the forests studied neither habitat space (amount of organic matter in L/F and H/Ah layers) nor the amount of microbial biomass controlled microbi‐detritivores. Rather, the quality of litter materials and the concentration of microbial biomass therein appeared to be most important. Herbivores and predators also were favoured by beech: the biomass of one (rhizophagous nematodes) of the three herbivorous groups studied were significantly increased in beech stands and none in spruce stands; the biomass of four (predatory nematodes, centipedes, carabid and cantharid beetles) of the seven carnivorous groups studied were increased in beech stands, none in spruce stands. Generally, the biomass ratio between prey and predators was at a minimum in mature beech and mixed stands indicating more intense top‐down control in these forests. Overall, the study documents that replacement of beech by spruce strongly alters the soil food web. Mixed stands were more similar to spruce stands in respect to the biomass of soil animal groups but predator–prey interactions appeared to be more similar in mature beech and mixed stands. Differences between tree species usually were more pronounced in 120 compared to 30 yr old stands indicating that the development of stand characteristics is slow.     

Increasing vole numbers cause more lethal damage to saplings in tree monocultures than in mixed stands

Overall, mammalian herbivores are more harmful in mixed plantations than in monocultures, but the effect of herbivore abundance has not been experimentally tested in this context. It has been proposed that there is a critical threshold density where herbivore pressure spreads from preferred plants to everything edible, leading to non-linear density effects on low-quality plants. We experimentally investigated whether survival of an unpalatable plant is similarly related to herbivore density in both monocultures and mixed stands. This we did by establishing monocultures of unpalatable black alder (Alnus glutinosa) and mixed stands of black alder and five more palatable tree species in enclosures, where Microtus voles were introduced and their abundances monitored.The effect of stand diversity tended to depend on vole abundance. Vole damage of tree saplings did not differ between monocultures and mixed stands, but at higher vole abundances attacks had a stronger effect on sapling survival in the monocultures. Sapling survival showed a significant drop in the monocultures at peak abundance of approximately 300 voles ha^?1. In monocultures herbivores do not have alternatives and therefore are forced to become deadlier consumers.     

The ectomycorrhizal community structure in high mountain Norway spruce stands

The species composition of ectomycorrhizal (ECM) fungal communities can be strongly influenced by abiotic and biotic factors, which determine interactions among the species such as resource partitioning, disturbance, competition, or relationships with other organisms. To verify whether ectomycorrhization of the root tips and composition of the ECM community in Norway spruce vary according to site features and if ECM species peculiar to these environmental variables can be detected, ten comparable stands differing in bedrock pH and exposure were selected and studied. The results demonstrated that tips vitality and ectomycorrhization degree do not change significantly either on the same tree, or among trees growing in the same stand, whereas they differ greatly with bedrock pH and exposure, even if no spatial or temporal trend were found. ECM species composition revealed instead a significant connection with the two environmental features, with a few species significantly associated to them. The results suggest that pH/exposure patterns play a primary role in the adaptive selection of ECM species constituting the consortium.     

Soil acidity and exchangeable base cation stocks under pure and mixed stands of European beech,Douglas fir and Norway spruce

Plant and Soil - The establishment of mixed forest stands is nowadays seen as an opportunity to maintain forest services in the course of global climate change. Thus, we determined forest floor and...     

Mycorrhizosphere responsiveness to atmospheric ozone and inoculation with Phytophthora citricola in a phytotron experiment with spruce/beech mixed cultures

The aim was to analyze functional changes in the mycorrhizosphere (MR) of juvenile spruce and beech grown in a mixture under ambient and twice ambient ozone and inoculated with the root pathogen Phytophthora citricola. The phytotron experiment was performed over two vegetation periods, adding the pathogen at the end of the first growing season. Root biomass data suggest that the combined treatment affected spruce more than beech and that the negative influence of ozone on stress tolerance against the root pathogen P. citricola was greater for spruce than for beech. In contrast, beech was more affected when the pathogen was the sole stressor. The functional soil parameter chosen for studies of MR soil samples was activity of extracellular enzymes. After the first year of ozone exposure, MR soil samples of both species showed increased activity of almost all measured enzymes (acid phosphatase, chitinase, beta-glucosidase, cellobiohydrolase) in the O3 treatment. Species-specific differences were observed, with a stronger effect of P. citricola on beech MR and a stronger ozone effect on spruce MR. In the second year, the effects of the combined treatment (ozone and P. citricola) were a significant increase in the activity of most enzymes (except cellobiohydrolase) for both tree species. The results indicated that responsiveness of MR soils towards ozone and P. citricola was related to the severity of infection of the plants and the reduction of belowground biomass, suggesting a strong, direct influence of plant stress on MR soil enzyme activity. Additional research is needed using different species and combined stresses to determine the broader ecological relevance of shifts in rhizosphere enzymes.     

Survival of Norway spruce remains higher in mixed stands under a dryer and warmer climate

Shifts in tree species distributions caused by climatic change are expected to cause severe losses in the economic value of European forestland. However, this projection disregards potential adaptation options such as tree species conversion, shorter production periods, or establishment of mixed species forests. The effect of tree species mixture has, as yet, not been quantitatively investigated for its potential to mitigate future increases in production risks. For the first time, we use survival time analysis to assess the effects of climate, species mixture and soil condition on survival probabilities for Norway spruce and European beech. Accelerated Failure Time (AFT) models based on an extensive dataset of almost 65 000 trees from the European Forest Damage Survey (FDS) – part of the European‐wide Level I monitoring network – predicted a 24% decrease in survival probability for Norway spruce in pure stands at age 120 when unfavorable changes in climate conditions were assumed. Increasing species admixture greatly reduced the negative effects of unfavorable climate conditions, resulting in a decline in survival probabilities of only 7%. We conclude that future studies of forest management under climate change as well as forest policy measures need to take this, as yet unconsidered, strongly advantageous effect of tree species mixture into account.     

Effects of N-free fertilization on ectomycorrhiza community structure in Norway spruce stands in Southern Sweden

The application of N-free fertilizer (i.e. lime combined with nutrients such as P, Ca, K and Mg) has been suggested as one way of compensating for nitrogen-caused eutrophication and losses of base cations due to atmospheric pollution. To study the effects of such a treatment on mycorrhizal fungi, fine-root samples were collected from the LFH-layer in four Norway spruce stands in southern Sweden. One stand was part of a larger experiment (Skogaby) and had four replicates. It was fertilized twice in 1988–89 (P:K:Ca:Mg:S 48:43:218:46:75 kg ha^-1), and sampling was carried out once yearly during 1991–93. The other three stands were fertilized once in 1988–89 (P:K:Ca:Mg:S|25:62:33:12:54 kg ha^-1) and sampled in 1992.Ectomycorrhizal fine-roots were classified into morphotypes on the basis of the structure and colours of their external hyphae and fungal mantle. The fungal biomass was estimated in 1992 using ergosterol analysis. In Skogaby, N-free fertilizer had no apparent effects on fungal biomass or on the total number of ECM types. Similar results were obtained for the other three stands. Previously reported 50% reductions in sporocarp production on the fertilized plots at Skogaby can probably be explained by a decrease in carbon allocation to the roots and by a decline in the abundance of a single morphotype which accounted for 3% of the total number of root tips, but ca. 30% of the sporocarp biomass in the control plots in the present study. It is concluded that moderate levels of N-free fertilization are not likely to drastically affect the community structure of the dominating ectomycorrhizal fungi. This result should be interpreted with some caution, however, since it remains to be determined whether the fertilizer treatments affect the function of the nutrient-absorbing soil mycelium of the mycorrhizal fungi.     

The symmetry of competitive interactions in mixed Norway spruce,silver fir and European beech forests

Questions

We aim for a better understanding of the different modes of intra‐ and inter‐specific competition in two‐ and three‐species mixed‐forests. How can the effect of different modes of competitive interactions be detected and integrated into individual tree growth models? Are species interactions in spruce–fir–beech forests more associated with size‐symmetric or size‐asymmetric competition? Do competitive interactions between two of these species change from two‐ to three‐species mixtures?

Location

Temperate mixed‐species forests in Central Europe (Switzerland).

Methods

We used data from the Swiss National Forest Inventory to fit basal area increment models at the individual tree level, including the effect of ecological site conditions and indices of size‐symmetric and size‐asymmetric competition. Interaction terms between species‐specific competition indices were used to disentangle significant differences in species interactions from two‐ to three‐species mixtures.

Results

The growth of spruce and fir was positively affected by increasing proportions of the other species in spruce–fir mixtures, but negative effects were detected with increasing presence of beech. We found that competitive interactions for spruce and fir were more related to size‐symmetric competition, indicating that species interactions might be more associated with competition for below‐ground resources. Under constant amounts of stand basal area, the growth of beech clearly benefited from the increasing admixture of spruce and fir. For this species, patterns of size‐symmetric and size‐asymmetric competitive interactions were similar, indicating that beech is a strong self‐competitor for both above‐ground and below‐ground resources. Only for silver fir and beech, we found significant changes in species interactions from two‐ to three‐species mixtures, but these were not as prominent as the effects due to differences between intra‐ and inter‐specific competition.

Conclusions

Species interactions in spruce–fir–beech, or other mixed forests, can be characterized depending on the mode of competition, allowing interpretations of whether they occur mainly above or below ground level. Our outcomes illustrate that species‐specific competition indices can be integrated in individual tree growth functions to express the different modes of competition between species, and highlight the importance of considering the symmetry of competition alongside competitive interactions in models aimed at depicting growth in mixed‐species forests.

     

Crown allometry and growing space efficiency of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) in pure and mixed stands

In pure and mixed stands of Norway spruce ( Picea abies [L.] Karst.) and European beech ( Fagus sylvatica L.) we have analyzed crown allometry and growing space efficiency at the tree level and have scaled this from tree level to stand level production. Allometry is quantified by the ratio A between the relative growth rates of laterally and vertically oriented tree dimensions. Efficiency parameters, EOC for efficiency in space occupation, EEX for efficiency in space exploitation, and EBI for efficiency in biomass investment, were evaluated, based on quantity and quality of growing space and were measured using crown size and competition index. The evaluation reveals why pure stands of spruce are preferred by foresters, even though the natural vegetation would be dominated by beech. Spruce occupies its share of resources intensively by means of tightly packed pillar-like crowns, whereas beech seizes resources extensively by means of a multi-layered, veil-like canopy. With a given relative biomass increment, beech achieves a 57 % higher increment in crown projection area and a 127 % higher increment in height due to its particular capacity of lateral and vertical expansion. Beech trees are approximately 60 % more efficient in space occupation than spruce trees, however, on average, they are about 70 % less efficient in space exploitation. As a vertical fast growing tree, spruce is efficient in space exploitation under constant conditions, but far more susceptible to disturbances and less well equipped to overcome them when compared with beech. Beech is weaker in terms of space exploitation, while being superior in space occupation, where it encircles competitors and fills gaps after disturbances, which is a successful long-term strategy. A mixture of the two species reduces stand level production by 24 % in comparison to a pure spruce stand, however, when considering enhanced stabilization of the whole stand and risk distribution in the long term, the mixed stand may exceed the production level of pure spruce stands. EEX reflects a strong ontogenetic drift and competition effect that should be considered when scaling from tree to stand level production.     

Relationships between tree dimension and coarse root biomass in mixed stands of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies[L.] Karst.)

Relationships between tree parameters above ground and the biomass of the coarse root system were examined in six mixed spruce-beech stands in the Solling Mountain region in northwest Germany. The selected stands were located on comparable sites and covered an age range of 44 to 114 years. Coarse roots (d?ge?2 mm) of 42 spruce and 27 beech trees were sampled by excavating the entire root system. A linear model with logarithmic transformation of the variables was developed to describe the relationship between the coarse root biomass (CRB, dry weight) and the corresponding tree diameter at breast height (DBH). The coefficients of determination (R ²) attained values between 0.92 for spruce and 0.94 for beech; the logarithmic standard deviation values were between 0.29 and 0.43. A significantly different effect of tree species on the model estimates could not be detected by an analysis of co-variance (ANCOVA). For spruce, the derived relationships were similar to those reported in previous studies, but not for beech. Biomass partitioning in the tree compartments above and below ground differs significantly between spruce (coarse root/shoot ratio 0.16±0.06) and beech (coarse root/shoot ratio 0.10±0.03) in the mixed stands. These results are similar to those given in other studies involving pure spruce and beech stands on comparable sites in the region, although the ratios of pure stands in other regions growing under different site conditions are somewhat higher. Comparing trees of the same DBH classes, root/shoot ratios of spruce are 1.2 to 3 times higher than those of beech. Dominant spruce trees (DBH>60 cm) attained the highest ratios, suppressed beech trees (DBH<10 cm) the lowest. Site conditions of varying climate and soils and interspecific tree competition are likely to affect root/shoot ratio and DBH-coarse root biomass relationships. The greater variability in beech compared with spruce indicates a high 'plasticity' and adaptability of beech carbon allocation. Thus, the derived equations are useful for biomass estimates of coarse roots involving trees of different ages in mixed stands of spruce and beech in the Solling Mountains. However, application of these relationships to stands in other regions would need further testing.     

Size‐dependence of tree growth response to drought for Norway spruce and European beech individuals in monospecific and mixed‐species stands

• Climate anomalies have resulted in changing forest productivity, increasing tree mortality in Central and Southern Europe. This has resulted in more severe and frequent ecological disturbances to forest stands. This study analysed the size‐dependence of growth response to drought years based on 384 tree individuals of Norway spruce [Picea abies (L.) Karst.] and European beech [Fagus sylvatica ([L.)] in Bavaria, Germany.
• Samples were collected in both monospecific and mixed‐species stands. To quantify the growth response to drought stress, indices for basal area increment, resistance, recovery and resilience were calculated from tree ring measurements of increment cores. Linear mixed models were developed to estimate the influence of drought periods.
• The results show that ageing‐related growth decline is significant in drought years. Drought resilience and resistance decrease significantly with growth size among Norway spruce individuals. Evidence is also provided for robustness in the resilience capacity of European beech during drought stress. Spruce benefits from species mixing with deciduous beech, with over‐yielding spruce in pure stands.
• The importance of the influence of size‐dependence within tree growth studies during disturbances is highlighted and should be considered in future studies of disturbances, including drought.

     

Greater accumulation of litter in spruce (Picea abies) compared to beech (Fagus sylvatica) stands is not a consequence of the inherent recalcitrance of needles

Background and aims

Replacement of beech by spruce is associated with changes in soil acidity, soil structure and humus form, which are commonly ascribed to the recalcitrance of spruce needles. It is of practical relevance to know how much beech must be admixed to pure spruce stands in order to increase litter decomposition and associated nutrient cycling. We addressed the impact of tree species mixture within forest stands and within litter on mass loss and nutritional release from litter.

Methods

Litter decomposition was measured in three adjacent stands of pure spruce (Picea abies), mixed beech-spruce and pure beech (Fagus sylvatica) on three nutrient-rich sites and three nutrient-poor sites over a three-year period using the litterbag method (single species and mixed species bags).

Results

Mass loss of beech litter was not higher than mass loss of spruce litter. Mass loss and nutrient release were not affected by litter mixing. Litter decay indicated non-additive patterns, since similar remaining masses under pure beech (47%) and mixed beech-spruce (48%) were significantly lower than under pure spruce stands (67%). Release of the main components of the organic substance (C_org, N_tot, P, S, lignin) and associated K were related to mass loss, while release of other nutrients was not related to mass loss.

Conclusions

In contradiction to the widely held assumption of slow decomposition of spruce needles, we conclude that accumulation of litter in spruce stands is not caused by recalcitrance of spruce needles to decay; rather adverse environmental conditions in spruce stands retard decomposition. Mixed beech-spruce stands appear to be as effective as pure beech stands in counteracting these adverse conditions.     

Structural crown properties of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica [L.]) in mixed versus pure stands revealed by terrestrial laser scanning

How tree morphology develops in mixed-species stands is essential for understanding and modelling mixed-stand dynamics. However, research so far focused on the morphological variation between tree species and neglected the variation within a species depending on intra- and interspecific competition. Our study, in contrast, addresses crown properties of nine mature Norway spruces (Picea abies [L.] Karst.) of a pure stand and compares them with ten spruces growing in mixture with European beech (Fagus sylvatica [L.]). The same was done with 11 pure stand beeches and 12 beeches growing in mixture with spruce. Through application of a terrestrial laser scanner and a new skeletonization approach, we deal with both species’-specific morphological traits such as branch angle, branch length, branch bending, crown volume and space occupation of branches within the crown, some of which were hardly accessible so far. Special attention is paid to distinct differences between trees growing in mixed and pure stands: for spruce, our study reveals significantly longer branches and greater crown volumes in the mixed stand when compared to the pure stand. In case of European beech, individuals growing in mixture show flatter branch angles, more distinct ramification, greater crown volumes and a lower share of a single branch’s space occupation in the total crown volume. The results show that the presented methods yield detailed information on the morphological traits analyzed in this study and that interspecific competition on its own may have a significant impact on crown structures. Implications for production ecology and stand dynamics of mixed-species forests are discussed.     

Changes in soil mineralogy and exchangeable cation pools in stands of Norway spruce planted on former pasture land

Chemical and mineralogical properties of the soils in 35- and 70-year-old stands of Norway spruce (Picea abies (L.) Karst), planted on former pasture and were studied at Asa Experimental Forest, southern Sweden. Remnant deciduous forests bordering the spruce stands were used as controls to assess possible tree-species-related effects on soil development. All soils are acid with little difference in soil pH between the spruce and deciduous stands. However, the saturation of the exchange complex with Mg is lower beneath spruce and the total exchangeable Mg pool in the upper meter of these soils is one third of the Mg store beneath the deciduous stands. Amphibole, biotite and chlorite are the major sources of Mg in the parent soil. The clay fraction of the topsoil beneath spruce has been depleted of all these easily weatherable ferromagnesian minerals. Apart from weathering-resistant primary silicates, the clay fraction consists almost exclusively of expandable, smectitic mixed-layer minerals, which are believed to be the products of advanced stages of biotite weathering. In contrast, vermiculite is the dominant secondary mineral in the A-horizon in the deciduous stands, and some chlorite has survived. Moreover, a greater depth of in situ weathering is indicated for the soil of the old spruce stands where biotite/vermiculite mixed-layers have formed in the C-horizon as products of early stages of biotite weathering. Thus, differences between the paired sites in soil solution chemistry are supported by the qualitative differences in soil mineralogy, and are believed to reflect divergent biotic and/or abiotic processes in the different stand types. This revised version was published online in August 2006 with corrections to the Cover Date.     

Root turnover in a beech and a spruce stand of the Belgian Ardennes

The theoretical basis of fine root turnover estimation in forest soils is discussed, in relation to appropriate experimental techniques of measurement. After sequential coring, the correct expression is the sum of significant positive increments of live and dead roots of the various diameter categories, to which the transfer of dead roots to organic matter derived from roots, OMDR, has to be added. This should not be confounded with dead root mineralization. The transfer rates should first be estimated in root dimensions and not in weight of dry matter. The measurements were carried out in a 120 year old beech (Fagus sylvatica L.) stand and a 35 year old Norway spruce (Picea abies Karst) stand, in the Eastern Ardennes, Belgium. The turnover rate of fine roots (diam. <5 mm) was 4393 kg ha⁻¹ year⁻¹ (root dry weight), including 711.2 kg ha⁻¹ year⁻¹ for dead root transfer to OMDR, for beech. For spruce, turnover rate was 7011 kg ha⁻¹ year⁻¹ (root dry weight), including 1498 kg ha⁻¹ year⁻¹ for dead root transfer to OMDR. Under beech, there was a slight root density increase in spring. No seasonal fluctuations were observed under spruce, but a strong irreversible drop in live root growth was found in the later season 1980–1981, corresponding to a decrease of tree height growth and trunk radius increment. Turnover rates were further expressed in dry weight and in amounts of elements (kg ha⁻¹ year⁻¹) (Ca, Mg, K, Na, Al, N, P, S). Correlative relations between root dimensions and dry weight and element concentrations show that the derived values, and in particular root specific density (dry weight volume⁻¹) vary according to species, root category, and seasonal sampling. Various schemes of seasonal variations of root growth, described in Europe, show that the major dependance on general climate is obscured by environmental factors (soil, exposure, species). It is suggested that root density fluctuation approach the steady state on an annual basis under mild Atlantic conditions.     

筛选生物转化H_2/CO_2气体产乙酸的同型产乙酸菌混培物

同型产乙酸菌是一类具有巨大工业应用潜力的微生物类群,可利用合成气生成乙醇和乙酸等燃料和化学品。本研究采集城市污泥样品利用Hungate滚管法进行同型产乙酸菌的筛选,并利用其进行H2/CO2气体的生物转化,研究了p H对其乙酸和乙醇生成情况的影响。结果表明,所获得的同型产乙酸菌混培物组成为永达尔梭菌,纺缍形赖氨酸芽胞杆菌和蜡样芽胞杆菌等。该混培物最适p H为5-7。p H为7时混培物利用H2/CO2气体得到乙酸浓度可达到31.69 mmol/L。本研究获得了一种可利用H2/CO2合成乙酸的同型产乙酸菌混培物,为合成气生物转化的工业应用提供了有效的微生物资源。     

Fire severity mediates climate‐driven shifts in understorey community composition of black spruce stands of interior Alaska

Question: How do pre‐fire conditions (community composition and environmental characteristics) and climate‐driven disturbance characteristics (fire severity) affect post‐fire community composition in black spruce stands? Location: Northern boreal forest, interior Alaska. Methods: We compared plant community composition and environmental stand characteristics in 14 black spruce stands before and after multiple, naturally occurring wildfires. We used a combination of vegetation table sorting, univariate (ANOVA, paired t‐tests), and multivariate (detrended correspondence analysis) statistics to determine the impact of fire severity and site moisture on community composition, dominant species and growth forms. Results: Severe wildfires caused a 50% reduction in number of plant species in our study sites. The largest species loss, and therefore the greatest change in species composition, occurred in severely burned sites. This was due mostly to loss of non‐vascular species (mosses and lichens) and evergreen shrubs. New species recruited most abundantly to severely burned sites, contributing to high species turnover on these sites. As well as the strong effect of fire severity, pre‐fire and post‐fire mineral soil pH had an effect on post‐fire vegetation patterns, suggesting a legacy effect of site acidity. In contrast, pre‐fire site moisture, which was a strong determinant of pre‐fire community composition, showed no relationship with post‐fire community composition. Site moisture was altered by fire, due to changes in permafrost, and therefore post‐fire site moisture overrode pre‐fire site moisture as a strong correlate. Conclusions: In the rapidly warming climate of interior Alaska, changes in fire severity had more effect on post‐fire community composition than did environmental factors (moisture and pH) that govern landscape patterns of unburned vegetation. This suggests that climate change effects on future community composition of black spruce forests may be mediated more strongly by fire severity than by current landscape patterns. Hence, models that represent the effects of climate change on boreal forests could improve their accuracy by including dynamic responses to fire disturbance.     

Carbon dynamics in successional and afforested spruce stands in Thuringia and the Alps

Changes in the carbon stocks of stem biomass, organic layers and the upper 50 cm of the mineral soil during succession and afforestation of spruce (Picea abies) on former grassland were examined along six chronosequences in Thuringia and the Alps. Three chronosequences were established on calcareous and three on acidic bedrocks. Stand elevation and mean annual precipitation of the chronosequences were different. Maximum stand age was 93 years on acid and 112 years on calcareous bedrocks. Stem biomass increased with stand age and reached values of 250–400 t C ha^?1 in the oldest successional stands. On acidic bedrocks, the organic layers accumulated linearly during forest succession at a rate of 0.34 t C ha^?1 yr^?1. On calcareous bedrocks, a maximum carbon stock in the humus layers was reached at an age of 60 years. Total carbon stocks in stem biomass, organic layers and the mineral soil increased during forest development from 75 t C ha^?1 in the meadows to 350 t C ha^?1 in the oldest successional forest stands (2.75 t C ha^?1 yr^?1). Carbon sequestration occurred in stem biomass and in the organic layers (0.34 t C ha^?1 yr^?1on acid bedrock), while mineral soil carbon stocks declined. Mineral soil carbon stocks were larger in areas with higher precipitation. During forest succession, mineral soil carbon stocks of the upper 50 cm decreased until they reached approximately 80% of the meadow level and increased slightly thereafter. Carbon dynamics in soil layers were examined by a process model. Results showed that sustained input of meadow fine roots is the factor, which most likely reduces carbon losses in the upper 10 cm. Carbon losses in 10–20 cm depth were lower on acidic than on calcareous bedrocks. In this depth, continuous dissolved organic carbon inputs and low soil respiration rates could promote carbon sequestration following initial carbon loss. At least 80 years are necessary to regain former stock levels in the mineral soil. Despite the comparatively larger amount of carbon stored in the regrowing vegetation, afforestation projects under the Kyoto protocol should also aim at the preservation or increase of carbon in the mineral soil regarding its greater stability of compared with stocks in biomass and humus layers. If grassland afforestation is planned, suitable management options and a sufficient rotation length should be chosen to achieve these objectives. Maintenance of grass cover reduces the initial loss.