Total Amount Of Carbon Research Articles

Estimation of biomass and sequestered carbon on farm forest plantations in northern New South Wales, Australia

Tree stem diameters were measured in a stratified random sample of plots in each of 19 forest plantation estates in northern New South Wales. The estates were 0.2– 170 ha in area and the plantations were 1–10 years old, growing eucalypts, sub-tropical rainforest species or an exotic conifer, both in single-species and mixed-species plantations. A sample of trees was measured also for biomass and estate- and region-specific allometric relationships developed to predict tree biomass from tree diameter. With the stratified random sample data, the allometric relationships were used to predict the total amount of carbon sequestered in tree biomass, and its 95% confidence limit, across each estate. These results were compared with estimates made using an allometric relationship from Nova Scotia, Canada, and a stand-based relationship from Australia. Bias in estimates made using the region-specific or Nova Scotia relationships appeared to be unimportant if the confidence limit was >10% of the estimate. Bias was greater using the stand-based relationship and was unimportant only if the confidence limit was >30% of the estimate. It was concluded that using sampling intensities of around 2–4% of the estate area, the total carbon sequestered by an individual small plantation estate in the region could generally be estimated satisfactorily with a 95% confidence limit of about 30–40% of the estimate or better, with a minimum of about 10%. Generally, the younger the plantation estate, the higher was the sampling intensity necessary to achieve the same precision of estimate as in older estates. If small plantation owners in the region are intending to offer sequestered carbon for sale as carbon credits, it appeared it will be difficult for them to estimate carbon sequestration by their trees with a 95% confidence limit as low as the present Australian recommendation of 10% of the estimate. If owners pooled their estates in a cooperative, they should be better able to achieve the required confidence limit from the much larger, pooled estate. Analysis of organic carbon contents of soil below plantations and adjacent pasture paddocks suggested there was a decline in soil carbon with time following plantation establishment. Growers will need to account for these losses when estimating the total carbon sequestered by their plantations ecosystems.

Carbon solubility in olivine and the mode of carbon storage in the Earth's mantle.

The total amount of carbon in the atmosphere, oceans and other near-surface reservoirs is thought to be negligible compared to that stored in the Earth's mantle. Although the mode of carbon storage in the mantle is largely unknown, observations of microbubbles on dislocations in minerals from mantle xenoliths has led to the suggestion that carbon may be soluble in silicates at high pressure. Here we report measurements of carbon solubility in olivine, the major constituent of the upper mantle, at pressures up to 3.5 GPa. We have found that, contrary to previous expectations, carbon solubility in olivine is exceedingly low--of the order of 0.1 to 1 parts per million by weight. Together with similar data for pyroxenes, garnet and spinel, we interpret this to imply that most carbon must be present as a separate phase in the deeper parts of the upper mantle, probably as a carbonate phase. Large-scale volcanic eruptions tapping such a carbonate-bearing mantle reservoir might therefore rapidly transfer large amounts of carbon dioxide into the atmosphere, consistent with models that link global mass extinctions to flood basalt eruptions via a sudden increase in atmospheric carbon dioxide levels.

Spatial Analysis of Soils, Vegetation, Productivity, and Carbon Stored in Mountain Tundra Ecosystems, Khibiny Mountains, Russia

Data on the distribution of plant communities, their productivity, and major carbon stores held in mountain tundra vegetation and soils are presented. Extreme snow-bed communities had the lowest total biomass (662 g/m2), primarily in the main root portion in mineral soil horizons. Dwarf shrub-dominated heath on a gentle mountain slope had the highest total biomass (2406 g/m2), with woody perennial stems prevailing in the above-ground portion, and the main root portion concentrated in the organic horizon. Grass and sedge meadows situated in a hollow had the greatest total net primary production (215 g/m2), and roots were evenly distributed throughout the soil profile. The total amount of carbon stored in the ecosystem included carbon stored in above- and below-ground biomass, in the organic horizon, and in mineral soil horizons to a depth of 30 cm. Total carbon was lowest in snow-bed and lichen-dominated tundra (6183 g/m2 and 6337 g/m2, respectively), and highest in dwarf shrubs and grass-dominated tundra (25,261 g/m2 and 20,407 g/m2, respectively), the latter being comparable to total carbon stored in boreal forest ecosystems. Most of the carbon (95-97%) in tundra ecosystems was stored in soils (organic and mineral soil horizons).

Scenario analysis of the impacts of forest management and climate change on the European forest sector carbon budget

Analysis of the impacts of forest management and climate change on the European forest sector carbon budget between 1990 and 2050 are presented in this article. Forest inventory based carbon budgeting with large scale scenario modelling was used. Altogether 27 countries and 128.5 million hectare of forests are included in the analysis. Two forest management and climate scenarios were applied. In Business as Usual (BaU) scenario national fellings remained at the 1990 level while in Multifunctional (MultiF) scenario fellings increased 0.5–1% per year until 2020, 4 million hectare afforestation program took place between 1990 and 2020 and forest management paid more attention to current trends towards more nature oriented management. Mean annual temperature increased 2.5 °C and annual precipitation 5–15% between 1990 and 2050 in changing climate scenario. Total amount of carbon in 1990 was 12 869 Tg, of which 94% in tree biomass and forest soil, and 6% in wood products in use. In 1995–2000, when BaU scenario was applied under current climatic conditions, net primary production was 409 Tg C year −1, net ecosystem production 164 Tg C year −1, net biome production 84.5 Tg C year −1, and net sequestration of the whole system 87.4 Tg C year −1 which was equal to 7–8% of carbon emissions from fossil fuel combustion in 1990. Carbon stocks in tree biomass, soil and wood products increased in all applied management and climate scenarios, but slower after 2010–2020 than that before. This was due to ageing of forests and higher carbon densities per unit of forest land. Differences in carbon sequestration were very small between applied management scenarios, implying that forest management should be changed more than in this study if aim is to influence carbon sequestration. Applied climate scenarios increased carbon stocks and net carbon sequestration compared to current climatic conditions.

Influences of forest decline on various properties of soils on Mt. Hirugatake, Tanzawa Mountains, Kanto District, Japan

At Mt. Hirugatake, Tanzawa Mountains, the deciduous broadleaved forest has declined rapidly since the 1970s. Six study sites under different degrees of forest decline were selected at Mt. Hirugatake, Tanzawa Mountains as follows: site with healthy deciduous broadleaved forest (DBF), site with slight forest decline (SFD), site with distinct forest decline (DFD), sites with heavy forest decline 1 and 2 (HD1 and HD2), and site with Sasa-type grassland (SG). In the present study, the changes in the physical and chemical properties of the surface soil to the depth of 10 cm with that order of forest decline were investigated in nine sub-samples from each quadrat (10 m × 10 m) at each site. With forest decline, the bulk density tended to increase, and porosity, especially macropores, tended to decrease significantly. Although the soil pH decreased at the SFD site, no significant differences were found in the soil pH between the DBF site and the other sites. The amount of exchangeable aluminum was well correlated with the soil pH, but showed no significant differences between the DBF site and other sites, except for the SFD site. Thus, forest decline at Mt. Hirugatake, Tanzawa Mountains was not caused by aluminum stress, as suggested in the previous study (Higashi et al.: Soil. Sci. Plant Nutr., 49, 161'169, 2003). The amount of total carbon of soils markedly decreased at the early and the latest stages of forest decline; a decrease of about 34% was observed at the SG site compared with the DBF site.

Plankton carbon budget in a coastal wind-driven upwelling station off A Coruña (NW Iberian Peninsula)

Seasonal variations in phytoplankton and bacterial biomass along with rates of primary pro- duction, dissolved organic carbon (DOC) release, bacterial production, dark respiration and vertical par- ticle flux were determined from December 1998 to September 1999 at a coastal station off A Coruna (NW Spain) affected by episodes of wind-driven upwelling. Maximum phytoplankton biomass and produc- tion was associated with upwelling events. Bacterial biomass remained relatively constant throughout the study and was always lower than phytoplankton biomass. Depth-integrated rates of DOC release, which ranged from 0.2 to 3.1 gC m -2 d -1 , were not a constant fraction of the total amount of carbon incorporated by primary producers. On average, DOC release accounted for 37 ± 7% of total primary production, and the highest values were measured during low-productivity periods. The supply of DOC by microplankton was globally sufficient to support the estimated bacterial activity, although a tempo- ral shift between DOC release and bacterial consumption was observed. Primary production exceeded respiration during most of the seasonal study, with production/respiration ratios ranging from 1 to 7. The annual averaged daily net community production was 253 (±105) mmol O2 m -2 d -1 . The amount of par- ticulate organic carbon exported from the euphotic layer was 1 to 86% of total primary production. The results of this study indicate that the coastal system is autotrophic, and suggest that most of the organic matter produced photosynthetically was channelled through the microbial food web.

Peatlands of the Western Siberian lowlands: current knowledge on zonation, carbon content and Late Quaternary history

The Western Siberian lowlands (WSL) are the world's largest high-latitude wetland, and possess over 900,000 km 2 of peatlands. The peatlands of the WSL are of major importance to high-latitude hydrology, carbon storage and environmental history. Analysis of the existing Russian data suggests that the mean depth of peat accumulation in the WSL is 256 cm and the total amount of carbon stored there may exceed 53,836 million metric tons. A synthesis of published and unpublished radiocarbon dates indicates that the peatlands first developed at the end of the Last Glacial, with a rapid phase of initiation between 11,000 and 10,000 cal yr BP. Initiation slowed after 8000 cal yr BP and reached a nadir at 4000 cal yr BP. There has been renewed initiation, particularly south of 62°N, following 4000 cal yr BP. The initial development of peatlands in the WSL corresponds with the warming at the close of the Pleistocene. Cooling after 4000 Cal yr BP has likely led to increased permafrost and increased peatland development particularly in central and southern regions. Cold and dry conditions in the far north may have inhibited peatland formation in the late Holocene.

Specific dynamic action and carbon incorporation in Calanus finmarchicus copepodites and females

Specific dynamic action (SDA) and incorporation of carbon into protein, lipids, and polysaccharides were measured in copepodite CV and adult female Calanus finmarchicus during the spring/summer growth season in Raunefjorden, Norway. Organic carbon from the food ( Rhodomonas baltica) was allocated differently in the two developmental stages. Copepodites incorporated 50–80% of the carbon into lipids and only 7–22% into protein. Carbon incorporation into protein was higher in females, constituting 23% in May at 7 °C and 34% in June at 11 °C. This resulted in significant differences in the magnitude of SDA, measured as the increase in oxygen consumption during and after an 8-h feeding event. On average, the rate of carbon incorporation into protein was 2 times higher and the magnitude of SDA was 2.5 times higher in females than in copepodites. There was a significant correlation between the magnitude of SDA and carbon incorporation into protein suggesting that SDA is linked to protein synthesis. When comparing ATP equivalents of the magnitude of SDA with ATP equivalents of the total amount of carbon incorporated, more energy was produced than consumed. This supports speculations of an energy demand associated with a rapid turnover of newly synthesised protein.

Simple spatially distributed model of the global carbon cycle and its dynamic properties

A specially simplified spatially distributed model of the global carbon cycle (GCC) is presented that is allowed to get a general solution and to study its basic dynamic properties (like spectral portrait, composition and decomposition of solutions, etc.). Assuming that the productivity depends linearly on concentration of carbon in the atmosphere, the problem is reduced to a standard linear one. In order to exclude the oceanic part of the GCC a parameterisation based on a principal difference of characteristic times between the terrestrial and oceanic parts is used. For calibration the Bazilevich data containing information on plant productivity, living biomass and soil organic matter of different biomes is used. Calculating the matrix eigenvalues of the basic linear problem we get its spectral portrait. It shows that there are neither specific characteristic times nor a fibering of phase space, which could allow to construct correct asymptotics: characteristic times change sufficiently smoothly from several years to several hundreds. Among all the exponentially damped solutions there are three oscillating ones with very long periods: from 117 to 4000 years. This portrait is very stable in relation to variations in the areas, covered by different biomes. Therefore, the terrestrial part of the GCC is a well-structured dynamic system with very wide opportunities to compensate disturbances with different time characteristics. Note that the general solution is very sensitive to the spatial distributions of productivity, living biomass and soil organic matter but all these patterns are uncertain. Certainly, the atmosphere is a natural integrator of local carbon flows, and we can hope that then different uncertainties partially compensate one another, when we estimate the total amount of carbon in the atmosphere. On the other hand, any distribution is described by its statistical moments and namely these moments are very robust in respect to numerical meanings of the distributed value. A special operation of convolution to the general solution of a spatially distributed model is suggested. This allows getting a dependence of convoluted solution on first moments such as means and covariances. However, it is necessary to note that instead of the distributions of living biomass and dead organic matter in soils the distributions of inverse residence times of carbon in different types of vegetation and soils have to be considered. One can see that non-homogeneity of these distributions on the whole increases the amount of carbon in the atmosphere. If comparing our prognosis with the prognoses of others with using more ‘complex’ and ‘geographically explicit’ models, then the difference will be incidental.

Study of angular influence of C3H5+ ion deposition on polystyrene surfaces using molecular dynamics simulations

The influence of incident angle on the interaction of polyatomic hydrocarbon ions (C3H5+) with polystyrene surfaces is examined using classical molecular dynamics simulations. The forces are determined using the reactive empirical bond order method developed by Tersoff and parametrized by Brenner. The total incident energy is 50 eV and the angles considered are 0° (normal to the surface), 15°, 45°, and 75°. At each angle, the outcomes of 80 trajectories are compiled and averaged. The results show that intact ions scatter from the surface in only 2% of the trajectories and that the ions dissociate in 61% of the trajectories at normal incidence. At 75°, intact ions scatter away in 56% and they dissociate in only 30% of the trajectories. The largest total amount of carbon is deposited at normal incident angles. However, more ions or ion fragments are predicted to remain near the surface (penetrate 3.5–5.5 Å) at 45°. This is because ion fragments tend to penetrate more deeply (6–7 Å) into the surface at smaller angles. Consequently, some inclined angles are found to be most efficient for the deposition of the precursors necessary for polymer thin-film growth.

Variability in the emission of carbon‐based trace gases from wildfire in the Alaskan boreal forest

A study was carried out to assess the variability in trace gas emission from several factors and to estimate the immediate impact of fire on carbon exchange. Using geospatial data, a model of emission was developed for three carbon‐based gases, CO2, CO, and CH4, released during fires from 1950 through 1999 in the boreal region of Alaska. The effect of two factors in the model were investigated: the fractions of carbon consumed and the ratio of flaming to smoldering combustion. We chose 4 years with which to investigate the range of outcomes. An average of 4.5 teragrams of carbon (TgC) has been released annually over the past 50 years. Severe fire years can produce emissions as high as 38 TgC. Wide variations in emissions of total carbon and carbon‐based gas were seen between years. Variations in the estimates of the fractions of biomass consumed during the burn influenced the amount of total carbon emitted; however, the annual area burned strongly determines total carbon released each year, regardless of fraction consumed. Assumptions regarding flaming versus smoldering fire influenced levels of emissions of CO and CH4. These estimates show that wildfire in Alaska's boreal region has contributed a substantial amount of carbon‐based gas to the atmosphere over the five decades of fire records.

High-temperature oxidation of dispersed soot particles by O atoms

The reaction of O atoms with soot particles dispersed in 10 to 20 ppm N 2 O/Ar mixtures was studied at high temperatures behind reflected shock waves. Under the present conditions ( T >1900 K), N 2 O represents a fast thermal O-atom source, because it decomposes rapidly to form O atoms which in turn react with the dispersed soot particles. The progress in the heterogeneous reaction was determined by time-resolved measurements of O-atom concentration using the highly sensitive atomic resonance absorption spectroscopy. Besides the absorption of the OI radiation ( λ =130.5 nm) by O atoms, the absorption signal includes also particle light extinction. A separation of both influences is possible by performing additional experiments on pure soot/Ar aerosols. Laser light extinction measurements using an Ar + laser ( λ =488.0 nm) were performed simultaneously providing a relationship between the particle extinction at both wavelengths, which allows us to determine the pure O-atom absorption in aerosols. The reaction conditions were chosen such that the total amount of carbon is much higher than the total amount of atomic oxygen: that is, the reaction conditions are pseudo-first-order. A rate coefficient for the consumption of O atoms due to soot particle oxidation was determined. CO was identified to be the main reaction product. To determine the heterogeneous reaction probability from the O-atom consumption rate, it is essential to measure the reactive particle surface. This quantity can be determined from the soot volume fraction available from the laser light extinction.

Changes in Area and Carbon in Forests of the Middle Zavolgie: A Regional Case Study of Russian Forests

We studied forest land-use and carbon storage over a 40-year period in the Middle Zavolgie region of Russia, an area of approximately 287,000 km2. Data were obtained from state forest inventories for 1958 and 1995. In spite of the effects of disturbances and uncontrolled harvesting between 1958 and 1990, the forests of the Middle Zavolgie Region remained a considerable pool of ecosystem carbon (C). Over the study period the total area of forest lands decreased by approximately 2%, while the growing stock increased by 8%. There were significant changes in the age class structure of these forest ecosystems toward a larger proportion of young and middle aged stands. The total amount of carbon in the stem biomass of forests in all regions of Middle Zavolgie increased over the 40-year period and was equal to about 307 TgC in 1995. A regional approach for estimating the C dynamics of forest ecosystems in response to land use in the Middle Zavolgie region can contribute to understanding the potential role of Russian forests in C sequestration. This information is important for implementation of international conventions concerning national carbon budgets and reducing the potential negative impacts of climate change.

Which rotation length is favourable to carbon sequestration?

Regulating the rotation length of tree stands is an effective way to manage the carbon budget of forests. We analyzed, using models, how a 30-year change in rotation length from the recommended 90 years would change the carbon and energy budgets of typical wood-production and wood-use chains in Finland. Shortening the rotation length towards the culmination age of mean annual increment decreased the carbon stock of trees but increased the carbon stock of soil, because the production of litter and harvest residues increased. Changes in the carbon stock of wood products varied with tree species depending on volumes and timber sorts harvested, manufacturing processes and products manufactured. The Scots pine (Pinus sylvestris L.) chain stored the largest total amount of carbon when applying the longest rotation length and the Norway spruce (Picea abies (L.) Karst.) chain, when applying the shortest rotation length. Fossil carbon emissions and energy use in harvesting and manufacture increased when the rotation length was shortened and pulpwood harvests increased, especially in the spruce chain. We concluded that longer rotation length at the sites of both tree species would be favourable to carbon sequestration. The costs of this would be decreased timber harvests and decreased revenues of landowners. Our results demonstrate the importance of accounting for the whole wood-production and wood-use chain, including fossil carbon emissions, when analysing the effects of rotation length on forest carbon sequestration.

Nanoflagellate predation on auto- and heterotrophic picoplankton in the oligotrophic Mediterranean Sea

Dynamics of autotrophic and heterotrophic prokaryotes and their consumption by nanoflagellates were studied in the euphotic zone at nine stations located from the Levantine Basin (34°E) to the Balearic sea (5°E) in June 1999. Bacterial biomass constituted the largest proportion of living biomass at all stations. Integrated bacterial production at the furthest east station, was sixfold lower than integrated bacterial production at the furthest west (13 and 75 mg C m−2 d−1 respectively). Estimated heterotrophic nanoflagellate bacterivory accounted for 45–87% of bacterial production. Small protists (<3 μm) dominated the bacterivore assemblage and accounted for more than 90% of the heterotrophic bacterial consumption. Our results indicated that there was no negative selection against Synechococcus and that both picoplankton groups were grazed according to their standing stocks. An estimated consumption of Synechococcus derived from food vacuole content analysis of nanoflagellates revealed that they consumed from 0.5 to 45% (mean 13%) of Synechococcus stock per day. These data are among the first documenting the relative grazing impact of heterotrophic nanoflagellates on bacteria and Synechococcus in situ. Assuming that there was no selection for or against Prochlorococcus, heterotrophic nanoflagellates could ingest from 1.4 to 21% (mean 6%) of Prochlorococcus stock per day. The amount of organic carbon obtained by heterotrophic nanoflagellates from photosynthetic prokaryotes represented 27% of the total amount of carbon obtained from total prokaryotes

Influence of weather conditions and soil properties on degradation of biodegradable plastics in soil

Climatic and soil factors responsible for the degradation of biodegradable plastics in soil were analyzed by placing poly-(3-hydroxy-butylate-valerate) (PHB/V), poly-(ɛ:-caprolactone) (PCL), poly-(butylene succinate) (PBS), poly-butylene succinate and adipate) (PBSA), and poly-lactide (PLA) in soil at 19sites in Honshu Island, Japan for 12 months. Degradation was determined every 3 months by collecting sample specimens for the measurement of weight loss. All the polymers were found to be degradable in soil. The degradation was faster, with the following order: PBSA=PHB/V=PCL > PBS> PLA. The sum of effective temperatures (over 10°C) was correlated with the degradation of PHB/V, PCL, PBS, and PBSA. Among the soil factors, the amount of total nitrogen in soil showed a correlation with the degradation of the polymers at various sampling times. On the contrary, the amount of total carbon, the pH, and the soil texture did not show a good correlation with the degradation of the tested biodegradable plastics.

Carbon layers in the divertor of ASDEX Upgrade

One of the main disadvantages of carbon as first wall material in a fusion device is the co-deposition of hydrogen with the eroded carbon. These layers will contain a significant amount of the tritium inventory of a fusion reactor. After venting brownish layers and flakes were found under the divertor structure of ASDEX Upgrade. First investigations were made on these flakes. Due to the complicated structure beyond the divertor, shadowing effects occur indicating that the brown layers are deposited by ionised particles. The flakes were analysed using SEM and ion beam techniques. Two different types of hydrocarbon layers were found: The brownish hydrogen poor layer (D/C = 0.4) and transparent hydrogen rich layer (D/C = 1) The total amount of carbon beyond the divertor could be estimated to 1.5 g, deposited in 3000 s of plasma discharges. First measurement of the layer growth using a quartz crystal microbalance instrument is presented.

Productivity overshadows temperature in determining soil and ecosystem respiration across European forests

SummaryThis paper presents CO2 flux data from 18 forest ecosystems, studied in the European Union funded EUROFLUX project. Overall, mean annual gross primary productivity (GPP, the total amount of carbon (C) fixed during photosynthesis) of these forests was 1380 ± 330 gC m−2 y−1 (mean ±SD). On average, 80% of GPP was respired by autotrophs and heterotrophs and released back into the atmosphere (total ecosystem respiration, TER = 1100 ± 260 gC m−2 y−1). Mean annual soil respiration (SR) was 760 ± 340 gC m−2 y−1 (55% of GPP and 69% of TER).Among the investigated forests, large differences were observed in annual SR and TER that were not correlated with mean annual temperature. However, a significant correlation was observed between annual SR and TER and GPP among the relatively undisturbed forests. On the assumption that (i) root respiration is constrained by the allocation of photosynthates to the roots, which is coupled to productivity, and that (ii) the largest fraction of heterotrophic soil respiration originates from decomposition of young organic matter (leaves, fine roots), whose availability also depends on primary productivity, it is hypothesized that differences in SR among forests are likely to depend more on productivity than on temperature.At sites where soil disturbance has occurred (e.g. ploughing, drainage), soil espiration was a larger component of the ecosystem C budget and deviated fromthe relationship between annual SR (and TER) and GPP observed among the less‐disturbed forests. At one particular forest, carbon losses from the soil were so large, that in some years the site became a net source of carbon to the atmosphere. Excluding the disturbed sites from the present analysis reduced mean SR to 660 ± 290 gC m−2 y−1, representing 49% of GPP and 63% of TER in the relatively undisturbed forest ecosystems.

Influence of oxygen on the carbide formation on tungsten

As a first wall material in nuclear fusion devices, tungsten will interact with carbon and oxygen from the plasma. In this study, we report on the process of thermally induced carbide formation of thin carbon films on polycrystalline tungsten and the influence of oxygen on this process. All investigations are performed using X-ray photoelectron spectroscopy (XPS). Carbon films are supplied through electron beam evaporation of graphite. The carbidization process, monitored during increased substrate temperature, can be divided into four phases. In phase I disordered carbon converts into graphite-like carbon. In phase II significant diffusion and the reaction to W 2C is observed, followed by phase III which is dominated by the presence of W 2C and the beginning reaction to WC. Finally in phase IV only WC is present, but the total carbon amount has strongly decreased. Different mechanisms of oxygen influence on the carbide formation are proposed and measurements of the reaction of carbon on tungsten with intermediate oxide layers are presented in detail. A WO 2+ x intermediate layer completely inhibits the carbide formation, while a WO 2 layer leads to WC formation at temperatures above 1270 K.

Effects of management and altitude on bryophyte species diversity and composition in montane calcareous fens

Summary We examined patterns of bryophyte species richness and communities in 36 montane calcareous fens in Switzerland. Sites differed in management regime (grazing vs. mowing) and altitude. In addition, several environmental variables were measured. Bryophyte diversity was determined as species density (mean of 5 plots per site), as species richness (number of all species of a site) and as β-diversity. Species richness was 20% higher at grazed than at mown sites. We interpret this as the result of higher environmental heterogeneity at grazed sites. This could also be the cause for the significantly higher β-diversity at grazed sites. However, there was a significant management × altitude interaction caused by species-poor sites at low altitudes under grazing. This interaction might be caused by more intensive grazing at low altitude. Grazed sites contained the higher overall species richness (117 vs. 79), more exclusive species (47 vs. 9), and more Red List-species (12 vs. 6). Altitude had only an effect on the number of exclusive species, which was highest at high-altitude sites. No differences could be found for species densities both between management regimes and between altitude classes. This result indicates no differences in habitat heterogeneity at the within-plot scale. For analysis of effects of environmental variables on bryophyte communities, we used a direct ordination technique (CCA). The variables pH, amount of total carbon in the soil and management turned out to be the most important in explaining variation in the species data. However, variation explained by total carbon could also be explained in terms of total nitrogen or moisture. For preserving bryophyte diversity in montane wet meadows, extensive grazing by cattle is crucial. Due to slightly different bryophyte communities under the different management regimes, however, bryophyte diversity at the landscape level will be highest when both types of management are maintained.