Nutrient-rich Sites Research Articles

Diatom ecological guilds display distinct and predictable behavior along nutrient and disturbance gradients in running waters

Three diatom ecological guilds were distinguished based on their potential to tolerate nutrient limitation and physical disturbance, i.e. a low profile, high profile, and motile guild. The guild distributions were examined along nutrient and flow disturbance gradients and across habitats in two extensively sampled streams. The guilds showed distinct distributional patterns, i.e. the low profile guild was favored in nutrient-poor and high disturbance habitats; the high profile guild reached a maximum in nutrient-rich sites and in conditions of low flow disturbance; and the motile guild increased along the nutrient gradients and decreased along the disturbance gradient. Guild distribution was habitat-specific: the low profile guild dominated the epipsammon, the high profile guild showed preference for epilithon and epiphyton, and the motile guild—for epipelon. The highest guild diversity was observed at high nutrient levels across all habitats, at higher flow disturbance levels, and in the epipelon and epiphyton. Comparisons of species, guild, and environmental distances, derived from species counts, guild abundance, and physico-chemical data, respectively, revealed high congruence between species–environment and guild–environment correlations. The predictable behavior of the three ecological guilds along nutrient and disturbance gradients, and across major benthic habitats elucidates the functional value of different diatom growth morphologies in species–environment interactions and suggests a potential use in ecological assessments of human-impacted ecosystems.

Soil carbon stocks, mineralization rates, and CO2 effluxes under 10 tree species on contrasting soil types

Afforestation can increase soil organic carbon (SOC) storage, but the selection of tree species may be critical. This study explored soil CO2 production and effluxes in relation to SOC contents in temperate forests. Sites included even-aged (38 years) first generation stands of eight coniferous and two deciduous species planted at three sites along a gradient in soil fertility. SOC stocks (forest floor + mineral soil 0–50 cm) differed significantly between tree species, but soil type influenced SOC stocks the most. SOC stocks were significantly higher for stands on low-fertility sandy soils (141 ± 31 Mg C·ha–1) than stands on fertile loamy soils (62 ± 14 Mg C·ha–1). Soil CO2 effluxes were measured on two occasions in 2002 and varied between 18.7 and 36.3 kg C·ha–1·day–1. Variability within temperature-adjusted fluxes was not clearly related to tree species or soil type. Potential CO2 production rates in a laboratory incubation experiment (reported as CO2 produced per unit soil C) were mainly affected by site and were two times higher for soils from the nutrient-rich site compared with the most nutrient-poor site. Thus, the combined effect of contrasting CO2 production rates and stocks of soil C may explain the similar CO2 effluxes measured in the field. Results suggest that selection of soil type and tree species are important for SOC sequestration in future afforestation projects.

Ecological interpretation of changes in the dutch flora in the 20th century

This article presents an ecological interpretation of the changes in the vascular flora of the Netherlands during the 20th century, paying attention to survey bias and the impact of environmental and nature conservation policies from 1970 onwards. In the course of the 20th century, some 10 million records of 1500 vascular plant species were sampled on a 1 km grid scale. These data were divided into three periods: 1902–1950, 1975–1988 and 1988–2000, and for each period and species total national presence were calculated. To interpret the ecological significance species were aggregated into 83 ‘ecological groups’ using a classification based on five ecological site factors. The changes of these ecological groups were statistically analysed by redundancy analysis. The principal change observed throughout the whole of the 20th century is a marked decline in vegetation types of nutrient-poor sites, particularly those on neutral soils, and at the same time a large increase in those of (moderately) nutrient-rich sites. The second most important change was a decline in saline vegetation types especially between the first and second period. Other important changes were a decline in grassland vegetation types and an increase in tall herbaceous and woodland vegetation types. For certain pioneer vegetation types on nutrient-poor, neutral soils recovery was observed, probably as a consequence of nature restoration projects started in the 1980s. Despite measures to reduce environmental emissions, eutrophication remains a major threat to the flora of the Netherlands.

Effects of sediment nutrients and depth on small-scale spatial heterogeneity of submersed macrophyte communities in Lake Pleasant, Pennsylvania

Sediment concentrations of total and available nitrogen (N), phosphorus (P), and potassium (K) and organic matter from the littoral zone of Lake Pleasant, Pennsylvania, were highly variable. Only organic matter and total N were correlated with depth, however. This result suggests the existence of more complex environmental gradients than the prevailing paradigm of monotonic changes in sediment characteristics with increasing depth. The spatial heterogeneity of submersed aquatic plant communities was significantly correlated with depth, and available N and P. Canonical correspondence analysis demonstrated that these three factors explained 38% of the variance in community structure. Other sediment characteristics (available K, organic matter, and total N, P and K) were not significant by themselves, but all variables combined explained 63% of community-structure variance. Cluster analysis identified species or groups of species typical of endpoints on the depth versus nutrient axes. Myriophyllum exalbescens was typical of deep sites with relatively nutrient-rich sediments, whereas deep nutrient-poor sites were dominated by Vallisneria americana and Megalodonta beckii. Shallow nutrient-rich sites were dominated by several species of Potamogeton and Elodea canadensis, and shallow nutrient-poor sites were dominated by Heteranthera dubia and Najas flexilis. These results demonstrate the importance of sediment characteristics in determining macrophytes' community structure within lakes.

LARGE HERBIVORES SUPPRESS DECOMPOSER ABUNDANCE IN A SEMIARID GRAZING ECOSYSTEM

Ecosystem-level studies of producer–decomposer interactions have focused primarily on plant production and soil texture as regulators of decomposer abundance but have rarely considered the role of grazers in mediating such interactions. Here, we conducted replicated exclosure experiments at both high and low levels of soil fertility to investigate the effects of large, mammalian grazers on decomposer biomass and activity patterns in a semiarid grazing ecosystem in Kenya. Within only two years of grazer exclusion, microbial biomass was greater in soil of fenced grassland across all levels of soil fertility. This consistent negative effect of grazers on microbial biomass occurred despite the fact that grazers stimulated aboveground plant production in nutrient-rich sites and depressed it in nutrient-poor sites. A consideration of all the potential pathways by which grazers influence decomposer populations suggests that observed grazing-induced reductions in microbial biomass were predominantly associated with a depression in the amount of plant carbon inputs to soils. Finally, across all study sites, microbial biomass was highly correlated with soil carbon content, suggesting that landscape-scale constraints on soil organic matter content and plant production overarch grazer effects on microbial abundance. Our results support previous ecosystem-level studies showing that microbial biomass and growth are constrained by plant production and soil C availability. In addition, our findings demonstrate that decomposer abundance can be influenced by an ecosystem's trophic structure, with significant reductions in microbial biomass occurring as a result of herbivores diverting plant carbon away from soils.

Phenolic contents of two brown algae, Turbinaria ornata and Sargassum mangarevense on Tahiti (French Polynesia): interspecific, ontogenic and spatio-temporal variations

To elucidate the possible implications of phenolic content in survival strategies of two tropical brown fucaleans, Tur- binaria ornata and Sargassum mangarevense, we deter- mined total phenolic contents in relation to ontogenic stages, and then followed spatio-temporal variations. Samples were collected at different sites and seasons. Both species exhibited low phenolic contents with, how- ever, some differences: levels were higher in the algae from grazer- and nutrient-rich sites, and during the aus- tral summer. Moreover, adults produced more phenolic compounds than immature stages. In addition, Turbinaria ornata had higher levels than Sargassum man- garevense. Parent thalli may exert an indirect protection of easily-grazed recruits which settle in close vicinity. The differences between species in protection of recruits would, therefore, derive from the respective species mor- phologies. A mechanical protection can be hypothesized in S. mangarevense because of its soft flexible thallus: plants can sweep around their base and, therefore, would need to produce less phenolics as a repellent than Turbinaria. On the other hand, due to its relatively tough texture, together with its upright-thallus, Turbinaria has a greater need to protect recruits by chemicals. The low phenolic content observed from thalli collected at the outer barrier reef may be explained by an exudation of phenolics after dessication.

Production potential and ecological stability of mixed forest stands in uplands - V. A mixed spruce/beech stand on a nutrient-rich site of the Křtiny Training Forest Enterprise

The study is already the 5<sup>th </sup>account on the production potential and stability of mixed forest stands in uplands. A spruce/beech stand established in the mid-30s of the 20<sup>th</sup>century is assessed. The stand is situated at an altitude of 470 m and since 1960, it is left to its spontaneous development. At that time, the stand was characterized as a silviculturally neglected dense spruce young growth to a small pole-stage stand with an admixture of beech (spruce 71%, beech 13%). In the course of 41 years, spruce proportion in the stand without intentional thinning measures decreased from 71 to 56% and, vice versa, beech proportion increased from 13 to 31%. Present dominant and co-dominant position of spruce in the stand, its health condition and development in recent years indicate that the ecosystem under evaluation is stabilized fulfilling all functions on the given site at an age of 65 years. The stand is permanently fully stocked and its initial standing volume of 109 m<sup>3</sup>/ha at an age of 24 years in 1960 increased to 560 m<sup>3</sup>/ha at an age of 65 years in 2001.

Limit values for plant litter decomposing in two contrasting soils—influence of litter elemental composition

Abstract The decomposition dynamics of four types of needle litter and three types of leaf litter were followed for 3 years at two very contrasting coniferous forest systems, a nutrient-rich silver fir ( Abies alba Mill.) forest in south Italy (Monte Taburno) and a nutrient-poor Scots pine ( Pinus sylvestris L.) forest in central Sweden (Jadraas). Decomposition of the same litter type at the two sites did not differ in the early stages but proceeded further at the nutrient-rich forest site than at the nutrient-poor one. Limit values for decomposition were calculated and the differences for the same litter type between the two contrasting coniferous systems were investigated. At both sites six of the seven litter types gave significant (asymptotic) limit values for decomposition, which varied with litter type. For four litter types out of six the limit values differed significantly between the two sites and were always higher at the nutrient-rich site (Monte Taburno). Using all available data for litters incubated at the two sites revealed that at the nutrient-poor site (Jadraas) there was a significant negative relationship between litter N levels and limit values and there was also a significant negative relationship between initial concentrations of heavy metals (e.g. Zn, Cd, Cu) and limit values. In contrast, at the site Monte Taburno, rich in nutrients and in heavy metals, there was no such relationship.

Re-assessing the ecology of rare flood-meadow violets (Viola elatior, V. pumila andV. persicifolia) with large phytosociological data sets

This study demonstrates how conventional ecological knowledge on species together with models resulting from functional traits can be tested and refined by tapping large data sources that have been made available through recent electronic compilations. The study is based on the comparison of three rare, closely related flood-meadow violet species, which have been supposed to have similar ecological behaviour and niche occupation. In contrast, the analysis of 335 Central European releves using different methods of numerical ordination, classification and calibration revealed distinct differences in habitat preferences between the three species. Detrended correspondence analysis ordination, and multiple-response permutation procedures and TWINSPAN classification displayed the separation ofViola persicifolia fromV. elatior andV. pumila along a moisture and base-richness gradient, while the latter two differed mostly in terms of mowing compatibility. Although the three violets are considered to be weak competitors they may be found under nutrient-poor as well as nutrient-rich site conditions. The distribution of C-S-R strategy types in releves supported the hypothesis that at more fertile sites the violets crucially depend on disturbance by management or flooding events that create gaps and weaken strong competitors, while at less productive sites they may persist for a long time even under fallow conditions. The S/R strategy is shared by all three violets. Problems and perspectives arising with the use of phytosociological databanks as a source of ecological information are discussed.

Root distribution of Norway spruce in monospecific and mixed stands on different soils

Vertical root distribution was studied in pure Norway spruce ( Picea abies (L.) Karst.) stands and in adjacent mixed stands of spruce and European beech ( Fagus sylvatica L.) with comparable site conditions. The investigation was carried out in two regions of Austria with different bedrock material. One site was located on nutrient rich, poor-aerated stagnic cambisol, the other on nutrient poor, well-aerated podsolic cambisol. A modified trench profile wall technique was used to study the coarse root distribution on altogether 160 m 2 of profile walls. The fine root biomass was estimated using soil core cylinders. Coarse roots were more abundant on nutrient poor than on nutrient rich site, showing the greatest cross-section (CS-)area in the humus and upper mineral soil layer in all of the four investigated stands. No significant difference in total root CS-area was found between pure and mixed stand in both regions. Coarse roots of Norway spruce were markedly stronger limited to the upper soil layers in mixture with beech than in pure spruce stands. This limitation to the upper soil was especially pronounced for the mixed stand on stagnic cambisol. The fine root biomass was greater in spruce stand on nutrient poor, well-aerated soil than on stagnic soil, whereas the mixed stands did not differ. The fine root system of spruce was markedly shallower in stagnic than in podsolic cambisol in pure stands and, compared to the basal area, spruce fine roots were under-represented in the mixed stands on both soil types. Like the coarse roots, fine roots of spruce showed a clear shift towards the upper soil layers in mixture with beech. This shift towards a more superficially distributed root system of spruce in mixture with beech together with the under-represented fine root biomass of spruce in these stands indicates a higher belowground competitive ability of beech compared to spruce on both nutrient rich and nutrient poor sites.

N2O emissions from snow-covered soils in the Swiss Alps

N2O emissions were investigated at two sites in the Swiss Alps, Alptal (SZ) and Piora Valley (TI), using the closed, vented chamber method during the snow-free period and the snowpack diffusion method during snow cover. Significant spatial variations in surface N2O effluxes between different sampling subsites were observed in both summer and winter. While in winter N2O fluxes from a raw humus site in Alptal and from a site of neutral pH in the Piora Valley were very low (0.01–0.02 mg N2O-N m−2 d−1) and similar to other published values, N2O emissions for acidic and alder-covered sites were 0.3–0.4 mg N2O-N m−2 d−1 and reached 1.7–1.9 mg N2O-N m−2 d−1 for nutrient-rich sites. This suggests that the soil temperatures close to the freezing point were not limiting microbial activity under snow. Snow-covered soils are insulated from extreme air temperatures and stay constant between −0.3 and −1.1°C. They represent an environment where micro-organisms may remain active while vegetation is dormant. N2O liberation is repressed at neutral and raw humus sites, as nitrification is the main source of N2O. During summer the soil microbial activity is strongly related to water availability and temperature: in contrast, in winter both factors are rather constant and the controlling factors of heterotrophic activity are unknown. Our data show that N2O is a significant component of alpine N cycling and that winter N2O fluxes should not be neglected in the calculation of the annual budget for alpine ecosystems, considering that snow covers (sub-) alpine regions for a large part of the year.

Habitat preferences of red-listed fungi and bryophytes in woodland key habitats in southern Sweden – analyses of data from a national survey

The aim of this study was to identify habitat preferences of red-listedepiphytic and epixylic bryophyte, lichenized and non-lichenized fungi speciesinwoodland key habitats (WKHS) (areas less than 10 ha, where foreststructures indicate occurrence of red-listed species) in southern Sweden. Therelative importance of different groups of environmental factors was assessedwith partial canonical correspondence analysis techniques and across-validationapproach using data from 7196 selected WKHs. Different woody substrates (oldtrees, logs and snags) made up the most important variable group for occurrenceof red-listed species (30% unique explainable variation). Species associatedwith Fagus sylvatica and Picea abieshabitats, but also species associated with Quercus spp.andPopulus tremula habitats showed distinct habitatpreferences. The second most important variable group (16% unique explainablevariation) was geographical location. A west–east gradient was identified, andspecies concentrated to Baltic islands in the east were separated from otherspecies. This gradient, and an identified south–north gradient, probablyreflect differences in temperatures and rainfall between different regions.Among the remaining variable groups, historical land-use, ground conditions andforest stand composition were of similar importance (5–7% uniqueexplainable variation). Traditional management regimes resulting in semi-openforest habitats (leaf harvesting, forest grazing and selective cutting) wereassociated with the occurrence of many species, probably due to differences inmicroclimate between sites of different openness. Furthermore, a groundmoisturegradient extending from species associated with dry sites (mainly lichenizedfungi) to species associated with wet sites (mainly bryophytes), and a nutrientgradient from species associated with nutrient-poor sites to species occurringat nutrient-rich sites, were identified. Thus, conservation measures are neededin a broad spectrum of habitats with different substrates. Also sites withsimilar substrates, but situated in different regions (and climates), or withdifferent ground moisture and nutrient conditions are needed to cover the fullspectrum of habitat conditions suitable for different red-listed bryophytes andfungi.

Site fertility and the morphological and photosynthetic acclimation of Pinus sylvestris needles to light.

Morphological and photosynthetic acclimation of current-year needles to canopy gradients in light availability (seasonal mean integrated quantum flux density, Q(int)) was studied in the temperate conifer, Pinus sylvestris L., at two sites of contrasting nutrient availability. The nutrient-rich site supported a monospecific P. sylvestris stand on an old-field. The trees were approximately 30 years old and 19-21 m tall. Mean foliar N and P contents (+/- SD) were 1.53 +/- 0.11% and 0.196 +/- 0.017%, respectively. The nutrient-poor site was located on a raised bog supporting a sparse stand of 50- to 100-year-old trees, with a height of 1-2 m, and mean needle N and P contents of 0.86 +/- 0.12% and 0.074 +/- 0.010%, respectively. At both sites, needle thickness (T) and width (W) increased with increasing Qint, and leaf dry mass per unit leaf area (MA) was also greater at higher irradiance. The light effects on MA-the product of needle density (D) and volume to total area ratio (V/AT)-resulted primarily from large increases in V/AT with Qint rather than from modifications of D, which was relatively insensitive to light. Although needle morphology versus light relationships were qualitatively similar at both sites, needles were shorter, and the slopes of W, T, MA and V/AT versus light relationships were lower, at the nutrient-poor than at the nutrient-rich site, indicating that the plasticity of foliar morphological characteristics was affected by nutrient availability. As a result of lower plasticity, needles at the nutrient-poor site were narrower, thinner, and had lower MA at high irradiance than needles at the nutrient-rich site. The maximum carboxylase activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Vcmax) and the maximum photosynthetic electron transport rate (Jmax) scaled positively with foliar N and P contents. The correlations were generally stronger with P than with N, suggesting that needle photosynthetic capacity was more heavily limited by the availability of P than of N. The Jmax/Vcmax ratio was positively related to the foliar P/N ratio, indicating that Jmax was more strongly suppressed than Vcmax under conditions of low P availability. Phosphorus and N deficiency also limited the plasticity of foliar photosynthetic characteristics. There was a moderate increase in needle photosynthetic capacity of up to 1.6-fold from the bottom to the top of the canopy at the nutrient-rich site, but net assimilation rates were essentially independent of canopy position at the nutrient-poor site. Stomatal constraints on photosynthesis were similar between the sites, indicating that photosynthetic acclimation was curtailed at the biochemical level. We conclude that the foliar capacity for morphological and physiological acclimation to high light significantly decreases with decreasing nutrient availability in P. sylvestris, and that both N and P availability are potentially important determinants of foliar carbon gain capacities.

The effect of nitrogen on stolon and ramet growth in four genotypes of Fragaria chiloensis L.

Plant foraging response is a process in which clonal plants proliferate in nutrient-rich sites by shortening stolon length and increasing ramet density. Conversely, stolon length increases and ramet density decreases in nutrient-poor sites. Four genotypes of strawberry ( Fragaria chiloensis (L.) Duch.) were grown in a greenhouse for 10 weeks and treated with different concentrations of nitrogen. Genotypes differed in plant size, stolon and ramet production, and nitrogen distribution between parent and ramets. Genotype Q18 were the smallest plants with the greatest number of stolons and ramets, typical of the phalanx morphology. The other genotypes had fewer but longer stolons, typical of the guerrilla morphology. Number of stolons and ramet density increased with increased N more in Genotype Q18 than the other genotypes. Results indicate that vegetative growth changed in response to increasing N treatment of the parent plant by shortening the average stolon length, increasing the number of stolons, and increasing the number of ramets while maintaining total stolon length. Foraging response characteristics were observed in strawberry but varied among genotypes.

The response of male and female black poplar (Populus nigra L. subspeciesbetulifolia (Pursh) W. Wettst.) cuttings to different water table depths and sediment types: implications for flow management and river corridor biodiversity

Management of river flows has altered the pattern of flood arrival times and reduced their frequency and duration on many European floodplains. Floodplain tree species depend on floods both to provide new sites for their regeneration and to recharge water tables at various depths in the rooting zone. A reduction in floods is one factor that has led to loss of river corridor biodiversity, with early successional tree species from the Salicaceae being particularly adversely affected. Members of the Salicaceae are dioecious and it is possible that the males and females of these species have measurably different water table requirements, which might lead to spatial segregation of the sexes on a floodplain. This paper describes an investigation that was carried out into the response of male and female black poplar (Populus nigra L. subspecies betulifolia (Pursh) W. Wettst.) to different soil moisture conditions. An experiment was set up on an alluvial island in the River Great Ouse (UK) in which cuttings of male and female black poplar were grown in different sediment types with different water table levels. The experiment was carried out over two field seasons in 1997 and 1998. Results showed that females tended to prefer wetter and more nutrient-rich sites than males but that there was considerable overlap in their requirements. A complementary genetic study showed very little genetic variation in the experimental population, which may also partially explain the relatively low level of variation between the two sexes found in the study. It is suggested that some limited spatial segregation of the sexes does occur in response to soil moisture availability and that river flow management which aims to maintain or increase river corridor biodiversity may need to take this into account. Copyright © 2000 John Wiley & Sons, Ltd.

Lecanora Barkmaneana, a new Nitrophilous Sorediate Corticolous Lichen from the Netherlands

Lecanora barkmaneana, a sorediate corticolous lichen belonging to the Lecanora subfusca group, is described as a species new to science on the basis of numerous sterile collections and two richly fertile collections. It is known so far only from the Netherlands, where it often grows on roadside trees. It seems to be spreading rapidly at nutrient-rich sites.

LECANORA BARKMANEANAA NEW NITROPHILOUS SOREDIATE CORTICOLOUS LICHEN FROM THE NETHERLANDS

Lecanora barkmaneana, a sorediate corticolous lichen belonging to theLecanora subfuscagroup, is described as a species new to science on the basis of numerous sterile collections. It is known so far as only from the Netherlands, where it often grows on roadside trees. it seems to be spreading rapidly at nutrient-rich sites.

Carbon and nitrogen transformations in New Zealand plantation forest soils from sites with different N status

Interactions between soil nutrient cycling processes are likely to influence N losses following disturbance in forest ecosystems. During a 340-day laboratory incubation, we examined C and N transformations in three sandy soils of different N status from Pinus radiata D. Don plantations before clear-cutting. The soils were a high N status Andisol (losing -N in streamwater) and a fertilized and unfertilized Entisol. In contrast to other forest ecosystems, -N accumulated readily in all mineral soils and in the Andisol forest floor but did not accumulate until day 63 and 210 in the fertilized and unfertilized Entisol forest floor, respectively. However, gross nitrification occurred from day 42 in both Entisol treatments. Net nitrification in the Entisol forest floor began when substrate C/N ratio declined to about 40, possibly because of decreased C availability and decreased competition for both -N and -N in conjunction with a lower microbial C/N ratio. Carbon and gross N mineralization rates (per unit of C or N, respectively) correlated positively (r2 = 0.93) in mineral soil but correlated negatively in the forest floor, probably because of major differences in C and N quality and potential differences in microbial community structure. The mean residence time of N in mineral-N pools was higher for soils from the N-rich site, in part because of lower microbial N demand. These results suggest that sudden removal of C inputs (such as at harvest) may cause greater disruption of internal soil N cycles on nutrient poor sites, increasing the proportional losses of N as compared to nutrient-rich sites.

Monitoring organic pollution and eutrophication in the Grand River, Ontario, by means of diatoms

Diatom analysis discriminates between the impacts on river water quality of treated urban wastewaters and diffuse nutrient sources from farmland. Evaluation of organic pollution and trophic levels in the Grand River, Ontario, using two diatom indices shows a clear differentiation among 10 sampling sites over a distance of 214 km. Sites in the central reaches that are influenced by both urban discharges and agricultural runoff have the lowest water quality. The ranking of sites according to both diatom indices is consistently independent of substratum and seasonality. Ordination of samples by multivariate analysis results in a primary separation of the spring and summer communities and a secondary separation of upper, central, and lower reaches. Substratum differences are only apparent at the tertiary level, and mainly for midsummer samples from the upper reaches. Canonical correspondence analysis shows that the largest portion of the observed variability in species composition can be explained by a seasonal gradient related to temperature and by longitudinal gradients of nitrate-nitrogen, conductivity, and chloride. Differences in species composition between nutrient-rich sites and polluted sites are identified. Compared with a study conducted in the 1960s, the Grand River shows clear signs of increased eutrophication.

Post-drainage changes in vegetation composition and carbon balance in Lakkasuo mire, Central Finland

The post-drainage changes in vegetation composition and carbon balance were studied on four site types (from minero- to ombrotrophic conditions) in Lakkasuo mire, central Finland, by directly comparing undrained and drained parts (30 years ago) of the mire. Drainage had drastically changed the species composition of the sites, especially at the minerotrophic sites, where almost all Sphagna had been replaced by forest mosses. On the ombrotrophic sites much of the mire vegetation still remained 30 years after drainage. Drainage had decreased the C stores in ground vegetation on the minerotrophic sites but increased them on the ombrotrophic sites. The changes were, however, very small compared to the changes in the tree stand, where the C stores had increased at all sites (increasing with nutrient level). The change in peat C balance over the 30-year post-drainage period was negative on the most nutrient-rich site, and positive on the others, increasing with lower nutrient levels. The decrease in the peat C balance on the most nutrient-rich site was compensated by the greater increase in the tree stand C stores and the changes in the total C balance (peat+tree stand+ground vegetation) remained positive on all sites.