Patterns in vegetation, hydrology, and nutrient availability in an undisturbed river floodplain in Poland

In the undisturbed floodplain of the Biebrza river (N.E. Poland) wecompared vegetation composition, standing crop and the nutrients in standingcrop to site factors such as flood duration and inundation depth during springfloods, summer water levels and concentrations of chemical constituents inwaterand nutrient release rates from peat. Our analysis shows a number of clearspatial patterns of biotic and abiotic variables in the ca. 1 kmwide river marginal wetland. The distribution of vegetation types follows acertain pattern: Glycerietum maximae close to the river,followed by respectively Caricetum gracilis andCaricetum elatae and finally Calamagrostietumstrictae at the margin of the river plain. Species richnessincreasesand standing crop decreases from the river towards the margin. The elevation ofthe ground surface gently rises with increasing distance from the river; floodduration and flooding depths in spring decrease in the same direction.Groundwater tables in summer are less correlated to the elevation gradient buttend to be closer to the ground surface at the valley margin. These differencesalso lead to a higher amplitude close to the river and a fairly stable watertable far away from the river. Concentrations of major ions and ammoniumincrease towards the river. Nutrient release rates are also higher closer totheriver. Absence and presence of species and the variation in species compositionof the vegetation was explained best by flood variables; variables fromgroundwater explained much less of the variance. Variations in standing cropandnutrients in standing crop corresponded better to the rates of nutrient releasefrom the organic soil than to nutrient concentrations in the soil water. Weconcluded that river hydrology and nutrient release from the soil are clearlyrelated to vegetation composition, species richness and productivity of thevegetation.     

In search of a hydrological explanation for vegetation changes along a fen gradient in the Biebrza Upper Basin (Poland)

The understanding of succession from rich fen to poorer fen types requires knowledge of changes in hydrology, water composition, peat chemistry and peat accumulation in the successional process. Water flow patterns, water levels and water chemistry, mineralisation rates and nutrient concentrations in above-ground vegetation were studied along a extreme-rich fen-moderate-rich fen gradient at Biebrza (Poland). The extreme-rich fen was a temporary groundwater discharge area, while in the moderate-rich fen groundwater flows laterally towards the river. The moderate-rich fen has a rainwater lens in spring and significant lower concentrations of calcium and higher concentrations of phosphate in the surface water. Mineralisation rates for N, P and K were higher in the moderate-rich fen. Phosphorus concentrations in plant material of the moderate-rich fen were higher than in the extreme-rich fen, but concentrations of N and K in plant material did not differ between both fen types. Water level dynamics and macro-remains of superficial peat deposits were similar in both fen types.We concluded that the differences observed in the moderate-rich and the extreme-rich fens were caused by subtile differences in the proportion of water sources at the peat surface (rainwater and calcareous groundwater, respectively). Development of an extreme-rich fen into a moderate-rich fen was ascribed to recent changes in river hydrology possibly associated with a change in management practices. The observed differences in P-availability between the fen types did not result in significantly different biomass. Moreover, biomass production in both fen types was primarily N-limited although P-availability was restricted too in the extreme-rich fen. Aulacomnium palustre, the dominant moss in the moderate-rich fen, might be favoured in competition because of its broad nutrient tolerance and its quick establishment after disturbance. It might outcompete low productive rich fen species which were shown to be N-limited in both fens. We present a conceptual model of successional pathways of rich fen vegetation in the Biebrza region.     

Environmental conditions and fen vegetation in three lowland mires

The abiotic conditions and fen vegetation in three lowland mires were analysed. Two of these mires are in the Netherlands. They have deteriorated considerably as a result of human pressure. One mire complex is in Poland. Its hydrology is almost undisturbed. The variation in the water composition in the fens was associated with the variation in the amount of regional groundwater discharge originating from the uplands, and to a lesser extent by the infiltration of polluted water pumped into the fens.The 26 vegetation types ranged from poor fen to eutrophic reedland. Most types were typical for only one region.There were clear differences between the three regions. Both the species composition and the water quality for the vegetation types indicated that the fens in the Vecht river plain are eutrophicated, whereas the fens in Northwestern Overijssel suffer from acidification. The Biebrza valley fens are well developed and are mainly fed by fresh calcareous groundwater.Stepwise logistic regression performed on 28 fen species revealed that the hydrochemical variables explained only a part of the variance: the regional variable area explained a considerable amount of the variance for most species. In 27% of the cases it was possible to fit an optimum curve for the species response to relevant hydrochemical variables. Monotonic curves could be fitted in 64% of the cases; mostly they described the response to variables in a way that is supported by ecological literature. It was concluded that the dataset should be constructed differently to enable the calculation of generally applicable standards.     

Long-term effects of drainage and hay-removal on nutrient dynamics and limitation in the Biebrza mires,Poland

To provide a reference for wetlands elsewhere we analysed soil nutrients and the vegetation of floodplains and fens in the relatively undisturbed Biebrza-valley, Poland. Additionally, by studying sites along a water-table gradient, and by comparing pairs of mown and unmown sites, we aimed with exploring long-term effects of drainage and annual hay-removal on nutrient availabilities and vegetation response. In undrained fens and floodplains, N mineralization went slowly (0–30 kg N ha⁻¹ year⁻¹) but it increased strongly with decreasing water table (up to 120 kg N ha⁻¹ year⁻¹). Soil N, P and K pools were small in the undisturbed mires. Drainage had caused a shift from fen to meadow species and the disappearance of bryophytes. Biomass of vascular plants increased with increasing N mineralization and soil P. Annual hay-removal tended to have reduced N mineralization and soil K pools, but it had increased soil P. Moreover, N concentrations in vascular plants were not affected, but P and K concentrations and therefore N:P and N:K ratios tended to be changed. Annual hay-removal had induced a shift from P to K limitation in the severely drained fen, and from P to N limitation in the floodplain. The low nutrient availabilities and productivity of the undisturbed Biebrza mires illustrate the vulnerability of such mires to eutrophication in Poland and elsewhere. In nutrient-enriched areas, hay removal may prevent productivity increase of the vegetation, but also may severely alter N:P:K stoichiometry, induce K-limitation at drained sites, and alter vegetation structure and composition.     

Morava River alluvial meadows on the Slovak–Austrian border (Slovak part): plant community dynamics, floristic and butterfly diversity – threats and management

The Morava river forms a border 71 km in length between Slovakia and Austria. Along this stretch of river is the largest complex of flooded grasslands in Central Europe, most of which lays on the Slovak side. Most of the grasslands belong to the subcontinental vegetation alliance Cnidion, with smaller areas of Alopecurion and Molinion. The grasslands are biotopes of many endangered plant and animal species. The influence of water regime dynamics on species composition have been studied since 1992 along permanent transects. The results of studies on the relation between water regime dynamics, vegetation and soils on the whole section of the Morava River floodplain are presented.     

A comparison of fens in natural and artificial landscapes

Fens depend on inputs of groundwater or surface water. In Western Europe especially soligenous fens, receiving groundwater, are threatened by human hydrological intervention. We demonstrate the impact of artificial versus natural hydrologies on such fens by comparing 3 case areas: the Biebrza valley (reference) and the Gorecht and Vecht river plains (both reclaimed and drained). The patterns found in the fairly undisturbed Biebrza area suggest local water quality is governed by a strong regional groundwater flow emerging in the fen near the valley margins and seeping through it down to the river. Hence water quality gradients are smooth: there is little variation in water type over large distances. The pattern is determined by the natural geomorphology. In the reclaimed Vecht and Gorecht river plains large differences exist at short distance. Regional water flow from the adjacent ridges into the plains is weak here and governed primarily by water management (polders and pumping wells). However, the relations between specific water types and fen species and communities in this artificial pattern are quite similar to those found in the natural landscape. Low-productive rich fens are fed by calcium-rich and base-rich, nutrient-poor groundwater in both cases. While conservation of such rich fens is served best by maintaining the natural groundwater flow, some opportunities for restoration with an artificial hydrology are discussed.     

Vegetation dynamics related to sediment accumulation in Kushiro Mire, northeastern Japan

We investigated the relationship between vegetation changes and site condition in Kushiro Mire, northeastern Japan, where massive depositions of sediment from the watershed have been observed over the last several decades. These changes also included the changing area of floodplain forest. To determine the factors that induced the changing floodplain forest area and the effect of sediment accumulation on floodplain vegetation, we examined site conditions where vegetation had recently changed. We classified the pattern of vegetation change as new forest (formerly meadow), new meadow (formerly forest), stable forest (forest since 1967), and stable meadow (meadow since 1967) with the help of aerial photographs taken in 1967, 1977, and 2000. The survey results showed that the quadrats were divided into six vegetation types based on current vegetation composition. All new forests comprised alder (Alnus japonica) and were divided into two vegetation types. New meadows were also considered alder forest based on remnants of former forest and divided into two vegetation types. The site condition showed better correspondence to the pattern of vegetation change than the current vegetation composition, though it had a significant relationship with the latter. In new forests, high water table and a relatively high content of clay and silt characterized the site condition, whereas in new meadows, low water table and high sand content were the site characteristics. We discuss these site characteristics in the context of alder’s adaptability to site. It is suggested that coarse sediment probably along with intense flooding and fine sediment coupled with high water table contributed to the disappearance and establishment of alder forests, respectively.     

Vegetation dynamics in the fens of Chautagne (Savoie,France) after the cessation of mowing

The mechanisms controlling secondary succession on eutrophic peat are analyzed on an area of 500 ha marsh near the Lac du Bourget in the Rhône floodplain between Geneva and Lyon. After describing the succession, the authors compare the succession with that described for fens in England.During succession, three categories of phenomena occur:-Predictable phenomena based on the occurrence of well-established relationships between species with a high cover density. When mowing ceases, populations with increasingly higher biomasses reach dominance one by one.-Phenomena which were to be expected although the manner in which they occurred were more difficult to predict, such as the conditions in which woody plants take over.-Phenomena hidden in the framework of a synchronic analysis. The lowering of the water table, for example, can modify the entire community of species occurring in the sequence as well as the competition between species. The pecularities of each type of ecological situation made it difficult to develop general models.     

Hydrology,water chemistry and nutrient accumulation in the Biebrza fens and floodplains (Poland)

The composition, structure and above-ground biomass production of floodplain- and fen-vegetation of the Biebrza valley (N.E. Poland) are strongly correlated with water flow characteristics and water chemistry. Groundwater flow and flooding are the major conditioning factors for the vegetation in the valley.The highly productive vegetation is restricted to the dynamic floodplain where it receives nutrient-rich river water during spring floods. The non-flooded parts of the valley contain rich fen and transitional fen vegetation that have a lower biomass production. The rich fen is fed by calcareous and phosphate-poor groundwater coming from the moraines. In the transitional fen, where rainwater infiltrates, phosphate availability is large.Annual nutrient accumulation in the above-ground biomass of the floodplains is estimated to be about 8–9 § 10³ kg/km² for N and K and 1 § 10³ kg/km² for P. For the less-productive fens these figures are 60 to 70% lower. The total annual nutrient accumulation by vegetation of both floodplains and fens for the entire Biebrza valley is estimated to be about 5600 × 10³ kg N, 560 × 103 kg P and 4500 × 10³ kg K. This is high compared to the loading rates in the river near to where the Biebrza River discharges into the Narew River (N-, P- and K-loading rates are c. 900, 200 and 3000 × 103 kg/y, respectively). This implies that floodplain and fen vegetation are important sinks for nutrients, especially for N and P.This paper was presented at the INTECOL IV International Wetlands Conference in Columbus, Ohio, 1992, as part of a session organized by Prof. S. E. Jørgensen and sponsored by the International Lake Environment Committee.Corresponding Editor: J. Kvt     

A grass mire in Poland: Reserves of phytomass and deposited nutrition elements

The reserves of phytomass and deposited nutrition elements in a grass mire have been estimated. Two grass mires and one sphagnum bog are compared in these parameters. The sphagnum bog and one grass mire are in Poland, and the other grass mire is in Russia. As follows from the comparison, the common climatic and geochemical properties of location have effect on the chemical nature of phytomass. Grass mires have a higher content of nitrogen than sphagnum bogs. Both of the Polish bogs exhibit an increased content of K and a decreased content of Ca. The accumulation of P is characteristic of the Siberian grass mire and the accumulation of S is found in the Polish one.     

Nutrient dynamics in a floating mat and pond system with special reference to its vegetation

Chemical properties of waters and their seasonal changes were studied in Mizorogaike Pond, a system of pond and floating mat. The following six sites including contrasting habitats and water conditions were monitored to assess nutrient dynamics in the system: 1) a pool on the mat, 2) margin of aSphagnum cuspidatum community, 3) an artificial ‘well’ (water layer beneath the floating mat), 4) aMenyanthes trifoliata community in a hollow, and 5) & 6) two sites in the open water. On the floating mat, the water around theSphagnum community had lower pH values, while that in theM. trifoliata community had higher pH values. This difference was related to the influence of flood water, the extent of which was determined by the microtopography. Seasonal changes in water chemistry on the mat suggested that pond water flooding the mat in late autumn and winter is important for the nutrient supply to the mat surface vegetation in this system. Water chemistry of the ‘well’ suggested that the diffusion of inorganic nitrogen occurs from beneath the peat layer. Two types of cluster analysis based on the mean values for chemical variables and the patterns of fluctuation in these variables were performed. The six sites were classified into similar groups which were identified by water type (pool, hollow, well and open water) by both types of analysis. The results showed that a common kind of perturbation should operate in determining the status of nutrient dynamics in the various water types.     

Hydrobiological analysis of a peat bog with emphasis on its planktonic diversity and population dynamics in Bumdeling Wildlife Sanctuary, eastern Bhutan

A pioneering limnological investigation was carried out in Bhutan in a small peat bog in the Trashiyangtse district (1950 m above sea level) from February 2000 to January 2002. The sampled pond water had low transparency (55.0–95.0 cm), was typically acidic (pH 5.69–6.58) with soft water (alkalinity, 11.0–36.0 mg/l; total hardness, 10.0–34.0 mg/l), and had low to moderate specific conductivity (17.0–62.0 μS/cm). Further, moderate Na (2.0–6.8 mg/l), K (1.8–13.5 mg/l), sulphate (0.85–2.99 mg/l), and silicate (2.5–15.0 mg/l) concentrations as well as low nutrient levels such as phosphate (0.006–0.170 mg/l) and nitrate (0.003–0.180 mg/l) characterize the water in the peat bog. The recorded net plankton comprised 27 species of phytoplankton and 49 species of zooplankton, with the latter indicating greater homogeneity and breaking down into Rotifera (23 species) > Cladocera (13 species) > Rhizopoda (8 species) > Copepoda (3 species) > Ostracoda = Nematoda (1 species each). On the other hand, the net plankton density ranged between 93 and 692 number/l (n/l) with numerical dominance by phytoplankton (68.5% ± 12%), of which Chlorophyceae were predominant (90 ± 63 n/l). Zooplankton showed moderately high diversity (2.745 ± 0.293) and evenness (0.925 ± 0.049) and exhibited almost equal abundance of four recorded groups, namely Cladocera (20 ± 15 n/l) > Rotifera (15 ± 6 n/l) > Copepoda (14 ± 7 n/l) > Rhizopoda (14 ± 4 n/l). While no significant impact of abiotic factors was recorded on zooplankton density, rainfall alone was the most important factor that influenced net plankton and various groups of phytoplankton. Comments on some comparative limnological attributes are also made with similar as well as different habitats in the nearby Himalayan countries.     

Water table fluctuations and groundwater supply are important in preventing phosphate-eutrophication in sulphate-rich fens: Consequences for wetland restoration

Nitrate leaching from agricultural land leads to oxidiation of FeS _x in FeS _x -containing subsoils resulting in SO ₄ ²⁻ mobilisation. Pollution of the groundwater with SO ₄ ²⁻ causes a higher availability of o-PO ₄ ³⁻ , eutrophication and loss in biodiversity in groundwater fed fens with stagnating surface water. Under natural conditions, fens along the river Meuse are continuously fed by groundwater that besides SO ₄ ²⁻ mostly also contains high concentrations of NO ₃ ⁻ and bivalent cations (Ca²⁺ and mg²⁺). During summer groundwater input is restricted resulting in periodic drought. Under these conditions no SO ₄ ²⁻ induced o-PO ₄ ³⁻ eutrophication occurs. Periodic drought and a high discharge of NO ₃ ⁻ , have a strong effect on S and P biogeochemistry in sulphate-rich fens. NO ₃ ⁻ inhibits SO ₄ ²⁻ reduction and concomitant o-PO ₄ ³⁻ mobilisation in fen sediments by being an energetically more favourable electron acceptor. In addition, NO ₃ ⁻ is capable of oxidising reduced Fe compounds, including FeS _x , increasing the amount of oxidised Fe in the sediment capable of binding o-PO ₄ ³⁻ . Periodic drought is important in reincreasing the concentration of oxidised Fe in the top layer of S-rich sediments preventing o-PO ₄ ³⁻ mobilisation and an undesirable vegetation development. Damming of surface water, in order te restore desiccated sulphate-rich fens, prevents periodic drought and decreases groundwater input. This leads to NO ₃ ⁻ depletion, stimulation of SO ₄ ²⁻ reduction, Fe depletion, o-PO ₄ ³⁻ mobilisation and, in contrast to what was hoped for, in massive growth of algae, lemnids and fast growing wetland grasses. Therefore discharge of NO ₃ ⁻ – rich groundwater and the fluctuation of the water table are vital for succesful restoration of desiccated sulphate-rich fens. Successful rewetting of these type of fens, without causing stagnation of surface water and without preventing periodic drought, can be achieved by raising the water table to levels below the potential groundwater table using a controllable dam.     

Peat characteristics and groundwater geochemistry of calcareous fens in the Minnesota River Basin, U.S.A.

Calcareous fens in Minnesota are spring-seepage peatlands with adistinctive flora of rare calciphilic species. Peat characteristics andgroundwater geochemistry were determined for six calcareous fens in theMinnesota River Basin to better understand the physical structure andchemical processes associated with stands of rare vegetation. Onset of peataccumulation in three of the fens ranged from about 4,700 to 11,000 ¹⁴C yrs BP and probably resulted from acombination of climate change and local hydrogeologic conditions. Most peatcores had a carbonate-bearing surface zone with greater than 10%carbonates (average 27%, dry wt basis), an underlyingcarbonate-depleted zone with 10% or less carbonates (average4%), and a carbonate-bearing lower zone again with greater than10% carbonates (average 42%). This carbonate zonation washypothesized to result from the effect of water-table level on carbonateequilibria: carbonate precipitation occurs when the water table is above acritical level, and carbonate dissolution occurs when the water table islower. Other processes that changed the major ion concentrations inupwelling groundwater include dilution by rain water, sulfate reduction orsulfide oxidation, and ion adsorption or exchange. Geochemical modelingindicated that average shallow water in the calcareous fens during the studyperiod was groundwater mixed with about 6 to 13% rain water.Carbonate precipitation in the surface zone of calcareous fens could bedecreased by a number of human activities, especially those that lower thewater table. Such changes in shallow water geochemistry could alter thegrowing conditions that apparently sustain rare fen vegetation.     

Variation in habitat factors and species composition of Scorpidium scorpioides communities in NW-Europe

To assess the natural range in habitat parameters of the once common rich-fen bryophyte Scorpidium scorpioides, water chemistry and vegetation were studied in different regions characteristic of its NW-European distribution area: the Netherlands, Ireland, Denmark and Fennoscandia. Scorpidium scorpioides was found in an environment with circumneutral pH. The variation in solute content and composition was large and nutrient (N and P) concentrations ranged from zero to values indicative of more eutrophic conditions. Six different vegetation types with S. scorpioides were distinguished, resembling Caricion davallianae, Caricion curto-nigrae and Hydrocotylo-Baldellion communities. Type of substrate and solute levels were strongly correlated with the first ordination axis (DCA) and nutrient status and geographic position with the second axis. Habitat and vegetation characteristics in Dutch rich-fens with S. scorpioides indicated that mineral status was higher than in Fennoscandia and Ireland; solute-poor habitats with S. scorpioides have disappeared from the Netherlands. Trophic status was higher in the Netherlands than in Fennoscandia, but in some cases lower than in Ireland. Acidification and eutrophication may have played a role in the decrease of the species in the Netherlands. However, the wide ecological ranges suggest that the decrease of S. scorpioides is not a physiological effect of unsuitable environmental conditions per se.     

Effects of hydrologic changes on aboveground production and surface water chemistry in two boreal peatlands in Alberta: Implications for global warming

Aboveground net primary production (NPP) and surface water chemistryvariables were monitored in a lacustrine sedge fen and a bog for four years.There were no significant differences in precipitation, mean growing seasonannual temperature, and number of growing degree days from 1991 to 1994. Themean annual water levels in the lacustrine sedge fen differed significantly,whereas they were similar in the bog during these four years. We measured 15surface water variables in the lacustrine sedge fen and the bog, and foundthat only two correlated significantly with water level fluctuations. In thelacustrine sedge fen, calcium correlated positively (r²= 0.56) and nitrate correlated negatively (r² =0.20) with water levels. In the bog, potassium correlated positively(r² = 0.88) and total dissolved phosphorus correlatednegatively (r² = 0.62) with water levels. The remainingchemical variables showed no significant correlations with water levelfluctuations. Net primary production of the different vegetation strataappeared to respond to different environmental variables. In the lacustrinesedge fen, graminoid production was explained to a significant degree bywater levels (r² = 0.53), whereas shrub production wasexplained to a significant degree by surface water chemistry variables, suchas nitrate (r² = 0.74) and total phosphorus(r² = 0.22). In the bog, temperature was the onlyvariable that explained moss production to a significant degree(r² = 0.71), whereas ammonium explained graminoidproduction (r² = 0.66) and soluble reactive phosphorusexplained shrub production to significant degrees (r² =0.71). There are few direct data on the impact of climatic warming in borealwetlands, although paleoecological and 2×CO₂ model datahave provided some indications of past and possibly future changes invegetation composition, respectively. Our results suggest that thelacustrine sedge fen may succeed to a bog dominated by Sphagnum spp. andPicea mariana, whereas the bog may succeed to an upland-type forestecosystem. This revised version was published online in July 2006 with corrections to the Cover Date.     

Alternative life-history traits associated with reproduction in Oreochromis mossambicus (Pisces: Cichlidae) in small water bodies of the eastern Cape,South Africa

Synopsis Four wild populations of Oreochromis mossambicus were investigated to examine the effects of environmental factors on reproductive biology in contrasting habitats. Age at maturity, spawning-season length, spawning frequency, clutch size and nesting behaviour were influenced by the prevailing conditions for feeding, breeding and refuge. Even under a temperature regime that approached lethal limits during winter, and erratically fluctuating water levels, O. mossambicus demonstrated an ability to adopt a precocial life-history style in some habitats. In more hostile water bodies an increasingly altricial style was followed.     

Differences in CO2 dynamics between successional mire plant communities during wet and dry summers

Questions: What impact do a wet and a dry growing season have on CO₂ dynamics of mire plant communities along a primary succession gradient from the initiation stage to the bog stage? Location: Mires on a land uplift coast, Finland. Methods: We measured CO₂ dynamics and vascular plant green area development on five mires that form a sequence of mire succession. TWINSPAN was used to define successional mire plant communities and regression analyses were used to explore the temporal variation in CO₂ dynamics of the communities. Results: CO₂ dynamics of successional plant communities reacted differently to a wet and a dry growing season. The net CO₂ uptake rate of the earlier successional communities decreased in the dry growing season due to a decrease in photosynthesizing leaf area. Concurrently, CO₂ uptake of the later successional communities moderately increased or did not change. Generally, the difference in net ecosystem exchange (NEE) between a dry and a wet year resulted from the altered rate of gross photosynthesis (P_G) rather than ecosystem respiration (R_E). Conclusions: Critical factors for the more stable carbon (C) gas dynamics in the later stages of mire succession were (1) higher autogenic control of the physical environment and (2) an increase in the number of factors regulating the P_G rate. These factors may buffer mire ecosystems (in terms of the C sink function) from extreme and unfavourable variations in environmental conditions.     

Overgrazing and soil carbon dynamics in eastern Inner Mongolia of China

Eastern Inner Mongolia of China is a typical ecotone between sandy forests and steppe. Little is known about the effect of overgrazing on carbon loss from soil in semiarid steppe and sandy forests of the north of China. The soil carbon parameters were measured in a 10,000 ha natural reserve in eastern Inner Mongolia of China (43°30′–43°36′N, 117°06′–117°16′E). Three situations were compared: primary protected (PP), moderately protected (MP) and highly degraded (HD). Soil and litter samples were recovered in spring and summer. Soil organic carbon (SOC) and CO₂–C values decreased from the PP (9.23 kg m⁻² and 157 g m⁻²) to the HD (1.69 kg m⁻² and 57 g m⁻²) sites whereas the C mineralization rate increased toward the less restored sites (1.06–2.37). Surface-litter C was different in both sites under protection (PP 648 and MP 408 g m⁻²), an was low at the HD site (17 g m⁻²). Leaves from woody species dominated the surface litter at the PP site, whereas grass material was predominant at the MP site. During summer, both CO₂–C and SOC decreased, whereas the C mineralization rate increased. We calculated that C loss since the introduction of cattle into the forest was 77 M g ha⁻¹, reaching a total of 1.1×10¹⁵ g for eastern Inner Mongolia. These values are higher than those caused by the conversion of steppe and other ecosystems into agriculture or cultivated pastures. The amount of C fixed at the PP site (650 g ha⁻¹year⁻¹) indicates that the sandy soils have a significant potential as atmospheric carbon sinks. Foundation item: The National Natural Science Foundation of China (No. 39900019, 30070129).