Mercury, cadmium and lead biogeochemistry in the soil-plant-insect system in Huludao City.

Mercury, cadmium, and lead concentrations of ashed plants and insects samples were investigated and compared with those of soil to reveal their biogeochemical processes along food chains in Huludao City, Liaoning Province, China. Concentration factors of each fragments of the soil-plant-the herbivorous insect-the carnivorous insect food chain were 0.18, 6.57, and 7.88 for mercury; 6.82, 2.01, and 0.48 for cadmium; 1.47, 2.24, and 0.57 for lead, respectively. On the whole, mercury was the most largely biomagnified, but cadmium and lead were not greatly accumulated in the carnivorous insects as expected when the food chain extended to the secondary consumers. Results indicated that concentration factors depended on metals and insects species of food chains.

Distribution characteristics of dissolved organic carbon in annular wetland soil-water solutions through soil profiles in the Sanjiang Plain, northeast China.

Overwhelming evidence reveals that concentrations of dissolved organic carbon (DOC) have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solutions of watershed. Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems. This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland, i.e., a dishing wetland and a forest wetland together, in the Sanjiang Plain, Northeast China. The results indicate that DOC concentrations in soil-water solutions decreased and then increased with increasing soil depth in the annular wetland. In the upper soil layers of 0-10 cm and 10-20 cm, DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland (R2 = 0.3122 and R2 = 0.443). The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions. The concentrations of total organic carbon (TOC), total carbon (TC) and Fe(II), DOC mobility and continuous vertical and lateral flow affected the distribution variations of DOC in soil-water solutions. The correlation coefficients between DOC concentrations and TOC, TC and Fe(II) were 0.974, 0.813 and 0.753 respectively. These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments. However, the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale. These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports, which would bring negative environmental impacts in watersheds of the Sanjiang Plain.

[Soil Microorganism Characteristics and Soil Nutrients of Different Wetlands in Sanjinag Plain, Northeast China].

Four typical wetland types (i.e. wetlands with the following dominant plant species: Calamagrostis angustifolia + Salix brachypoda, Calamagrostis angustifolia, Carex lasiocarpa and Phragmites australis) of the Honghe reserve in Sanjiang Plain were studied to investigate the distribution of soil microorganism quantity and enzyme activity and their relationships with soil nutrients. The results showed that in 0-30 cm soil layer of these four wetlands: (1) Contents of soil total organic carbon, total nitrogen and total phosphorus decreased with the increase of soil depth, while available nitrogen, phosphorus and potassium did not exhibit regularly changes. Moreover, there were significantly different for soil nutrient contents among different wetland types (P < 0.05). (2) The number of soil microorganism was bacteria > actinomycetes > fungi, furthermore, the number of three microbial colonies all decreased with the increase of soil depth. Total soil microbial number of C. angustifolia wetland was the highest and that of C. lasiocarpa wetland was the lowest. (3) Soil invertase and cellulase activities decreased with soil depth, while soil catalase activity showed no consistent changes. Three kinds of enzyme activities in C. angustifolia + S. brachypoda and C. angustifolia wetlands were significantly higher than those of C. lasiocarpa and P. australis wetlands (P < 0.05). (4) The correlation analysis showed that soil bacteria, fungi and cellulose activity had a significant correlation with indicators of soil nutrients. But there was no correlation between actinomyces, invertase and available potassium, as well as between catalase and available potassium, available phosphorus. Overall, soil microorganism and enzyme activities are important indicators for reflecting the status of soil nutrients.

[Effects of land use on manganese distribution and fractions in wetland soil of Sanjiang Plain, Northeast China].

A detailed investigation was conducted to study the variations of manganese contents and fractions in soil under different land use patterns in Sanjiang Plain, Northeast China. The purpose of this work was to study the changes of manganese and its fractions during wetland cultivation and their relationships with environment factors. The results indicated that the total manganese contents (Mn(tot)) were relatively low in wetland soils. When wetland was cultivated into dry farmland (corn field), M(tot) showed an increasing trend, and when wetland was cultivated into rice paddy, Mn(tot) manifested a decreasing trend. Among the four fractions of manganese in soil, the residual part (Mn(res)) and the reducible part (Mn(red)) were predominant while the acid extractable part (Mn(ext)) and the oxidizable part (Mn(oxi)) were secondary. During the cultivation of wetlands to corn field or rice paddy, Mn(oxi) was the only part with significant change. Mn(tot) and the transformations among manganese fractions were affected by many environmental factors, with sulfur content, pH and dissolved organic carbon playing leading roles.

[Effect of reclamation on the vertical distribution of SOC and retention of DOC].

Contents and density of soil organic carbon (SOC) in soil profiles and dissolved organic carbon (DOC) of soil solution in different soil depths in wetland, soybean and paddy field reclaimed from the wetland around Xingkai Lake were determined to investigate how reclamation of wetland for soybean and rice farming impacts vertical distribution of SOC and retention of DOC. SOC contents in 0-40 cm soil layers were significantly influenced. SOC contents in 0-10, 10-20, 20-30 and 30-40 cm soil layers in soybean and paddy field were 79.07% and 82.01%, 79.01% and 82.28%, 79.86% and 92.90%, 37.49% and 78.05% respectively lower than those in wetland. Before and after reclamation, SOC contents in soil layers deeper than 40 cm were not significantly different. SOC densities in soybean and paddy field were 25.50% and 47.35% respectively lower than those in wetland. However, either in wetland or farm land, most of the SOC storage in 0-100 cm soil layer was stored in 0-50 cm soil layer. The relationships between SOC content and soil depth in wetland and two farm lands all could be described by exponential functions; cultivation did not change the variation of SOC content with soil depth. The retention of DOC was more obvious for soybean farming than wetland and rice farming, and that was roughly the same for wetland as rice farming.

[DNDC model, a model of biogeochemical processes: Research progress and applications].

Denitrification-decomposition (DNDC) model can estimate the emission fluxes of soil trace gases such as carbon dioxide (CO2), methane (CH4) , and nitrous oxide (N2O) via the coupling of the denitrification and decomposition processes driven by soil environmental factors. At present, DNDC model is one of the most successful models in the world in simulating the terrestrial biogeochemical cycles. This paper mainly reviewed the development process of the DNDC model, its structure, model validation, and sensitive factor analysis, and summarized the hot fields in the applications of the model.

[Waterborne iron migration by groundwater irrigation pumping in a typical irrigation district of Sanjiang Plain].

The iron concentration in groundwater, iron's seasonal migration from groundwater to sun-basked pools, paddy fields and drainage canals, and its distribution in the sediments/soils were observed in the Jiansanjiang Branch Bureau, Heilongjiang Agricultural Cultivation Bureau. The results suggested that the total iron mass concentration of the studied area was (1.73 +/- 0.41) mg x L(-1), ranging from 0.01 to 11.4 mg x L(-1), with the variation coefficient of 1.29%. The annual iron input mass from groundwater to paddy fields and other surface water bodies was 4 976.40 t in 2010, according to the rice planting area and rating irrigation volume. Dissolved Fe2+, Fe3+ and iron, as well as the total iron (dissolved and particle) had seasonal variation, with greater values presented in June and July. These waterborne irons in paddy field waters were greater than those in sun-basked pools and drainage canals. Obvious enrichment effect was observed in sun-basked pools and paddy fields, with their total iron mass concentrations were 6.17 and 21.65 times greater than that in groundwater. Either the total iron or iron oxides in sun-baked pool sediments were greater than that in paddy field soils, field canal and main canal sediments. The differences of the total iron and iron oxides in paddy field soils, field canal and main canal sediments were not significantly different. Considerable irons were precipitated within sun-basked pools and paddy fields during the transfer from groundwater to surface water, with a part of irons exporting into canals through drainage and then precipitated there. Not only the change of total iron mass, but the transformation of iron chemical speciation was observed during the transfer, which was affected by paddy irrigation management directly. The long-term irrigation pumping could cause the substantial enrichment of iron in paddy soils and canal sediments, resulting in the increase of potential pollution risk.

[Ichthyofauna and its community diversity in volcanic barrier lakes of Northeast China].

Based on the investigations of fish resources in Jingpo Lake and Wudalianchi Lakes in 2008-2011 and the historical data, this paper analyzed the characteristics of ichthyofauna and its community diversity in volcanic barrier lakes of Northeast China. The ichthyofauna in the volcanic barrier lakes of Northeast China was consisted of 64 native species, belonging to 47 genera, 16 families, and 9 orders, among which, one species was the second class National protected wild animal, four species were Chinese endemic species, and five species were Chinese vulnerable species. In the 64 recorded species, there were 44 species of Cypriniformes order and 37 species of Cyprinidae family dominated, respectively. The ichthyofauna in the volcanic barrier lakes of Northeast China was formed by 7 fauna complexes, among which, the eastern plain fauna complex was dominant, the common species from the South and the North occupied 53.1%, and the northern endemic species took up 46.9%. The Shannon, Fisher-alpha, Pielou, Margalef, and Simpson indices of the ichthyofauna were 2.078, 4.536, 0.575, 3.723, and 0.269, respectively, and the abundance distribution pattern of native species accorded with lognormal model. The Bray-Curtis, Morisita-Horn, Ochiai, Sørensen, and Whittaker indices between the communities of ichthyofauna in the volcanic barrier lakes of Northeast China and the Jingpo Lake were 0.820, 0.992, 0.870, 0.862 and 0.138, respectively, and those between the communities of ichthyofauna in the volcanic barrier lakes and the Wudalianchi Lakes were 0.210, 0.516, 0.838, 0.825, and 0.175, respectively. The ichthyofauna in volcanic barrier lakes of Northeast China was characterized by the mutual infiltration between the South and the North, and the overlap and transition between the Palaeoarctic realm and the Oricetal realm. It was suggested that the ichthyofauna community species diversity in the volcanic barrier lakes of Northeast China was higher, the species structure was more stable, but the species richness trended to decrease.

[Mn content in soil of Sanjiang Plain under different land use].

Mn content and its profile distribution characteristics were investigated in soils from the typical Deyeuxia angustifolia wetland, corn filed, paddy field, poplar forest and island forest in Sanjiang Plain. Results indicated that Mn content was relatively low and was in the range of 107.73-2 798.99 mg/kg with the average value of 403.24 mg/kg. Mn content significantly differed by land use (F = 9.272, P < 0.001) and was in the order of island forest > poplar forest > corn field > Deyeuxia angustifolia wetland > paddy field. On the whole, Mn content in each soil layer was in the order of corn filed > Deyeuxia angustifolia wetland > rice paddy in field and was in the order of island forest > poplar forest in the vertical direction. It suggested that Mn was enriched after wetlands were reclaimed in to the upland filed and Mn concentration was decreased when wetlands were changed into rice paddy. Correlation analysis showed that Mn content in soil significantly negatively related to pH (r = -0.279, P < 0.05), significantly positively related to sulfur (r = 0.383, P < 0.01) and dissolved organic carbon (r = 0.244, P < 0.05), and weakly related to soil organic matter and available sulfur, respectively. Changes of environmental factors had impacts on Mn species and then resulted in soil Mn content.

[Study on nutrient and salinity in soil covered with different vegetations in Shuangtaizi estuarine wetlands].

Nutrient elements and salinity in soil covered by different vegetations including Phragmites australis (Clay.) Trin., Typha orientalis Presl., Puccinellia distans Parl, and Suaeda salsa in Shuangtaizi estuarine wetlands were investigated to study their distribution characteristics and to reveal the nutrient element variation during the vegetation succession processes. Results indicated that total potassium, total phosphorus and salinity were different significantly in soil between different plant communities while available phosphorus, total nitrogen, available nitrogen, available potassium, total sulfur, iron and soil organic carbon were different insignificantly. Correlation analysis suggested that soil organic carbon were related significantly to total nitrogen, available phosphorus, available potassium, which implied that decomposition of plant litter might be the mail source of soil nitrogen and available nutrient. Salinity was significantly related to total phosphorus and iron in soil. In Shuangtaizi estuarine wetland soil, ratios of carbon to nitrogen (R(C/N)) was in the range of 12.21-26.33 and the average value was 18.21, which was higher than 12.0. It indicated that soil organic carbon in Shuangtaizi estuarine mainly came from land but not ocean and plants contributed the most of soil organic matters. There was no significant difference in R(C/N) between soil from the four plant communities (F = 1.890, p = 0.151). R(C/N) was related significantly to sol salinity (r = 0.346 3, p = 0.035 8) and was increasing with soil salinity.

[Research progress of the coupling process of Fe and N in wetland soils].

The coupling process of the earth system is the key research content of earth surface system at present. Wetland is an important ecosystem on the earth surface. Wetland soil is under anaerobic conditions seasonally or perennially because of waterlogging, where the redox of Fe and N can be coupled by microbiology. The coupling process lies in three aspects: the microbial coupling of NO(3-)-reduction and Fe(2+)-oxidation, coupling of Fe(3+)-reduction and NH(4+)-oxidation and the interaction of NO3- and Fe3+ during reduction. Getting the knowledge of the coupling process has important significance to understand the cycles of Fe and N in wetland soil. The article reviews the research status of the three aspects. In general, we have a comparatively deep understand of the coupling process of NO(3-)-reduction and Fe(2+)-oxidation than the latter two aspects. The research of microbial mechanism of the coupling process of Fe(3+)-reduction-NH(4+)-oxidation and the comprehensive evaluation of the environmental significance of coupling process of Fe and N in wetland soil should be strengthened in the future research, and then it can provide evidence for wetland protection and management.

[Dynamic change of dissolved iron in wetland soil solutions responding to freeze-thaw cycles].

The effects of five freeze-thaw cycles on the dynamic change of dissolved iron in three typical wetland soils (humus marsh soil in Carex lasiocarpa community, meadow marsh soil in Cares meyeriarna community, and meadow albic soil in Calamagrostis angustifolia community)of Sanjiang Plain, Northeast China, was analyzed through in-situ soil column simulation. One freeze-thaw cycle was conducted as freezing at -10 degrees C for 1 d and then thawing at 5 degrees C for 7 d. The thermostatically incubated soils at 5 degrees C were controls. The results showed that most pH and Eh values increased after the first freeze-thaw cycle, and then decreased after the subsequent cycles. 84.4% of the pH values of freeze-thaw treated soils were smaller than that of control, while 82.2% of the Eh values of freeze-thaw treated soils were greater than that of control. Most of the dissolved iron in all soil solutions were Fe3+ ions and colloids, and the reduction of these Fe3+ species were inhibited. The concentrations of Fe2, Fe3+, and total dissolved iron (TFe) of the freeze-thaw treated soils were all smaller than that of controls, with the means of (0.62 +/- 0.08) mg x L(-1) and (1.25 +/- 0.16) mg x L(-1), respectively. The variation trends of pH, Eh, and dissolved iron in the humus marsh soil were significantly different from that in the meadow albic soil. The trends in the meadow marsh soil, as the transitional soil type, were more similar to the meadow albic soil for pH, while more similar to the humus marsh soil for Eh and dissolved iron. Among the three soils, the difference between freeze-thaw treated columns and controls of the second layer were all smaller than that of the third and fourth layer, which indicated that the effect of freeze-thaw cycles were more significant for the upper annular wetland soil layers than the lower layers.

[Mercury contents and distribution characteristics in cicadae].

Total mercury contents of cicadae bodies, wings and exuviaes were studied in Huludao City to discuss mercury distribution characteristics in cicadae and to reveal the environmental mercury accumulation effects in the long life-cycle insects through comparing cicadae with other insect species. The average mercury contents of cicadae bodies were 2. 64 mg x kg(-1) and much higher than those in the contrast sites (1.00 mg x kg(-1) on average) in Huludao City. Mercury contents were found in the order of cicadae bodies > wings (0.98 mg x kg(-1) on average) > exuviaes (0.50 mg x kg(-1) on average). Sex differences of mercury contents and body weights of cicadae were significantly great. The females had larger body weights (1.11 g on average) and lower mercury contents (1.34 mg x kg(-1) on average) than the males (body weight: 0.54 g on average; mercury contents: 3.38 mg x kg(-1) on average), respectively. Mercury contents of cicada's bodies varied greatly with sample sites, mercury contents of wings changed little. No significant correlation was found between mercury contents of soil and cicadae bodies. Mercury contents of cicadae were lower than those of dragonflies, higher than those of other insects with shorter life-cycle periods and it reflected the accumulation effects of environmental mercury in the long life-cycle insects such as cicadae.

[Spatiotemporal distribution characteristics of soil iron in the annular wetland under different water regime].

The effect of water regime on the spatial distribution of total iron and the seasonal variation of dissolved iron in a typical annular wetland of Sanjiang Plain, Northeast China, was analyzed through in situ sampling of soils and soil solutions. The results showed that the average level of total iron of the wetland soil (0-60 cm) was (2.54 +/- 0.73) x 10(4) mg x kg(-1), which decreased gradually from the Calamagrostis angustifolia community in the edge of the annular wetland [(2.91 +/- 0.51) x 10(4) mg x kg(-1)], to the C. meyeriana community [(2.60 +/- 0.35) x 10(4) mg x kg(-1)], the C. lasiocarpa community [(2.48 +/- 0.31) x 10(4) mg x kg(-1)], and the of C. pseudocuraica community [(2.17 +/- 0.31) x 10(4) mg x kg(-1)] in the centre of the annular wetland. The iron solubility of perennial flooding soil was higher than seasonal flooding soil. The gross dissolved iron increased from soil thawing in the late spring [(0.35 +/- 0.086) mg x L(-1)] to freezing in the late autumn [(12.67 +/- 2.92) mg x L(-1)], because the soil iron was activated by continuous submergence. The reduced degree as shown by Fe3+/Fe2+ increased with the increment of water depth or flooding duration. Significant and extremely significant correlations were observed between dissolved Fe3+ or Fe2+ and pH, TOC, TN and PO4(3-), which suggested that the distribution of iron was influenced by the soil physical and chemical properties, and coupled with the transfer and transformation of C, N, and P elements.

[Distribution of sediment iron of the ditch system in Sanjiang Plain, northeast China].

The iron distribution of the multi-level ditch system (hair canal-field canal-lateral canal-branch canal-main canal) was studied through total iron determination of the sediments (0-60 cm). The results showed that the mean concentration was (3.02 +/- 0.10) x 10(4) mg x kg(-1). Extremely significant difference was obseved between different ditch level (F = 6.261, p << 0.001), and the highest and the lowest concentration were present in the farmland lateral canal (3.71 x 10(4) mg x kg(-1)) and wetland canal (2.43 x 10(4) mg x kg(-1)), respectively. The difference of different sediment layers was not significant (F = 0.093, p = 0.693), while the iron concentrations of 0-10 cm and 10-20 cm sediments were 51.96% and 62.22% higher than that of the natural wetland soil nearby, respectively. Iron can transfer with the runoff in a certain extent, but it was not cumulated along the ditch system with the largest cumulation location at the third level. The runoff containing iron decreased gradully because of the wetland protection and climate change nowadays. The horizontal transfer of iron along the ditch system indicated the timing and intensity of iron loss in the past since the canals were dredged.

[Response of meadow soil nitrogen to hydro-periods in Napahai plateau wetland].

A two-year field located monitoring was carried out to study the impacts of hydro-periods on the lakeshore meadow wetland soil total nitrogen (TN) and hydrolysable nitrogen (HN) in Napahai plateau wetland in northwestern Yunnan province. The results show that meadow soil alternate drying-wetting is the significant characteristic influenced by hydro-periods. Hydro-periods of meadow wetland control the physical environment of meadow soil, and the occurrence of TN in the upper layer (0-20 cm) was influenced more significantly than in the deeper layer (20-40 cm) by wetland hydro-periods. The dynamics of TN (0.96-1.30 g/kg) show a shape of anomalous "W" in the upper layer. And in the rainy season, the dynamics of TN was the same as the trend of water level fluctuation, while the HN was in the reverse trend. The enzyme activities were influenced by hydro-periods and then controlled the mineralization process of organic nitrogen. In August when wetland water fell, the highest amount of HN was 222.19 mg/kg (0-20 cm layer) and 47.41 mg/kg (20-40 cm layer) respectively. But when the wetland water level rose, the HN was moved to wetland water by the rising water level, and the decrease amplitude was 42% and 48% respectively. Therefore the deterioration of the environment of water was aggravated.

[Dynamic changes of Ruoergai Plateau wetland ecosystem service value].

Based on the satellite remote sensing data acquired in 1975 and 2006, and by using the assessment method of ecosystem service value, the dynamic changes of physical production value, gas regulation value, and water storage value of Ruoergai Plateau wetland ecosystem in 1975-2006 were studied. During study period, the total value of the three services decreased from 19.59 billion RMB Yuan to 12.38 billion Yuan RMB, among which, physical production value increased by 0.302 billion RMB Yuan, while the gas regulation and water storage value decreased by 7.507 billion RMB Yuan. The benefit from the increase of physical production was much less than the loss of ecosystem degradation. Overgrazing induced the biomass reduction and soil deterioration, resulting in the decline of Ruoergai Plateau wetland ecosystem service value and service capacity.

[Heavy metal contents in insects collected from the Huludao City suffering pollution by zinc smelting and cholor-alkai production].

14 insect species, which were classified to three groups: the herbivorous, the polyphagous and the carnivorous, and earthworms were collected from the grasslands in Huludao City, Liaoning Province, China. Mercury, cadmium and lead contents in biota were determined to discuss the heavy metal pollution in organisms. Mercury, cadmium and lead contents were 0.168, 9.19 and 12.58 mg x kg(-1) in the herbivorous insects, respectively; 0.375, 24.43 and 17.71 mg x kg(-1) in the polyphagous insects, respectively; 0.928, 29.78 and 18.39 mg x kg(-1) in the carnivorous insects, respectively. It showed that heavy metal pollution in biota in Huludao City was heavy. Bioaccumulation abilities to heavy metals significantly differed with insect species. Snails and dragonflies could accumulate more mercury than the other insects and spiders could accumulate the most cadmium and lead in all insect species. These three metals investigated in insects were all sorted as the herbivorous < the polyphagous < the carnivorous. Cadmium and lead contents between the polyphagous and the carnivorous varied slightly. Correlation analysis showed that cadmium and lead contents were significantly related, but mercury and cadmium or mercury and lead were not. It indicated that cadmium and lead in insects were from the same pollution sources while mercury was more complex.

[Characteristics of the wetland soil iron under different ages of reclamation].

The temporal-spatial trends of soil total iron concentration (Fet), free degree (Fed/Fet), activation degree (Feo/Fed) and complex degree (Fep/Fed) of soil iron oxides after reclamation were studied in Sanjiang Plain Wetlands. The result suggests that Fet in the upper tillage layers (0 - 20 cm) are influenced by reclamation more significantly than that in the lower ones (20 - 100 cm), and so does the early ages (0 - 1 years) than the late ages (1 - 25 years). Fet is negatively correlated with organic matter extremely significantly (R = - 0.62), while that with total phosphorus and pH are not significant. Fet of soil layer I (0 - 10 cm) increases obviously during the first 7 years after reclamation, and tends to become stable after 13 years, while those ages of soil layer II (10 - 20 cm) are 8 years and 15 years respectively. Soil layer I shows shorter responding time and better regularity than layer II. Fed/Fet increases rapidly after reclamation, decreases later and then increases again. Feo/Fed indicates exponential decrease with the reclamation ages as well as Fep/Fed. Feo/Fed of layer I decreases radically during the first 4 years after reclamation and tends to become stable after 13 years, while that of layer II decreases dramatically within the first year and keeps stable henceforth. The counterparts of Fep/Fed are 6 years, 14 years, and 2 years respectively. With the fitted experimental equations of Fet, Feo/Fed, and Fep/Fed, the ages of reclamation can be deduced reversely, which indicates the implication of iron on the shifts of soil environment.

[Beta diversity of successional series in mash communities of Sanjiang Plain, China].

Four typical successional series in the marsh communities of Sanjiang Plain were selected to investigate the changes of their beta diversity. The results indicated that from the 'starting community' to the 'end community', which had the most and the least moisture level in the series, respectively, the similarity coefficient between each community and 'starting' community decreased with decreasing moisture gradient and increasing horizontal distance. The species turnover speed among the communities in each series had an increasing trend from lowland to upland. In the process of succession, the general trend was that the total number of plant species increased while the common species decreased, with the beta diversity between communities increased gradually. The analysis of succession mechanism supported the 'initial floristics composition hypothesis', and the plant Calamagrostis angustifolia would intensify its dominance in the mash of Sanjiang Plain.