Impact of marsh changes on breeding cranes in Sanjiang Plain,northeastern China

In order to measure the impact of changes in the marsh on breeding Red-crowned Cranes (Grus japonensis) and White-naped Cranes (G.vipio) in the Sanjiang Plain,we conducted a complete crane súrvey in each of the summers of 2007 and 2008,and obtained information on the changes in its marsh through interpretation of satellite images in 1986,1995,2000 and 2005.A comparison between the 1984 and 2008 census shows that:1) the number of Red-crowned Cranes remained stable at about 300 birds,while the number of White-naped Cranes increased markedly; 2) the estimates of nests of Red-crowned cranes are close to the numbers of 1984,while approximately 90％ of the nests of these two crane species were distributed over five national nature reserves (NNRs); 3) the two crane species became more concentrated in three regions,i.e.,the Fuyuan Delta,the middle reaches of the Naoli and Qixing rivers,and the Xingkai Lake wetlands,rather as formerly in six regions.The area of the marsh decreased by 45％ within the 20-year period from 1986 to 2005.The major loss of the marsh area was in the form of a conversion to paddy fields and dry land,which can be primarily attributed to direct human activity under various economic and policy drivers.The disappearance of cranes in the Dulu and Abuqin rivers was induced by large-scale agricultural development.The fragmentation into and isolation of small areas of the marsh became increasingly more serious,which resulted in unsuitable condtions for crane breeding in small patches of the marsh.The number of cranes declined from 1984-1995 but had recovered remarkably by 2008,which may be due to theestablishment of a system of nature reserves,in place since 2000.The land ownership of the reserve plays a key role in maintaining the integrity of the wetland ecosystem,especially in Sanjiang,Honghe,Naolihe and Qixinghe NNRs,which together accommodated approximately 80％ of the population of cranes.However,we did not discover any nests at all in the provincial and municipal reserves,which may be attributed to high human disturbances in these areas.In the end,we propose some recommendations on reserve management.

Seasonal characteristics of Carex lasiocarpa biomass and nutrient accumulation in the typical wetland of Sanjiang Plain, China

Seasonal dynamics of above- and belowground biomass and nutrient characteristics （nitrogen, carbon, and phosphorus） of Carex lasiocarpa were investigated in the typical wetland of Sanjiang Plain, China from May 2007 to September 2008. The results show that the changes of aboveground biomass during the growing season are best described by the twice function curve model, whereas the changes of belowground biomass follow the exponential increase curve model. Both the organic carbon contents in the above- and belowground plant parts show significant positive linear correlations with the growing time, and the coefficients R2 are 0.983 and 0.746, respectively. The carbon accu-mulations of the above- and belowground plant parts during the growing season show the same dynamics as those of the biomass. However, the nitrogen contents and accumulation in C. lasiocarpa aboveground and belowground parts show exponential increase during the growing season. The dynamics of C. lasiocarpa phosphorus contents follows the twice function curve model, whereas the accumulation of phosphorus shows the linear increase. The ratios of C/N in different parts of C. lasiocarpa fit the negative linear relations with total nitrogen content in the growing season. Moreover, the ratios of C/P in C. lasiocarpa plant also fit the negative linear relations with total phosphorus content. The results show that nitrogen is the primary limiting nutrient for C. lasiocarpa growth as compared with carbon and phosphorus.

Influence of environment and substrate quality on the decomposition of wetland plant root in the Sanjiang Plain,Northeast China

The litterbag method was used to study the decomposition of wetland plant root in three wetlands along a water level gradient in the Sanjiang Plain,Northeast China.These wetlands are Calamagrostis angustifolia(C.aa),Carex meyeriana(C.ma)and Carex lasiocarpa (C.la).The objective of our study is to evaluate the influence of environment and substrate quality on decomposition rates in the three wetlands.Calico material was used as a standard substrate to evaluate environmental influences.Roots native to each we...

Nitrogen cycling of atmosphere-plant-soft system in the typical Calamagrostis angustifolia wetland in the Sanjiang Plain,Northeast China

The nitrogen （N） distribution and cycling of atmosphere-plant-soil system in the typical meadow Calamagrostis angustifolia wetland （TMCW） and marsh meadow Calamagrostis angustifolia wetland （MMCW） in the Sanjiang plain were studied by a compartment model. The results showed that the N wet deposition amount was 0.757 gN/（m^2·a）, and total inorganic N （TIN） was the main body （0.640 gN/（m^2·a））. The ammonia volatilization amounts of TMCW and MMCW soils in growing season were 0.635 and 0.687 gN/m^2, and the denitrification gaseous lost amounts were 0.617 and 0.405 gN/m^2, respectively. In plant subsystem, the N was mainly stored in root and litter. Soil organic N was the main N storage of the two plant-soil systems and the proportions of it were 93.98% and 92.16%, respectively. The calculation results of N turnovers among compartments of TMCW and MMCW showed that the uptake amounts of root were 23.02 and 28.18 gN/（m^2·a） and the values of aboveground were 11.31 and 6.08 gN/（m^2·a）, the re-translocation amounts from aboveground to root were 5.96 and 2.70 gN/（m^2·a）, the translocation amounts from aboveground living body to litter were 5.35 and 3.38 gN/（m^2·a）, the translocation amounts from litter to soil were larger than 1.55 and 3.01 gN/（m^2·a）, the translocation amounts from root to soil were 14.90 and 13.17 gN/（m^2·a）, and the soil （0-15 cm） N net mineralization amounts were 1.94 and 0.55 gN/（m^2·a）, respectively. The study of N balance indicated that the two plant-soil systems might be situated in the status of lacking N, and the status might induce the degradation of C. angustifolia wetland.

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 soilwater 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 （R^2 = 0.3122 and R^2 = 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 affectext 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.

Dynamics of dissolved organic carbon in the mires in the Sanjiang Plain,Northeast China

Mires in boreal area had proved to be an important dissolved organic carbon （DOC） reserve for the sensitivity to climate change and human interfering. The study was focused on the temporal and spatial dynamics and controlling factors of DOC in a seasonallywaterlogged mire （SLM） and perennially-waterlogged mire （PLM） in the Sanjiang Plain, Northest China. In the two mires, DOC concentrations in both surface water and upper soil strata experienced pronounced seasonal variation. DOC concentrations in the surface waters were the greatest and averagely was 47.82 in SLM and 34.84 mg/L and PLM, whereas that in soil water at 0.3-m depth had little difference （20.25 mg/L in SLM and 26.51 mg/L in PLM）. Results revealed that DOC concentrations declined 5-8 times vertically from the surface down to groundwater. DOC in the groundwater only was in a very small part with the average concentration of 5.18 mg/L. In relation to the surface water, DOC concentrations varied positively with temperature just before 8 August, and only in early spring and later autumn DOC concentrations exhibited identifiable spatial trends along with standing water depths in PLM. It was supposed that the influences from standing water depth took effect only in conditions of low temperature, and temperature should be the most powerful factor controlling DOC dynamics in the mires. Redox potential （Red） showed negative relationship with DOC values while total nitrogen （TN） and the majority of free ions in the soil solution exhibited no relationship. High soil TOC/TN ratio and low redox potentials also led to DOC accumulation in the mires in the Sanjiang Plain.

Effects of Nitrogen Addition on Plant Functional Traits in Freshwater Wetland of Sanjiang Plain,Northeast China

To clarify the responses of plant functional traits to nitrogen(N) enrichment, we investigated the whole-plant traits(plant height and aboveground biomass), leaf morphological(specific leaf area(SLA) and leaf dry mass content(LDMC)) and chemical traits(leaf N concentration(LNC) and leaf phosphorus(P) concentration(LPC)) of Deyeuxia angustifolia and Glyceria spiculosa following seven consecutive years of N addition at four rates(0 g N/(m2·yr), 6 g N/(m2·yr), 12 g N/(m2·yr) and 24 g N/(m2·yr)) in a freshwater marsh in the Sanjiang Plain, Northeast China. The results showed that, for both D. angustifolia and G. spiculosa, N addition generally increased plant height, leaf, stem and total aboveground biomass, but did not cause changes in SLA and LDMC. Moreover, increased N availability caused an increase in LNC, and did not affect LPC. Thus, N addition decreased leaf C∶N ratio, but caused an increase in leaf N∶P ratio, and did not affect leaf C∶P ratio. Our results suggest that, in the mid-term, elevated N loading does not alter leaf morphological traits, but causes substantial changes in whole-plant traits and leaf chemical traits in temperate freshwater wetlands. These may help to better understand the effects of N enrichment on plant functional traits and thus ecosystem structure and functioning in freshwater wetlands.

The current status, threats and protection way of Sanjiang Plain wetland, Northeast China

The Sanjiang Plain is a vast area of alluvial floodplains and low hills in northeast Heilongjiang Province. It is the largest tract of wetlands in China and East Asia outside of Siberia. 28 wetland nature reserves exist on the Sanjiang Plain, and three of them have been listed as wetlands of international importance to water bird conservation by the Ramsar Convention Bureau. The wetlands of Sanjiang Plain are noteworthy for its rich biodiversity, but they continue to decline in area and deteriorate in quality currently. The main threats or constrains, immediate cause, root cause and required response are analyzed in this paper, and the four aspects opinion such as improvement of watershed management, enhancement of protection and restoration of habitats and biodiversity, alternative livelihoods of rural residents living in and near natural wetland reserve, and reinforcement of capacity building of natural reserves are brought forward as the effective measures for the Sanjiang Plain wetland protection.

DYNAMICS OF LITTER DECOMPOSITION AND SEASONAL DYNAMICS OF PHOSPHORUS IN DECOMPOSED RESIDUA OF Calamagrotis augustifolia IN THE WETLAND OF THE SANJIANG PLAIN

During the period of May to October in1999,systematical studies were giv en to the rate of decomposition of Calamagrostis angustifolia litter,the phosphorus content and weight in decomposed residua of litte r,and phosphorus content in the corresponding soil in the Sanjiang Plain.At the same time,the simulation models were listed in the paper.The results showed that the rate of we ight lost of decomposition of Calamagrostis angustifolia litter is 29.80%and the maximum of daily rate of weight lost i s 0.25%,which appeared in July.The c hange trend of phosphorus content an d weight in the decomposed residua of l itter is to reduce with the decomposing process,when it comes to the day of157,the decrement amount of the both were respectively 57.69mg /kg and 1.6199mg,which were 72.80%and 76.30%of its previous amount.In addition,th ere is a polynomial minus correlatio nship of phosphorus content between the variation in corresponding soil and the decomp osed residua of litter at the corresp onding period.The study will be help ful to further understand the process and mechanis m of biochemical cycling of nutrient elements in wetland ecosystems,in a ddition,it will also be helpful to the restoration and rebuilding of retrogressive wetlands and reasonable development and utilization of wetlands in the Sanjiang Plain.

Effects of Wetland Reclamation on Soil Nutrient Losses and Reserves in Sanjiang Plain,Northeast China

The carbon （C）, nitrogen （N） and phosphorus （P） variations of a temperate wetland soil under continuous cultivation for 40 yr were determined and evaluated in the Sanjiang Plain, Northeast China. The results showed that the soil organic carbon （SOC） and total nitrogen （TN） contents in each soil layer decreased sharply after cultivation for 2-3 yr, and exhibited minor differences after cultivation for 11 yr, which showed an exponential decline curve with the increase of cultivation years. The reduction rates of carbon and nitrogen reserves were 14.79% and 28.53% yr^-1 at the initial reclamation stages of 2-3 yr and then decreased to 2.02-3.08% yr^-1 and 1.98-2.93% yr^-1 after cultivation for 20 yr, respectively. Soil total phosphorus （TP） reserves decreased within cultivation for 5 yr, and then gradually restored to the initial level after cultivation for 17 yr. Both SOC and TN could be restored slightly when the farmland was left fallow for 8 yr after reclamation for 11 yr, whereas TP had no significant difference. These results demonstrated that wetland cultivation was one of the most important factors influencing on the nutrient fate and reserves in soil, which could lead to the rapid nutrient release and slow restoration through abandon cultivation, therefore protective cultivation techniques preventing nutrients from loss should be immediately established after wetland reclamation.

Contribution of winter fluxes to the annual CH_4, CO_2 and N_2O emissions from fres hwater marshes in the Sanjiang Plain

Wetlands at the interface of the terrestrial and aquatic ecosystems are intensive sites for mineralization of organic matter, but the contribution of winter season fluxes of CH4, CO2 and N2O from wetland ecosystems to annual budgets is poorly known. By using the static opaque chamber and GC techniques, fluxes of CH4, CO2 and N2O at two freshwater marshes in the Sanjiang Plain were measured during the winter seasons of 2002/2003 and 2003/2004 with contrasting snow conditions and flooding regimes. The results showed that there were significant interannual and spatial differences in CH4, CO2 and N2O fluxes. The Carex lasiocarpa marsh emitted more CH4 and CO2 while absorbed less N2O than the Deyeuxia angustifolia marsh during the winter seasons. Over the winter season, emissions of CH4, CO2 and N2O ranged from 0.42 to 2.41 gC/m^2, from 24.13 to 50.16 gC/m^2, and from -25,20 to -148.96 mgN/m^2, respectively. The contributions of winter season CH4 and CO2 emission to the annual budgets were 2.32% 4.62% and 22.17%- 27.97%, respectively. Marshes uptake N2O during the freezing period, while release N2O during the thawing period. The winter uptake equaled to 13.70%-86.69% of the growing-season loss. We conclude that gas exchange between soil/snow and the atmosphere in the winter season contributed greatly to the annual budgets and cannot be ignored in a cool temperate freshwater marsh in Northeast China.

EFFECTS OF AGRICULTURE RECLAMATION ON THE HYDROLOGIC CHARACTERISTICS IN THE SANJIANG PLAIN, CHINA

The Sanjiang Plain is the largest and most concentrated wetland region in China, the total area is about 1.088×107ha with rich marsh resources and biodiversity. Before 1949, the Sanjiang Plain was a large untravelled wild plant and waterfowl habitat, and there were some rare swans, red-crowned cranes and thousands of hydrophytes. From 1950, the local government began to reclaim the marsh in the Sanjiang Plain, built the commodity grain base of Northeast China, and developed the industry of grain processing, animal husbandry, etc. Up to now, there are 54 farms which control 3.5087×106ha agriculture field. The marsh areas are reduced by 1/2; many rare animals and plants are near extinction. The human activities and agriculture reclamation made a great change on the environment, especially made water balance change and regional climate change. So to study and protect the wetland ecosystem and marsh resource are extremely urgent. This paper focus on the hydrology change and climate change before and after marsh reclamation, including evapotranspiration, run off, soil character, micro-climate on both marsh and agriculture field, and the reason that cause seasonal drought, waterlogging and degeneration of marsh.

The renewability and quality of shallow groundwater in Sanjiang and Songnen Plain, Northeast China

Groundwater is a key component for water resources in Sanjiang and Songnen Plain, an important agriculture basement in China. The quality and the renewability of irrigation groundwater are essential for the stock raising and agricultural production. Shallow groundwater was sampled and analyzed for various variables. The salinity sodium concentration and bicarbonate hazard, were examined with regard to the United States Department of Agriculture （USDA） irrigation water standards. The concentration of chlorofluorocarbons （CFCs） was determined to analyze the age of groundwater. Most groundwater samples labeled as excellent to good for irrigation with low salinity hazard or medium salinity hazard. Four groundwater samples were good and suspected for irrigation with high salinity hazard. Generally groundwater in Sanjiang Plain was younger than the groundwater in Songnen Plain. Meanwhile, groundwater nearby river is younger than the groundwater further away inside the watershed. The mean age of groundwater in Sanjiang Plain is in average of 44.1,47.9 and 32.8 years by CFC-11 （CCI3F）, CFC-12 （CCI2F2） and CFC-113 （C2CI3F3）, respectively. The mean ages of groundwater in Songnen Plain is in average of 46.1, 53.4, and 40.7 years by CFC-11, CFC-12 and CFC-113, respectively. Thus, groundwater nearby rivers could be directly exploited as irrigation water. Partial groundwater has to be processed to lower the salt concentration rather than directly utilized as irrigation water in Songnen Plain. Both water quality and renewability should be put in mind for sustainable agricultural development and water resources management.

Mapping the fallowed area of paddy fields on Sanjiang Plain of Northeast China to assist water security assessments

Rice growth requires a large amount of water,and planting rice will increase the contradiction between supply and demand of water resources.Paddy field fllowing is important for the sustainable development of an agricultural region,but it remains a great challenge to accurately and quickly monitor the extent and area of fallowed paddy fields.Paddy fields have unique physical features associated with paddy rice during the flooding and transplanting phases.By comparing the differences in phenology before and after paddy field fllowing,we proposed a phenology-based fallowed paddy field mapping algorithm.We used the Google Earth Engine(GEE)cloud computing platform and Landsat 8 images to extract the fllowed paddy field area on Sanjiang Plain of China in 2018.The results indicated that the Landsat8,GEE,and phenology-based fllowed paddy field mapping algorithm can effectively support the mapping of fallowed paddy fields on Sanjiang Plain of China.Based on remote sensing monitoring,the total fallowed paddy field area of Sanjiang Plain is 91543 ha.The resultant fallowed paddy field map is of high accuracy,with a producer(user)accuracy of 83%(81%),based on validation using ground-truth samples.The Landsat-based map also exhibits high consistency with the agricultural statistical data.We estimated that paddy field fallowing reduced irigation water by 384-521 million cubic meters on Sanjiang Plain in 2018.The research results can support subsidization grants for fallowed paddy fields,the evaluation of fallowed paddy field effects and improvement in subsequent fallowed paddy field policy in the future.

ESTIMATION AND EXPLOITATION OF WATER RESOURCES IN THE SANJIANG PLAIN

According to practical measurement and related data, the writer discusses the main features of rivers in the Sanjiang Plain and the change of water balance with time and space, and then estimates water resources of five types, namely, runoff, ground water, soil water, and water supplied by three rivers and lakes (or reservoirs).The total volume of the above-mentioned water resources can be up to 31.5 billion m3. But they are rather unevenly distributed and the annual change is considerable, too. Up to now, only 8.3% of water resources have been utilized. According to a programme, 17.5 billion m3 will be utilized in the future in the district. Rationally exploiting water resources in the district should be combined with protection and management, and the sole criterion for judging rationality of utilization is that whether it is beneficial to economic, ecologic and social aspects.

Mercury Distribution and Accumulation in Typical Wetland Ecosystems of Sanjiang Plain,Northeast China

Total mercury in soil,water,plant,insects,fishes and bird feathers were determined to study mercury distribution and accumulation in typical wetland ecosystems in the Sanjiang Plain,Northeast China.Results show that total mercury concentrations in soils of Deyeuxia angustifolia wetland and Carex lascarpa wetland are 0.046 mg/kg and 0.063 mg/kg,respectively.Total mercury concentration in water bodies is 0.053 μg/L on average.Of four plants studied,total mercury in moss is the highest with the mean of 0.132 mg/kg.Of 10 terrestrial insect species studied,total mercury in centipede(Scolopendra spp.) is the highest with the mean of 0.515 mg/kg while total mercury in grasshopper(Oxya spp.) bodies is the lowest.Total mercury concentrations in the herbivorous,omnivorous and predatory insects are 10.18 ng/g,16.47 ng/g and 213.35 ng/g on average,respectively.Total mercury concentrations of the adult feather(549.88 ± 63.04 ng/g),nestling feather(55.15 ± 23.53 ng/g),and eggshell(22.05 ± 5.96 ng/g) of the Grey heron(Ardea cinerea) are higher than those of the Great egret(Egretta alba)(adult feather:446.57 ± 90.89 ng/g;nestling feather:32.99 ± 17.15 ng/g;eggshell:21.02 ± 3.17 ng/g) in the wetlands of the Sanjiang Plain.The bioconcentration factors decrease in the order of piscivorous fish muscle > omnivorous fish muscle > herbivorous fish > insect.

REGULARITY AND ESTIMATION OF METHANE EMISSION FROM MARSHLAND IN THE SANJIANG PLAIN

The regularity of CH 4 emission from marshland in the Sanjiang Plain was studied by sampling in the open field and analyzing under laboratory condition, the annual emission amount is also estimated. By Grey Relatively Analysis we know that the soil temperature in the 10 cm depth of grass root layer is close related with CH 4 emission. CH 4 emission has different kinds of diurnal emission modes:before dawn maximum mode, night maximum mode and irregular fluctuation mode. The seasonal variation trend of CH 4 emission rates is going up steadily from May to August and dropping down from September,the maximum lies behind the maximum of temperature. CH 4 emission rates of different marshland types are different, the CH 4 emission rate of Glyceriaspiculosa-Carex marshland is always higher than that of Carex lasiocarpa marshland. The paper also studies the difference of CH 4 emission rates in different managing modes and analyzes the emission rates between China and U.S.A. The result shows: the average value of CH 4 emission rate is 17.26mg/(m 2·h),the annual amount of CH 4 emission is about 0.75Tg.

DISTRIBUTION OF MERCURY IN TYPICAL WETLAND PLANTS IN THE SANJIANG PLAIN

Total mercury concentration of typical wetland plants was analyzed in thispaper. There were great differences of total mercury concentration among different plants:moss>hydrophyte>sedge>herbage>shrub. Total mercury concentrations show an increasing trend fromvascular plants to bryophytes, and from dry to wet lands. The mercury concentration of wetlandplants was higher than that of crops. The wetland soil was the source of mercury in the air close tothe ground, so it affected the concentration of mercury in the plant. In different parts of aplant, mercury concentration was in the order of: dead stand>root>leaf>stem. Mercury concentrationincreased at the initial stage and decreased in the end of the growing season. According to themercury content and biomass, mercury stock of plants was 39.4μg/m^2 above ground in Calamagrostisangustifolia wetland and 35.8μg /m^2 in Carex lasiocarpa wetland.

Analysis of developing non-timber forest products of Sanjiang Plain, Northeast China

The Sanjiang Plain is a vast area of alluvial floodplains and low hills in northeast Heilongjiang Province. Because of the excessive land reclamation in the past, the whole forest area and the quality have decreased. In the view of sustainable development, this paper analyzed the possibilities for Non-timber Forest Product in terms of developing potentialities, markets, social effects and the status of NTFPs in several counties of Sanjiang Plain. The result showed that, active development and management for NTFPs is an optimistic option to how to balance the wetlands conservation and sustainable economic development.

Effect of Nitrogen and Phosphorus on Tissue Nutrition and Biomass of Freshwater Wetland Plant in Sanjiang Plain,Northeast China

Nitrogen (4, 10, 20 and 40g/m2) and phosphorus (1.2, 4.8 and 9.6g/m2) were applied to tanks to evaluating the effects of N and P additions on plant tissue nutrition and the biomass of two freshwater wetland plants in the Sanjiang Plain of Northeast China, namely Carex lasiocarpa and Carex meyeriana. For C. lasiocarpa, the total N concentration (TN) of plant tissues under the treatment of 10g/m2 was lower compared with the other N treatments. Initially, C. lasiocarpa exhibited a significant increase of biomass as compared with the control value, reaching the maximum of 31.20±4.01g/tank under the treatment of 10g/m2, and then dropped to 18.02±1.53g/tank under the treatment of 40g/m2. For C. meyeriana, TN generally increased with increasing amount of N applied. High N applied produced more aboveground biomass than low N applied. C. meyeriana, as the accompanying species, can adapt itself to the wetland enriched by N, and it may replace C. lasiocarpa as the dominant species of wetland. The total P concentration (TP) in tissues of C. lasiocarpa increased with P addition. The aboveground biomass of C. lasiocarpa increased with P addition, and it changed from 18.77±3.29g/tank to 46.03±3.95g/tank. However, TP of tissue may accelerate the C. meyeriana development under the treatment of 1.2g/m2. P accumulation contributes to the dominance of C. lasiocarpa but limits the production of C. meyeriana, and the latter may disappear gradually from the wetland enriched by P. Increased input of N and P might have an influence on wetland plant community composition and structure, so the effects of nutrient inputs and accumulation should be considered to protect the freshwater wetland.