[Changes of soil carbon, nitrogen and phosphorus and stoichiometry characteristics in marsh invaded by Spartina alterniflora]. / äº’èŠ±ç±³è‰å ¥ä¾µä¸‹æ¹¿åœ°åœŸå£¤ç¢³æ°®ç£·å˜åŒ–åŠåŒ–å­¦è®¡é‡å­¦ç‰¹å¾.

To clarify the effect of invasive alien plants on ecosystem functions, soil total carbon (TC), total carbon (TN), and total phosphorus (TP) contents were studied in the exotic invasive plant Spartina alterniflora marsh with different durations and the native species Cyperus malaccensis marsh in the Minjiang River estuary. The results showed that there were different variations of TC, TN and TP at 0-50 cm soil layer in the C. malaccensis marsh invaded by S. alterniflora, but the changes of TC and TN were similar and the change of the TP lagged behind them. Soil C/N increased continually with the increase of TC. Soil TP was a key factor affecting soil C/P and N/P during the S. alterniflora invasion, and the change of C/P and N/P followed a similar trend. The changes of TC, TN and TP were influenced by abiotic factors such as soil salinity, bulk density, soil water content and clay composition. C, N and P stoichiometric ratios were influenced mainly by soil salinity and grain composition. C/N and C/P were the good indicators for soil carbon enrichment ability in S. alterniflora marsh. S. alterniflora invasion induced the change of biomass and marsh habitats. Soil carbon, nitrogen, phosphorus contents, and their ecological stoichiometric ratios changed significantly in the C. malaccensis marsh invaded by S. alterniflora and showed diffe-rent change characteristics with different invasion duration.

[Diurnal and seasonal variations of surface atmospheric CO2 concentration in the river estuarine marsh].

Characteristics of diurnal and seasonal variations of surface atmospheric CO2 concentration were analyzed in the Minjiang River estuarine marsh from December 2011 to November 2012. The results revealed that both the diurnal and seasonal variation of surface atmospheric CO2 concentration showed single-peak patterns, with the valley in the daytime and the peak value at night for the diurnal variations, and the maxima in winter and minima in summer for the seasonal variation. Diurnal amplitude of CO2 concentration varied from 16.96 micromol x mol(-1) to 38.30 micromol x mol(-1). The seasonal averages of CO2 concentration in spring, summer, autumn and winter were (353.74 +/- 18.35), (327.28 +/- 8.58), (354.78 +/- 14.76) and (392.82 +/- 9.71) micromol x mol(-1), respectively, and the annual mean CO2 concentration was (357.16 +/- 26.89) micromol x mol(-1). The diurnal CO2 concentration of surface atmospheric was strongly negatively correlated with temperature, wind speed, photosynthetically active radiation and total solar radiation (P < 0.05). The diurnal concentration of CO2 was negatively related with tidal level in January, but significantly positively related in July.

[Litter decomposition and its main affecting factors in tidal marshes of Minjiang River Estuary, East China].

By using litterbag method, this paper studied the decomposition of the leaf- and flower litters of two emergent macrophytes, native species Phragmites australis and invasive species Spartina alterniflora, and related affecting factors in the Minjiang River estuary of East China. In the decomposition process of the litters, the decay of standing litter (0-90 days) was an important period, and the loss rate of the flower- and leaf litters dry mass of P. australis and S. alterniflora was 15.0 +/- 3.5% and 13.3 +/- 1.1%, and 31.9 +/- 1.1% and 20.8 +/- 1.4%, respectively. During lodging decay period (91-210 days), the loss rate of the flower- and leaf litters dry mass of P. australis and S. alterniflora was 69.5 +/- 0.6% and 71.5 +/- 2.5%, and 76.8 +/- 1.9% and 67.5 +/- 2.1%, respectively. In standing decay period, the decomposition rate of the two plants litters was positively correlated with the litters C/N but negatively correlated to the litters N/P, and the litters P was an important factor limiting the litters decay. In lodging decay period, the effects of the litters C/N, C/P, and N/P decreased, while the environment factors (climate, soil moisture, soil acidity and salinity, and sediment properties) acted more important roles. The differences in the factors affecting the decay of the litters in different decomposition periods were mainly related to the micro-environment and tidal process for the two plant communities.

[Methane fluxes of Cyperus malaccensis tidal wetland in Minjiang River estuary].

By using enclosed static chamber-gas chromatograph techniques, this paper measured the methane fluxes of Cyperus malaccensis tidal wetland in Minjiang River estuary. The diurnal variation of the methane fluxes in summer and winter were in the range of 1.29-2.93 mg x m(-2) x h(-1) and 0.06-0.22 mg x m(-2) x h(-1), respectively. The methane fluxes before flooding, in the process of flooding and ebbing, and after ebbing were 0.11-1.52 mg x m(-2) x h(-1), 0.10-1.05 mg x m(-2) x h(-1), and 0.05-1.70 mg x m(-2) x h(-1), and the monthly averaged fluxes were 0.73, 0.47, and 0.72 mg x m(-2) x h(-1), respectively. The methane fluxes peaked in September and reached the lowest in March, and were significantly lower in the process of flooding and ebbing than before flooding and after ebbing (P < 0.05). The seasonal variation of the methane fluxes was in the order of summer > autumn > spring > winter. Tide was the key factor affecting the diurnal variation of the methane fluxes, while plant growth stage and temperature were the key factors determining the monthly or seasonal variation of the methane fluxes.

Methane (CH4) emission from a tidal marsh in the Min River estuary, southeast China.

The total methane emission to the atmosphere and hydrosphere, and its seasonal variation, were estimated using an enclosed static chamber technique from a tidal marshes dominated by Phragmites australis (common reed) in the Min River estuary, southeast China. Measurements were taken at three tidal stages (before flood, during the flooding and ebbing process, and after ebb). Potential rates of methane production from the marsh sediment layers were also measured using an incubation technique. This P. australis tidal marsh was a net methane source, emitting 32.59 and 6.87 g CH(4) x m(-2) x yr(-1) to the atmosphere and hydrosphere, respectively. There was considerable monthly variation with emissions greater before flood in some months, whereas at other months emission was greater after ebb. The average methane fluxes were 5.13, 5.06 and 4.74 mg CH(4) m(-2) h(-1) before flood, during flooding and ebbing, and after ebb, respectively. Emissions to the tidewater and the atmosphere during the flooding and ebbing process were 2.98 and 2.08 mg CH(4) m(-2) h(-1),respectively. Sediment methane production potential (0-40 cm depth) ranged from 0.028-0.123 micro g CH(4) x g(-1) x d(-1), with the greatest production was in the surface soil. Methane fluxes had a significant correlation with atmospheric, sediment temperature and above ground biomass. The implications of these data for global warming are discussed briefly.

[Effect of human disturbance on ecological stoichiometry characteristics of soil carbon, nitrogen and phosphorus in Minjiang River estuarine wetland].

To clarify responses of soil ecological stoichiometry in wetland to human disturbance, the ecological stoichiometry characteristics of carbon, nitrogen and phosphorus elements of soil in Phragmites australis marsh, grassland, flat breed aquatics, cropland, pond aquaculture after human disturbance and abandoned cropland after human disturbance restoration in Minjiang River estuary were analyzed. The results showed: averaged values of C/N, C/P, N/P ratios were declined as the human disturbance increment, which appeared that Phragmites australis marsh, grassland (lower human disturbance, 25.53, 156.06, 6.11 and 27.58, 158.99, 5.78) were bigger than flat breed aquatics (medium human disturbance, 25.02, 96.90, 3.87), and flat breed aquatics (medium human disturbance) were bigger than cropland, pond aquaculture (higher human disturbance, 17.55, 46.19, 2.65 and 22.30, 57.51, 2.62). Compared with cropland, C/N, C/P, N/P ratios in abandoned cropland (human disturbance restoration) were (19.95, 63.81, 3.18) higher. The influencing factors were changed with the human disturbance intensity. Soil C/N ratios showed relatively small variation between different human disturbance and soil depth, while C/P and N/P ratios showed a high heterogeneity. The ratio of carbon to nutrition had preferable indication for carbon storage.

[Seasonal dynamics of nitrogen- and phosphorus absorption efficiency of wetland plants in Minjiang River estuary].

Taking the native Phragmites australis and invasive Spartina alterniflora in Minjiang River estuary as test objectives, this paper studied the seasonal dynamics of their biomass and nitrogen- and phosphorus absorption efficiency. A typical single-peak curve was presented for the seasonal dynamics of aboveground biomass and nitrogen- and phosphorus absorption efficiency of the two species. P. australis had the maximum aboveground biomass (2195.33 g X m(-2)) in summer, while S. alterniflora had it (3670.02 g X m(-2)) in autumn. The total nitrogen (TN) and total phosphorus (TP) contents of P. australis reached the peak (21.06 g x m(-2) of TN and 1.12 g x m(-2) of TP) in summer and in autumn, respectively, while those of S. alterniflora all reached the peak (26.76 g x m(-2) of TN and 3.23 g x m(-2) of TP) in autumn. Both of the two species had a higher absorption efficiency in TN than in TP (P < 0.01), and S. alterniflora had a significantly higher absorption efficiency of TN and TP than P. australis (P < 0.05). To some extent, the N/P, C/N, and C/P ratios of plants could indicate the nitrogen- and phosphorus absorption efficiency of the plants.