| Soil respiration is one of the largest fluxes in global carbon cycle. Land-use changes is a crucial factor for the raise of the atmospheric CO2. Hence, several typical land-use patterns in three study areas, located in the east mud of Chongming, were taken as research objects with details as follows:Scirpus mariquete, Phragmites australis and Spartina alterniflora in non-reclamation areas; dry farmland, flood drought rotation field, Metasequoia forest belt and fish pond in 98-92 reclamation areas; dry farmland, flood drought rotation field, Metasequoia forest belt, fallow land and Poplar forest belt in 92-68 reclamation areas. With the measurements of soil respiration rates, temperature humidity, organic carbon and so on, the influence of different land-use patterns and reclamations upon soil respiration was studied in the east mud of Chongming, together with the study of soil respiration dynamics and its control factors, which expected to deeply understand the soil carbon cycle process under different land-use patterns in east mud of Chongming, therefore to provide the scientific guidance for the management and recovery of natural wetlands and wetlands after reclamation, the evaluation and optimization of land-use patterns in reclamation areas and the establishment of low carbon economic experimental areas.The results showed that:1. The influence of land-uses upon soil respiration rates:(1) non-reclamation area the sequence of soil respiration intensity was as follows:Phragmites australis (0.26±0.03 mol·m-2·d-1)> Spartina alterniflora (0.24±0.03 mol·m-2·d-1)> Scirpus mariquete (0.20±0.03 mol·m-2·d-1). The trend of annual variation of soil respiration showed to be the same with that of temperature variation in 5cm deep of soil whereas the time each patterns reached to the highest point showed to be different. The soil respiration of Spartina alterniflora reached to the highest point in growth period, which might form the physiological and ecological basis for its spread in east mud. For Scirpus mariquete, the organic carbon turned out to be low and its soil respiration stayed at a low level. Compared with Phragmites australis, Spartina alterniflora turned out a higher level of organic carbon and a low level of soil respiration, which was of high emission reduction potential. In months of spring, the diurnal variation vibration curve showed great whereas that of Phragmites australis and Spartina alterniflora were gentle. The annual soil respiration values and temperature in three patterns accorded with index model, in which Phragmites australis showed a good correlation.(2) Reclamation areas the sequence of annual average soil respiration intensity in 98-92 reclamation area was as follows:dry farmland (0.38±0.08 mol·m-2·d-1)> Metasequoia forest belt (0.22±0.02mol·m-2·d-1)> flood drought rotation field (0.21±0.03mol·m-2·d-1)> fish pond (0.05±0.01 mol·m-2·d-1). The sequence of annual average soil respiration intensity in 92-68 reclamation areas was as follows:dry farmland (0.56±0.07 mol·m-2·d-1)> Metasequoia forest belt (0.41±0.03 mol·m-2·d-1)> Poplar forest belt (0.35±0.02 mol·m-2·d-1)> flood drought rotation field (0.32±0.03 mol·m-2·d-1)> fallow land (0.25±0.02mol·m-2·d-1).The annual variation of soil respiration rates generally kept a basically identical trend with that of temperature in 5cm deep of soil. There was a generally high level of soil respiration and organic carbon in dry farmland. The soil respiration rate curve of flood drought rotation field and dry farmland intersected in May, which both showed an X style.Flood drought rotation field turned out a high level of soil respiration rate during wheat culture periods, whereas there was a significant decrease of soil respiration rate after the irrigation in May. Besides in the rice cropping period of flood drought rotation field, the soil respiration rate showed a relative low value compared with other patterns, which would play a positive role for the soil carbon sequestration in farmlands.The Metasequoia forest belts turned out a relative high content of soil organic carbon but a low soil respiration rate, which would be an ideal land pattern for soil carbon sequestration and emission reduction of farmlands.In spring, there was a non-fixing relationship between soil respiration diurnal variation and temperature, which mostly showed a consistent variation trend. The Metasequoia forest turned out a gentle change but the other two farmland patterns showed a relative large fluctuation. There was no good correlation between all farmland patterns and soil temperature moisture.2. The influence of whether reclaimed or not and the time length of reclamation upon soil respiration:(1) The sequence of annual soil respiration intensity for Phragmites australis was as follows:reclamation areas (0.32±0.04 mol·m-2·d-1)>non-reclamation areas (0.26±0.03mol·m-2·d-1)(2) The sequence of annual soil respiration intensity for dry farmland, flood drought rotation field and Metasequoia forest belts was as follows:92-68 reclamation area>98-92 reclamation area, with their details as follows:dry farmland 92-68 (0.56±0.07mol·m-2·d-1)>98-92 (0.38±0.08mol·m-2·d-1); flood drought rotation field 92-68 (0.32±0.03mol·m-2·d-1)> 98-92 (0.21±0.03mol·m-2·d-1); Metasequoia forest belt 92-68 (0.41±0.03mol·m-2·d-1)＞98-92 (0.22±0.02mol·m-2·d-1). |
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