The Effects Of Salt Marsh Vegetaiton On Soil Organic Carbon Fractions, Sources And Distirbution

Yancheng coastal wetland is an important ecoregion.To study the effects ofsalt marsh vegetation on soil organic carbon （SOC） fractions, sources anddistribution, topsoil （0～20cm） samples of mudflat （G）, Spartina alterniflorasalt marsh of1-year （M1a）,3-year （M2a）,5-year （M5a）,12-year （M12a）,S. alterniflora-Suaeda salsa plot（MJ-M）, S. salsa-S. alterniflora plot（MJ-J）,S. salsa salt marsh（J）, S. salsa-Scirpus mariqueter plot（HC-J）, S. mariqueterplot（HC-H）, and Phragites australis plot（HC-HL） of grass salt marsh werecollected along Xinyanggang coastal wetland. The soil characteristic, SOC,recalcitrant carbon（RC）, labile carbon（LC）, C/N ratio, and δ¹³C value weredetermined and the results showed that:（1）There were significant differences in soil characteristic amongvegetation zones. The grain size were between3.95～6.64; soil bulk densitieswere between1.34～2.08g/cm³; S. alterniflora vegetation decreased soil bulkdensity significantly（P<0.05）, soil water content were between34.98%～50.97%, and the average value is43.2%; soil salinity were between0.22%～2.33%; soil pH values were between8.05～8.56.（2）There were significant differences in soil organic carbon fractions andtotal nitrogen of vegetation zones. The SOC, RC and LC were between0.81～7.60mg/g,0.58～4.02mg/g and0.24～3.90mg/g, the average values of whichwere3.57mg/g,1.88mg/g and1.60mg/g respectively; the TN were between141.05～863.58mg/kg; the C/N were between5.38～11.69, the average value ofwhich was7.49.（3） The contribution of S. alterniflora to SOC, RC and LC significantlyincreased with invasion time（P<0.01）.In seaward avasion area of S. alterniflora,the SOC, RC and LC were between0.82～7.60mg/g,0.58～4.02mg/g and 0.23～3.58mg/g respectively, and the highest value of SOC occurred in M12a,where the SOC accumulated by1.8tC/ha per year. The fraction of SOC, RC andLC derived from S. alterniflora were5.75～47.40%,6.77～31.77%and3.20～64.40%, respectively. The fraction of SOC, RC and LC derived from S.alterniflora were39.06%,32.66%and44.49%in MJ-M plot, respectively;17.02%,13.96%and21.61%in MJ-J plot, respectively;9.56%,6.33%and16.59%in Jplot, respectively.（4）The contribution of S. salsa to SOC was less than7%. The contributionof S. mariqueter to SOC were30.21%,18.52%, and38.51%respectively. Thecontribution of Phragites australis to SOC were20.18%,13.54%,25.91%respectively.