Studies On The Sensitive Limiting Factors Of Competition Between Exotic Invasive Plant Spartina Alterniflora And Scirpus Mariqueter

Spartina alterniflora is a typical exotic invasive plant in coastal wetlands ofChina. The sensitive limiting factors of competition between exotic invasiveplant S. alterniflora and Scirpus mariqueter were tested in the laboratory. Thepotential mechanism of the invasion of S. alterniflora was also studied toprovide some scientific suggestion for the restoration and protecting theJiuduansha wetland national nature reserve from invasion of S. alterniflora.In this study, four salinity level and four nitrogen level were established toexamined the interactive effects of salt and nitrogen on seed germination andseedling growth of S. alterniflora as well as S. mariqueter. Two salinity leveland six nutrient addition level were established to test the growth andinter-competition of S. alterniflora and S. mariqueter. Besides, the iron plaqueand its effect on phosphorus transformation in root of S. mariqueter and S.alterniflora were investigated. The results we acquired were as follows:(1) The seed germination percentage of S. alterniflora improved atLow-salinity levels but decreased slightly at relatively High-salinity conditions.However, the seed germination percentage of S. mariqueter decreased with anincrease on salinity. Nitrogen promoted an increasing in the germination ratio ofS. mariqueter in low salinity and exhibited no significantly effect ongermination ratio of S. alterniflora.(2) The seedling root length, shoot length and fresh weight of S. mariqueterdecreased significantly with increasing salinity, in contrast to the results for S.alterniflora. Nitrogen promoted an increasing in the seedling shoot length andthe fresh weight in S. alterniflora, but inhibited root elongation of the seedling.However, few defects were found in the seedling growth of S. mariqueter undernitrogen addition.(3) The growth of S. mariqueter was significant inhibited by high salinity, nitrogen addition facilitated the growth of S. mariqueter slightly in low salinitylevel. However, the growth of S. alterniflora was hardly inhibited by highsalinity, the nutrient addition, especially the nitrogen addition significantlyimproved the aboveground biomass of S. alterniflora.(4) Both the growth of S. mariqueter and S. alterniflora were inhibited bythe inter-competition. The high salinity and nutrient addition increased thecompetition intensity of S. alterniflora to S. mariqueter, which cause the inferiorof S. mariqueter in the competition.(5) The iron plaque amount in root of S. alterniflora was higher than S.mariqueter in field environment. What’s more, the iron plaque amount in root ofS. alterniflora increased with the increasing of invasion time.(6) S. alterniflora could utilize more phosphorus nutrient than S.mariqueter through the more amount of iron plaque. Therefore, the advantage inutilize phosphorus may be a potential mechanism of the invasion of S.alterniflora.