Eco-chemical factor evaluation among different types of wetlands on Qi'ao Island, Zhuhai

Some ecological factors and plant leaf greenness of Spartina alterniflora, Sonneratia apetala, Aegiceras corniculatum, and Cyperus malaccensis wetlands were determined at fixed times, and the significance of differences were analyzed in order to explore potential habitat changes due to species invasion. The results showed that the leaf greenness was in order of S. alterniflora (47.37) < A. corniculatum(58.92) < S. apetala(65.35). The pH value in the upper surface soil within S. alterniflora wetland was 6.33 and significantly lower than that of A. corniculatum wetland (6.71). No significant difference in the redox potential (Eh) was found between overlying water and lower surface soil within S. alterniflora wetland, but the Eh in overlying water was significantly lower than that in lower surface soil within three other wetlands. The Eh in upper surface soil within S. alterniflora wetland was 39.16 mV and significantly higher than that in A. corniculatum wetland (24.04 mV). The conductivity of overlying water within S. alterniflora wetland was 7.96 ms/cm and significantly higher than that in C. malaccensis wetland (6.92 ms/cm); the conductivity of lower surface soil within S. alterniflora wetland was 4.42 ms/cm and significantly higher than that of S. apetala wetland (3.26 ms/cm). Therefore, as an invasive plant, the growth of S. alterniflora had led obvious changes of some ecological factors within habitat, including the significant pH decrease in upper surface soil, the subdued difference of Eh between overlying water and lower surface soil, the significantly higher Eh in upper surface soil than native plant A. corniculatum wetland, the significantly higher conductivity in overlying water than C. malaccensis wetland, and so on. Considering their ecological effects, we strongly suggest that strict management measures should be implemented to limit the growth of invasive species S. alterniflora. Further study for S. apetala is warranted in order to better analyze its potential ecological effects.