VEGETATION CHARACTERISTICS AND CONTROL TECHNIQUES OF SPARTINA ALTERNIFLORA IN DIFFERENT TIDAL FLAT HABITATS

Spartina alterniflora is one of the most harmful alien invasive species in the coastal areas of China. It is of great significance to explore efficient and feasible control technology of S. alterniflora to protect the intertidal ecological environment. Based on the long-term field investigation and in-situ experiments in the Yellow River Delta, this study revealed the efficacies of different control techniques of S. alterniflora. From the middle of June, 2018, 2 to 4 times of mowing (the stubble height was less than 3cm, and the interval between adjacent mowing events was approximately 15 days) could eliminate more than 99% of S. alterniflora, and the control efficacy was still as high as 98.8% at the end of the second growing season. Mowing plus ploughing in mid-December resulted in a controlled efficacy of 99.7% at the end of the second growing season. The tidal flat elevation gradually increased from sea to land, and the environmental factors such as soil s physical and chemical properties changed accordingly. The density, plant height and biomass of S. alterniflora increased first and then decreased with the increase of elevation. Considering the growth characteristics, habitat characteristics of S. alterniflora and the efficacies of different control techniques, a control technology system of S. alterniflora suitable for different tidal flat habitats was summarized. In the low tidal flat, middle tidal flat and high tidal flat, mowing close to the ground, mowing plus waterlogging, and mowing plus tilling were recommended, respectively. For S. alterniflora in river channels or ditches, mowing plus tilling or mowing plus waterlogging were recommended according to the factors, such as the width of the channels or ditches. For S. alterniflora on the ditch slope, mowing plus shading was recommended

Effects of Spartina alterniflora Invasion on Soil Carbon, Nitrogen, Phosphorus and Their Ecostoichiometric Characteristics in the Yellow River Estuary Wetlands

Spartina alterniflora invasion has severely threatened the ecological integrity of coastal wetland ecosystems. The carbon, nitrogen, phosphorus and ecostoichiometric characteristics of soils in different layers were investigated under different stages of S. alterniflora invasion in the Yellow River Estuary wetlands. Using the method of substituting space for time, 0-100 cm soil samples were collected in wetlands of different stages of S. alterniflora invasion (SA3, invaded in 2016;SA8, invaded in 2011;SA13, invaded in 2006)and uninvaded bare flats (SA0). The contents of total carbon (TC), total nitrogen (TN)and total phosphorus (TP), were then measured and analyzed by the stoichiometric ratios of carbon, nitrogen and phosphorus. Results showed that (1)S. alterniflora invasion increased the content of TC and TN in surface soils, but had little effects on TP. (2)TC contents in the 0-10 cm soil layer of SA16, SA11 and SA06 were 18.9%, 27.6% and 57.6% higher than that of SA0, respectively, and TN contents were 1.39, 2.37 and 3.66 times higher than that of SA0, respectively. (3)S. alterniflora invasion didn't significantly affect soil w(C)/w(N), but increased w(C)/w(P)and w(N)/w(P)in shallow soils, and decreased w(C)/w(P)and w(N)/w(P)in deep soils. The order of soil w(C)/w(P)and w(N)/w(P)in the 0-10 cm soil layer was SA13>SA8>SA3>SA0. In the 0-100 cm soil layer, the order of soil w(C)/w(N)was SA0>SA8>SA13>SA3, that of soil w(C)/w(P)was SA13>SA8>SA0>SA3, and that of soil w(N)/w(P)was SA13>SA0>SA3>SA8. In the 0-100 cm soil layer, soil pH, electrical conductivity, bulk density and water content were important environmental factors affecting the contents of carbon, nitrogen and phosphorus. There were no significant correlations between w(C)/w(N)and soil environmental factors, but w(C)/w(P)and w(N)/w(P)were significantly correlated with environmental factors. In conclusion, S. alterniflora invasion changed the contents of soil carbon and nitrogen in the salt marsh wetlands of the Yellow River Estuary and affected the balance of soil nutrient resources