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

Determination of the number of ψ(3686) events taken at BESIII

The number of ψ(3686) events collected by the BESIII detector during the 2021 run period is determined to be (2259.3±11.1)×106 by counting inclusive ψ(3686) hadronic events. The uncertainty is systematic and the statistical uncertainty is negligible. Meanwhile, the numbers of ψ(3686) events collected during the 2009 and 2012 run periods are updated to be (107.7±0.6)×106 and (345.4±2.6)×106, respectively. Both numbers are consistent with the previous measurements within one standard deviation. The total number of ψ(3686) events in the three data samples is (2712.4±14.3)×10^