Comparison of growth and photosynthesis characteristics of native and exotic salt marsh vegetation under elevated temperature[2mm] and waterlogging conditions
Growth and photosynthesis characteristics of native Phragmites australis and exotic Spartina alterniflora, the dominant salt marsh species in China's coastline, grown under elevated temperature and waterlogging conditions, were investigated. The results showed that elevated temperature increased the shoot height, leaf area, maximum rate of photosynthesis, and the apparent quantum yield of $P$. australis under non-waterlogging (Non-W) and shallow-waterlogging (S-W) conditions. However, the effect was negligible for the growth and photosynthesis parameters of $P$. australis in deep-waterlogging (D-W) conditions. The shoot height of $P$. australis reached a maximum, but the leaf area was lowest in a D-W state, indicating morphological adaption to waterlogging. D-W conditions significantly decreased the photosynthesis and chlorophyll fluorescence parameters of $P$. australis during the middle and later growth periods, compared to Non-W and S-W conditions. Both temperature elevation and waterlogging increased the growth, photosynthesis and chlorophyll fluorescence parameters of $S$. alterniflora, and the degree of increase under elevated temperature was greater than that of $P$. australis. Differences in growth and photosynthesis of $S$. alterniflora between the waterlogging treatments were not notable throughout the growing period. Analysis of variance showed that the effect of elevated temperature on the eco-physiological characters of $P$. australis was season-dependent, and the impact of waterlogging treatment was more notable with some interaction between the treatments. The effect of temperature elevation on photosynthesis parameters of $S$. alterniflora was notable, but not for the waterlogging treatment. We suggest that anticipated climate warming and rises in sea level might be beneficial to the exotic marsh species.