ABSTRACT
Diurnal variation and its influencing factors of leaf water potential (ψl) of Spinifex littoreus on the nebkhas in two succession periods were measured on the coast of Pingtan Island, Fujian Province. The results showed that the diurnal variation of ψl of S. littoreus mainly demonstrated a 'W' curve pattern, with a temporary rise at midday. The mean ψl of S. littoreus on the nebkhas at developing stage was higher than that at stabilizing stage, and recovered better during the night. ψl of S. littoreus was positively related to the atmospheric water potential (ψa) and relative humidity, negatively related to air temperature, but had no significant correlation with the soil water potential at different depthes. ψl of S. littoreus on the interdune depression at developing stage was higher than that on the windward slope and on the leeward slope from 10:00 to 16:00, and that on the windward slope was lower than that on the leeward slope all day long except at 10:00 and at 12:00. The variation of ψl of S. littoreus on the leeward slope was higher than that on the windward slope, and the minimal variation was found on the interdune depression, without statistical significance. ψl of S. littoreus on the windward slope was positively correlated with ψa and relative humidity, while negatively correlated with air temperature. ψl of S. littoreus on the leeward slope and the interdune depression were correlated with meteorological factors, but they had no significant relationship.
Subject(s)
Plant Leaves , Water , China , Islands , SoilABSTRACT
Soil and vegetation community were investigated using the method of kilometer grid sampling. In addition, using the maximum entropy (MaxEnt) and the GIS spatial analysis technique, the potential distribution of dominant species in the Yellow River Delta and their major environmental variables and ecological parameters were quantitatively analyzed. The results showed that the dominant species of the coastal wetland were Tamarix chinensis, Phragmites australis and Suaeda salsa in the Yellow River Delta. Among the environmental variables, six variables were significant contributors to the potential distribution model of T. chinensis: NO3--N, salt, slope, Mg, altitude and NH4+-N. The environmental variables influencing the distribution of P. australis were NO3--N, salt, TP, pH, altitude and NH4+-N. NO3--N, salt and NH4+-N were the significant factors determining the potential distribution of S. salsa. The probability of presence of dominant species of the coastal wetland in the Yellow River Delta was positively correlated with salt, but it was negatively correlated with the other major environmental variables. The model predicted that the core potential distribution of dominant species in the Yellow River Delta was mainly in the coastal areas. In addition, P. australis had a wider range of distribution, compared with T. chinensis and S. salsa.
