Impact of Spartina alterniflora invasion on evapotranspiration water loss in Phragmites australis dominated coastal wetlands of east China

A comparative analysis of co-existing invasive and native wetland plants is a practical approach to exploring exotic plant invasiveness. Spartina alterniflora is an invasive C4 grass, prevalent in China's coastal wetlands and other parts of the world, posing a risk to the hydrological cycle. While the crop coefficient Kc and evaporative water loss of the invasive S. alterniflora are still considerably unexplored, we utilized field measurements and a modeling technique to evaluate water loss to Evapotranspiration ET in marshes with S. alterniflora and P. australis. Changes in surface resistance, canopy height, and the technique used to calculate net radiation from incoming solar radiation have all been shown to influence the Penman–Monteith methodology for estimating ET. Overall, S. alterniflora surpassed P. australis in leaf area index LAI, ET, crop coefficient Kc, peak net photosynthetic rate, and growing season. Daily ET values in both plants ranged from 0.98 to 6.35 mm/day and 1.91 to 8.16 mm/day during the monitoring period. According to regression analysis, the key driving factors of ET from both plant communities throughout the growing season are net radiation, soil moisture, relative humidity, air temperature, and surface temperature. These findings highlight the necessity of precisely determining these parameters based on site-specific data instead of depending on empirical models developed mainly for crops and forests. Given the mean ET rates found in this study, S. alterniflora invasion in China currently accounts for ~4.3 × 106 m3 day−1 of water loss to ET, posing a severe threat to the availability of water resources in China's wetlands. Our findings contribute to a better understanding of the link between plant invasiveness and water loss in wetlands, offering stakeholders a benchmark for achieving future goals and plans related to the utilization of wetland water resources worldwide.