Abstract: To reveal the photosynthetic response mechanism of Spartina alterniflora to shading and mowing, we investigated the effects of different treatments (0% shading + no mowing, 0% shading + mowing, 30% shading + no mowing, 30% shading + mowing, 50% shading + no mowing, 50% shading + mowing, 70% shading + no mowing, 70% shading + mowing, 90% shading + no mowing, 90% shading + mowing) on the photosynthetic characteristics of S. alterniflora. Seven photosynthesis-related indices were measured, including daily average photosynthetic rate, maximum net photosynthetic rate, light compensation point, dark respiration rate, chlorophyll a, chlorophyll b, and carotenoids. The results showed that shading significantly inhibited daily average photosynthetic rate (P<0.01), which decreased with increasing shading intensity. The contents of chlorophyll a and carotenoids increased significantly with increasing shading intensity (P<0.01). Mowing significantly inhibited daily average photosynthetic rate, chlorophyll a, chlorophyll b, and carotenoid content (P<0.01). Shading and mowing interacted to affect light compensation point of S. alterniflora (P<0.05), but did not affect other indices. Principal component analysis revealed that the combination treatment of 90% shading and no mowing exhibited the strongest inhibition on photosynthetic activities of S. alterniflora.

Key words: Spartina alterniflora, shading, mowing, photosynthetic characteristics, principal component analysis