Abstract: The study on the effects of different cutting intensities on the eco-physiological characteristics and growth status of Stylosanthes guianensis showed that moderate cutting could promote the regrowth capacity of the grass.The total content of leaf chlorophyll had no significant difference between zero,light-and heavy cutting,but the ratio of leaf chlorophyll a/b increased to 1.59∶1 and 1.52∶1 under light-and heavy cutting,respectively, compared with 1.22∶1 under zero-cutting,which could be very helpful for the plant to over-compensate itself.Cutting also affected the growth status and activities of plant roots.At the earlier stage of heavy cutting,the total length, total surface area and mean diameter of plant roots decreased by 54.9%, 66.5% and 27.2%,respectively,and root activities also decreased greatly,in comparing with zero-cutting.But,the above-mentioned indices could be recovered to a higher level under different cutting treatments than under zero-cutting at the later growth period of the grass.As for the total annual yield of the grass,it was 3 179.8 g·m^-2 under light-cutting,3 006.1 g·m^-2 under heavy-cutting,and 2 936.98 g·m^-2 under zero-cutting,indicating that rational cutting could improve grass productivity.

Key words: Phytoplankton, Estuarine ecosystem