Abstract: Macrozoobenthic assemblages were investigated monthly in Lake Changdang from June 2011 to May 2012, and bioassessment of water quality was conducted based on biological indexes. A total of 28 taxa were identified, including 10 Chironomidae larvae, 7 Oligochaetes, 5 molluscs and 6 other species. Bellamya aeruginosa, Limnodrilus hoffmeisteri, Tanypus chinensis, Microchironomus tabarui, Branchiura sowerbyi and Chironomus semireductus dominated the community with high abundance and biomass. Annual average density and biomass of macrozoobenthos were 769 ind·m^-2 and 74.89 g·m^-2, respectively. Marked spatial differences were found for the annual average density and biomass of macrozoobenthos in Lake Changdang with a higher spatial difference for the mean biomass than for the mean density. Higher mean biomass values were found in littoral sampling sites but lower values in open lake sampling sites. The results of Wright index, Goodnight-Whitley index, BPI index (biological pollution index) and Shannon index suggested that Lake Changdang suffered slight to moderate pollution.

Key words: understory removal experiment, plant-plant interaction, understory vegetation, forest management