How do droppings of wintering waterbird accelerate decomposition of Carex cinerascens Kükenth litter in seasonal floodplain Ramsar Site?

The decomposition of wetland plant litter is pivotal in the functioning of wetland ecosystems in terms of organic matter mineralization progress and nutrient cycling. Aiming to investigate the effects of the droppings of wintering herbivorous waterbirds on the decomposition of Carex cinerascens Kükenth litter a newly designated Ramsar Site, decomposition patterns of three types of samples were characterized and compared by waterbird dropping addition and litterbag in situ experiment. The three types of samples are OCL (only C. cinerascens litter), OWD (only waterbird droppings) and CMD (C. cinerascens litter mixed with waterbird droppings), respectively. A total of 105 decomposition bags were placed and the experiment lasted 150 days. The results showed that the average decay rate of C. cinerascens cellulose increased by approximately 32.12% by the addition of bird droppings, while the C. cinerascens lignin decay rate increased by approximately 83.05%. And the release of carbon, nitrogen and phosphorous of C. cinerascens increased by approximately 18.3%, 61.09%, and 66.71%, respectively. We concluded that the addition of waterbird droppings significantly accelerated the decomposition of C. cinerascens litter and the release of carbon, nitrogen, and phosphorus. We have a preliminary deduction that waterbird droppings (1) altered the original stoichiometric ratio of the litter, (2) increased the available nutrient content, (3) increased the colonization ability of the microorganisms, and (4) stimulated the production of a series of extracellular degradation enzymes. This study provides a thinking that the important role of waterbirds should be given full attention in wetland restoration planning and management.