Goose Faeces: A Source of Nitrogen for Plant Growth in a Grazed Salt Marsh

(1) Effects of faeces of lesser snow geese on salt-marsh vegetation at La P6rouse Bay, Manitoba together with the processes of faecal decay, were studied in order to determine how goose grazing significantly increased the net above-ground primary production of forage species, Puccinellia phryganodes (Trin.) Scribn. & Merr., and Carex subspathacea Wormsk. (2) Addition of fresh faeces to experimental plots at densities comparable to those recorded in the salt-marsh, resulted in significant increases in standing crop compared with untreated plots. The nitrogen content of shoots collected from treated plots was also higher. (3) Much of the nitrogen initially present in faeces was soluble (60% w/v ethanol extraction), but within 48 h the soluble N content fell greatly. Faeces placed in mesh bags for 2 5 months lost dry matter and soluble nitrogen; little decomposition of organic nitrogen was detected. (4) Except for the period immediately after the hatch of goslings, much of the soluble nitrogen in faeces was ammonia. The nitrogen content of droppings (faeces) differed within and between droppings. (5) The role of lesser snow geese in accelerating the transfer of mobile nitrogen, which results in a higher production of the forage species, is discussed.