Energy flow and organic matter decomposition in an abandoned beaver pond ecosystem.

A beaver pond can be considered an open ecosystem with a number of energy inputs and outputs. The net difference between input and output represents the accumulation of energy within the system. During 1973 input-output parameters were measured independently for one spring fed pond (surface area 736 m2) in the Kananaskis Valley, Alberta, Canada. The yearly energy budged indicated that allochthonous energy inputs into the pond were much greater than autochthonous inputs. Of the total yearly energy input 18% was exported, 26% was respired and 56% accumulated in the sediments. This percentage utilization for respiration was low when compared with similar data from the literature for live aquatic ecosystems elsewhere. However the actual annual mean sediment respiration rate of 8.4 ml m-1 hr-1 compared favourably with the figure of 6.1 ml m-2 hr-1 predicted from Hargrave's 1969 respiration equation for benthic communities. This situation suggests that the allochthonous input, while dominant, is highly refractive and rapidly becomes locked up in the sediments. The high photosynthesis-respiration ratio of 0.81 together with the results of earlier litter bag experiments (Hodkinson, 1975) support this conclusion. Thus the beaver pond is a highly accretive heterotrophic ecosystem.