Abstract: The simulation study on the energy conversion and nutrient cycling in the grndyke-fish pond ecosystem shows that for this ecosystem, the photo-utilization rate of forage is 0.83%, and the conversion efficiency of feed energy into fish is 7.3%. Comparing with grain for fish farming, the efficiency of forage is 1.6 times greater. The conversion efficiency of feed nutrients (CEFN) to fish is 16.8, 32.3 and 2.0% respectively for N, Pand K. The recovery of nutrients in fishpond sediment is 23.4% for Nand 56. 1% for P, and the CEFNto hog carcass is 20.5, 33.6 and 4.6%, respectively for N, P and K. The recovery of nutrients in the feces is 36.4% for N, 63.8% for P and 39.4% for K. The conversion efficiency of fed energy and nutrients to fish is higher in compound system than in single one.

Key words: Grass dyke-fish pond, Ecosystem, Energy conversion, Nutrient cycling, Yihe basin, landscape index, driving factors, landscape pattern