System with grass and herbivores
Elsa Boogaard
(delta Grass / delta T) = [WUEg]*[Water]*[Grass]*(([Kg]-[Grass])/[Kg])
(delta H / delta T) = [FUEh]*[Herbivores]*[Grass]*[Grazing rate]*(([Kh]-[Herbivores])/[Kh])*.5*[Water]
