Grass conservation

We can model this behaviour with a set of three reactions and their differential equations, (a) In the first reaction the sheep are breeding. Note, that there is a constant supply of grass and this reaction could go on forever. As it is written, this reaction violates the law of conservation of mass, it is only an empirical rate law. In a second reaction (b), wolves eat sheep and breed themselves. The third reaction (c) completes the system, wolves have to die a natural death. 

Moore-Colyer, M.J.S. and Longland, A.C. (2000) Intakes and in vivo apparent digestibilities of four types of conserved grass forage by ponies. Animal Science 71, 527-534. 

Pike, D.R., E.L. Knake, and J.L. Hill (1994). Survey of management practices used for reserve acreage and grassed waterways. J. Soil and Water Conserv., 49(6) 612-615. 

Changes in Organic Acid Content of Perennial Rye-grass During Conservation, E. L. Hirst and S. Ramstad, J. Set. Food Agric., 8, 727 (1957). 

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