Effects of temperature and rainfall in plant-herbivore interactions at different altitude

In ecology, plant-herbivore relationships are the crucial link generating animal biomass from mere sunlight through photosynthesis. These interactions are basic in understanding ecology and evolution of virtually any ecosystem. The relationship depends also on environmental factors like rainfall, temperature and altitude. Understanding patterns of these environment-dependent interactions will help to make better predictions and recommend possible conservation strategies. Many of existing mathematical models for plant-herbivore interactions and their analysis do not include these environmental factors. In this study, a mathematical model that incorporates variations of some of the parameter values due to changes in temperature and rainfall is formulated and used to determine necessary threshold values for co-existence, To validate the results of the mathematical model, real data from the Genale-Dawa river basin in the southern part of Ethiopia, is collected and used. The river basin represents the three major climatic zones of the country, the cool zone, temperate zone and hot lowlands. Numerical simulations were done using the collected data and it is observed that coexistence is possible in all the three regions but it is sensitive to the change in rainfall and temperature. If the change is within 10% there is a possibility of population extinction. Hence this paper shows that co-existence of population is highly dependent on the environmental changes.