The population starts out small due to a recent epidemic and has caused grass to be plentiful. This large amount of grass causes the birth rate to increase.
The population quickly starts to grow and resources are still plentiful. This causes immigration of zebra from other herds and creates further growth in the population. However growth will not be sustained for ever and resources will start to drain.
The population has reached carrying capacity. The grass is greatly depleted and the population will soon decrease greatly. This decrease in population is due to several factors. The density dependent factor of predation from Lions causes many deaths. The increase in the Zebra population caused an increase in the Lion population causing more and more Zebra to be eaten. The density dependent factor of crowding has also caused the decrease. Zebra can not find space to mate and therefore leads to less births. Along with these there is also the factor of emigration. These Zebra emigrate to find land with plentiful amounts of grass. Along with these density dependent factors, the population is being greatly depleted due to density independent factors such as poaching for their hide. A flood has also caused a large amount of the already picked clean soil to wash away along with what little grass was left. While not represented currently by the graph it will follow if further record is made.
This chart represents logistic growth, the slow growth followed by exponential growth and followed by a plateau in growth, and the effects of the limiting factors on the population and how the carrying capacity of a population will eventually be met due to a limited amount of grass and space along with other factors. Eventually the population will greatly decrease.