Homework Help?? Biology Question?? Anyone Can help me answer this...?

An Ecologist studying desert plants preformed the following experiement...she stalked 2 identical plots that included a few sagebrush plants and numerous small annual wildflowers. she found the same 5 wildflopwer species in simular numbers in both plots. Then she enclosed one plot with a fence to keep the kangaroos,rats out. after 2 years 4 species of wildflowers were no longer present in the in the fenced plot,but one wildflower species had incresed dramatically . the unfenced control ploot had not changed significantly in the species composition. using the concepts....what do you think happened?