I plotted species richness using chao estimator and I got a drop in the middle of the graph and then it picked up again. What is the significance of that or what did I do wrong?
Did you study Catastrophe theory? I think that point is one of such kind. One need to know more details about your model so that one may give the right answer.
Read the data intensely. Some changes in related factors may have taken place. You need to explain rather than smoothen it. Use dummy for that point after you get to know the process behind the data point