Final answer:
Without the specific figures showing the relationship between mean number of species per plot and nitrogen deposition, we cannot determine how much each kilogram of nitrogen reduces species diversity.
Step-by-step explanation:
The question relates to the impact of inorganic nitrogen deposition on the diversity of species within an ecosystem. Unfortunately, without the specific figures from the original experiment that shows the relationship between the mean number of species per plot and the deposition of inorganic nitrogen, it's not possible to accurately provide the reduction in species diversity. Typically, such a question would be answered by looking at a graph or data set that shows a clear decline in the number of species as nitrogen deposition increases. The students would use the information from the graph to calculate how many species are lost per kilogram of nitrogen added. Without the actual figures, we can't perform this calculation or pick the correct answer from the options provided.