Question

Ecosystems like fields are naturally patchy with respect to nutrients, meaning within a single field there are high, medium, and low nutrient patches. Arbuscular mycorrhizal fungi (AMF) species can be helpful for plants to gain nutrients especially in low nutrient patches. The addition of nutrients to a field through fertilization reduces the natural nutrient heterogeneity and creates consistently high levels of nutrients throughout the field. Ecologists conducted a 5-year experiment to determine how the addition of fertilizer to a field every year affects AMF diversity. Which set of rank abundance curves below best represents the change in AMF diversity over the 5 year experiment due to the addition of fertilizer? Proportional Abundance Proportional Abundance Year 1 Year 2 Year 3 Year 4 Year 5 2 4 10 12 14 0 2 4 10 12 14 6 8 Abundance Rank 6 8 Abundance Rank Proportional Abundance Proportional Abundance 0 2 4 10 12 14 0 2 4 10 6 8 Abundance Rank 12 14 6 8 Abundance Rank 0 0 0 0

Answer 1

Introduction: Arbuscular mycorrhiza (AM) belongs to fungi. It exhibits a symbiotic relationship between plants and mycorrhiza. The common association exists with plants such as shrubs, and trees. The main function of AMF is to provide water and nutrients from the soil for the plants. A rank abundance curve is also known as Whittaker plot. It is used to demonstrate the relative species abundance. Species abundance is an important factor in biodiversity. Species richness is the number of species found in an ecosystem. The rank abundance graph determines the evenness and richness of a particular species in a specific ecosystem or location.

Answer: The rank abundance curve which best represents the change in AMF diversity for period of 5 years by addition of fertilizer is Graph "A".

Explanation:

The rank abundance graph indicates two aspects a steep gradient and a shallow gradient. The steep gradient is shows low evenness whereas the shallow gradient shows high evenness. The species abundance is better in shallow one than steep ones. The graphs provided shows, the AMF diversity on addition of fertilizer is better for the "graph A" shows a geometric plot for year 1 to 4 years showing abruptness and steep plot indicating loss of species, whereas in the 5th year an evenness in the graph is observed indicating richness in the AMF. Since in the 5th year a shallow plot is seen, it indicates that the AMFs have adapted itself to fertilizer addition each year and grows better in good numbers. Graph B, shows shallow gradient in 2nd and 4th year whereas the 5th year a steep plot is seen. Graph C and D show shallow gradient in 1st and 2nd year and 5th year shows a steep plot. Thus graph A, shows richness in species after addition of fertilizer every year into the fields.