Question

You perform an experiment to compare the breakdown rate of leaves of four tree species. Species A has a solubility of 3 mg C/g dry leaf and a lignin/nitrogen ratio of 4:1. Species B has a solubility of 15 mg C/g dry leaf and a lignin/nitrogen ratio of 3:1. Species C has a solubility of 8 mg C/g dry leaf and a lignin/nitrogen ratio of 1:1. Species D has a solubility of 1 mg C/g dry leaf and a lignin/nitrogen ratio of 2:1. Which species would you expect to have the fastest decay rate within the first 50 days (first answer), and which species do you predict will have the fastest decay rate after 50 days (second answer)?

a. species A; species C
b. species C; species D
c. species B; species C
d. species C; species B
e. species D; species A

Answer 1

Species B is expected to decay fastest within the first 50 days due to its high solubility, while Species C is predicted to decay fastest after 50 days because of its optimal lignin/nitrogen ratio for continued microbial activity.

Step-by-step explanation:

In considering the breakdown rate of leaves from four different tree species, we look at two factors: solubility of carbon (mg C/g dry leaf) and the lignin/nitrogen ratio. Higher solubility often indicates faster decay due to easier microbial access to the carbon within the leaves, while a lower lignin/nitrogen ratio indicates a higher nitrogen content relative to lignin, which also supports quicker decomposition as nitrogen is crucial for microbial growth.

Species B, with a solubility of 15 mg C/g dry leaf and a lignin/nitrogen ratio of 3:1, would be expected to have the fastest decay rate within the first 50 days due to its high solubility. After 50 days, when most of the easily decomposable material has been consumed, species C, with its balanced lignin/nitrogen ratio of 1:1, would likely have the highest decay rate due to its more favorable conditions for sustained microbial activity.

Therefore, the answer is c. species B; species C.