Skip to content
📢We are still a growing community and would love some help. Want to contribute? Join us by mailing an e-mail of interest to "r6394175@gmail.com"
Start helping our community →
← Theoretical A

Q13 — Nitrogen Limitation of Legumes in Steppes

Theoretical A Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Ecology

Legumes can fix nitrogen from the air. Anecdotal evidence showed industrial pollution with nitrogen and other macronutrients making legumes less fit for nitrogen-poor steppes and other grasslands, which make up half of Kazakhstan.

Six bar-chart panels (2 rows x 3 columns) showing normalized change (NC) in legume cover (A), species richness (B), and biomass (C) after 3 years (top row) and 6 years (bottom row) of soil treatment with combinations of nitrogen (N), phosphorus (P), and potassium (K+), relative to control soil (CTL). Black dots mark bars that are statistically significant versus control; nitrogen-containing treatments are consistently negative. Figure 1. The graph shows the effect of increased nutrients on the legumes in steppe field plot study. They had control soil (CTL), as well as soil enriched with N (nitrogen), P (phosphorus), K⁺ (potassium), and combinations of these elements. The top row is the normalized change (NC) after 3 years of treatment, and the bottom row is the NC after 6 years of treatment. Letters represent NC in A) legume cover B) species richness C) biomass of legumes. Black dots represent a statistically significant difference from control. Whiskers stand for the Standard Error of Mean (SEM).

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. Potassium coupled with nitrogen has a non-significant effect on legume cover.
B. Legume biomass has the opposite response to changes in soil nutrients after 3 years and 6 years of treatment.
C. The graphs support steppe being, in general, a nitrogen-limited ecosystem.
D. In analogous graphs for non-nitrogen fixing plants, the NC values for nitrogen-enriched soil will be positive.
← Previous: Q12 Next: Q14 →

Question reproduced from IBO 2024, Theoretical Exam Part A, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)