Read the following passage and match each of the researcher's theoretical claims regarding the mycorrhizal network (listed on the left) with the specific textual evidence that supports it (listed on the right).
Passage
For years, popular science writers have championed the 'Wood Wide Web' hypothesis, which posits that mycorrhizal fungi networks facilitate a cooperative, altruistic exchange of nutrients between mature trees and struggling seedlings. However, plant ecologist Dr. Elena Vance argues that these underground networks are sites of resource competition rather than community aid. According to Vance, mature trees use the fungal connections to actively suppress the growth of understory competitors by absorbing disproportionate amounts of soil phosphorus, effectively starving nearby seedlings. Vance's team monitored phosphorus-32 isotopes in a mixed temperate forest and found that oak seedlings connected to mature oak networks exhibited a 40% reduction in phosphorus uptake compared to isolated seedlings. Furthermore, Vance points out that the carbon transferred from mature trees to seedlings via these networks is negligible—accounting for less than 1% of the seedlings' daily carbon requirements. Critics of Vance's model suggest that the reduced phosphorus levels are merely a byproduct of soil saturation, but Vance counter-argues that the isotopic tracing showed direct transport paths leading away from seedling root zones toward mature trees. Ultimately, Vance contends that mycorrhizal networks are best understood as biological conduits exploited by dominant species to maintain canopy supremacy.
- The claim that fungal networks do not provide a significant source of energy to growing seedlings.The finding that the carbon transferred accounts for less than 1% of the seedlings' daily carbon requirements.
- The claim that mature trees actively suppress competitor growth by depleting nutrients.The finding that oak seedlings connected to mature networks showed a 40% reduction in phosphorus uptake compared to isolated seedlings.
- The claim that nutrient depletion in seedlings is caused by transport to mature trees rather than general soil conditions.The finding that isotopic tracing showed direct transport paths leading away from seedling root zones toward mature trees.