Soru

Passage A
In recent decades, the traditional view of forests as battlegrounds where individual trees compete relentlessly for sunlight and soil nutrients has been fundamentally challenged. At the center of this paradigm shift is the discovery of mycorrhizal networks—vast, subterranean webs of fungal mycelia that interconnect the root systems of most plant species in a given forest. These networks, formed primarily by ectomycorrhizal fungi that colonize the root systems of multiple host trees, function as a biological superhighway. Through this "wood wide web," trees can actively share resources. Groundbreaking experiments in the 1990s used radioactive carbon isotopes to trace the movement of carbon between Douglas fir and paper birch trees, revealing a complex, bidirectional flow. During the summer months, when the paper birch was fully leafed out and photosynthesizing rapidly in the canopy, it transferred its excess carbon through the fungal network to the shaded Douglas fir saplings in the understory. In the spring and fall, when the deciduous birch lacked leaves, the flow reversed, with the evergreen fir supporting the birch. This evidence suggests that trees operate less as isolated, selfish competitors and more as a cooperative, interdependent community. By using the fungal network to allocate resources to the most vulnerable individuals, the forest ensures its collective survival and bolsters its overall resilience against environmental stress.

Passage B
The popular, almost romanticized characterization of forests as cooperative communities nurtured by altruistic fungal networks is deeply appealing, yet it remains scientifically problematic. While it is undeniably true that mycorrhizal networks—created when ectomycorrhizal fungi colonize the root systems of multiple host trees—facilitate the movement of resources between plants, attributing cooperative or egalitarian intent to this phenomenon fundamentally misreads evolutionary biology. Fungi are not benevolent facilitators acting for the good of the forest; they are independent organisms driven strictly by their own evolutionary self-interest. The transfer of carbon and other nutrients between trees via these subterranean networks is most likely a byproduct of the fungi optimizing their own resource acquisition and distributing those resources where it maximizes fungal growth. For instance, when a fungus moves carbon from a nutrient-rich, mature tree to a struggling, shaded sapling, it is essentially diversifying its host portfolio to ensure a steady, diversified future supply of carbohydrates for itself. Furthermore, recent botanical studies indicate that these exact same networks can also transport allelopathic chemicals—toxic compounds produced by one plant to inhibit the growth of another. This allows certain trees to actively suppress the growth of nearby rivals. Thus, the forest remains primarily a fiercely competitive environment. The fungal network is merely a shared infrastructure that individual plants and the fungi themselves ruthlessly exploit for competitive advantage.

Based on the passages, the authors of both Passage A and Passage B explicitly affirm which one of the following details regarding mycorrhizal networks?