Practice question

The keyed response, rapid nutrient cycling, is better understood as a consequence and reinforcing correlate of fast decomposition than as its primary external cause. Tropical forest litter usually decomposes rapidly because warm temperatures and adequate moisture sustain enzymes, microbes, and detritivores throughout much of the year. Rapid mineral release then supports plant uptake and high productivity, creating tight nutrient cycling. Among the listed choices, the key captures this coupled regime, but the causal wording is scientifically imprecise and should be flagged as a mismatch. Environmental effects are often nonlinear; drought suppresses microbial access to substrates, waterlogging restricts oxygen, and extreme heat can reduce activity despite faster kinetics. Substrate stoichiometry links carbon processing to nutrient demand, so identical mass loss can accompany mineralization in one litter type and immobilization in another. Microbial enzymes act outside cells, making surface area and molecular accessibility as important as the nominal energy content of the dead material.