Practice question

Leaching is the physical removal of water-soluble substances from fresh litter or soil organic matter. Rain or flowing water dissolves sugars, amino acids, tannins, mineral ions, and dissolved organic carbon and transports them into deeper soil horizons or aquatic systems. It can cause rapid initial mass loss without requiring enzymatic digestion. Leaching may also alter subsequent microbial activity by removing labile substrates or inhibitory compounds, so its effect on later decomposition depends on which solutes are exported. Mass loss alone cannot identify mechanism, because leaching, fragmentation, respiration, assimilation, and stabilization can produce different fates for carbon and nutrients. The distinction between gross transformation and net nutrient release is important: simultaneous microbial uptake can conceal substantial biochemical turnover. 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.