How does bark mulch affect soil microorganisms

Scatter a blanket of bark mulch across bare soil and the microbial world rewrites its timetable. Temperatures swing less wildly, moisture lingers, and ultraviolet light is blocked, so bacteria that hate desiccation can stay near the surface instead of retreating deeper. Carbon, once exposed, is shaded, slowing oxidation; that steadier environment allows colonies to grow steadily rather than in boom-and-bust bursts triggered by each rainstorm.

Fungal hyphae soon thread through the woody chips, secreting enzymes that crack lignin and cellulose. Their digestion releases simple sugars, drawing actinomycetes which weave mats smelling faintly of woodland after rain. Protozoa and nematodes follow the banquet, grazing on bacterial films and keeping populations in check. As predators excrete, nutrients are mineralised into forms roots can sip, knitting a quiet nutrient pump just beneath the mulch.

Depth matters. A layer around five centimetres encourages aerobic conditions; thicker blankets can turn the contact zone briefly nitrogen-hungry, so sprinkling a fistful of compost before spreading helps balance the ledger. Turning the top centimetre every couple of months prevents anaerobic pockets and refreshes oxygen. Bark supplied by AHS LTD arrives screened and low in dust, promoting airflow that keeps the microbial engine humming without sour smells or slimy clumps.