Influence of resource unit distribution and quality on the activity of soil fungi in a particulate medium

Experiments were set up to assess the relative impacts of grass lamina frag ment density, size and quality on the activity and growth of four fungi in a particulate soil-like matrix. The fungi studied were Cladosporium cladosp orioides, Fusarium lateritium, Phoma exigua and Trichoderma viride, all of which are common inhabitants of UK upland grassland soils. Resource duality was varied by using three contrasting grasses as sources of lamina fragmen ts: Lolium perenne, Agrostis capillaris and Nardus stricta. All the fungi w ere able to forage effectively through the soil-like matrix (at a rate of 1 -2 mi matrix d(-1)) and colonize and partially decompose available lamina f ragments (up to 40% d. wt loss). Foraging rates (ml matrix d(-1)) were affe cted by lamina fragment species but not by fragment density or size. In gen eral, F. lateritium and T. vivide foraged at a faster rate than the other s pecies. Mycelial activity in the soil-like matrix was directly proportional to total lamina fragment availability and was unaffected by fragment size. Biomass production on solid media was also directly related to substrate ( carbohydrate) availability. The results indicate that these fungi can adjus t their growth patterns in response to fragment density so as to maximize f oraging efficiency (energy acquired per unit exploratory biomass production ). Differences in lamina fragment species were responsible for up to 50% re duction in mycelial activity.