Decomposer fungi continually deplete the organic resources they inhabit, so successful colonization of new resources is a crucial part of their ecology. Colonization success can be split into (i) the ability to arrive at, gain entry into, and establish within a resource and (ii) the ability to persist within the resource until reproduction and dissemination. Fungi vary in their life history strategies, the three main drivers of which are stress (S-selected), disturbance (ruderal, or R-selected), and incidence of competitors (C-selected); however, fungi often have combinations of characteristics from different strategies. Arrival at a new resource may occur as spores or mycelium, with successful entry and establishment (primary resource capture) within the resource largely dependent on the enzymatic ability of the fungus. The communities that develop in a newly available resource depend on environmental conditions and, in particular, the levels of abiotic stress present (e.g., high temperature, low water availability). Community change occurs when these initial colonizers are replaced by species that are either more combative (secondary resource capture) or better able to tolerate conditions within the resource, either through changing abiotic conditions or due to modification of the resource by the initial colonizers. Competition for territory may involve highly specialized species-specific interactions such as mycoparasitism or may be more general; in both cases combat involves changes in morphology, metabolism, and reactive oxygen species production, and outcomes of these interactions can be altered under different environmental conditions. In summary, community development is not a simple ordered sequence, but a complex ever-changing mosaic.