Abstract:Although increased cloud-cover may reduce global temperature response to trace gas emissions, it is an important climatic change from an ecological perspective. For plants, cloud-cover reduces photosynthesis and alters establishment; these effects differ among species. The differential effects may be modified, however, by pattern at the landscape level, such as forest edges. Here we include cloud-cover and the edge effects of a snow avalanche path in a simulation of the dynamics of a montane forest using a spatially explicit implementation of the JABOWA-FORET model. Cloud cover is simulated by a 10% reduction in ambient light. Alternately we forced constant full sunlight, constant mortality for conifers, or both, on a strip of simulated cells in order to maintain an avalanche path. Higher light levels maintained on the path allow the persistence of shade-intolerant species that otherwise decline under a scenario of increased cloud-cover (deciduous proportion on 800 cells changes from 0.19 to 0.11 rather than 0.15 to 0.04). A constant population on the path maintains temporary populations elsewhere. Diversity would decline with increased cloud-cover (from 2.3 to 2.0 mean richness), but in cloudier conditions an avalanche path supports higher diversity (2.1) across the entire landscape. Similarly, basal area on sites is reduced by cloud-cover with (6 683 cm2- 5 957 cm2) or without (6 180 cm2- 4 988 cm2) the edge effects, but a path does contribute to higher overall basal area. Spatial structure at such fine scale must be considered in projecting the effects of global climatic change on plant communities and the effect of regional diversity on local diversity.