Reference no: EM133663319

Question: The four stages of stand dynamics are a way of predicting the events of stand development. The stages are initiation, stem exclusion, understory re-initiation, and old growth. In Southern Oregon often the disturbance resetting the proverbial clock is fire. Fire has a direct link to establishment in Oregon. Depending on the area, the fire can result in initiation or understory re-initiation. Shrubs are an important part of the understory, and fires allow for understory re-initiation opening the growth potential for shrubs and trees in the understory. When the understory is disturbed but the canopy remains mostly intact shrubs have great opportunity for growth. The shrubs that grow can change greatly based on the size of the disturbance. Oregon grape likes undisturbed soils, so any area in a disturbance that didn't get touched allows for Oregon grape to take advantage of the newly available resources, but in a limited space. In contrast a species like snowbrush grows quickly and densely on disturbed sites limited the potential for new tree establishment, instead competing for resources in the newly available area. Figure 1 Based on Oliver & Larson, 1996 After a large-scale high intensity fire that restarts the system, the stand dynamics completely reset along with the biomass. There is very little life remaining in the system, and everything has to grow anew. This unlocks new potential as the resources are currently widely available for any species that can grow after the fire. Species like snowbrush may develop fast and quickly start to dominate the region. The understory is all there is, and you see a wide range of diversity as there is yet to be a dominant species. The stem exclusion phase is a building on the biomass, but the system is not very efficient. All the single aged trees are competing for resources in the same way, now allowing for any diversity in resource use. As understory reinitiation occurs, there is more potential for resource use, shrubs, smaller plants, and mid-sized trees can grow and use resources more efficiently than before. Peak biomass happens during the old-growth stage as a wide variety of organisms have started to work together to use all the available resources and continually renew them.