Part Two of Five –
What is a forest? It would be easy to assume that a forest is nothing but one big woods; especially when we read a map and see large expanses of land labeled as “…National Forest” or “…State Forest.” However, a robust forest is actually a collection of ecosystems that are shaped by distinct growth stages and disturbance factors, along with geology, climate, and location. In the next few paragraphs I want to look more closely at the ideas of growth stages and disturbance factors because I think those are ones that have the potential to cause the greatest impact to the dynamics of Northwest Forest ecology since they are factors often manipulated in forest management processes. Oregon geology, climate, and location, on the other hand, are relatively stable conditions that dictate what will grow in a Temperate Zone, and are not manipulated by human means. (Except for the impacts of Climate Change/Global Warming… but that’s another topic for discussion!)
In a White Paper written by David C. Powell for the USDA Forest Service, “A Stage is a Stage… or Is It?”, I learned that there are three ways to describe forest growth stages and that they are not synonymous. The first, Successional Stage, describes a forest in terms of its development from the bare ground to fully matured trees. Two primary criteria are: tree-size class and stand age. Thomas (1979) defined six distinct Successional Stages for coniferous trees: Grass-forb, Shrub-seedling, Pole-sapling, Young, Mature, Old Growth. The second, Structural Stage, describes a forest by its appearance, how the trees look- their physical size and arrangement of the tree canopy. O’Hara, et al (1996), as well as, Oliver and Larsen (1996) described the Structural Stages: Stand initiation, Stem exclusion, Young forest multi strata, Understory reinitiating, Old forest. The third, Seral Stage, refers to changes that occur in a plant community after a stand-initiating disturbance. Hall et al.(1995) recognized four Seral Stages: Early Seral, Mid Seral, Late Seral, Potential Natural Community. For a detailed description of all the stage categories, Powell’s White Paper can be accessed through this link: “A Stage is a Stage… or Is It?”
Mark E. Swanson, in his report, “Early Seral Forest in the Pacific Northwest: A Literature Review and Synthesis of Current Science,” details the disturbance factors that are associated with early serial forests: fire, wind, volcanic eruption, snow/avalanche, insects and disease. The disturbance aspect of forest dynamics is receiving more and more attention by Forest Managers due to contemporary management practices that have suppressed one of the historically main disturbance factors- fire. Suppression of fire, and, as a result, forest disturbance, has reduced early serial forest acreage.
Why are forest growth stages and disturbance factors important to understanding Northwest forest dynamics? All influence the composition, structure, and function of forest ecosystems. In a nutshell, they determine what organisms will thrive or decline in a given area…in a given habitat. This strongly impacts forest biodiversity. I understand from my studies in the Oregon State University Master Naturalist program that all contribute to the population dynamics, flora/fauna community composition, trophic interactions, and the organization of habitat. Given there are eleven different forest types of forests in Oregon, each with its unique growth and disturbance factors, there is a complex mosaic of systems at play… vital in the support of a rich network of wildlife. All are important concepts to be considered by Forest Managers and Silviculturists when assessing forest areas for management purposes. All are important concepts to be considered by legislators and stakeholders in the design of laws that govern forest practices. Forest legislation is the idea I will explore in Step B: Understanding the Northwest Forest Plan (1994), and Step C: Understanding Oregon and California Land Grant Act of 2013. My final goal is to pull all these understandings together- as a Naturalist, Citizen Scientist, Educator, and Oregon resident- to form an informed opinion about “What’s Best for Oregon Trees?” How I will use this opinion is waiting to be discovered…