The Changing Forest

Though they often appear static, forests are actually very dynamic, changing on a variety of time scales. They respond to disturbances, like storms or pest outbreaks, to annual cycles of climate, especially the deciduous forests typical of the SERC region, and over the long term. The development sequence from a young stand through the mature or old-growth stage is called "succession".

Much of the differences between forests in the SERC region are related to the ages of the stands, how long they have grown since the land was logged or abandoned from other uses. We have studied these patterns using a network of study sites in forests of different ages in the main forest type around SERC (the "tulip poplar" association).

When we assemble our observations from short-term measurements in these stands into a single picture, we see some general developmental patterns. As this forest ages, it loses many stems, but increases in the amount of leaves, the height, the biomass, and the complexity of canopy organization.

Early stages of tulip-poplar association forests have abundant fast-growing sweetgums (Liquidambar styraciflua) and tulip poplars (Liriodendron tulipifera). In later stages slower-growing oaks (Quercus), hickories (Carya), and beech (Fagus grandifolia) are dominant

In a young forest, most of the leaf surface area is concentrated in a narrow height band within the canopy. As the forest ages, the original trees get taller and an understory begins to develop.