The forest ecosystem is the basis of forestry, and knowledge about the patterns and process of the forest informs all elements of forestry from silviculture to road building and maintenance. The forest ecosystem of the SFMA is marked by a diversity of forest conditions that span a broad spectrum of natural community types.
- Species specific characteristics
influence how and where trees grow
Soils are literally the foundation of forest ecosystems and different soil conditions such as dry vs. wet or deep vs. shallow generally determine what species or groups of species grow on a given acre. Nearly all tree species prefer to grow on well drained deep soils; however such sites are rare in the SFMA and most parts of the Northeast. Each tree species has evolved to tolerate less than perfect growing conditions but to varying degrees. Some species can grow well on very wet soils while others cannot, thus those species tolerant of wet conditions often occupy wet sites. Soils in the SFMA are of average quality with areas of alternating ledge outcrops and poorly drained lowlands being common.
Tree Growth Dynamics:
Tree species have also evolved different growth strategies, meaning that some trees grow very quickly while others can grow slowly. Some trees can survive in dark shaded forest understories while others can only survive in fully sunlight. In a forest trees compete with one another for available soil nutrients and sunlight resources. The result is that the species that are best adapted to the specific soil and sunlight conditions in a given forest area will be the most likely to occupy that site.
- View of tree crowns from below.
Forests often seem to be static and unchanging to the human eye since change generally happens over many years or decades. However, change is the only true constant in the SFMA forests and disturbance to the forest in the form of tree mortality is basic to this change. Forests structures in the SFMA region take many forms but in general trees will fill available growing space with crowns and photosynthesizing foliage. When trees die their space in the forest canopy is vacated, but only temporarily, as other trees will seek to take advantage of access to sunlight and will fill the space with new foliage. Trees can die individually as in the case of single tree affected by a root disease, often leaving a small hole in the tree canopy. Trees can also die in groups in the case of strong wind events creating canopy openings equal in size to multiple tree crowns. Such openings stimulate the germination and growth of new trees normally from seed. These young trees known as “regeneration” will crow to fill the opening. Large areas of trees can die due to large scale fires of hurricanes. When mortality occurs on large scale, potentially 1,000s of acres, a new generation of trees will emerge from seed or root sprouts to colonize the area. The types of species that compete best in these situations depends on the type of soils present and the growth strategy of the species.
- SFMA 2011 stand type map
In forests the influences of soil, species growth strategies, and past disturbance events combine to shape the species present, and the structure of the stand canopy. Foresters refer to common species groupings and canopy structures as stand types, where a stand is a discrete forest area where these two elements are fairly consistent. Stand types for the basis for much of forest management.
Biodiversity and Habitat:
Biodiversity represents the complete assemblage of all species in a given ecosystem and the complex inter-relationships and associations between species. The scientific understanding of the complex web of species interactions in forest ecosystems has expanded rapidly in recent decades yet many mysteries persist regarding such relationships and their implications for ecosystem dynamics. Forest ecosystems provide important habitat for a variety of wildlife. Whether it is an individual standing dead tree, a downed log, a dense softwood sapling thicket, or a protective canopy of tall softwood trees, such forest structures and conditions are utilized by many species.