Ecological dynamics

The information contained in the state and transition model (STM) and the ecological site description was developed using archeological and historical data, professional experience, and scientific studies. The information presented is representative of a very complex set of plant communities. Not all scenarios or plants are included. Key indicator plants, animals and ecological processes are described to help guide land management decisions.

A red spruce mosaic forest historically covered 1,500,000 acres in West Virginia (Hopkins, 1899). Industrial logging and subsequent burns have reduced the coverage to roughly 60,000 acres (Adams and Stephenson, 1989; Pielke, 1981). This dramatic decrease of the red spruce-influenced forest has spurred the effort to quantify the former extent of red spruce for restoration purposes. Tools that can target restoration efforts include predictive models (Nowacki and Wendt, 2010) and witness tree databases (Thomas-Van Gundy et al., 2012 (a) (b)). An additional tool may be found through soil morphology, chemistry, and taxonomy. Soils harbor tell-tale signs of past red spruce occurrence through the presence of spodic materials. (Teets and Nowacki, 2012; Nauman et al., 2015 a,b).

Spodic materials can be formed by organic acids produced from decomposition or leaching of coniferous or ericaceous plant litter strongly reacting within the soil matrix. This soil chemical condition facilitates the transfer of humus and poorly crystalline aluminum and iron from surface (A and E horizon) to lower horizons (Bh/Bhs/Bs horizons). This process is called podsolization (Lundstrom et al., 2000). Spodosols are identified if the horizons made of spodic materials are well developed and the meet criteria of spodic horizon (Soil Survey Staff, 2010). Spodosols serve as definitive markers that conifers once existed on site (Teets and Nowacki, 2012; Nauman et al. 2015 a,b). Spodosols develop within cool, humid climates beneath conifers and thick snow packs (Stanley and Ciolkosz; Ciolkosz et al., 1989; Ugolini et al., 1990; Schaetzl and Isard, 1996).

The plant community composition of this site is relatively stable in the absence of human-caused disturbance. Red spruce and hemlock are long-lived and very shade-tolerant species. Natural disturbances in this community are characterized by windthrow of individual trees. Wildlife herbivory is relatively insignificant. Stand-replacing, lightning-ignited fires may affect large forest patch sizes but occur rarely, at 300 to 1,000-year intervals; large-scale wind events are likely at more frequent intervals of 100 to 200 years (Gorman, 2007) . Human-initiated disturbances have included agriculture (currently abandoned), logging, and slash fires.

Recent disturbances include accumulation of atmospheric pollutants and land conversion for resorts and second homes.

Historic accounts indicate that red spruce forests formed nearly pure stands of red spruce on the high, rocky ridges and plateaus, where nutrient-poor soils and abundant moisture favored spruce over hardwoods (Hopkins, 1899; Brooks, 1910; Korstian 1937; Clarkson, 1964 and references therein; Core, 1966 and references therein). Spruce-dominated old-growth forests of West Virginia and Virginia are rare, but include many individual dead spruce, making up 36 percent of all spruce stems and 44 percent of the total basal area (Adams and Stephenson, 1989). Annual mortality has been estimated at about 1 percent for spruce-fir forests of North Carolina and Tennessee (Busing and Wu, 1990), which is similar to the rate found in second-growth red spruce-northern hardwood forests of West Virginia at 1.4 percent (Rentch, et al. 2010). Diameter distributions of old growth stands show large numbers of small diameter trees mixed with scattered large trees that contain most of the basal area (Korstian, 1937; Oosting and Billings, 1951;Adams and Stephenson, 1989; Busing and Wu, 1990; Nicholas et al., 1992). Sizes of canopy gaps in spruce-dominated old-growth forests across northeastern North America have been found to have mean diameters of 24 to 126 meters squared (Seymour et al., 2002). For spruce-fir forests in Tennessee, major natural disturbance regimes include fire, debris avalanches, and wind with return intervals of more than 1,000 years for large gaps (greater than 200 meters squared from fires and debris avalanches) and 100 years for small gaps (less than 200 meters squared from wind events; White et al., 1985). Fire and debris avalanches are not likely to play as large of a role in the spruce-northern hardwood forests of West Virginia; although, the role of fire after exploitative logging of the 1900s is well documented (Clarkson; 1993). In northern Appalachian old-growth forests dominated by spruce and fir, no evidence of stand-replacing disturbances was found in the tree ring record (Fraver and White, 2005; Fraver et al., 2009). As these forests are dominated by a very shade-tolerant and long-lived species, we can infer that vertical and horizontal heterogeneity was high before the 1880s beginning of the industrial logging era.Sub-dominant trees in old-growth stands in West Virginia and Virginia were found to have a mean age of 157 years (Adams and Stephenson, 1991) and others have determined that in the southern Appalachians, red spruce required multiple release events to reach the canopy (Wu et al., 1999). Spruce-dominated old-growth in both Tennessee and New Hampshire were determined to have uneven-aged structure (Oosting and Billings, 1951).

A state-and-transition model for the site follows this narrative. Descriptions of each state, transition, plant community, and pathway follow the model. Experts base this model on available experimental research, field observations, professional consensus, and interpretations. It is likely to change as knowledge increases.

The reference state of this ecological site consists of one community phase; the reference state and community phase tends to remain stable for long periods of time. Fire is not an important factor due to the moist climate and soil conditions. Change within the community results primarily from single tree disturbance. The small openings from single tree disturbance allow the release of small suppressed spruce trees. Hardwoods such as yellow birch or other species germinate in these openings relatively quickly at locations mineral soil is exposed (i.e. tree throw tip-up pits and mounds). Lack of fire and the nature of conifer (red spruce) litter and root dynamics permit the accumulation of a deep layer of organic matter forest floor up to several feet thick. The forest floor helps maintain moist conditions, its chemical and physical characteristics favor the germination and survival of conifers over hardwoods.

Clearcutting of spruce and hemlock in the time period 1880-1920 not only removed the conifer overstory, but also destroyed much of the deep organic soil horizon and the conifer seed bank within it due to logging practices and low intensity fires common during the era.

Logs where skidded across the soil and slope on cable strung from the summit of the slope to the valley floor; occasionally, low intensity slash fires occurred at these sites. The new conditions exposed large areas of mineral soil that allowed hardwood trees, especially species such as American beech and black cherry which have heavy seed rain and seeds that spread rapidly over long distance due to transport by wind and birds, to invade these sites. Many areas still had remnant midstory spruce trees present and small understory spruce trees were abundant. Seeds of red spruce and hemlock typically travel a maximum of 200 meters. Red spruce and hemlock are able to re-establish sites canopy dominance if a few trees remain, but the process may take hundreds of years without restoration efforts such as timber harvesting, thinning, or applying herbicide to release suppressed understory conifers. Once a trajectory of conifer dominate overstory is set, the conifer will eventually shade many species out of existence and create edaphic conditions relatively adverse to hardwood regeneration. The site will be restored to the reference vegetative community, and over the period of hundreds of years will rebuild the thick forest floor through litter accumulation.

The logged states both share a common dominant (or co-dominant) tree – red maple and the occurrence of subdominant red spruce/eastern hemlock in the overstory or understory. Red maple has a large seed rain, is quick to establish, and is common throughout the range of this ecological site. The division between the two logged states is based upon the occurrence of co-dominant American beech or black cherry in the respective states. Sites with a history of soil erosion exposing extensive areas of mineral soil or light burning often have higher overstory canopy cover of black cherry; sites with relatively less disturbance have higher overstory canopy cover occurrence of beech.

In areas that experienced intense logging slash fires caused by railroad sparks and negligent fire management, the site was sent on an entirely new vegetation trajectory and often entirely different soil was formed through depozolization (see WV127XY002). In areas that maintained the Spodosol soil, the thick forest floor and conifers were burned and large areas of mineral soil were exposed. During the Great Depression until World War II, the Civilian Conservation Corps (CCC) and the U.S. Forest Service (USFS) re-vegetated many of these burned locations and abandoned marginal farmland with conifer plantations.
These areas were planted to prevent soil erosion and to provide timber products and wildlife habitat. The current condition of these areas is a plantation of mature even-aged Norway spruce and occasional plantations of red or white pine timber, or both. These species are not endemic to the ecological site area and have created an artificial ecological condition.

Distinguishing soil characteristics beyond the strong evidence of podzolization and the formation of Spodosol is the occurrence of thick organic forest floors. These folistic epipedon likely take hundreds of years of litter accrual to form once the overstory canopy is conifer dominant. Disturbed states often lack thick forest floors and they are unlikely to re-establish old growth characteristics (e.g. thick Oa horizons) within current human lifetime scale.(See Nauman et al. (2015 a,b) for a discussion of “deep” forest floor accretion within human lifetime scale.) The thick forest floor harbors soil micro and macro species that facilitate unique ecological (see Bonan and Shugart, 1989) and soil chemical processes (see discussion of podzolization above).

Plant communities will differ across the MLRA because of the naturally occurring variability in weather, soils, and aspect. The Reference Plant Community is not necessarily the management goal. The biological processes on this site are complex. Therefore, representative values are presented in a land management context. The species lists are representative and are not botanical descriptions of all species occurring, or potentially occurring, on this site. They are not intended to cover every situation or the full range of conditions, species, and responses for the site