Ecological dynamics
These sites are found in the rainshadow of the Olympic Mountains in the Puget Trough, on somewhat moist to moist soils. Western redcedar is the dominant overstory species for these sites, with a varying amount (to 50%) of Douglas-fir. Grand fir, red alder, western hemlock, lodgepole pine and big-leaf maple may be present but only as minority components. The historic fire regime would have been one of low frequency (150-300+ years) and moderate to high intensity. These fires would, in effect, be stand-replacing although individual trees would survive, providing a seed source. The heavy shade of a redcedar forest favors the gradual replacement of Douglas-fir with more shade tolerant redcedar in the absence of a major disturbance. The most common natural disturbances on these sites are small pockets of wind-thrown or diseased overstory trees. The resulting openings in the canopy allow some sunlight to reach the forest floor, which benefits the often sparse understory. This is especially true in mid-successional (75-150 years) stands, which have very little height differentiation. Western swordfern is frequently the most common understory species; salal, baldhip rose, snowberry, dull Oregongrape and stinging nettle are also regularly found on these sites. Most of these sites have been harvested for timber since European settlement although all of the various plant communities may have remnant mature trees.
State 1
PC 1.1 Western redcedar - Douglas-fir/salal/western swordfern
Community 1.1
PC 1.1 Western redcedar - Douglas-fir/salal/western swordfern
Structure: multistory with small gap dynamics.
Western redcedar is the most common overstory species in the historic climax plant community. Douglas-fir can compose up to 50% of this community with grand fir and western hemlock being much smaller components. The most common natural disturbance on these sites would be the small gap dynamics following the death of one or two trees. Cedar is prone to a few different types of rot, and while these rarely kill a tree, they can cause the stem to break at location of the rot. Due to its shallow root system, western redcedar is susceptible to windthrow on wetter sites and the resulting tip-ups also create small canopy gaps. These limited openings allow some sunlight to reach the forest floor, promoting advanced regeneration and understory species. Although rare, stand-replacing fires have occurred historically in these forests. Cedar is only intermediate in fire resistance, so the majority of trees would be killed by a moderate or intense event. Douglas-firs are much more adapted to fire; consequently, this type of fire would have the ability to significantly alter the historical species distribution.
Community Pathways:
1.1a: this pathway is one of minor disturbances which maintain the overall structure of the HCPC. The death of one or two trees allows sunlight into the understory, promoting forbs and shrubs as well as the regeneration of overstory species. This perpetuates a multi-storied forest.
1.1b to PC 1.2: this pathway represents a larger disturbance – a moderate-intensity fire or wind storm would have historically created this forest structure; uneven-aged management techniques such as group selection or shelterwood with reserves may also lead to this community. Areas of regeneration would range from 2 to 5 acres.
1.1c to PC 1.3: this pathway denotes a major disturbance such as a high-intensity fire, large scale wind even or clear-cutting followed by prescribed burning.
1.1d to PC 1.4: this pathway signifies the conversion of forestland to either cropland or pasture.
State 2
PC 1.2 Western redcedar – Douglas-fir/salal – oceanspray/western swordfern
Community 2.1
PC 1.2 Western redcedar – Douglas-fir/salal – oceanspray/western swordfern
Structure: mosaic of mature overstory and regenerating openings.
Plant community 1.2 retains some areas that resemble the HCPC but also contains moderate sized (2-5 acres) openings. Historically, this spatial pattern would have been caused by low- to moderate-intensity fires or pockets of disease (such as laminated root rot); uneven-aged management techniques such as group selection or shelterwood with reserves can also create this plant community. Depending on the seed sources present, the patches may contain any of the previously mentioned overstory species. Redcedar seedlings are highly preferred browse for deer and this, if deer populations are high, can affect the species composition of the regeneration. Most of the understory shrub species will also compete for the increased sunlight and could delay reforestation, especially for the less shade-tolerant species.
1.2a to PC 1.1: this pathway represents growth over time with no further significant disturbance. The areas of regeneration pass through the typical stand phases – competitive exclusion, maturation, understory reinitiation – until they resemble the old-growth structure of the HCPC.
1.2b to PC 1.3: this pathway represents either a high-intensity fire or a change to intensive management (block harvest, post-harvest burn). Both situations lead to the stand initiation phase of forest development.
State 3
PC 1.3 Salal – snowberry/Douglas-fir – western redcedar
Community 3.1
PC 1.3 Salal – snowberry/Douglas-fir – western redcedar
Structure: single story/shrub.
PC 1.3 is forestland in regeneration; species composition depends on the natural seed sources present and the intensity of management. When resulting from a moderate- to severe fire event, there is a good possibility for shrubs to out-compete tree seedlings. Oceanspray, snowberry, salal, trailing blackberry, red elderberry and salmonberry (which may have been only moderately abundant previously) all have the capability to rapidly recover and spread when top-killed, even by intense fires. If there is a seed source present, however, western redcedar, Douglas-fir and red alder will regenerate on the newly exposed mineral soil. The success of seedlings will depend, in part, on the amount of competition from the shrub layer. Site preparation prior to planting seedlings should suffice to control the shrub species. Without active management these sites may be dominated by shrubs for many years.
Community Pathways:
1.3a to PC 1.6: this pathway signifies growth over time with active management, maximizing timber development. Precommercial and/or commercial thinning, combined with understory control, would lower stand density and decrease competition for water and nutrients.
1.3b to PC 1.5: this pathway indicates no further management, denoting only growth over time.
State 4
PC 1.4 Pasture grasses/snowberry/Douglas-fir – lodgepole pine (western redcedar)
Community 4.1
PC 1.4 Pasture grasses/snowberry/Douglas-fir – lodgepole pine (western redcedar)
Structure: abandoned pasture with regeneration.
PC 1.4 is abandoned pasture or crop land. This community will be dominated by non-native grasses but may have some native species present. Shrubs and trees will gradually encroach from the surrounding forest. The environmental conditions favor Douglas-fir and lodgepole pine over western redcedar at this stage and those species (dependent on a seed source) will begin to create an overstory canopy. As the shade intolerant non-native species diminish, the abundance of redcedar and native understory plants such as oceanspray, snowberry and salal will increase.
Community Pathways:
1.4a to PC 1.5: this pathway represents the shift from field to forest without any external management. Whatever seed sources are present will provide the basis of the future forest.
1.4b to PC 1.3: this pathway indicates active management in order to restore the forest. Site preparation (most likely mechanical tilling, possibly combined with herbicides) and planting of preferred species bring about the change.
State 5
PC 1.5 Douglas-fir – western redcedar/salal – oceanspray
Community 5.1
PC 1.5 Douglas-fir – western redcedar/salal – oceanspray
Structure: single story with diminished understory.
PC 1.5 is a forest in the competitive exclusion stage. Because this community is indicative of no active management, there is increasing competition among individual trees for the available water and nutrients. Canopy closure is almost 100%, leading to a diminished understory. Over time the forest will begin to self-thin due to the elevated competition.
Community Pathway:
1.5a to PC 1.6: this pathway represents grow over time, with or without active management. Precommercial or commercial thinning can decrease competition by removing a portion of the trees. Without management, intermediate and suppressed trees will begin to die.
State 6
PC 1.6 Douglas-fir – western redcedar/salal - oceanspray/western swordfern
Community 6.1
PC 1.6 Douglas-fir – western redcedar/salal - oceanspray/western swordfern
PC 1.6 is a maturing forest which is starting to differentiate vertically. Individual trees are dying (whether due to insects, disease, competition or windthrow) allowing some sunlight to reach the forest floor. This allows for an increase in the understory as well as some overstory tree species regeneration. Cycling between PC 1.3 and PC 1.6, through even-aged management, will generate maximum wood fiber.
Community Pathways:
1.6a to PC 1.1: this pathway is one of no further management. Continued growth over time, as well ongoing mortality, leads to continued vertical diversification. The community begins to resemble the structure of the HCPC, with small pockets of regeneration and a more diversified understory.
1.6b to PC 1.3: this pathway represents intensive management focusing on wood products. Clear-cutting, some type of site preparation, planting of preferred species and timely thinnings are the steps to achieve this goal.
