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Target Forest Types - Luke McGuff

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September 29th, 2014


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09:00 am - Target Forest Types

“Target forest types” are reference communities for the forest steward to target in their plant selections.

The “forest type” is based on research by Chappell (1999, 2006) for the Washington Department of Natural Resources. Each forest type is based on an observed community in areas that are as undisturbed as possible. Chappell’s research concentrates on the Puget Trough Ecoregion (the lowland areas surrounding the Puget Sound), the region Seattle occupies. Selecting which forest types specifically applied to Seattle was based on research by Larson (2005) and by using a key based on GSP inventory site data (Denovan 2012). There are currently twenty-three target forest types assigned to Seattle forests and natural areas. Four of these (discussed below) have been assigned to North Beach Park.

The name of the target forest type is derived from the dominant plant species at every canopy layer. The species are listed by their four letter code in the order of constancy with which they occurred in the sampled plots. Dashes separate species at the same canopy layer, slashes separate canopy layers.

For example, “THPL-TSHE/OPHO/POMU” is “THuja-PLicata – TSuga HEterophylla / OPlopanax HOrridus / POlystichum MUnitum” (Western red-cedar – Western hemlock/Devil’s club/Sword fern). This means that there was more Western red-cedar than hemlock in the sampled plots, Devil’s club is the dominant species at the shrub layer, and sword fern the dominant species at the groundcover layer.

Lists of forest plant association names can look bewilderingly similar. The distinguishing characteristics come with the non-dominant species, especially at the herbaceous level.

Why Target Forest Types

Target forest types were selected by Parks Department plant ecologists to promote heterogeneity among the natural areas undergoing restoration in Seattle. They noticed that, over the years at the city scale, plant selections were very similar.

At first, target forest types were promoted as prescriptive; that is, forest stewards had to consider the TFTs for their park a goal, and select their plants accordingly.

This lead to pushback and confusion from forest stewards. Now forest types are grouped into the seven reference ecosystems as a more general planting palette. Of the two reference ecosystems for North Beach Park, “mesic-moist conifer and conifer deciduous mixed forest” has four target forest types; “riparian forest and shrubland” has nine.

All information about the target forest types is taken from the descriptions by Chappell at the website referenced below. The descriptions are attached to this book as Appendix C, “Target Forest Type Descriptions.” The TFTs are discussed in the order of number of HMUs to which they are assigned.

TSHE-PSME/POMU-DREX

This target forest type is assigned to the following HMUs: North Slope, 91st St. Slope, West Slope, South Slope, South Plateau. Together, they comprise 3.85 acres of North Beach Park.

This forest type is dominated by Western hemlock and Douglas-fir at the canopy level, with sword fern and spreading wood fern at the ground cover level. It is found almost everywhere in the Puget Trough except in San Juan County. Globally, it is vulnerable to apparently secure; at the state level, it has been reduced in frequency by logging and is threatened by development and invasion by non-native species.

This association is found in moist sites with nutrient-rich soils, and more commonly on lower slopes and riparian terraces. This relates well to the reference ecosystem of mesic-moist conifer and conifer-deciduous mixed forest.

Other plants in this community include Berberis nervosa (Dull Oregon-grape) which grows with sword fern in many places in North Beach Park.

Chappell says that Red alder regenerate after disturbance and that alder typically die out after 80-100 years. The alder canopy in North Beach Park is very mature, and is decaying at the rate of one to three trees per year.

Chappell notes that Hedera helix (English ivy) does well in this association and can overwhelm native understories. This was the case with the South Plateau, South Slope, and West Slope, which had poor native shrub layers and (on the slopes) no native tree regeneration.

Euonymous occidentalis (Western wahoo) and Cimicifuga elata (tall bugbane), which are respectively threatened and sensitive at the state level, are found in this association.

Table 1, below, lists selected species from the DNR description of this forest type. For an explanation of the columns, please see the key after the table.

Table 1: Selected Species of the TSHE-PSME/POMU-DREX target forest type.

Scientific Name Common Name WIS Const. % Cover
Trees
Acer macrophyllum Big leaf maple FACU 73 18
Alnus rubra Red alder FAC 44 9
Pseudotsuga menziesii var. menziesii Douglas-fir FACU 94 45
Thuja plicata Western red-cedar FAC 81 33
Tsuga heterophylla Western hemlock FACU 96 36
Shrubs
Acer circinatum Vine maple FAC 41 20
Corylus cornuta var. californica Beaked hazelnut FACU 29 3
Gaultheria shallon Salal FACU 46 2
Mahonia nervosa Low Oregon-grape FACU 54 4
Rubus spectabilis var. spectabilis Salmonberry FAC 48 4
Rubus ursinus var. macropetalus Trailing blackberry FACU 68 3
Sambucus racemosa var. racemosa Red elderberry FACU 60 2
Vaccinium parvifolium Red huckleberry FACU 86 3
Graminoids
Bromus vulgaris Columbia brome FACU 21 2
Carex deweyana var. deweyana Dewey’s sedge FAC 21 2
Forbs and Ferns
Athyrium filix-femina ssp. cyclosorum Lady fern NI 54 2
Blechnum spicant Deer fern FAC 24 2
Dryopteris expansa Spreading woodfern FACW 78 3
Galium triflorum Sweet-scented bedstraw FACU 71 2
Polystichum munitum Sword fern FACU 100 54
Pteridium aquilinum var. pubescens Bracken fern FACU 38 3
Tiarella trifoliata var. trifoliata Three-leaf foamflower FAC 54 5
Trientalis borealis ssp. latifolia Western starflower FAC 59 1
Trillium ovatum ssp. ovatum Western trillium FACU 51 1
Vancouveria hexandra Inside-out flower NI 22 7

Key:“WIS” is Wetland Indicator Status. “Const.” column is the constancy with which the plant was found in the sample plots (n=63). “% Cover” is the percent canopy cover of the plant.

ALRU/RUSP/CAOB-LYAM

This target forest type is assigned to the Central Valley and Headwaters’ Bowl HMUs. Because these are the two largest HMUs in North Beach Park, this is the second largest forest type by acreage at 3.36 acres.

This forest type has Alnus rubra (Red alder) almost exclusively in the canopy layer, with a dense shrub layer formed mostly of Rubus spectabilis (salmonberry). The herbaceous layer is dominated by Tolmiea menziesii (piggyback). We saw this combination pretty continuously through the Central Valley during the belt transect.

In North Beach Park both Carex obnupta (slough sedge) and Lysichiton americanum (skunk cabbage) were growing before restoration, but not together. In general, the herbaceous layer in these HMUs is not as well developed as described for this community.

Chappell describes this community as existing in palustrine scrub-shrub wetlands, which fits with the riparian forest and shrubland reference ecosystem.

Table 2: Selected species of the ALRU/RUSP/CAOB/LYAM target forest type.

Scientific Name Common Name WIS Const. % Cover
Trees
Alnus rubra Red alder FAC 100 93
Picea sitchensis Sitka spruce FAC 67 8
Shrubs
Acer circinatum Vine maple FAC 67 4
Rubus spectabilis Salmonberry   100 57
Forbs and Ferns
Angelica genuflexa Kneeling angelica FACW 33 20
Athyrium filix-femina Lady fern NI 100 4
Chrysosplenium glechomifolium Pacific golden-saxifrage OBL 67 15
Circaea alpina Enchanter’s nightshade FAC 67 3
Erhythranthe guttata Yello monkey-flower OBL 67 3
Lysichiton americanus Skunk cabbage OBL 33 30
Oenanthe sarmentosa Pacific water parsley OBL 100 6
Oxalis oregana Oregon oxalis FACU 67 8
Polystichum munitum Sword fern FACU 100 6
Ranunculus repens Creeping buttercup FAC 33 20
Stachys mexicana Mexican hedge-nettle FACW 100 4
Tolmeia menziesii Piggy back FAC 100 34
Graminoids
Carex obnupta Slough sedge OBL 100 30
Poa trivialis Rough-stalk blue grass FAC 33 30

THPL-TSHE/OPHO/POMU

This target forest type is assigned to the 92nd St. Wetlands HMU, comprising .69 acres of North Beach Park.

This forest type has Thuja plicata (Western red-cedar) and Tsuga heterophylla (Western hemlock) dominant in the canopy layer, with Oplopanax horridus (Devil’s club) in the shrub layer and Polystichum munitum (Sword fern) in the ground layer.

Red alder and Big leaf maple are the current dominant trees in the canopy of North Beach Park. The 92nd St. Wetlands is the only HMU where the coniferous canopy cover is more than 10%, mostly Western hemlock.

Although Chappell rates this community as secure at both the global and state level, he says there are “very few good quality stands remaining.”

We attempted to reintroduce Devil’s club into the park from seed but were unsuccessful. Devil’s Club was reintroduced to the park in the Central Valley HMU in November 2014, using container plants from Green Seattle Partnership.

Table 3: Selected plants of the THPL-TSHE/OPHO/POMU target forest type.

Scientific Name Common Name WIS Const. % Cover
Trees
Acer macrophyllum Big leaf maple FACU 86 7
Alnus rubra Red alder FAC 29 6
Pseudotsuga menziesii var. menziesii Douglas-fir FACU 86 22
Thuja plicata Western red-cedar FAC 100 31
Tsuga heterophylla Western hemlock FACU 86 42
Shrubs
Acer circinatum Vine maple FAC 57 8
Oemlaria cerasiformis Osoberry FACU 57 2
Oplopanax horridus Devil’s club FAC 100 23
Rubus spectabilis var. spectabilis Salmonberry FAC 86 17
Rubus ursinus ssp. macropetalus Trailing blackberry FACU 57 +
Sambucus racemosa var. racemosa Red elderberry FACU 71 6
Vaccinium parvifolium Red huckleberry FACU 71 5
Forbs and Ferns
Athyrium filix-femina ssp. cyclosorum Lady fern NI 100 12
Claytonia sibirica var. sibirica Siberian springbeauty FAC 57 1
Dicentra formosa ssp. formosa Pacific bleeding heart FACU 43 2
Dryopteris expansa Spreading woodfern FACW 86 3
Galium triflorum Sweet-scented bedstraw FACU 100 1
Hydrophyllum tenuipes Pacific waterleaf FAC 43 5
Polystichum munitum Sword fern FACU 100 34
Tiarella trifoliata var. trifoliata Threeleaf foamflower FAC 86 6
Tolmeia menziesii Piggyback FAC 71 6
Trillium ovatum ssp. ovatum Western trillium FACU 57 +
Graminoids
Luzula fastigiata Small-flowered wood-rush FAC 43 +

“+” = trace, less than 0.5% cover.

TSHE-THPL-ACMA/ACCI/LYAM

This forest type is assigned to the Fletcher’s Slope HMU, comprising 0.53 acres..

Unlike the rest of the target forest types assigned to North Beach Park, this forest type is based on research by Kunze (1994). In general, Chappell is preferred because he provides constancy across sampled plots and percent cover of all species. Kunze provides percent cover for only indicator species. All information below was taken from a PDF excerpt of her work supplied by Green Seattle Partnership.

In North Beach Park, Fletcher’s Slope has greater than 10% Western hemlock in the community, with some Douglas-fir. Kunze says either TSHE or THPL can dominate this community. Acer macrophyllum (Big leaf maple) is the dominant deciduous tree in the dryer sections of the park. Lysichiton americanum (skunk cabbage) grows throughout the park, but we have not seen Acer circinatum (vine maple) that wasn’t planted during restoration activities.

This once-common community has few undisturbed examples. Kunze describes it as occurring in conditions that are very similar to North Beach Park: on flat ground, in depressions, with small streams and seeps, with the water level at or slightly below the soil surface.

Table 4: Selected plants of the TSHE-THPL-ACMA/ACCI/LYAM target forest type.

Scientific Name Common Name WIS % Cover
Trees
Alnus rubra Red alder FAC
Frangula purshiana Cascara FAC
Picea sitchensis Sitka spruce FAC
Salix spp. Willow FACW
Thuja plicata Western red-cedar FAC 5-80%
Tsuga heterophylla Western hemlock FACU 10-50%
Shrubs
Acer circinatum Vine maple FAC
Cornus canadensis Dwarf dogwood FAC
Cornus stolonifera Red-osier dogwood FACW
Gaultheria shallon Salal FACU 20-50%
Lonicera involucrata Twinberry FAC
Rubus spectabilis Salmonberry FAC
Spiraea douglasii Douglas’ spirea FACW
Vaccinium alaskense Alaskan blueberry FAC
Vaccinium parvifolium Red huckleberry FACU
Graminoids
Carex canescens Gray Sedge OBL
Glyceria elata Tall manna-grass FACW
Forbs and Ferns
Atyhyrium filix-femina Lady fern NI
Blechnum spicant Deer fern FAC
Galium spp. varies
Luzula sp. FAC
Lysichiton americanum Skunk cabbage OBL 10-80%
Maianthemum dilatatum False lily of the valley FACU
Menziesia ferruginea Rusty menziesia FACU
Stellaria sp. varies

Adapting the TFT concept to specifics of North Beach Park

Examining the target forest types above against the current conditions in North Beach Park indicates that more restoration needs to happen at the herbaceous level. To date, we’ve concentrated mostly on the tree and shrub layers. We plan to increase our reintroduction of under-represented herbaceous plants.

Putting different forest types into the buckets of reference ecosystems both allows for a greater planting selection and strategy, and perhaps even a climate change adaptation.

Research with grasslands shows that productivity increases with biodiversity (Tilman, 2001). Making several TFTs available for every reference ecosystem can help with climate change and prevent biodiversity loss through both component redundancy (increased species and community redundancy) and functional redundancy (introduction of ecologically equivalent species or novel associations) (Dunwiddie 2009).

References

Chappell, C.B. 1999. Ecological Classification of Low-Elevation Riparian Vegetation on the Olympic Experimental State Forest: A First Approximation. Washington Department of Natural Resources, Natural Heritage Program, Olympia , Wash.

— 2006. Upland plant associations of the Puget Trough ecoregion, Washington. Natural Heritage Rep. 2006-01. Washington Department of Natural Resources, Natural Heritage Program, Olympia , Wash. [http://www1.dnr.wa.gov/nhp/refdesk/communities/ ].

Denovan R., and Salisbury, N. 2012. GSP Target Forest Type Assignment Key Using GSP Site Inventory Data. (unpublished document)

Dunwiddie, P.W., S.A. Hall, M.W. Ingraham, J.D. Bakker, K.S. Nelson, R. Fuller, E. Gray. 2009. “Rethinking Conservation Practice in Light of Climate Change.” Ecological Restoration 27:3 320-329

Kunze, M. 1994. Preliminary Classification of Native, Low Elevation Freshwater Wetland Vegetation in Western Washington. Washington Department of Natural Resources, Natural Heritage Program, Olympia, WA.

Larson, R.J. 2005. The Flora of Seattle in 1850: Major Species and Landscapes Prior to Urban Development. (Unpublished thesis).

Tilman, D., P.B. Reich, J. Knops, D. Wedlin, T. Mielke, C. Lehman. 2001. “Diversity and Productivity in a Long-Term Grassland Experiment.” Science, Vol. 294, 843-845

Mirrored from Nature Intrudes. Please comment over there.


 


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