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Uplands and Slopes: North Slope
Dec. 1st, 2014 09:00 amDescription
The North Slope starts at the main entrance to the park and runs between the main trail and NW 90th St., as it rises up to 25th Ave. from 24th Ave. At 1.14 acres, it is the third largest HMU in North Beach Park.
The trail side has vertical stretches, with bare dirt and roots exposed. These stretches occasionally have heavy trees on top of them. These have been protected with wattles (burlap sacks half-filled with woodchips) held in place with ninebark stakes.
Further into the park, some of the trailside reaches of the slope widen out and become more volunteer accessible. There is still a lot of slope above the accessible areas, however.
The percent tree cover is about 85% deciduous, almost exclusively Acer macrophyllum (Big leaf maple); 5-10% is Thuja plicata (Western red-cedar), and the remaining 5-10% is gaps. The regenerating tree cover is less than 5% deciduous and less than 1% conifer.
The target forest type for the North Slope is Tsuga heterophylla – Pseudotsuga menziesii/Polystichum munitum – Dryopteris expansa (Western hemlock – Douglas fir/Sword fern – Spreading wood fern; TSHE-PSME/POMU-DREX). The reference ecosystem is Mesic-moist conifer and conifer-deciduous mixed forest.
Water Flow
The coniferous tree canopy over most of the North Slope is dense enough that it intercepts most of the water that would fall onto the slope. However, there are places where water flows from the North Slope onto the main trail during heavy rains. The main trail could use some water bars to help deal with this situation.
Furthermore, there are bare places in the groundcover that should get some attention. See “Invasive Removal and Restoration Plan” below.
In the summer of 2013, the Parks Department Natural Area Crew put coir logs underneath the intersection of 90th St. and 25th Ave.
Figure 1: Coir logs on the North Slope.
Side view of erosion control. A narrow trench was dug at the top of the slope, the netting was laid in and staked with 2×2 stakes, and then the trench was reburied.
Vegetation
No invasive plants had established an area of monoculture on the North Slope. What is visible from the trail is a canopy of Acer macrophyllum (Big leaf maple) and a shrub layer of Polystichum munitum (Sword fern) and Mahonia nervosa (Low Oregon-grape). This association is encouraged through occasional spreading of Mahonia berries.
Observed during the belt transect (see below) was a stand of Holodiscus discolor (Ocean spray), the first observed in the main body of the park, and the only known instance of Stellaria crispa (Crisp sandwort) that we know of in the park. (Neither of these were in a transect plot.) The upper reaches of the North Slope have many daffodils, bluebells and other garden plants and escaped ornamentals.
The June, 2014 belt transect laterally crossed the North Slope; eight plots were established from the trailside up to the street end. See “Monitoring” for a full discussion of the belt transect protocol. Most of the area crossed by the transect had received some restoration, by volunteers at the lower end and Natural Area Crew at the upper end.
Table 1, below, shows the target forest type indicator species for the North Slope and all species found in our survey. Please see the Key, below the table, for a full explanation of the numbers.
Table 1: Target forest type and transect species for the North Slope
| Binomial | Common Name | % Cover | TFT Goal |
|---|---|---|---|
| Abies grandis | Grand fir | 0.06 | 14.00 |
| Acer circinatum | Vine maple | 0.00 | 20.00 |
| Acer macrophyllum | Big leaf maple | 83.88 | 18.00 |
| Aesculus hippocastanum | Horse chestnut | 0.06 | 0.00 |
| Alnus rubra | red alder | 11.25 | 9.00 |
| Athyrium filix-femina | Lady fern | 2.00 | 2.00 |
| Mahonia nervosa | Dull Oregon-grape | 11.38 | 4.00 |
| Blechnum spicant | Deer fern | 0.00 | 2.00 |
| Bromus vulgaris | Columbia brome | 0.00 | 2.00 |
| Calystegia sepium | false bindweed | 0.13 | 0.00 |
| Carex deweyana | Dewey’s Sedge | 0.00 | 2.00 |
| Claytonia sibirica | Siberian miner’s lettuce | 0.38 | |
| Corylus cornuta | Beaked hazelnut | 0.38 | 3.00 |
| Cymbalaria muralis | Kenilworth ivy | 0.06 | 0.00 |
| Dryopteris expansa | Spiny wood fern | 0.00 | 3.00 |
| Eurhynchium oreganum | Oregon beaked moss | 0.13 | |
| Galium aparine | cleavers | 0.44 | |
| Galium triflorum | Sweet-scented bedstraw | 0.00 | 2.00 |
| Gaultheria shallon | Salal | 0.00 | 2.00 |
| Geranium robertianum | Robert’s geranium | 0.81 | 0.00 |
| Geum macrophyllum | Large-leaved avens | 0.06 | |
| Hedera helix | English Ivy | 1.63 | 0.00 |
| Holcus lanatus | velvet grass | 0.06 | 0.00 |
| Hyacinthoides hispanica | Bluebells | 0.13 | 0.00 |
| Hydrophyllum tenuipes | Pacific waterleaf | 7.19 | |
| Lapsana communis | Nipplewort | 0.75 | 0.00 |
| Lunaria annua | Silver dollar | 0.13 | 0.00 |
| Moss | 1.63 | ||
| Mycelis muralis | Wall lettuce | 0.81 | 0.00 |
| Oemlaria cerasiformis | Indian plum | 0.06 | |
| Oenanthe sarmentosa | Water parsley | 0.13 | |
| Osmorhiza berteroi | Sweet cicely | 0.31 | |
| Polystichum munitum | sword fern | 12.88 | 54.00 |
| Prunus avium | Bird cherry | 0.63 | 0.00 |
| Pseudotsuga menziesii | Douglas-fir | 0.00 | 45.00 |
| Pteridium aquilinum var. pubescens | Bracken fern | 0.00 | 3.00 |
| Ranunculus repens | Creeping buttercup | 0.06 | 0.00 |
| Ribes sanguineum | Red flowering currant | 0.19 | |
| Rubus spectabilis | Salmonberry | 0.06 | 4.00 |
| Rubus ursinus | Trailing blackberry | 0.19 | 3.00 |
| Sambucus racemosa | Red elderberry | 0.06 | 2.00 |
| Symphoricarpus albus | Snowberry | 0.13 | |
| Taraxacum officinale ssp. officinale | Common Dandelion | 0.06 | 0.00 |
| Tellima grandiflora | Fringecup | 0.19 | |
| Thuja plicata | Western red-cedar | 0.00 | 33.00 |
| Tiarella trifoliata var. trifoliata | Threeleaf foamflower | 0.00 | 5.00 |
| Tolmiea menziesii | Piggyback | 0.75 | |
| Trientalis borealis ssp. latifolia | Western starflower | 0.00 | 1.00 |
| Trillium ovatum | Western trillium | 0.06 | 1.00 |
| Tsuga heterophylla | Hemlock | 0.06 | 36.00 |
| Urtica dioica | Stinging nettle | 12.00 | |
| Vaccinium parvifolium | Red huckleberry | 0.00 | 3.00 |
| Vancouveria hexandra | Inside out flower | 0.00 | 7.00 |
Key: “0.00” in Pct. Cover column indicates a target forest type indicator species not found during the survey. No value in the TFT Goal column indicates a native species not listed in the target forest type. “0.00” in the TFT Goal column indicates an invasive species to be removed.
Invasive Removal and Restoration Plan
Figure 2: North Slope
A: Trailside, less-steep area accessible to volunteers. B: Slope area to be worked on by Natural Area crew.
Subarea A
Subarea A measures approximately 13,200 feet. Volunteers can work in the trailside sections and along some of the more gradual slopes at the western edge. Of particular interest are gullies and washes that form from the steeper parts of the slope. These could be controlled with dikes and careful live staking and planting at the lower sections, and coir logs or other erosion control methods above. The soil in these washes is uncompacted, and likely to slip if too heavily stepped on.
Trailside sections of Subarea A have received plantings every year, by both Natural Area Crew and volunteers. The western edge of Subarea A has received plantings of Abies grandis (Grand fir) and Tsuga heterophylla (Western hemlock).
Suggested tasks for Subarea A:
- Continue spreading Mahonia grapes, as possible.
- Add dikes and wattles to areas experiencing erosion. Live stake above the wattles.
- Plant trees along the lower reaches of the slopes to provide buttressing.
Subarea B
Subarea B measures nearly 36,400 square feet. The rim along 90th St. has received some plants and mulch from volunteers. Below the rim, the Parks Department Natural Area Crew did invasive removal (by hand), erosion control, and planting in 2013.
Forest stewards can visually monitor this area from the street rim and the trail, but further work in this area will have to be done by the Natural Area Crew.
References
Green Seattle Partnership, 2014. GSP Reference Map on ArcGIS.com. http://www.arcgis.com/home/webmap/viewer.html?webmap=9be9415001144aa383e5b86e481d2c45&extent=-122.5312,47.374,-121.7945,47.7577 Dates of accession various.
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