Thursday, June 21, 2018

A proposal for experimental restoration of long-term bare ground die-off sites at Seward Park

Submitted to Seattle Parks & Verdant LLC on May 31st 2018


Here for your consideration and critique is my strawman proposal for experimental restoration in two small die-off regions at Seward Park. 

- Paul

Premises:

1) We do not know the cause/s of the die-off, nor its expected duration
   and eventual extent.  Crucially, we do not know if this is a transient, cyclic,
   or endemic phenomenon.

2) We DO know that in Seward Park, die-off of formerly sword fern dominated
   areas are not, after four years, regenerating.   This is in marked
   contrast to post-disturbance regimes of natural restoration described
   by Swanson, Franklin et al (2002), "The Forgotten State of Forest: Early
   Successional Ecosystems on Forest Sites".  The cumulative effects, upon
   general forest health, of unregenerated bare ground, may be significiant.

3) The selection of restoration strategies may benefit from an evaluation of
   the differennce between S&F's intense disturbances(fire, volcano,
   clearcut, insects, wind) and the context in which their regeneration
   occurs.  Specifically, our sites have an intact overstory and
   a possibly reduced local seed sources.

4) Ground Zero is in GSP zone "MF4", with target forest type PSME-ARME/HODI/LOHI
   (doug fir, madrone, ocean spray, hairy honeysuckle).  "Extended
   ground zero" - across the Hatchery Trail to the north, MF7, has
   target forest type PSME-TSHE/MANE-POMU.  A good case can be made
   that ground zero is PSME-TSHE/MANE-POMU as well.

5) My immediate concern is with the previously sword fern dominated bare
   ground sites.  That fern dominance may not be a necessary feature of
   those bare ground sites:  this may have been a contingent assemblage
   produced by quirks in the plant geography and historical dynamics of the forest.
   Given that the (still unknown) cause of the die-off may be still be present,
   or may return, it is unwise to restore these areas to anything like the
   sword fern (near) monoculture which existed there before.


Proposal:

  1) To choose two small currently mostly bare areas (70' x 70'?), one north and
     one south of the Hatchery Trail for restoration planting and seeding, using
     the characteristic species of the PSME-TSHE/MANE-POMU forest type, as
     described in Christopher Chappell's DNR report, "Upland Plant
     Associations of the Puget Trough Ecoregion", 2004, page 109, as listed below.

   2) Perhaps conventional 1-gallon pot seedling planting can be accompanied by
      judicious experiments with direct seeding.

   3) There may be some urgency to returning these moribund areas to
      good health - made up from a heterogeneous community with complex
      food webs, nutrient flows and physical structure inspired by some of the
      intact heterogeneous late succession plant communities found elsewhere
      in the forest at Seward.  We may therefore wish to perform careful
      monitoring of survival rates for both seeds and plants, and to
      inistitute manual watering protocols through the first two summers,
      to maximize the chances of successful restoration, and to refine
      practices for reuse elsewhere.


Candidate Plant species

Douglas-fir                                                       Pseudotsuga menziesii var. menziesii 100 48
western hemlock                                                   Tsuga heterophylla 87 38
western redcedar                                                  Thuja plicata 82 35
bigleaf maple                                                     Acer macrophyllum 60 19
grand fir                                                         Abies grandis 22 7

Shrubs and Dwarf-shrubs
dwarf Oregongrape                                                 Mahonia nervosa 100 18
red huckleberry                                                   Vaccinium parvifolium 80 3
trailing blackberry                                               Rubus ursinus var. macropetalus 78 1
salal                                                             Gaultheria shallon 73 3
vine maple                                                        Acer circinatum 49 15
beaked hazelnut                                                   Corylus cornuta var. californica 42 5
baldhip rose                                                      Rosa gymnocarpa 40 1

Graminoids
Coast Range fescue                                                Festuca subuliflora 33 1

Forbs and Ferns
sword fern                                                        Polystichum munitum 100 23
sweet-scented bedstraw                                            Galium triflorum 62 2
western starflower                                                Trientalis borealis ssp. latifolia 62 2
bracken fern                                                      Pteridium aquilinum var. pubescens 49 1
western trillium                                                  Trillium ovatum ssp. ovatum 47 1
spreading woodfern                                                Dryopteris expansa 42 1
vanillaleaf                                                       Achlys triphylla 36 3
twinflower                                                        Linnaea borealis ssp. longiflora 31 3
inside-out flower                                                 Vancouveria hexandra 29 5
threeleaf foamflower                                              Tiarella trifoliata var. trifoliata 29 1