Possibly related, at least of interest: diseased and dying western hemlocks at Seward Park

Seven years ago, in 2010, I noticed a cluster of four mature dying hemlocks at the dog-leg bend in the sqebeqsed trail.   I had witnessed the death and disappearance of eastern hemlocks in Shenandoah National Park in the 1990s due to the wooly adelgid.   Concerned that something similar was taking place in this related species, I began an informal survey.   Which I happily abandoned after a few months, discovering that all the hemlocks in other regions of the forest were apparently in good health.

Unfortunately this no longer seems to be true.  Many mature hemlocks have recently been affected by factors unknown, many of them dying.   Perhaps the annosus fungus is responsible, as was suggested to me by UW's Bob Edmonds in 2010.  There is now a loose cluster of tall dead hemlocks on the Huckleberry Trail, and Kramer pointed out many dead or dying hemlocks just south of sword fern ground zero.

Here are my unedited notes from 2010, the result of informal research and email exchanges:

   Notes from 2010

Die-off on Hornby Island's Helliwell Provincial Park

Catherine Alexander, the observant citizen scientist who first detected the Seward Park sword fern die-off four years ago, has just returned from Hornby Island - just east of Vancouver Island, 135 miles north of Victoria, between Nanaimo and Campbell River:

Catherine spent most of a day exploring Helliwell Provincial Park, and reports:

Much of the park is old forest, Doug Fir, western red cedar, madrona.  Similar to Seward, Sword fern makes up a good part of the understory. I noticed wilted ferns immediately as we started out, and continued seeing them as we explored. In some places it looked as if most of the ferns visible from the trail were affected. In other areas the ferns on one side of the trail looked healthy while the other side of the trail was affected.  Below are a couple of pictures of small groups of dying ferns, as well as a map of the park with our route through the forested areas marked in red. 

Catherine reports that the islanders became aware of the problem only this year, and considered it the result of an unusually hot and dry summer.   We cannot be sure that that is not so - absent a biological marker of the presumed pathogen - but to both Catherine and me this does not look like a drought affect.   Seattle had less that < 0.1 inch of rain this summer, and Seward's sword ferns weathered this without evident damage.   That is: the effects of the putative pathogen - the die-off - are apparently not difficult to distinguish from drought effects.

Results of June 2017 Soil Tests

Nelson Salisbury of EarthCorps, assisted by me, collected 10 samples each from three disparate 400 sq.ft. at Seward Park, following the protocol provided by the UMass Extension Service.  Here is a map and site summary, followed by lab reports for each site.
Site #1 is ground zero - no surviving ferns.
Site #2 is just west, across the sqebeqsed trail, where ferns are currently dying.
Site #3 is at the north end, a healthy site, almost exclusively populated by ferns.

Extensive Die-Off at Fort Worden State Park

We received photos and video of a large die-off at Fort Worden State Park.   A representative photo and site map will be found below.

The die-off apparently covers several acres, and is quite dramatic.  This is the most northwesterly die-off report received thus far.  It is about eighteen miles north of Port Ludlow, which was previously the most northerly site.  Fort Warden overlooks both Puget Sound and the Straits of Juan de Fuca.

Our Kitsap citizen scientist, Heidi, reports:

I just spent the afternoon traipsing around Fort Worden State Park in Port Townsend and found extensive fern die-off.  It was in the classic pattern of crispy fern, next to mostly dead, next to sparse flat and failing ferns.  It was everywhere.  We went all around Artillery Hill and found that most of the place is affected.  There’s still “healthy” stands of fern, mostly on the North side, which helped to give a stark contrast to the sad desolation of the remaining hill.

It looks to me like it probably started 2-3 years ago.   It is a very large site and I’ve only explored a small part of the park (2+ miles). 

Interestingly, the first patch of die off I found was near an otter den.   I’m making note of wildlife corridors in case that is a part of the spread. We have a lot of otters that traverse my property to nest across the street. The fern die off seems to follow along their path. 

Bainbridge Island Report

2 new reports; hypotheses now organized

Reports of plausible, small die-off sites have come in from Blakeley Harbor, on the southern part of Bainbridge Island, and Timberlake Park,  Issaquah.  I have not yet visited these sites.

We now have a web site on which we collect hypotheses to explain the die-off.  None have yet been validated.

HYPOTHESES

Sword Fern Die-Off Overview: short video, narrative essay

The Sword Fern Die-Off at Seward Park 

 (and a few other Puget Sound locations)

Paul Shannon, Friends of Seward Park

pshannon@systemsbiology.org

May 5th, 2017

Ecologist Tim Billo, UW teacher and part-time stay-at-home dad, noticed something strange three years ago on one of his frequent visits to the Magnificent Forest at Seattle’s Seward Park. This 100 acre forest, by a combination of good luck and good planning, has never been logged. It is home to 500 year-old trees and nesting eagles, to Douglas squirrels and pileated woodpeckers, to ravens and the occasional coyote. It is a tiny remnant of the million acres of ancient forest that covered the Puget Lowlands after the retreat of the glaciers 15,000 years ago. With his one-year-old daughter in a sturdy stroller, walking up the Hatchery Trail, Tim noticed that a hillside previously covered with waist-high sword ferns was now entirely bare. All the ferns were dead.

Tim's daughter is now four years old. The sword fern die-off Tim first noticed three ago has spread rapidly, now covering ten acres. By the time his daughter is in her teens, extrapolating from current rates of spread, very few ferns will be left in the 120 acres of rare and beautiful urban old growth forest.

Not only are the ferns dying: the new bare regions, emptied of ferns, are not regenerating. No new plants, neither weeds nor native species, have sprouted in the bare ground left by the dying ferns. So as the ferns die, the understory structure of the forest disappears, and the overall structure of the forest - its interwoven ecology - is compromised. Tim's daughter, by the time she is a young woman, may find that the Magnificent Forest at Seward Park is but a weak and reduced version of what, for centuries, it has been. We will lose an intricate and beautiful ancient plant and animal community, that rare wonderful thing, a wilderness in the city.

Tim joined with an ad hoc network of volunteers including amateur citizen naturalists, the Friends of Seward Park (including the author), UW ecologist Patrick Tobin, UW undergraduates, the staff of the WSU Puyallup Plant and Insect Diagnostic Laboratory, and plant ecologist Lisa Cieko from Seattle Parks. We scoured the reference literature, consulted fern experts, cultured and sequenced DNA from plant tissue and soil samples, measured soil nitrogen, monitored mountain beavers and insect activity. After three years and the death of hundreds of ferns, and in the presence of its continuing spread, no cause has been found, and no remedy is available.

In the last few months, we have learned of and followed up on reports of sword fern die-off from other parts of the Puget lowland. There is an earlier and still continuing dramatic die-off on the Kitsap Peninsula which began in 2010. There is a more recent and less extreme die-off on Mercer Island. From these three sites, and from observations of healthy sword fern stands in regional forests, we have identified these (conservative) criteria by which to recognize a sword fern die-off site:

1.  at least 400 square feet in extent
2.  approximately symmetrical in shape (a circle or a square)
3.  understory previously dominated by sword ferns (few or no Oregon grape, salal or shrubs) 4) has 25-40 dead crowns approximately evenly distributed across the 400 sq ft area
4.  very few (<5) or no surviving ferns.
5.  the affected area grows larger with each passing year

We initially hoped to discover that the die-off was part of the natural cycle of the forest. Many ask, when encountering the barren ground at Seward Park, if Seattle's recent dry weather, perhaps the drought of 2013, played a role. Some shocked visitors ask "did someone spill toxic chemicals up there?".

None of the many hypotheses we have come up with, or that others have suggested, have withstood the scrutiny of our lab and field testing. The die-off remains a mystery. It appears to be spreading with increasing speed, both at Seward Park and now in a few isolated spots elsewhere in the region. We have reports of die-off from other areas, in the city and further afield, which either do, or do not quite yet, meet the six criteria listed above.

We have received help in our work from some expert fern biologists. Dr. Robbin Moran, Curator of Ferns & Lycophytes at the New York Botanical Garden, and Dr. David Barrington, Professor of Plant Biology, University of Vermont (and world expert on the genus Polystichum to which sword ferns belong) attest that this pattern of die-off is unique: they have never seen anything like this before. This view is echoed by Dr. Alan Smith, research botanist emeritus at the UC Berkeley Herbarium, and Dr. David Wagner of the Northwest Botanical Institute. (See discussion elsewhere on this blog.)

These four scientists also cautiously concur on a most surprising feature of sword fern biology - the discovery which has been one delightful high spot in our work, which is that individual sword ferns in old-growth forests live a long time. For centuries! Sword ferns colonize bare ground left after fire, glaciation, or logging. Once established, and once the forest canopy forms

above them, they rarely (possibly never) reproduce by spore and gametophyte. Vegetative reproduction by rhizome is very limited. Thus there are almost no new young ferns sprouting up in the midst of an old forest.

So when you see ferns beneath big trees at Seward Park, in lush stands, in the die-off area, or in areas where the ferns are now dying, the odds are good that each individual plant you see has been rooted at the spot for hundreds of years.

Urban forests are more fragile than those found in suburbs and rural areas, due to a combination of air pollution, relative isolation from seed and spore sources, overuse by people and dogs, and a higher risk of introduced pathogens. It is plausible, therefore, that the sword fern die-off at Seward Park, which we now are starting to see elsewhere, may be an early sign of a larger Pacific Northwest regional phenomenon.

Tim and the ad hoc research group - our unfunded band of enthusiasts - have now established, by careful field observation and measurement, that the die-off is spreading rapidly throughout Seward's Magnificent Forest. We have documented its appearance in a few thus far isolated sites elsewhere in the region.

It is time now to develop and implement a research program to identify the causes of the die-off. The results of this research will shape our search for remedies, and guide replanting and restoration strategies. The results of the research may offer broad, timely benefits to the region as a whole. Action is imperative: our centuries old understory is dying as we watch.