Visit to NatureBridge School in Olympic National Park

With an invitation from education manager Chris Morgan, I paid a visit and gave a talk to the educational staff at NatureBridge, on the shore of Lake Crescent.   I had an engaging exchange with about twenty staff members, all of them environmental educators whose mission

"is to connect young people to the wonder and science of the natural world, igniting self-discovery and inspiring stewardship of our planet. Through our overnight, hands-on environmental science programs, we take more than 35,000 children and teens each year into our national parks to explore the outdoors, connect with their peers, discover themselves and develop a lasting relationship with the environment." 

The low elevation mature and old-growth forests surrounding Lake Crescent are healthy.  Sword ferns dominate large areas of undergrowth - with no sign of any die-off.

We emerged from this meeting, which concluded with a walk in the woods, with a tentative plan: that NatureBridge staff and their students may contribute to understanding the die-off, and more fundamentally to the understanding the ecology and biology of sword ferns, through careful  observations over the coming years. 

Some of the topics we discussed:

1.  Sword ferns rarely reproduce under a closed forest canopy.  See Robbin Moran's  Natural History of Ferns report that the prothallus (the gametophyte) needs recently exposed bare soil (and presumably ample sunlight) for propagation.  
2. Individual plants (the familiar sporophyte generation) are very long-lived ("a thousand years is not out of the question" - David Barrington, University of Vermont polystichum expert)
3.  Are there any signs of fern mortality, or propagation, in the healthy fern communities in Olympic National Park?  To suppport or contradict topics 1 and 2?

 We know little about the variability of the annual life cycle of healthy ferns and their fronds.   Perhaps a multi-year phenology project would be a good match for NatureBridge students?   A combination of careful observation in the forest, data collection, hypothesis generation and testing?

In this scenario, student scientists, backed up by trained academics (we have contacts with some helpful ones) could contribute new understanding of this signature PNW species, and provide baseline and background information we need to explore the die-off

Is there a pattern to the 10% sword fern survival at Ground Zero?

In 2013, 215 large healthy sword ferns occupied the understory of the quarter-acre of Seward Park's Ground Zero.  Twenty of those ferns survive six years later. Is there a pattern to that survival, perhaps some clue to the cause of the die-off?  It appears that proximity to trees or logs correlates with survival - but does that stand up to close inspection?  We found that there is a small but statistically significant association.

In this map dead ferns are black circles, survivors are in light green, trees are larger solid circles, and logs are thick black lines.

Leo Shannon and I collected the location and status of all ferns, trees and logs in this quarter acre on May 18th and 19th, 2019.   Dylan Mendenhall did the analysis.   Results are summarized below the map.

Dylan's summary and suggestions:

The survival rate was 10.2% for sword ferns within 15 ft of a tree or log. In contrast, the survival rate was 2.3% for sword ferns further than 15 ft from a tree or log... the odds of a fern surviving are 4.8 times greater if it is located within 15 ft of a tree or log. 

Based on these findings, management recommendations are to:

• Maintain or increase coarse woody debris and mature trees in natural areas
  susceptible to sword fern die-offs
• Prioritize restoration planting within 10 ft of CWD or mature trees

All preliminary data, subsequent revisions, R scripts and figures are available on github .