Conservation History

Invasive Species Control History

Invasive Species Control History

Updated: January 2013 Invasive nonnative plant species have existed in the Park since before its establishment in 1971.  Ring counts of English ivy stems cut on trees in the year 2000 were as high as 35 years.  The earliest known attempts at control focussed on the ivy, the most visible and pervasive of the many nonnative species.  In those days it was also the largest known threat to the ecosystem of the Park. Elinor Levin started removing ivy occasionally in 1983, and more often starting in 1988.  During her first few years of this effort, complaints about it at the front desk were common.  At that time she collected the ivy in plastic bags for removal from the Park. At a 1993 retreat, the Board of Directors of the Friends of the Park established a “Kill the Ivy” program under Elinor’s leadership.  Thus began in 1994 the second Saturday (each month) community “ivy pulls” which were advertised for anyone to participate in.  Help was also solicited from schools, some of which sent groups of students to perform community service under Friends’ leadership.  The Multnomah County Community Corrections Dept. was also invited to send crews of people performing court-mandated community service, and did so at times. Herbicide treatment of ivy was tested in a remote upland area of the Park with promising results.  Due to concerns about effects on other species no broader application was tried. In 1995 the Ivy Subcommittee was established after the Board retreat proposed developing an Adopt-A-Plot (AAP) program for control of ivy and other invasive nonnative plants. A draft proposal developed by Mel Taylor was reviewed by the Friends’ Board and Park staff, all supporting the program.  Phil Hamilton agreed to coordinate the effort. With these expanded efforts involving many people, the ivy pulled was no longer removed from the Park but was piled and left to die and compost.  Second Saturday work parties cut mature ivy growing up trees in the vicinity of the Nature Center during the next few years and, with help from other groups, pulled ground ivy along trails in that area.  In the early 1990s one busy volunteer cut ivy growing up trees on over a hundred acres.  The AAP program quickly grew to about 10 adopters, where it plateaued, with most plots near Tryon Creek or the Nature Center.  Six of the adopters aggressively attacked their plots and made noticeable differences. In 1997 Dave Kruse got involved in the effort and took over management of the AAP program in 1998 while Phil, as Eco/Trails (formerly Building & Trails) Committee Chair, coordinated the various other nonnative species removal efforts.  Within a couple of years the AAP program had 20 adopters, with many of the new plots concentrated on the west side of the Park near adopters’ homes. Simultaneously, the effort to cut mature ivy infesting trees expanded, with a few dedicated individuals plus volunteer groups from PGE (enlisted by Dave) working throughout the Park to save trees. Attention started to broaden to other nonnative species in 1999, first focussing on Himalayan blackberries along Tryon Creek, where George Toepfer and Brent Foster began digging them. Dave Kruse and Phil Hamilton continued this work and later got help from several others.  In 2000 observers first became aware of the invasiveness of clematis...

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Invasive Species Control Status by Plant Grouping

Invasive Species Control Status by Plant Grouping

Updated: January 2013 By the end of 2012 the status of control efforts was as follows: Ground ivy:  Less than 5% of the Park only slightly infested and untended, with an additional 35% of the Park initially controlled (pulled at least once).  Ivy in almost all locations visible from the upper loop trails near the Nature Center, and on the east side of the Creek from Red Fox Bridge almost to 4th Avenue, has been pulled at least once, and much of that area more than once.  A similar effort has occurred on the west side of the Creek between Obie’s and High bridges.  Recent efforts have extended north from the upper loop trails and in 2008 began moving into the North Horse Loop (NHL).  By the end of 2012 nearly 90 percent of the interior of the NHL had been initially controlled.  One area remaining there is the very steep head of the south ravine in NHL, where very steep slopes limit both the work season and the types of volunteers who can safely work there.  Similar steep slopes remain to be cleared in the upper reaches of the two main branches of High Creek, the ravine south of NHL What became notable in the spring of 2003 was the recovery of the trillium.  When first released from the smothering ivy, the trillium responded well, but mostly as single plants; by 2003 many had reproduced to form clumps. At the end of 2012 there were only half a dozen truly active adopted plots plus as many more with occasional activity.  The number of plots peaked at 32 in 2004, but many adopters  quickly lost interest.  Most long-term adopters are returning periodically to get re-sprouts and new seedlings, an essential maintenance step.  Many areas west of the Creek which were pulled once aren’t being maintained, due to abandonment of adopted plots. Ivy threatening trees:  Cut once in over 95% of the Park, with most remaining uncut areas being steep slopes or difficult to access. In 2010 cutting began in the largest uncontrolled area, the often steep slope between Lake Oswego’s First Addition and the Creek. A second cutting has been done in most areas of the Park where substantial ground ivy remains, with additional cutting of re-growth continuing where trees are threatened again or ivy on them is flowering.  Cutting the re-growth (stems usually no more than an inch in diameter) is less time consuming than initial cutting of stems that were often over two inches and as large as seven inches. Himalayan blackberry:  Dug and controlled in much of the riparian zone of Tryon Creek north of Iron Mountain Trail and below the 4th Avenue entrance, and many trail-side large patches.  Some large patches remain, most being west of the bike path north of Iron Mountain Trail or east of the Creek south of that trail.  Along the bike path digging has been done to reduce encroachment on the path.  Locations where dense patches have been dug have been planted with conifers and shrubs and are receiving periodic maintenance to remove new blackberry plants until the planted trees create shade. Clematis:  North of Iron Mountain Trail all known patches (an estimated 600) have been dug at least once, and most, twice or more.  Some are considered eradicated but...

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Trail Maintenance History

Trail Maintenance History

Tryon Creek State Natural Area As of January 2012 Most of the seven miles of hiking trails and four miles of equestrian trails in the Park were completed within a few years of creation of the Park in 1971, with most work done by volunteers. The Friends sponsored “Trail Days” on a weekend in April of 1973. Friends’ Board member Jean Siddall flagged trails and recruited leaders to supervise this major trail-building effort. Several miles of trail were cleared and graded, including the current loops near the Nature Center. So they could withstand the wear of horses’ hooves, the equestrian trails were surfaced with gravel early. In contrast the loop trails around the Nature Center were originally surfaced with wood chips donated by PGE. Replenishing the chips continued for years, until the decomposing chips became ankle-deep compost. To solve the problem, in the mid-1990s the Friends, with Park support, decided to scrape off the ooze and gravel the hiking trails. This effort was accomplished by once-a-month volunteer work parties, supported by gravel deliveries to accessible sites by Park staff. The trails where small vehicles could go were covered fairly quickly but Cedar and Lewis & Clark trails took about two years each, as the gravel could only be transported along them by wheelbarrow, with some hauls approaching a quarter mile. Trail maintenance since then has continued to be primarily a volunteer operation, much of it by fourth Saturday work parties. A significant exception has been the occasional relocation of trail segments to skirt slides, which has often been led by Park staff. The latter have also typically led efforts to stabilize some small slides at trail edges. Some trails have been completely rebuilt in recent years following substantial disturbance of them by crews protecting the Portland BES sewer line that follows the Creek. These segments are Iron Mtn. Trail E of the Creek, the S leg of N Horse Loop, the E leg and part of the N leg of W Horse Loop and Boones Ferry Horse Trail. Volunteer-led trail maintenance efforts are ongoing through the wet season and have several elements: Scraping leafy debris and mud off trails down to the original gravel base. This is primarily done in autumn after the maple leaves have fallen. Starting in 2009 this became a progressively more comprehensive element. Multnomah County alternative community service crews covered the horse loops, some loop trails around the Nature Center and a few west-side trails, while volunteers handled many others. Spreading fresh, usually thin layers of gravel on trail segments that have become soggy. This has been ongoing for years since the original gravel surface was formed. By the very wet rainy season of 2010-2011, both Cedar and Lewis & Clark trails needed a fresh layer of gravel on many sections. A significant part of the latter was graveled in 2011 and gravel piles were pre-positioned by Park staff in the summer of 2011 to facilitate 2012 work. Adding deeper layers of gravel mixed with dirt to spots that are ponding during rainstorms, to elevate them. Widening trail segments that have been narrowed by slow erosion from their uphill sides. Cleaning out and occasionally replacing culverts and adding new ones. Restoring or adding ditches beside and across trails, to keep water off them. On some...

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