Habitat Restoration and Management: 2017/2018

 

 

2017: Based on the demonstrated effectiveness of the 2016 habitat enhancement, similar measures, including grass mowing, manual removal of tussocks, and spoil-hauling along pathways, were repeated in the same approximate area in 2017. Additional measures were also implemented: (1) smaller satellite pools were created and two existing breeding pools were deepened to supplement larval habitat and provide habitat for metamorphosed young-of-year; (2) Pool A was deepened slightly and enlarged by about 20 percent by removing part of the adjacent floating mat in late summer; and (3) another pool (Pool B) comparable in size to Pool A was created on the floating mat approximately 25 meters from Pool A. The location of Pool B was determined based on measurements of water depth below the dry surface on July 28, 2017, with the intention that Pool B could provide year-around habitat because of deeper, more persistent water.

This aerial photograph shows Pool A (darker oval shaped area at lower center of the photo) and associated aquatic pathways on May 18, 2017. South Pond is at upper right. (Photo by Dr. David Wallin)

August 12, 2017: We began work on Pool B in August by removing reed canary-grass to expose water below the dry surface.

The new pool, completed by September 2017, was quickly adopted by young-of-year OSF emigrating from Pool A and several adults.

OSF tadpoles were much more abundant at Southeast Meadow in 2017 than we had observed in previous years. In addition, tadpoles in 2017 were larger and more advanced in development than those at comparable times in 2016 or 2014. Pool A was inhabited by a large number of tadpoles, who had largely completed metamorphosis by early July.

This Oregon Spotted Frog tadpole in an advanced stage of metamorphosis is from Pool A (July 1, 2017) (Photo copyright S. Nyman)

Metamorphosing frogs face many perils, including hungry gartersnakes. Here we see a transforming Northern Red-legged Frog about to be consumed by a Common Gartersnake at Pool A. (July 1, 2017) (Photo copyright S. Nyman)

The total number of Oregon Spotted Frogs that metamorphosed and dispersed from restored habitat in 2017 is unknown, but was almost certainly much more than in previous years. How many frog faces can you find in this photo? (August 4, 2017). (Photo copyright S. Nyman)

Reed canary-grass re-sprouted on the floating mat surrounding Pool A, but generally remained sparse compared to unmanaged areas, and provided openings for other plant species to appear. Removal of the sod layer in the pool and at the margins also may have been effective in removing most of the viable reed canary-grass seeds from the soil: few  seedlings of this species appeared as Pool A gradually dried, and these were easily removed. In contrast, seedlings of native wetland plant species, including Manna-grass and Bur-reed, were numerous. By the time that Pool A was refilled by autumn rain, these species were well established and subsequently spread within the pool. Although it is unrealistic to assume that reed canary-grass can be permanently removed or replaced so easily, the results demonstrate initial habitat restoration need not include planting or reseeding, provided that the soil seed bank is comprised of native species. In addition, the restored pools favor Manna-grass, Bur-reed, and other native species adapted for prolonged periods with roots underwater.

Native plants appeared in Pool A from seeds in the soil seed bank beginning in late summer 2017 and continued to spread as the pool refilled with autumn rain (October 26, 2017) (Photo copyright S. Nyman)

 

2018:

This is our third pool – Pool C – early in the process of removing a rooted floating mat of reed canary-grass to expose aquatic habitat. We subsequently moved the piles of extracted root clumps out of the wetland. (August 30, 2018)

The completed Pool C (upper center of photo) is situated between Pool A and B and connected by channels to other habitats. In the left foreground is an existing breeding pool that was deepened and enlarged. Note the presence of floating leaves of Manna-grass. (November 19, 2018)

The restored pools are used by three species of frogs (OSF, Northern Red-legged Frog, and Pacific Chorus Frog) and Northwestern Salamander. Here a recently metamorphosed Northern Red-legged Frog is flanked by two OSF in late stages of metamorphosis at Pool A (July 28, 2018) (Photo copyright S. Nyman)

Native plants continued to flourish in Pool A in 2018. Manna-grass and Rush shown here in flower. Unlike reed canary-grass, Manna-grass does not produce woody stems or accumulate thick layers of thatch.(June 12, 2018) (Photo copyright S. Nyman)