This IBA is a relatively intact contiguous riparian corridor surrounded by developed residential area. It consists of the riparian corridor, featuring some scenic ravines with a small amount of hemlock, and includes Holden Arboretum, Little Mountain, Penitentiary Glen, North Chagrin Reservation, South Chagrin Reservation, and Chapin Forest.
Holden Aboretum is a largely (75%) forested site with old agricultural fields and meadows (25%). Its forests are mostly mature, over 75 years in age, with a mixture of beech-maple to hemlock-hardwood. It includes nineteen constructed ponds and lakes and numerous natural wetlands. There is a 90-acre cultivated core of horticultural collections. Penitentiary Glen is a 425-acre property located in Kirtland. It is a mix of hemlock-hardwood forest, beech-maple forest, and old-field habitat. Chapin Forest is a 390-acre property located in Kirtland. Chapin was donated to the state of Ohio in 1949 and is currently being leased to the Lake Metroparks through the Ohio Division of Forestry. Chapin Forest is a mix of northern hardwood and beech-maple forests. North Chagrin Reservation is an excellent example of beech-maple climax forest and hemlock ravines. There are also various managed meadows and wetlands. A. B. Williams Memorial Woods (65 acres) is the highest quality beech-maple forest. This woodland is a registered national landmark, and was the site of the namesake's PhD research.
Still relatively intact, this corridor harbors several peripheral populations of high-priority species. Ravines are home to Dark-eyed Juncos, perhaps 20% of the Ohio breeding population (Lake county 70-90 pairs[?]; South Chagrin 35 pairs[?])
The Holden Arboretum is the largest contiguous landowner in either Lake or Geauga county. It is largely forested, featuring a variety of forest cover with numerous microclimates, and a wide variety of forest-interior birds use the site during migration or for nesting. Holden's fields are managed for field-nesting birds and ponds and wetlands provide food and cover for other bird species.
North Chagrin Reservation has very high-quality habitat for nesting forest birds. Hemlock ravines support state-endangered Dark-eyed Junco, Winter Wren, Acadian Flycatcher, Louisiana Waterthrush, and Black-throated Green Warbler. Also nesting are Red-headed Woodpecker, Scarlet Tanager, Wood Thrush, Ovenbird, Veery, Cerulean Warbler, and other representative forest birds.
The hemlock-lined gorge of Penitentiary Glen has breeding populations of Dark-eyed Junco and Winter Wren. The old-field areas have breeding populations of Bobolink. Cerulean Warbler and Brown Creeper also occasionally breed in the area. Penitentiary Glen is home to 17 species of state-listed plants and animals. Ten species of state-listed birds have been found breeding on the property, including Least Flycatcher.
Chapin Forest's north-facing hemlock slopes annually get breeding Dark-eyed Junco, Magnolia Warbler, and Winter Wren. The demonstration confier plantings have had breeding Golden-crowned Kinglet, Red-breasted Nuthatch, Pine Siskin, Purple Finch, and Pine Warbler. Cerulean Warbler and Brown Creeper also occasionally breed in the area. Blue Grosbeak have been found in the abandoned quarries in two years. Chapin Forest is home to 18 species of state-listed plants and animals, with 13 found breeding on the property. Bald Eagles nest along the Chagrin River.
Certain habitats of the Holden Arboretum are more subject to invasive exotic plant species, and management programs are being developed to mitigate their influence and exclude them from priority conservation sites. Deer have had an impact on the lower forest layers and harvest programs have been developed.
According to an ODNR-DNAP report, a plant community survey of the Lake Erie drainage lists Holden Arboretum as having the following "A"-ranked sites - Stebbins Gulch, Little Mountain for hemlock-hardwood forests, and one "B"-ranked site - Brainard Bog. Sections of the Holden Arboretum-Bole Woods and Stebbins Gulch-are designated as natural history landmarks by the Department of the Interior.
North Chagrin Reservation has a very high-quality beech-maple forest, probably one of the best examples in Ohio, with 300-400 yr. old beech trees. A.B. Williams did his PhD research on beech-maple climax forests here in the 1930s, so we have a great snapshot of this forest from 65-70 yrs. ago. Other bird survey work, including nesting success of key forest species by Lisa Petit from the Smithsonian, has occurred here. Deer population is a key issue in North Chagrin Reservation, with Cleveland Metroparks attempting to address it through deer culling. Cowbird parasitism, raccoon predation, and disturbance by people are of concern.