Makiki Loop Trail hike: Learn about forest ecology in a lush valley, Saturday. Two and a half miles, three hours. Costs $5. Call the Hawai'i Nature Center at 955-0100.
Sumo demonstration: The All Japan National Collegiate Sumo Team practices 1 to 2:30 p.m. Saturday at the Japanese Cultural Center. The wrestlers will be available for autographs and photographs. Free admission; $2 parking with validation. Call 945-7633.
Ahuimanu hike: Two-mile stroll through a Kahaluu valley with Donna Brown of the Hawaiian Trail & Mountain Club, 9 a.m. Saturday. Costs $2. Call 422-7830.
Aiea Ridge hike: Twelve miles to the Ko'olau Summit with Dave Sanford of the Hawaiian Trail & Mountain Club, 8 a.m. Sunday. Costs $2. Call 488-4419.
Sierra Club trail building: Help work on the Maunawili Falls access trail, Sunday. Bring backpack, lunch, two liters of water, shoes and rain gear. Call 538-6616. Continues July 13, 14, 21, 27 and 28.
The Club works to eradicate miconia, a plant that has overrun Tahiti, July 20. Bring lunch and canteen; tools and refreshments provided. Call 538-6616.