Water, Flowers and Nest Holes
1Oksana Petrenko and the garden club at Northgate Middle School look after a small greenhouse and an outdoor garden. Their adviser, Mr. Kwabena Asante, gave the club a question that ecologists ask about every ecosystem: what happens to living things when a resource they need is scarce, and what happens when there is plenty of it?
2First, the club tested water. Inside the greenhouse, where no rain falls, they built four beds, each 1 m², side by side along the same sunny wall and filled with the same soil. They sowed 40 bush bean seeds of one variety in each bed. A drip line gave each bed a different amount of water every week: 5 L, 10 L, 20 L or 30 L. After 8 weeks, they counted the living plants, measured each plant's height and counted its pods (Table 1). Bean plants use water, carbon dioxide and light to make their food. A plant that is short of water often closes the tiny pores in its leaves, so it also takes in less carbon dioxide.
3Outside, the club studies blue orchard mason bees, a native bee that does not live in a hive. A female nests in a hollow tube, such as a hole in dead wood or a paper tube in a nest block. She gathers pollen and nectar from flowers, packs a ball of it at the back of the tube, lays one egg on the ball and seals it in with a mud wall. That makes one cell. Then she builds the next cell in front of it. Females do not share a tube, and each larva eats only the food ball in its own cell. The new adults come out the next spring.
4The club put up a nest block with 60 paper tubes in spring 2022. That fall they planted a strip of native wildflowers beside the garden, and in fall 2023 they made the strip about twice as big. In 2025 they added a second block, for 120 tubes in all. Each spring, the club counted the plants in bloom within 30 m of the blocks, the tubes that were filled and the cells inside them (the paper tubes can be unrolled and closed again). The next spring, they counted the new bees that came out and weighed a sample of the new females (Table 2). In late spring 2024, club members watched many females land on the full block and fly away again.