The Role of Nurse Plants in the Survival of Saguaro Cacti
In the harsh environment of the Sonoran Desert, the towering saguaro cactus stands as a symbol of resilience and life. Its crimson fruits, which appear before the monsoon rains, are a critical food source for desert wildlife during the most challenging time of the year. Additionally, these massive cacti provide shade, creating small areas where the conditions are more favorable for life to thrive.
However, despite the saguaro’s robust nature, young cacti face significant challenges. In their early stages, they are vulnerable to the desert’s extreme temperatures and conditions. The concept of facilitation in plant communities highlights how one species can aid another’s survival. In the case of saguaros, “nurse” plants like mesquite, palo verde, and certain cacti play a crucial role. These plants offer shade, lower temperatures, decrease wind exposure, shield seedlings from predators, and enrich the soil with nutrients.
Research in Sonora, Mexico, revealed the importance of these nurse plants, as evidenced by the discovery of 83 saguaro cacti growing under a single mesquite tree. Saguaros also benefit from “nurse rocks,” which release heat at night, providing warmth during cooler temperatures.
Indigenous communities, such as the Tohono O’odham, have long understood this relationship. Anthropologist Ruth Underhill documented how Tohono O’odham elders likened young saguaros to vulnerable children, needing the nurturing environment provided by palo verde trees, which act as protective figures.
During the summer, the cycle continues as birds, bats, mammals, and insects feast on saguaro fruit beneath the protective canopy of nurse plants, perpetuating the dynamic ecological process.
This Earth Note was written by Danika Thiele and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.
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