The long lifespans of saguaros (Carnegiea gigantea) can complicate scientists' attempts to understand their population patterns.

Now, researchers have used a 48-year data set to see how topography can influence how climate affects the plants.

The findings appear in the journal Ecosphere.

Saguaros, which range from southern Arizona through Sonora and into northwestern Sinaloa, Mexico, are an essential keystone species and provide food and habitat for a number of species.

Prior research has tied expansions and contractions to climate effects: Saguaros would spread during wet periods and die off during droughts and deep freezes.

But when the authors studied more than 5,800 saguaros at Tumamoc Hill in Tucson, they found an interplay between local topography and climate conditions created pockets with differing growth and survival patterns.

"By doing it in different places — you know, north, south, east and west slopes – we found some fairly different patterns. And, if you just looked at an average plot, you'd make mistakes about projecting towards the future," said co-author Larry Venable of the University of Arizona Department of Ecology and Evolutionary Biology.

In one surprising example, young saguaros spread across a northern plot in years with several extremely warm days during a severe drought period.

Venable, who is also director of research at the Desert Laboratory on Tumamoc Hill, said such spatial variability can help protect plants from disasters.