Ironwood

Have you ever met an Ironwood tree? They only exist in Arizona, in an area that President Bill Clinton On June 9, 2000, established Ironwood Preserve as a national monument to protect these endemic trees and to the thousands of artifacts, and over 200 Hohokam archaeological sites that remain here. It protects 129,000 acres (almost 300 sq. mi) of Sonoran Desert habitat from just west of Saguaro National Park on the west side of Tucson almost to Casa Grande, Arizona. The Monument is administered by the Department of Interior, Bureau of Land Management (BLM). The local Friends of Ironwood National Monument take great care of the place and you can find more information here https://ironwoodforest.org/

On my way back from a NOLS Wilderness Medicine week in Flagstaff, I wanted to come walk through this amazing forest. I was amazed and thrilled to see the huge Palo Verde so green on the landscape, with Cholla, Mesquite, Ironwoods, Prickly Pears, and the Sea of Saguaros. Taking the W. Silverbell Rd. that runs East to West north of Ragged Top mountain, is quiet silence with an occassional pecary, or trogan passing by.

I had never met a Desert Ironwood (Olneya tesota) before, and knew they were in the same family as Mesquite (Prosopis spp) – Fabaceae. I looked for the wood, as the trees grow older they become more wooly barked, and if you find a branch that is broken perhaps you will see the iron colored heartwood deep inside which gave the tree its name. There are more than 40 species of Mesquite tree and what I saw more often in the Ironwood National Monument were velvet mesquites (Prosopis velutina).

“Ironwood functions as a habitat modifying keystone species, that is, a species that exhibits strong influences on the distribution and abundance of associated species. Ironwood generates a chain of influences on associated understory plants, affecting their dispersal, germination, establishment, and rates of growth as well as reproduction. Scientists call these ecological dynamics “nurse plant ecology”. Mesquites and palo verde also play this role, however, each tree caters to slightly different sets of plants in its “nursery”. Ironwood is the dominant nurse plant in some subregions of the Sonoran Desert. Like other legumes, they alter the soil composition beneath their canopies, enriching the soil with nutrients such as nitrogen.” (FIWF) More info here: https://ironwoodforest.org/about/the-monument/nature/desert-ironwood-tree

The photos here introduce you to these amazing trees, and this desert forest ecosystem:

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