Mesquite (Prosopis spp.) forests or Bosques are unique and biodiverse riparian forests. Bosques occur primarily along high floodplains in riparian ecosystems below 1200 m in elevation. Today, bosques are composed of dense stands of small young trees. Mesquite is the dominant overstory species with a variety of small shrubs and herbaceous plants making up the understory. With a deep root system almost reaching the water table and a symbiotic relationship with nitrogen-fixing bacteria, Mesquite is a highly productive species promoting biodiversity and providing habitat to wildlife. With this high biodiversity, Mesquite Bosques has a higher density of breeding bird species than any other habitat in the southwest (Stromberg, 1993).
Species Composition
There are three native mesquite species found in the Bosques of the southwest; honey mesquite (Prosopis glandulosa) and velvet mesquite (P. velutina) which are in riparian and upland ecosystems and screwbean mesquite or tornillo (P. pubescens) which is restricted to riparian ecosystems and floodplains. Less than 25% of overstory trees in bosques are species other than mesquite (Stromberg, 1993) mainly including cottonwood and willow species (Carothers et al., 2020) (table x). Bosques have a middle stratum comprised of vine and shrub species and an herbaceous understory (Stromberg, 1993).
Table 4. Bosque Overstory Vegetation Species. Adapted from Stromberg (1993)
| Common Name | Scientific Name |
| Honey mesquite | Prosopis glandulosa |
| Velvet mesquite | Prosopis velutina |
| Screwbean mesquite/tornillo | Prosopis pubescens |
| Fremont cottonwood | Populus fremontii |
| Goodding willow | Salix gooddingii |
| Catclaw acacia | Acacia gregii Gray |
| Netleaf hackberry | Celtis reticulata |
| Blue palo verde | Cercidium floridum |
| Arizona walnut | Juglans major |
| Texas muberry | Morus microphylla |
| Desert willow | Chilopsis linearis |
| Velvet Ash | Fraxinus pennsylvanica Marsh, ssp. velutina |
| Mexican elder | Sambucus mexicana |
| Soapberry | Sapindus saponariaL. var. drummondii |
Historical Conditions
Historically, Bosques were the most abundant riparian forest type in the southwest. At one point, these forests occupied floodplains and often spanned hundreds of kilometers along rivers such as the Gila and Colorado (Stromberg, 1993). Today, bosques are significantly reduced to remnants as anthropogenic changes have eliminated or significantly reduced this forest type. Many species rely on Bosques so this reduction in forest area, has also led to a loss of other plant and animal species (Carothers et al., 2020; Stromberg, 1993).
Climate Impacts
Human activities such as groundwater pumping, land clearing, and livestock grazing threaten Southwestern Bosques. Few bosques remain and few to none are in pristine condition (Stromberg, 1993). Despite the significant decline from historic composition, Bosques are well-adapted to arid environments. Mesquites have Dimorphic root with a deep tap root that reach alluvial aquifers and lateral roots that reach surface water and flooding (Leenhouts et al., 2006), allow them to replace willow and cottonwood in these systems (Carothers et al., 2020) escape seasonal droughts by storing viable seeds in seed banks, long life span (Stromberg, 1993).