Mesquite is the common name for the genus Prosopis, containing over 40 species of small leguminous trees. They are native to the southwestern United States and Mexico (even the creeping mesquite, which is invasive in southern California). The mesquite originates from the Tamaulipan mezquital ecoregion, in the deserts and xeric shrublands biome, located in the southern United States and northeastern Mexico. The region covers an area of 141,500 km2 (54,600 sq mi), encompassing a portion of the Gulf Coastal Plain in southern Texas, northern Tamaulipas, northeastern Coahuila, and part of Nuevo León. As a legume, mesquite is one of the few sources of fixed nitrogen in the desert habitat.
This tree blooms from spring to summer. It often produces fruits known as "pods". Prosopis spp are able to grow up to 8 m tall, with regards to site and climate. It is deciduous and depending on location and rainfall can have either deep or shallow roots. Prosopis spp is considered long-lived because of the low mortality rate after the dicotyledonous stage and juveniles are also able to survive in conditions with low light and drought. The Cahuilla indigenous people of western North America were known to eat the seeds of mesquite.
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History
Prosopis spp has been in North America since the Pliocene era and its wood is dated 3300 yr BP. It is thought to have evolved with megafauna in the New World. The loss of North American megafauna at the end of the Pleistocene era gave way to one theory of how the Prosopis spp was able to survive. The loss of the megafauna allowed Prosopis spp to potentially able to utilize its fruit pods to attract other organisms to spread its seeds. Then with the introduction of livestock it was able to spread into grasslands. Another theory is that Prosopis spp was always present in grasslands but reoccurring fires postponed plant and seed development. Then with the emergence of livestock and grazing the seeds were able to increase and develop.
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Etymology
The English word mesquite is borrowed from the Spanish word mezquite, which in turn was borrowed from the N?huatl term mizquitl.
Habit and uses
The mesquite grows as a small shrub in shallow soil or as tall as 50 ft in deep soil with adequate moisture and forms a rounded canopy nearly as wide. They may have one or multiple trunks, a multitude of branches with bipinnate leaflets of a light green to blue hue that cast a light to deep shade depending on the species. Spikes of flowers form in spring and summer that form a flat pod of beans 2-6 inches long. Once the pod is dry the whole pod is edible and can be ground into flour and made into bread. Many varieties form thorns. When cut to the ground level, the tree can often recover. Mesquite is one of the most expensive types of lumber in the US. A mature tree can be milled and sold for thousands of dollars. It was a popular type of wood used by early Spaniards to build ships, but is now used most commonly for high-end rustic furniture and cabinets. Scraps and small pieces are used commonly as wood for cooking with smoke in southern states, and bring a premium on the market.
As an introduced and invasive species
Honey mesquite has been introduced to parts of Africa, Asia, and Australia and is considered by the World Conservation Union as one of the world's most problematic invasive species. The spread into grasslands is mostly attributed to the introduction of domestic livestock, although other factors include climate change, overgrazing, and the reduction of fire frequency. Although Prosopis spp is naturally occurring in these areas these changes have resulted in Prosopis spp being able to successfully outcompete other native plants and is now considered an invasive species due to the fact that it was able to take advantage of vulnerable ecosystems.
Prosopis spp is different from most invasive species because it is highly invasive in its native range as well as introduced ranges. Its impacts on the invaded ecosystems include changes to hydrological, energy, and nutrient cycling, as well as consequences to biodiversity and primary production. Prosopis spp density and canopy cover influence the herbaceous layer and native shrubs and are factors in the changes to the ecosystem.
In the United States, Prosopis spp has become the dominant woody plant on 38 million ha of semiarid grasslands. North America is its native range and due to an imbalance within this ecosystem has been able to spread rapidly. It is considered the most common and widely spread "pest" plant in Texas. It is estimated that about 25% of Texas' grasslands are infested and 16 million acres are so invaded that it is suppressing the majority of grass production. In Mexico and the US the two most problematic species are honey mesquite (Prosopis glandulosa) and velvet mesquite (Prosopis velutina). Australia is also impacted by the introduction of Prosopis spp, in particular, the P. pallida, P. glandulosa, P. velutina, and their hybrid P. juliflora. Prosopis spp is ranked nationally as one of the twenty most significant weeds. It now covers almost 1 million hectares of land . Prosopis spp was originally introduced to help with erosion because of its deep root system. It also has immediate uses to humans through timber and providing a food source through its pods. Since Australia is a hot and semi-arid region, Prosopis spp has been able to become naturalized.
In India Prosopis spp had been introduced decades ago but it wasn't until recently that its effects had been studied. This plant species has been pushing out the Indian wild ass (Equus hemionus khur). This herbivorous mammal eats the pods of Prosopis spp, which is one of the intended purposes of its introduction. Through digesting and excreting the seeds the Indian wild asses are providing the habitat needed for germination. The 5,000 square-kilometer Indian Wild Ass Sanctuary is experiencing mesquite invasion of roughly 1.95 square-kilometers a year. By overtaking the land, the dense canopy cover of Prosopis spp has made it so native vegetation cannot grow. It has also made watering holes inaccessible to the animals within this region. This lack of resources and range is forcing the endangered Indian wild ass into human landscapes and agriculture fields and locals are killing these asses in order to protect their crops.
Control strategies
Controlling Prosopis spp is a challenging task. One method that is often used is mechanical control. This can be effective with high mortality rates if stems are cut at least 20 cm underground. Another method is through the application of herbicides and this is done on an individual plant basis. Basal application is effective to Prosopis spp of all sizes while foliar application is best for plants smaller than 1.5 m. Another physical option for control is through fires. Some species of mesquite are fire sensitive while others are fire tolerant. For those that are fire sensitive this method can be highly effective but those that are fire tolerant require hot and intense fires to be effective. In Australia scientists are trying biological control methods. They have introduced multiple insects but the most effective in causing high population level impact is the leaf tying moth (Evippe spp). The most recommended method for managing Prosopis, both in native and introduced ranges, is by targeting large amounts of plants either through herbicide or physical removal. There is also new research being done on using satellite and aerial images to assess canopy cover and determine which ranges should be targeted.
Species
- Prosopis alba (white mesquite)
- Prosopis cineraria
- Prosopis chilensis (Chilean mesquite)
- Prosopis glandulosa (honey mesquite)
- Prosopis humilis
- Prosopis juliflora
- Prosopis laevigata (smooth mesquite)
- Prosopis nigra (black mesquite)
- Prosopis pallida
- Prosopis pubescens (screwbean mesquite)
- Prosopis reptans (tornillo)
- Prosopis strombulifera (creeping mesquite)
- Prosopis velutina (velvet mesquite)
Source of the article : Wikipedia
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