Ambrosia dumosa

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Ambrosia dumosa
Ambrosia dumosa in the garden of Springs Preserve in Las Vegas, Nevada

Ambrosia dumosa in the garden of Springs Preserve in Las Vegas , Nevada

Systematics
Asterids
Euasterids II
Order : Astern-like (Asterales)
Family : Daisy family (Asteraceae)
Genre : Ragweed ( Ambrosia )
Type : Ambrosia dumosa
Scientific name
Ambrosia dumosa
( A.Gray ) WWPayne

The plant Ambrosia dumosa , a Traubenkrautart is an essential part of Kreosotbuschgemeinschaft that in the Mohave Desert ( California ) and in the Sonoran Desert ( Arizona and northwestern Mexico , the dominant plant community). English terms are (white) bursage , bur sage , burro (w) (-) weed and burro bush .

description

Ambrosia dumosa is a heavily branched shrub that is 20 to 90 centimeters tall. The many thin and stiff branches usually form quite compact hemispherical cushions. Younger branches are densely covered with soft gray-white hair. The stem axis forms rhizomes .

Leaves and flowers of Ambrosia dumosa

The leaves are composed and consist of approximately ovate, two- to three-fold, deeply indented pinnate leaves. They stand in association on short branches, are 5 to 40 millimeters long and are also covered by gray-white hair.

The monoecious plant has yellow flowers . The numerous male heads are multi-flowered with a five- to eight-lobed bract and have a diameter of 3 to 5 millimeters, the female heads consist of a double flower without a crown. Female heads mix with male heads over the entire length of the racemous inflorescence.

The burdock-like, 5 to 20 millimeter long fruits of Ambrosia dumosa are spherical (obovoid), their hue varies from gold to purple to brown. In addition to microscopic hairs, they have 12 to 35 flattened, straight spines that are between 5 and 9 millimeters long and are irregularly distributed over the surface. They can get stuck in the fur and hair of animals and then be scattered over large areas. The fruits produce abundant seeds, which usually begin to germinate in open terrain after heavy rainfall.

Burdock-like fruit clusters of Ambrosia dumosa

The root system of Ambrosia dumosa starts out from a segmented root crown and consists mainly of lateral roots. The roots can reach five to fifteen times the length of the stem axis and penetrate the soil to a depth of 70 centimeters.

Ambrosia dumosa can reproduce vegetatively as well as sexually. Due to the vegetative mode of reproduction, the plant can reach a very old age. However, this view is not shared by all research groups - after all, conservative estimates also assume an age of around 50 years. Flowering from Ambrosia dumosa is usually spring and summer, when enough rainfall even in the fall.

During periods of drought, the plant goes into a dormant state and loses all of its leaves in order to be able to counteract transpiratory water loss. At rest it can be identified by the longitudinal grooves on the shorter stems.

Similar to other grape herbs, Ambrosia dumosa pollen can cause severe allergies.

distribution

Ambrosia dumosa is one of the character plants of the Mohave Desert, but is also found in the Sonoran Desert. They are distributed in the US states of Arizona , California , Nevada and Utah , in Mexico the states of Baja California and Sonora . The northernmost point of this area is southwestern Utah, the southern border is formed by the island of Tiburon in the Gulf of California and the Bahía de los Ángeles in Baja California .

Ecosystem and Associations

Ambrosia dumosa belongs to the desert shrub ecosystem. The plant usually occupies a dominant or co-dominant position in association with the creosote bush , Larrea tridentata (creosote bush community of the Sonoran and Mohave deserts). In addition, it occurs in the following plant associations:

Environmental factors and location

Ambrosia dumosa is exposed to very high temperature (−15 ° C to 47 ° C) and precipitation fluctuations (annual precipitation usually between 100 and 300 millimeters) in its locations. In extreme cold or heat, the plant goes into a dormant state, in extreme drought it also sheds its leaves. It thrives in arroyos , on bajadas (coalescing alluvial fans ), on gentle slopes, in valley floors and on sand dunes. The soils are of calcareous, sandy or alluvial origin and are often underlain by a caliche horizon. Ambrosia dumosa is usually found below 900 meters, but can occasionally rise to 1,600 meters. It is a pioneer plant and prefers free locations.

Interactions with other plants

Studies on Ambrosia dumosa showed an allelopathic interaction with creosote bush ( Larrea tridentata ), the latter secreting a growth-inhibiting chemical agent against Ambrosia dumosa . Other studies, on the other hand, indicate that the roots of Ambrosia dumosa produce an active substance that keeps neighboring shoots of its own species away in order to prevent unnecessary competition for groundwater.

Individual evidence

  1. ↑ Fonteyn, PJ; Mahall, BE 1981. An experimental analysis of structure in a desert plant community. Journal of Ecology . 69: 883-896
  2. ↑ Shreve, Forrest; Wiggins, Ira L. 1964. Vegetation and flora of the Sonoran Desert. Stanford, CA: Stanford University Press. 1575 p
  3. ^ Munz, Philip A .; Keck, David D. 1959. A California flora. Berkeley & Los Angeles: University of California Press. 1104 p
  4. ↑ Wright, SJ; Howe, HF 1987. Pattern and mortality in Colorado desert plants. Oecologia. 73: 543-552
  5. ^ Muller, Cornelius H. 1953. The association of desert annuals with shrubs. American Journal of Botany. 40: 1-52
  6. ↑ McAuliffe, Joseph R. 1988. Markovian dynamics of simple and complex desert plant communities. American naturalist. 131 (4): 459-490

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