Editing Oasis (section)

== Agroforestry ==
[[File:Bled El Hadhar valley in Tozeur, Tunisia (Djerid Oasis).jpg|thumb|Djerid Oasis, Tunisia]]

People who live in an oasis must manage land and water use carefully. The most important plant in an oasis is the date palm ([[date palm|''Phoenix dactylifera'' L.]]), which forms the [[Ecological succession|upper layer]]. These palm trees provide shade for smaller understory trees like [[apricot]]s, [[Date palm|dates]], [[Common fig|figs]], [[olive]]s, and [[peach]] trees, which form the middle layer. Market-garden vegetables, some cereals (such as [[sorghum]], [[barley]], [[millet]], and [[wheat]]), and/or mixed animal [[fodder]], are grown in the bottom layer where there is more moisture.<ref name=":0">{{Cite news|url=https://www.britannica.com/science/oasis-geological-feature|title=Oasis, geological feature|work=Encyclopedia Britannica|access-date=2018-04-30|language=en|archive-date=2018-06-16|archive-url=https://web.archive.org/web/20180616155810/https://www.britannica.com/science/oasis-geological-feature|url-status=live}}</ref> The oasis is integrated into its desert environment through an often close association with nomadic [[transhumant]] livestock farming (very often pastoral and sedentary populations are clearly distinguished). The fertility of the oasis soil is restored by "cyclic organic inputs of animal origin."<ref name="biskra" /> In summary, an oasis palm grove is a highly anthropized and irrigated area that supports a traditionally intensive and polyculture-based agriculture.<ref name=":1" />

Responding to environmental constraints, the three strata create what is called the "[[oasis effect]]".<ref name=":1" /> The three layers and all their interaction points create a variety of combinations of "horizontal wind speed, relative air temperature and relative air humidity."<ref name="Jaradat" /> The plantings—through a [[virtuous cycle]] of wind reduction, increased shade and [[evapotranspiration]]—create a [[microclimate]] favorable to crops; "measurements taken in different oases have showed that the potential evapotranspiration of the areas was reduced by 30 to 50 percent within the oasis."<ref name="biskra" />

The keystone date palm trees are "a main income source and staple food for local populations in many countries in which they are cultivated, and have played significant roles in the economy, society, and environment of those countries."<ref>{{Cite journal |last1=Chao |first1=Chih Cheng T. |last2=Krueger |first2=Robert R. |date=2007-08-01 |title=The Date Palm (Phoenix dactylifera L.): Overview of Biology, Uses, and Cultivation |url=https://journals.ashs.org/view/journals/hortsci/42/5/article-p1077.xml |journal=HortScience |volume=42 |issue=5 |pages=1077–1082 |doi=10.21273/HORTSCI.42.5.1077 |issn=0018-5345 |doi-access=free |access-date=2022-09-22 |archive-date=2024-09-23 |archive-url=https://web.archive.org/web/20240923070657/https://journals.ashs.org/view/journals/hortsci/42/5/article-p1077.xml |url-status=live }}</ref> Challenges for date palm oasis polycultures include "low rainfall, high temperatures, water resources often high in salt content, and high incidence of pests."<ref>{{Cite journal |last1=Cherif |first1=Hanene |last2=Marasco |first2=Ramona |last3=Rolli |first3=Eleonora |last4=Ferjani |first4=Raoudha |last5=Fusi |first5=Marco |last6=Soussi |first6=Asma |last7=Mapelli |first7=Francesca |last8=Blilou |first8=Ikram |last9=Borin |first9=Sara |last10=Boudabous |first10=Abdellatif |last11=Cherif |first11=Ameur |last12=Daffonchio |first12=Daniele |last13=Ouzari |first13=Hadda |date=2015-08-01 |title=Oasis desert farming selects environment-specific date palm root endophytic communities and cultivable bacteria that promote resistance to drought: Oasis palm endophytes promote drought resistance |url=https://onlinelibrary.wiley.com/doi/10.1111/1758-2229.12304 |journal=Environmental Microbiology Reports |language=en |volume=7 |issue=4 |pages=668–678 |doi=10.1111/1758-2229.12304 |pmid=26033617 |hdl=10754/566005 |hdl-access=free |access-date=2022-09-22 |archive-date=2024-09-23 |archive-url=https://web.archive.org/web/20240923070805/https://onlinelibrary.wiley.com/doi/10.1111/1758-2229.12304 |url-status=live }}</ref>

{{Blockquote|The oases consist of almost unbroken forests of date palms, divided up into many gardens that are separated by mud walls and intersected by innumerable irrigation and drainage ditches… In the shade of the palms are grown many other kinds of fruit trees—oranges, olives, figs, apricots, peaches, pomegranates, and jujubes—interlaced with large grape vines that often hang in festoons from the palm trunks. Beneath the trees are small plots of garden vegetables, barley, and alfalfa. Neither date palms nor other trees are planted with any regularity, and the growth is often so dense that the garden resembles a tropical jungle. Very beautiful are these gardens in the spring, when the apricot and peach trees are in blossom here and there among the palms and the figs and vines are putting forth their leaves. In autumn, when the dates are ripening, the color effects, especially when the tops of the palms are lit up by the last rays of the setting sun, are something that once seen can never be forgotten. The great clusters of fruit, displaying every tint from bright yellow, through orange, vermilion, and maroon, to plum purple and chestnut brown, with their brilliant yellow or rich orange ivory-like stalks, contrast superbly with the dull bluish or gray green of the feathery crowns of foliage. It is small wonder that a whole folklore of poetic legends and proverbs has grown up around the date palm in the regions where it flourishes.
| source = Kearney, Thomas H. (1906-09-06). ''Bulletin: Date Varieties and Date Culture in Tunis.''
}}