Acacia melanoxylon (Blackwood acacia)
Acacia trees have an ancestral quality. Native to tropical Australia and Africa where they demarcate savannah and veld, they form complex relations and support grassland inhabitants. The savannas of Africa are where humans emerged millions of years ago, and these ecosystems nurtured human evolution. Acacia trees were likely part of our ancestral landscape. In Africa, Acacias leaves are eaten by giraffes, and yet the trees release tannins into leaves after 10-15 minutes of foraging, and this bitter taste dissuades the giraffes from eating. They also release a phytochemical that travels on the wind, signaling other Acacias in the area to produce tannins. In Africa, they have a mutualistic symbiosis in which ants protect the tree while gaining sap and shelter. These interspecies relationships with ants and giraffes are examples of co-evolution. One type of Acacia is hailed as a possible healer of African soils, providing fertilizer for crops when planted in fields, while providing timber, fuel, medicine in the bark, windbreaks, and erosion control.
Blackwood acacia, in the Fabaceae family, is native to Australia, though offers coastal California a host of benefits, though is considered somewhat invasive. The Acacia genus with 1600 species of trees and shrubs, is economically significant and the trees have been introduced in many countries for wood and flowers; Blackwood acacia wood is tough but also bends, working well for guitar making and boat building. They produce luminous yellow flowers, and feathery young leaves are replaced by photosynthesizing phyllodes, which is actually a leaf stem. They fix nitrogen in the soil through relations with Rhizobia bacteria that enter through root hairs and form nodules on roots. Rhizobia and other nitrogen fixing bacteria provide critical nitrogen for plant life to exist. Acacias are resistant to fire, drought tolerant, and provide coastal protection.
Elizabeth Oriel 2022
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