Copyright©2007
The Murulle Foundation
All Rights Reserved.

Updated: December 11, 2007

Information on Ethiopian...

Flora   |   Wildlife   |    Culture

Articles: Afro-alpine Extremes Mesquite Mountain Bamboo Grasslands Kosso (Hagenia abyssinica)

---

Afroalpine Extremes

As one observes the Ethiopian wolf moving through the landscape of the upper portions of the Bale Mountains, one's attention is immediately drawn to the remarkable environment the wolf inhabits. The vegetation of the Bale mountains differs greatly from the surrounding plains. In the uppermost elevations, above 4,000 m, a peculiar flora emerges that is so different from the flora at lower elevations on the same mountain that it has been treated as a separate floristic region, referred to as the Afroalpine. Here we describe a sample of the unique flora and several of its special adaptations to the harsh conditions of the Afroalpine environment.

Few environments populated by plants on this planet have greater claims to extremes than the Afroalpine belt of East Africa and Ethiopia. The noted botanist Olav Hedberg describes the Afroalpine climate as having "winter every night and summer every day." This characteristic is fundamentally governed by two geographical circumstances, the close proximity to the equator and the high elevations above sea level. The combined effect of intense solar radiation and a thin atmosphere results in pronounced daily temperature extremes. Rapid heating after sunrise and cooling after sunset, as well as the occasional change in cloud cover, can mean violent temperature changes (up to 10 degrees C in less than half an hour). Night frosts are frequent, even in summer, and snow is also common. In fact, glaciers are present in the highest of these mountains, such as Kilimanjaro and Mt. Kenya. In addition to the temperature extremes, dry spells are prevalent and high winds are very common.

Within this extreme environment, you will find very specialized plants that are well adapted to the harsh conditions. On the Sanetti Plateau, the most conspicuous of these unique lifeforms are the giant lobelias. They are characterized by thick, unbranched stems, each carrying a continuously growing, large rosette of leaves, terminated by an immense flower. During the day, the outermost leaves are more or less flat and spread outward to capture sunlight. For protection against the cold nighttime temperatures, the leaves curl inward and are pressed up against the plant to protect the inner shoot. A thick and light colored waxy indumentum covering both sides of the leaves protects them against the intense solar radiation during the day. In other species, a dense pubescence can cover the leaves. The pubescence helps to reflect the intense radiation during the day and diminish outward radiation at night. The waxy surface of the giant lobelia leaves may also serve as a reflector in this regard. The giant lobelia is just one example of the array of specialized plants adapted to the harsh conditions of the Afroalpine.

---

Mesquite
Exotic tree makes an impact

Family: Fabaceae Evergreen tree up to 15 meters tall, known to grow through the floor of huts Three- to four-inch-long thorns can puncture the feet of farmers, animals, and vehicle tires Tolerant of saline and alkaline soils Incredibly heat and drought tolerant, but requires the presence of a water table (up to 35 meters deep) to grow and survive

According to the Ethiopian Agricultural Research Organization, Ethiopia's number one, priority invasive seed is Prosopis juliflora, otherwise known as mesquite. Native to Mexico and Centrala and South America, mesquite was intentionally introduced to the Awash Basin in the 1970s and 1980s as an agroforestry species; it had a reputation as a tree that could grow anywhere. Indeed, since then the tree has invaded pastoral areas, displacing native trees, forming impenetrable thickets (the thorns will punch through the soles of shoes), and reducing grazing potential.

The major conflict in Ethiopia is over whether to control the plant through eradication or utilization. In an artilce published in the Journal of Arid Environments, researchers identified several characteristics of mesquite that will make it diffcult to eradicate. Primarily, mesquite has a "remarkable copicing ability." Chopping down the tree merely stimulates aggressive re-growth from the damaged stumps. In addition, its fleshy, sweet pods are sought after by domestic and wild animals. The seeds survive passage through the animals' digestive tracts and are then distributed across the countryside. Researchers found that, of the animals studied, cattle are the major dispersers of seeds followed by warthogs, camels, and goats. Finally, the small, hard seeds are long-lived, remaining viable in the seed bed for many years. According to an article in the Asian Journal of Plant Sciences, mesquite seeds will even prevent the germination of other native Prosopis plants.

Although it has taken over areas where it was introduced, mesquite is a useful species; it provides shelter, building materials, shade, and it can be used as firewood and charcoal. As an alternative to eradication, the government is investigating alternatives to control the spread of mesquite through utilization. The Afar regional government has bought four machines to crush mesquite pods, which will reduce the number of viable seeds. The activity will also create protein-rich feed for cattle that can be sold by pastoralists. Additionally, the Afar regional government and Farm Africa are working to turn a profit from the tree by marketing the wood as high-quality flooring. The government has also allowed a charcoal association (illegal in most of Ethiopia) to open in the Middle Awash Valley where mesquite is most abundant.

---

Mountain Bamboo

The Odo Bulu Mountains of Ethiopia support very large tracts of rare bamboo forests. Typically found in tropical climates where high temperatures and humidity provide more favorable climatic conditions, bamboo is relatively rare in the temperate climates of higher elevations. It is most abundant in the monsoon areas of Eastern Asia, very few species of bamboo are found in the former USSR, North America, South and Central Australia, or near the poles.

A member of the grass family, bamboo is a perennial plant with round, hollow, woody stems or culms. Most grass culms contain some amount of silica. However, the unusually high amounts of silica in the culms of bamboo make the wood very hard. It's leaf structure and size also separate it from the more traditional species of grass. It's leaves are evergreen or deciduous, and unlike other grasses, are supported by petioles or branches at their base. It's size is impressive. Most members of this group are giants with the tallest specimens reaching a height of approximately 100 feet. Growth of a culm occurs in a single season and can be extrememly fast. Rates of 88 cm in 24 hours or 25 feet in 31 days have been recorded in Japan and India, respectively. With average heights of 20-30 feet and with culm diameters of 15-20 inches, green mountain bamboo (Sinarundinaria alpina) is the primary species found in the forests of Odo Bulu.

The size and strength of bamboo culms have been factors in its historical use by humans. Utilization of bamboo has included fencing, construction, water harvesting, pulp and paper, food and foliage, and medicinal purposes. The hollow culms can also provide ideal piping for water. Bamboo stems can be used for scaffolds, oars, masts, and fishing poles and can be stripped and woven into furniture, baskets, and mats. Bamboo sprouts are eaten as a vegetable, and the grains of some species are also utilized for food. Bamboo is an important resource for the communities surrounding Odo Bulu where harvested bamboo is utilized predominantly for household goods and construction material.

Bamboo also plays a useful role in protecting against environmental degradation, especially soil erosion. Dense stands will form equally dense systems of underground roots that hold soil together and increase infiltration of precipitation. This helps to control flooding by maintaining the water table level and regulating the flow of rivers downstream. Over-utilization, clear cutting, or burning of a forest can depress its rate of recovery and compromise the stability and health of the ecosystem.

The continued presence of the unique bamboo forest in Odo Bulu demonstrates the local communities' commitment to its protection and conservation. Local villagers walk three to four miles into the forest to harvest the bamboo and use donkeys and horses to haul it out. These traditional harvesting methods result in minimal soil compaction and erosion. At the current rate of utilization, this practice does not pose a threat to the ecological stability of the bamboo forests in Odo Bulu.

---

The Resiliency of Grassland

The grasslands of the lower Omo valley of Ethiopia, located in the southwestern portion of the country, are one of the most important resources for the area, providing forage for a variety of wild ungulates as well as domestic livestock and subsistence hunting by the local people. The arid and semi-arid regions of tropical Africa, such as the Omo Valley, are the most variable of terrestrial ecosystems, characterized by marked fluctuations in resource abundance. Extended periods of dryness are punctuated by erratic rainfall and brief eruptions of forage production. How these grassland ecosystems respond to varying intensity of land-use, specifically grazing, has been a question ecologists have long tried to answer.

The most important variable in explaining a grasslands response to grazing appears to be the combination of the evolutionary history of grazing and the moisture regime. Grass species that dominate grasslands with long evolutionary histories of grazing, such as those in Omo, appear to be generally tolerant of grazing regardless of the amount of rainfall. However, variation in rainfall can affect species composition and diversity. Regions that receive more rainfall (between 700 and 1000 mm/yr) are subject to increased changes in species composition and diversity as a result of increased grazing, while arid regions (<400 mm/yr) are more stable.

The ability of a grassland to tolerate heavy grazing has been studied by many scientists. In fact, grass cover can increase due to grazing as a result of increased tillering. Grass that remains ungrazed will simply heighten and go to seed. While the removal of aboveground biomass by grazing stimulates root growth and new shoot production. This can be beneficial to subsequent grazers who move in after cattle or wildebeest have fed on an area. For example, dense herds of migratory wildebeest can reduce green plant biomass by almost 85% of the initial standing crop. However, this grazing prevents flowering and senescence and stimulates net primary productivity, which herds of gazelle that follow the migration of the wildebeest, take ready advantage of.

Although grazing is a natural part of grassland ecosystems, excessive grazing, where cattle are concentrated and confined to one area for an extended period of time, can suppress the dominant grasses. The intense trampling compacts the soil, which results in increased runoff and soil erosion. Ironically, complete protection from grazing disturbance can also induce negative consequences in vegetation structure. As one of the most dynamic ecosystems, stability is not a major feature of grasslands. Their resilience or capacity to absorb disturbance is.

---

Hagenia abyssinica
Kosso Tree

• Characteristics: Tree up to 20m tall with brownish bark peeling in strips. Young branches are pubescent with stiff hairs 3-4mm long. Flowers reddish-orange to white.
  
• Distribution: Montane forest and grassland, 2450-3250m. Hagenia abyssinica was once the dominant tree in the upper montane forest belt in Ethipia, but now only scattered trees remain in most areas. Although they are protected by law, kosso trees are rare in Ethiopia. They are illegally harvested for their high quality wood and cleared from the land to allow for agricultural expansion.
• Locally referred to as kosso, it is known for its medicinal purposes including its ability to expel 'kosso,' the Amharic name for tapeworm.