scholarly journals Alluvial records of the African Humid Period from the NW African highlands (Moulouya basin, NE Morocco)

2021 ◽  
Vol 255 ◽  
pp. 106807
Author(s):  
Bruno Depreux ◽  
David Lefèvre ◽  
Jean-François Berger ◽  
Fatima Segaoui ◽  
Larbi Boudad ◽  
...  
Keyword(s):  
African Highlands ◽  
Humid Period

Rock varnish record of the African Humid Period in the Lake Turkana basin of East Africa

The Holocene ◽  
2021 ◽  
pp. 095968362110116
Author(s):  
Tanzhuo Liu ◽  
Christopher J Lepre ◽  
Sidney R Hemming ◽  
Wallace S Broecker
Keyword(s):  
East Africa ◽  
Lake Level ◽  
Drainage System ◽  
Early Holocene ◽  
Lake Turkana ◽  
Moisture Condition ◽  
Turkana Basin ◽  
Rock Varnish ◽  
Geomorphic Features ◽  
Humid Period

Rock varnish is a manganiferous dark coating accreted on subaerially exposed rocks in drylands. It often contains a layered microstratigraphy that records past wetness variations. Varnish samples from latest Pleistocene and Holocene geomorphic features in the Lake Turkana basin, East Africa display a regionally replicable microstratigraphy record of Holocene millennial-scale wetness variability and a broad interval of wetter conditions during the African Humid Period (AHP). Three major wet pulses in the varnish record occurred during the generally wet interval of the early Holocene (11.5–8.5 ka) when the lake attained its maximum high stand (MHS) at 455–460 m. A >23 m drop from the MHS occurred between 8.5 and 8 ka. Subsequently two additional wet pulses occurred during the early to middle Holocene (8–5 ka) when the lake occupied its secondary high stand at 445 m. Collectively, these five wet phases represent an extended wet interval coincident with the AHP in the region. One moderate wet phase occurred during the subsequent climatic transition from the humid to arid regime (5–4.3 ka) after the lake level dropped rapidly from 445 m to <405 m. Five minor wet phases took place during the overall arid period of the late Holocene (4.3–0 ka) when the lake level oscillated below 405 m. These findings indicate that the AHP terminated rapidly around 5 ka in the Turkana basin in terms of lake level drop, but the regional shift in relative humidity from the AHP mode to its present-day condition lagged for about 700 years until 4.3 ka, hinting at a gradual phasing out in terms of moisture condition. These findings further suggest that Lake Turkana overflowed intermittently into the Nile drainage system through its topographic sill at 455–460 m during the early Holocene and has become a closed-basin lake thereafter for the past 8 ky.

scholarly journals Short term fallow and partitioning effects of green manures on wheat systems in East African highlands

2021 ◽  
Vol 269 ◽  
pp. 108175
Author(s):  
Tilahun Amede ◽  
Gizachew Legesse ◽  
Getachew Agegnehu ◽  
Tadesse Gashaw ◽  
Tulu Degefu ◽  
...  
Keyword(s):  
Green Manures ◽  
East African ◽  
Short Term ◽  
African Highlands ◽  
East African Highlands

scholarly journals Effect of Seasonal Drought on the Agronomic Performance of Four Banana Genotypes (Musa spp.) in the East African Highlands

Agronomy ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 4
Author(s):  
Brigitte Uwimana ◽  
Yasmín Zorrilla-Fontanesi ◽  
Jelle van Wesemael ◽  
Hassan Mduma ◽  
Allan Brown ◽  
...  
Keyword(s):  
Yield Traits ◽  
East African ◽  
Ploidy Levels ◽  
Early Effect ◽  
Seasonal Drought ◽  
Musa Spp ◽  
Drought Tolerant ◽  
Genome Group ◽  
African Highlands ◽  
East African Highlands

Banana (Musa spp.), a perennial (sub-)tropical crop, suffers from seasonal droughts, which are typical of rain-fed agriculture. This study aimed at understanding the effect of seasonal drought on early growth, flowering and yield traits in bananas grown in the East African highlands. A field experiment was set up in North Tanzania using four genotypes from different geographical origins and two different ploidy levels. The treatments considered were exclusively rain-fed versus rain supplemented with irrigation. Growth in plant girth and leaf area were promising traits to detect the early effect of water deficit. Seasonal drought slowed down vegetative growth, thus significantly decreasing plant girth, plant height and the number of suckers produced when compared to irrigated plants. It also delayed flowering time and bunch maturity and had a negative effect on yield traits. However, the results depended on the genotype and crop cycle and their interaction with the treatments. “Nakitengwa”, an East African highland banana (EAHB; AAA genome group), which is adapted to the region, showed sensitivity to drought in terms of reduced bunch weight and expected yield, while “Cachaco” (ABB genome group) showed less sensitivity to drought but had a poorer yield than “Nakitengwa”. Our study confirms that seasonal drought has a negative impact on banana production in East Africa, where EAHBs are the most predominant type of bananas grown in the region. We also show that a drought-tolerant cultivar not adapted to the East African highlands had a low performance in terms of yield. We recommend a large-scale screening of diploid bananas to identify drought-tolerant genotypes to be used in the improvement of locally adapted and accepted varieties.

Arctic climate response to the termination of the African Humid Period

2015 ◽  
Vol 125 ◽  
pp. 91-97 ◽  
Author(s):  
Francesco Muschitiello ◽  
Qiong Zhang ◽  
Hanna S. Sundqvist ◽  
Frazer J. Davies ◽  
Hans Renssen
Keyword(s):  
Arctic Climate ◽  
Climate Response ◽  
Humid Period

scholarly journals Stepwise drying of Lake Turkana at the end of the African Humid Period: an example of forced regression modulated by solar activity?

2016 ◽  
Author(s):  
Alexis Nutz ◽  
Mathieu Schuster
Keyword(s):  
Solar Activity ◽  
Lake Level ◽  
Controlling Factors ◽  
Lake Turkana ◽  
Turkana Basin ◽  
Orbital Precession ◽  
Forced Regression ◽  
Humid Period

Abstract. Although timing of the termination of the African Humid Period (AHP) is relatively well-established now, modes and controlling factors are still being determined. Here, through a geomorphological approach, we characterize the evolution of the final regression of Lake Turkana at the end of the African Humid Period. We show that lake level fall during this period was not constant, yet rather stepwise consisted of five periods marked by rapid rates of lake level fall separated by periods of lower rates of lake level fall. Even the overall regressive trend is associated with regional decreased precipitations due to reduced insolation controlled by orbital precession, we discuss the origin of the five periods of accelerated rates of lake level fall. Finally, we propose that accelerations are associated with periods marked by solar activity minima that locally resulted in the repeated westward displacement of the Congo Air Boundary (CAB), thereby reducing rainfall across the Lake Turkana basin.

Fragile East African Highlands: a Development Vision for Smallholder Farmers in the Ethiopian Highlands

1995 ◽  
Vol 24 (2) ◽  
pp. 111-116 ◽  
Author(s):  
M. A. Mohamed Saleem
Keyword(s):  
Large Scale ◽  
Smallholder Farmers ◽  
Land Resource ◽  
East African ◽  
Ethiopian Highlands ◽  
Ethiopian Highland ◽  
African Highlands ◽  
East African Highlands ◽  
Resource Environment

For societies that depend on agriculture, the process of meeting current or future welfare demands should not continue without regard to the potential long-term dangers of land resource over-use. With an increasing human and animal population in the Ethiopian highlands development efforts so far have been hasty and disjointed, and have sidetracked issues of production base security and conservation. As a result, large-scale degradation has ensued, and if the trend continues the agricultural future of the country is threatened. Cohesive land-use practices are needed in order to manage the fragile Ethiopian highland resource environment properly and to support growing human demands.

Pollen record of early- to mid-Holocene vegetation and climate dynamics on the eastern coast of the Yellow Sea, South Korea

The Holocene ◽  
2018 ◽  
Vol 28 (6) ◽  
pp. 1011-1022 ◽  
Author(s):  
Bing Song ◽  
Sangheon Yi ◽  
Wook-Hyun Nahm ◽  
Jin-Young Lee ◽  
Limi Mao ◽  
...  
Keyword(s):  
South Korea ◽  
Yellow Sea ◽  
Asian Summer Monsoon ◽  
Climate Dynamics ◽  
Cold Climate ◽  
The Yellow Sea ◽  
Eastern Coast ◽  
Pollen Record ◽  
Vegetation And Climate ◽  
Humid Period

To understand the early- to mid-Holocene vegetation and climate dynamics on the eastern coast of the Yellow Sea, we obtained a sedimentary core with high-resolution accelerator mass spectrometry (AMS) carbon 14 (14C) data from the Gunsan coast in South Korea. The palynological analysis demonstrated that the riverine wetland meadow from 12.1 to 9.8 cal. kyr BP changed to temperate deciduous broad-leaved forest in 9.8–2.8 cal. kyr BP. In addition, the cold climate from 12.1 to 9.8 cal. kyr BP became warmer from 8.5 to 7.3 cal. kyr BP. This was followed by another relatively cold period from 7.3 to 2.8 cal. kyr BP. The temperature change was mainly in response to solar factors. However, there are two relatively humid periods from 12.1 to 9.8 and 8.5 to 7.3 cal. kyr BP, which arose for different reasons. The earlier humid period resulted from strong westerlies and a rapidly rising sea level. The later humid period was produced mainly by the strong East Asian summer monsoon (EASM) and may also be linked to La Niña–like activity. The cold ‘Younger Dryas’ event from 12.0 to 11.4 cal. kyr BP recorded in this study may have been produced by a North Atlantic meltwater pulse. This would have reduced temperatures that were already low because of weak insolation, and the strong winter monsoons would have increased the precipitation.

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