Short-term response of rangeland botanical composition and productivity to fertilization (N and P) in a semi-arid climate of South Africa

2002 ◽  
Vol 50 (1) ◽  
pp. 167-183 ◽  
Author(s):  
H.A. Snyman
Keyword(s):  
South Africa ◽  
Arid Climate ◽  
Botanical Composition ◽  
Short Term ◽  
Term Response ◽  
Semi Arid

Pliocene short-term climate changes preserved in continental shallow lacustrine-palustrine carbonates: Western Opache Formation, Atacama Desert, Chile

2019 ◽  
Vol 132 (9-10) ◽  
pp. 1795-1816 ◽  
Author(s):  
Carol B. de Wet ◽  
Andrew P. de Wet ◽  
Linda Godfrey ◽  
Elizabeth Driscoll ◽  
Samuel Patzkowsky ◽  
...  
Keyword(s):  
Atacama Desert ◽  
Arid Climate ◽  
Short Term ◽  
Surface Water Flow ◽  
Depositional System ◽  
Setting Events ◽  
Climate Shifts ◽  
Short Time ◽  
Climate Proxies ◽  
Semi Arid

Abstract Multiple climate proxies indicate episodic changes in moisture levels within an ∼1 Ma duration (early–mid Pliocene) interval. Limestones within the Opache Formation, Calama Basin, Atacama Desert region, Chile, contain evidence for wetter and drier periods on short time scales. Proxies include carbonate lithological changes, paleontology (stromatolites, oncolites, gastropods, ostracods and diatoms), O and C stable isotopes, geochemistry, and mineralogical changes (aragonite, calcite, Mg-calcite, dolomite and gypsum) throughout a 30 m stratigraphic section. Stromatolite fossil cyanobacteria dark and light laminations and mesohaline to hypersaline diatom species suggest Pliocene annual seasonality. Short-term changes between wetter and drier conditions indicate that at least this part of the Atacama region was experiencing relatively rapid early–mid Pliocene climate instability. The predominance of limestone in the Opache Formation, in contrast to the 1500 m of Oligocene-Miocene siliciclastic conglomerates and sandstones, interpreted as arid climate alluvium, that underlie it, indicates a shift from arid or hyperarid climate to a semi-arid climate. Semi-arid conditions promoted limestone deposition in a shallow lacustrine-palustrine environment. In this setting, events such as storms with associated surface water flow, erosion, siliciclastic sand, gravel, and intraclast deposition, coupled with significant biological activity, represent sedimentation during more humid periods in a shallow lacustrine depositional environment. In contrast, limestone characterized by mudcracks, Navicula diatoms, and vadose syndepositional cementation, reflect periods of enhanced evaporation, water shallowing, and episodic desiccation, characteristic of a palustrine depositional system. These facies shifts, in conjunction with geochemical and isotopic proxy evidence, yield a sedimentary record of wetter and drier climate shifts.

scholarly journals Conservation Agriculture Practices Can Improve Earthworm Species Richness and Abundance in the Semi-Arid Climate of Eastern Cape, South Africa

Agriculture ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 576
Author(s):  
Sixolise Mcinga ◽  
Lindah Muzangwa ◽  
Kudzayi Janhi ◽  
Pearson Nyari Stephano Mnkeni
Keyword(s):  
South Africa ◽  
Species Richness ◽  
Conservation Agriculture ◽  
Residue Management ◽  
Arid Climate ◽  
Eastern Cape ◽  
Earthworm Species ◽  
No Till ◽  
Semi Arid ◽  
Residue Retention

Earthworms play a pivotal role in the regulation of soil health. Studies that explore the effects of conservation agriculture (CA) principles on earthworms under the semi-arid climate of the central Eastern Cape (EC) of South Africa (SA) are limited. Therefore, this study investigated the effects of tillage, crop rotations, and residue management on earthworms’ abundance and species richness. The study design followed a split-split plot with three replicates. The main plot was allocated to tillage treatment, which had conventional tillage (CT) and no-tillage (no-till) as factors. Crop rotation treatment was allocated to a subplot, and had maize (Zea mays)–fallow–maize (MFM), maize–fallow–soybean (Glycine max) (MFS), maize–wheat (Triticum aestivum)–maize (MWM), and maize–wheat–soybean (MWS). Residue management was in the sub-subplot with residue retention and residue removal. The study was carried out over four cropping seasons: summer 2015–2016, winter 2016, spring 2016, and summer 2016–2017. The results showed that the genera Amynthas and Lumbricus, both belonging to the anecic group, and Dendrobaena, belonging to the epigeic group, were present. Earthworm species diversity and density were highest under no-till than under CT. Residue retention improved earthworm density regardless of tillage management. Rotations that had fallow periods recorded lower earthworm numbers as compared to continuous cropping systems where wheat was grown in winter. The study concluded that maize–wheat–soybean (MWS) rotation with residue retention results in the highest earthworm abundance and species richness.

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