scholarly journals The effects of abiotic factors in South African semi-arid grassland communities on Seriphium plumosum L density and canopy size

PLoS ONE ◽  
2018 ◽  
Vol 13 (8) ◽  
pp. e0202809
Author(s):  
Hosia T. Pule ◽  
Julius T. Tjelele ◽  
Michelle J. Tedder
Keyword(s):  
South African ◽  
Abiotic Factors ◽  
Grassland Communities ◽  
Canopy Size ◽  
Semi Arid

scholarly journals Spatial-temporal analysis of the diet of a non-native fish in the Santa Cruz Reservoir, Brazilian semi-arid

2018 ◽  
Vol 30 (0) ◽  
Author(s):  
Jônnata Fernandes de Oliveira ◽  
Jean Carlos Dantas de Oliveira ◽  
José Luís Costa Novaes ◽  
Antonia Elissandra Freire de Souza ◽  
Marla Melise Oliveira de Sousa ◽  
...  
Keyword(s):  
Environmental Variables ◽  
Abiotic Factors ◽  
Temporal Analysis ◽  
Arid Environment ◽  
Temporal Variations ◽  
Environmental Data ◽  
Animal Origin ◽  
Santa Cruz ◽  
Main Item ◽  
Semi Arid

Abstract Aim The diet of Plagioscion squamosissimus present in the Santa Cruz Reservoir, Rio Grande do Norte, Brazil, was investigated, evaluating the influences of spatial and temporal variations and abiotic factors in the utilization of food resources. Methods The samplings were performed quarterly between February 2011 and November 2014. Of the 525 specimens captured, 375 presented food items in the stomachs. The diet was determined using: (i) Feeding Index (IAi); (ii) and the graphical interpretation of the food strategy through non-metric multidimensional scaling (NMDS) analyzes, the differences in diet being tested from Permutational Multivariate Analyzes of Variance (PERMANOVA). To verify if environmental variables influence the Canonical Correspondence Analyzes (CCA) were used, using the data from the IAi the environmental data, being the significance of the axes tested through Monte Carlo simulations. Results The species feed mainly on items of animal origin, vegetable being a resource ingested accidentally. The diet was composed of shrimp, fish, insect, mollusk and vegetable, the latter rarely found. The shrimp was the main item (92.57%) and the insects (7.24%) accessory items. Spatial and temporal ordering demonstrated that the species didn’t present variation in diet composition, as well as a low association between diet and environmental variables. Conclusion P. squamosissimus is characterized as carcinophagous, due to the predominance of shrimp in its diet, evidencing that the species is adapted to the conditions offered by the Brazilian semi-arid environment.

scholarly journals Effects of biotic and abiotic factors on soil organic carbon in semi-arid grassland

2016 ◽  
pp. 0-0 ◽  
Author(s):  
Fuping Tian ◽  
Zhinan Zhang ◽  
Xiaofeng Chang ◽  
Lei Sun ◽  
Xuehong Wei ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Abiotic Factors ◽  
Biotic And Abiotic Factors ◽  
Semi Arid

scholarly journals Multi-year CO<sub>2</sub> budgets in South African semi-arid Karoo ecosystems under different grazing intensities

2020 ◽  
Author(s):  
Oksana Rybchak ◽  
Justin du Toit ◽  
Jean-Pierre Delorme ◽  
Jens-Kristian Jüdt ◽  
Kanisios Mukwashi ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Carbon Source ◽  
South African ◽  
Water Availability ◽  
Carbon Sink ◽  
Grazing Intensity ◽  
Livestock Grazing ◽  
Carbon Uptake ◽  
The Past ◽  
Semi Arid

Abstract. Climatic and land management factors, such as water availability and grazing intensity, play an important role in seasonal and annual variability of the ecosystem–atmosphere exchange of CO2 in semi-arid ecosystems. However, the semi-arid South African ecosystems have been poorly studied. Four years of measurements (November 2015–October 2019) were collected and analysed from two eddy covariance towers near Middelburg in the Karoo, Eastern Cape, South Africa. We studied the impact of grazing intensity on the CO2 exchange by comparing seasonal and interannual CO2 fluxes for two sites with almost identical climatic conditions but different intensity of current and historical livestock grazing. The first site represents lenient grazing (LG) and the vegetation comprises a diverse balance of dwarf shrubs and grasses, while the second site has been degraded through heavy grazing (HG) in the past but then rested for the past 10 years and mainly consists of unpalatable grasses and ephemeral species. Over the observation period, we found that the LG site was a considerable carbon source (82.11 g C m−2), while the HG site was a slight carbon sink (−36.43 g C m−2). The annual carbon budgets ranged from −90 ± 51 g C m−2 yr−1 to 84 ± 43 g C m−2 yr−1 for the LG site and from −92 ± 66 g C m−2 yr−1 to 59 ± 46 g C m−2 yr−1 for the heavily grazed site over the four years of eddy covariance measurements. The significant variation in carbon sequestration rates between the last two years of measurement was explained by water availability (25 % of the precipitation deficit in 2019 compared to the long-term mean precipitation). This indicates that studied ecosystems can quickly switch from a considerable carbon sink to a considerable carbon source ecosystem. Our study shows that the CO2 dynamics in the Karoo are largely driven by water availability and the current and historical effects of livestock grazing intensity on aboveground biomass (AGB). The higher carbon uptake at the HG site indicates that resting period after overgrazing, together with the transition to unpalatable drought-tolerant grass species, creates conditions that are favourable for carbon sequestration in the Karoo ecosystems, but unproductive as Dorper sheep pasture. Furthermore, we observed a slight decrease in carbon uptake peaks at the HG site in response to resuming continuous grazing (July 2017).

Hydrological implications of desertification: Degradation of South African semi-arid subtropical thicket

2013 ◽  
Vol 91 ◽  
pp. 14-21 ◽  
Author(s):  
G. van Luijk ◽  
R.M. Cowling ◽  
M.J.P.M. Riksen ◽  
J. Glenday
Keyword(s):  
South African ◽  
Semi Arid
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