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Climate Change in Grassland Ecosystems
Published in Brenda Groskinsky, Climate Actions, 2022
Jesse Nippert, Seton Bachle, Rachel Keen, Emily Wedel
The distribution of savannas is determined by a seasonal climate, occurring in locations with hot, wet summers and cooler, dry winters. The cycle of the wet and dry seasons has shaped the savanna ecosystem by driving the distribution and migration of large mammals and promoting hot fires after the dry season. These climate and land-use drivers have complex interactions maintaining an open canopy with low tree: grass ratios. African savannas are unique in that they span a large precipitation gradient (150–1,200 mm mean annual precipitation) and host a large diversity of mammals that feed on grasses (grazers) and woody plants (browsers). While precipitation determines the amount of woody plants the system can support, herbivory and fire suppress woody plant growth and kill woody saplings. It is hypothesized that semiarid savannas are stable systems where low water availability (<650 mm yr1) maintains low tree:grass ratios (Sankaran et al. 2008). In contrast, mesic savannas are reliant on frequent fires to maintain low tree abundance. Mesic savannas are considered particularly vulnerable to woody encroachment because of increased water availability and are reliant on frequent and intense fires to maintain low tree abundance. However, woody encroachment is occurring across the precipitation gradient in lowveld savannas, including mesic savannas that experience historical fire frequencies, suggesting global drivers likely interact with local changes to fire frequency and herbivore abundance (Stevens et al. 2016; Case and Staver 2017).
Why agricultural production in sub-Saharan Africa remains low compared to the rest of the world – a historical perspective
Published in International Journal of Water Resources Development, 2020
Vibeke Bjornlund, Henning Bjornlund, Andre F. Van Rooyen
Different resource endowments in forest and savanna areas resulted in different production responses (Tosh, 1980). Forests have fertile soils and well-distributed rainfall and are suitable for crops that are rich in calories and provide high financial returns, for example yam, banana, palm oil, coffee and cocoa. Farmers integrated export crops with subsistence crops by intercropping or double cropping, using family labour or hired labour when profit margins justified it (Austin, 2005). Savannas have brief and erratic rainy seasons. Tsetse prevented the use of draught animals, and there was therefore a strong reliance on labour for grain cultivation for food security. Labour was abundant during the dry season, but scarce during the agricultural season; hence, there could be little labour allocated to cash crop production otherwise food security would be reduced (Fafchamps, 1992).
Profiling and occupational health risk assessment study on coal ashes in terms of polycyclic aromatic hydrocarbons (PAHs)
Published in Journal of Environmental Science and Health, Part A, 2022
Abhrajyoti Tarafdar, Alok Sinha
The eastern coalfield is one of the principal mining sectors of India. The area undergoes an alteration among humid subtropical and tropical savanna climate that has hugely contrasting temperature range for summer and winter. The winter (from December to February) is followed by summer (from mid-March to mid-June) and the monsoon season (from mid-June to September). The highest temperature in midsummer can get to ∼48 °C. Though, all winter, thermal reading commonly stays between ∼4 °C and ∼21 °C. The average yearly precipitation varies between 650 mm to 1000 mm.