Effects of increased temperature on growth and nutritional value of mesic grasslands, with or without woody legume seedling competition.
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Date
2020
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Abstract
Mesic grasslands are complex ecosystems covered in grasses and other graminoid vegetation.
The species composition varies due to variation in rainfall and temperature; these grasslands
are climatically supported. They also vary in nutritive value and grasslands with high species
richness have low nutritive value because grasses differ genetically. Grasses’ response to
high temperature and competition is species dependent. Grasslands are ideal for ecological
experiments because grasses grow fast and their response to environmental changes is
noticeable. Therefore, an experiment of induced warming with legume seedlings interaction
was conducted at the University of KwaZulu-Natal, using open top chambers and Vachellia
sieberiana var. woodii. This was done to determine the effect of increased temperature on the
biomass, growth, morphology and nutritive value of Themeda triandra and Aristida
junciformis. These species were chosen because they occur naturally and dominate in the
Ukulinga farm, where the experiment was conducted. They also have contrasting palatability,
T. triandra is highly palatable and A. junciformis is less palatable. Vachellia sieberiana
seedlings were grown from seed and transplanted after two months to the field to interact
with grasses for four months. The results suggest that the interaction of warming and woody
seedlings reduces the biomass of the investigated species. This implies that warming reduces
grass biomass. Plant traits such as grass height, leaf area, tiller width and tuft diameter
responded differently to the treatments. The fibre (neutral detergent fibre) of T. triandra was
increased by warming. The interaction of warming and woody seedlings had no effect on the
regrowth fibre content. The interaction of warming and woody seedlings increased the
protein content of A. junciformis. Warming and woody seedlings independently increased the
protein content of T. triandra. The response of plants to increased warming will help
ecologists understand the effects of global warming. To provide more insight into these
findings, further research on specific species with longer experimental duration and high
woody seedling neighbour density is of importance.
Description
Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.