Influence of Grazing on Plant Diversityproductivity Relationship in Semi-Arid Grassland of South Africa

Abstract

Abstract.The relationship between plant diversity and productivity has been hotly debated over the last two decades. What makes the relationship complex is, in part, the interplay of several biotic and abiotic effects, which include rainfall variability, soil characteristics and grazing. We investigated the influence of grazing intensity on the diversity-productivity relationship in a wide range of soil pH along a rainfall gradient in semi-arid grassland. Vegetation and soil surveys were conducted in high grazing (HG) and low grazing (LG) grasslands around Bethlehem (716 mm mean annual rainfall, moderately acidic soil), Bloemfontein (543 mm, slightly acidic/neutral soil) and Kimberley (467 mm, neutral/slightly alkaline soil) in South Africa. Plant species occurring in the study area were recorded, and aboveground biomass was estimated by clippings. Soils sampled were analysed for chemical properties. Species richness increased with increasing biomass and decreasing pH in Kimberley and Bloemfontein and subsequently declined with increasing biomass and decreasing pH in Bethlehem. The relationship between species richness and biomass was hump-shaped across the study area but when we differentiated between the degrees of grazing, we found linear positive relationships at both LG and HG sites. This suggests that the diversity-productivity relationship needs to be carefully examined in grazing land.

The impact of the plateau pika on the relationship between plant aboveground biomass and plant species richness

“…This study further shows that plateau pika disturbance can alter the relationship between plant aboveground biomass and plant species richness, similar to large grazing herbivores (Burkepile et al, 2017; Dingaan et al, 2016; Oba et al, 2001), a result that supports the third hypothesis. At present, many previous studies have treated plant productivity as a response variable of species richness (Assaf, Beyschlag, & Isselstein, 2011; Hector et al, 1999; Yuan, Yu, Epstein, Stefanova, & Zhang, 2015), whereas other studies treated species richness as a response variable of plant productivity (Bai et al, 2007; Fraser et al, 2015; Oba et al, 2001).…”

“…The disturbance‐productivity interaction is an important determinant of species richness (Kondoh, 2001). Similar to large herbivore disturbance (Burkepile et al, 2017; Dingaan et al, 2016; Oba et al, 2001), this study also treats species richness as a response variable of plant aboveground biomass because plateau pika disturbance has been verified to have no effect on plant aboveground biomass. In undisturbed plots, plant communities of alpine meadows are in relatively stable situation in which the different plant populations with various ability of utilize resources are well organized and ordered.…”

“…Previous studies have documented that relationships between plant productivity and species richness can be positive (Bai et al, 2007), negative (Gough et al, 1994), undimodal (Fraser et al, 2015), or inconsistent (Adler et al, 2011). The lack of consistency in correlational studies is not surprising, since this relationship is dependent on plant species richness, plant productivity, or both, aspects that can be regulated by a multitude of abiotic and biotic factors, such as precipitation (Bai et al, 2007), latitude (Pärtel, Laanisto, & Zobel, 2007), and livestock grazing (Burkepile et al, 2017; Dingaan, Walker, Tsubo, & Newby, 2016; Oba, Vetaas, & Stenseth, 2001).…”

“…Herbivores are one of the important biotic factors that modify plant productivity and species richness in a grassland ecosystem. Large grazing herbivores have been confirmed to impact plant aboveground biomass (Oba et al, 2001), plant species richness (Wu, Wang, Liu, Ding, & Liu, 2017), or both (Altesor, Oesterheld, Leoni, Lezama, & Rodríguez, 2005), while only a few studies have examined whether these herbivores alter the relationship between plant aboveground biomass and plant species richness (Burkepile et al, 2017; Dingaan et al, 2016; Oba et al, 2001). In addition to large grazing herbivores, small burrowing herbivores, while underappreciated, are key functional mammals that, in large numbers, can create an extensive disturbance to a grassland ecosystem (Davidson, Detling, & Brown, 2012; Retzer, 2007), and they are closely related to grassland degradation or development (Case, Halpern, & Levin, 2013; Hagenah & Bennett, 2013; Yu et al, 2017).…”

Introductory Chapter: The Main Directions and Tasks of Pure and Applied Biogeography in Solving the Global Problems of Our Time

“…Human activity is causing the greatest damage and dangers by breaking down the healthy functioning and regulatory capacity of the Earth's biosphere, eradicating primeval forests and rainforests, draining bogs and swamps, and reducing forest cover. The importance of grazing is also well known in the diversity of nature or near-nature grasslands [32].…”