Invasion of Euryops floribundus in degraded South African communal grassland: Unpacking the invasion relationship with elevation, soil properties, the quality and quantity of the herbaceous layer

Abstract

Shrub invasion is a recent occurrence in African grassland ecosystems. This study assessed the distribution of Euryops floribundus (a native shrub species) along an elevation and invasion intensity gradients, and its relationship with soil and herbaceous vegetation in a South African grassland. Shrub density increased (p < 0.05) from the uplands (2,301 plants/ha) to the bottomlands (4,888 plants/ha). Themeda triandra (a highly palatable grass) was dominant at the uplands and sloping sites, whereas Eragrostis plana and Sporobolus africanus (poorly palatable grasses) dominated the bottomlands. Upland soils had the highest organic carbon (OC), phosphorous (P), calcium and nitrogen (N) contents, but the lowest shrub density and herbaceous biomass. Canonical correspondence analysis indicated that elevation, soil OC and N contents determine important vegetation variables along the elevation gradient. In the shrub density gradient, soil P, OC and N responded positively to E. floribundus density. Grass biomass in the moderate and heavily invaded sites was high, but the abundance of palatable grasses declined, suggesting that E. floribundus invasion may be concomitant with a decrease in rangeland condition in terms of quality forage provision.

The role of topographic and soil factors on woody plant encroachment in mountainous rangelands: A mini literature review

“…The slope position, defined as the relative height on the hillside is another key topographic factor influencing woody plant encroachment [ [81] , [82] ]. It is generally divided into three categories in the current literature: upslope, midslope, and downslope [ 38 , 40 ].…”

“…In mountainous rangelands, slope position regulates the microclimate and the physico-chemical characteristics of the soil, which in turn impacts the growth of woody plants [ 40 , 83 ]. Despite this, little is known about how slope position affects the encroachment of woody plants as some authors report that encroachment is higher on upslope position [ 48 , 52 , 57 , 58 , [84] , [85] , [86] , [87] ], while others report higher encroachment on the midslope position [ 88 ]5; [ 78 ] as well as downslope position [ 53 , [82] , [89] , [90] ] or no significant changes [ 76 , [91] , [92] , [93] ].…”

Naturally recovery of old crop fields in a South African Grassland biome

“…Many South African studies focused on the influence of cropping, including the use of different cropping techniques, on soil quality (Gura & Mnkeni, 2019;Mupambwa & Wakindiki, 2012;Muzangwa et al, 2021;Njaimwe et al, 2018). Some studies also assessed the change in soil properties due to factors such as soil erosion (Ighodaro et al, 2013;Oluwole & Sikhalazo, 2008), woody vegetation encroachment (Masibonge et al, 2020) and change in vegetation type (Mills & Fey, 2004), which can be linked to improper livestock management practices. Shackleton et al (2013) performed a soil health assessment of a series of old crop fields in the Wild coast region of the Eastern Cape (South Africa).…”

Natural recovery of old crop fields in a South African Grassland biome

“…Many South African studies focused on the in uence of cropping, including the use of different cropping techniques, on soil quality (Gura & Mnkeni, 2019;Mupambwa & Wakindiki, 2012;Muzangwa et al, 2021;Njaimwe et al, 2018). Some studies also assessed the change in soil properties due to factors such as soil erosion (Ighodaro et al, 2013;Oluwole & Sikhalazo, 2008), woody vegetation encroachment (Masibonge et al, 2020) and change in vegetation type (Mills & Fey, 2004), which can be linked to improper livestock management practices. Shackleton et al (2013) performed a soil health assessment of a series of old crop elds in the Wild Coast region of the Eastern Cape (South Africa).…”