Effects of the invasive shrub,Lantana camara, on soil properties in the Eastern Cape, South Africa

Abstract

Lantana camara L. is an invasive alien shrub of worldwide significance due to its impacts on biodiversity. It can alter the soil properties of invaded ecosystems and, as a result, affect management outcomes. However, knowledge on the impacts of L. camara on soil properties is scanty, especially in South Africa, despite the pervasive presence of the plant in the country. In this comparative study, the soils underneath L. camara were assessed in order to determine if they had different properties (soil physico‐chemical properties, penetration resistance, infiltration, hydraulic conductivity and water repellency) in comparison to the soils in adjacent natural sites in the Eastern Cape, South Africa. Soil samples were collected from the top soil beneath the canopy of both L. camara‐invaded and adjacent natural sites in five different locations over three summer months. The soils that were collected from underneath L. camara had a significantly higher total C, total P, gravimetric soil moisture (in November and December) and were repellent, compared to the soils in the adjacent natural sites. Soil penetration resistance was significantly higher in the natural sites than in the L. camara‐invaded sites. The soil hydraulic conductivity, soil infiltration rate, soil pH, exchangeable cations and total N showed no significant difference between the invaded and the natural sites. It appears that the soils underneath L. camara have a high total C and total P, soil moisture and are repellent, thus influencing nutrient cycling, potentially making the soil properties underneath it ideal for its own growth. This could contribute to the success of L. camara as an invasive species.

Effects ofSolanum mauritianumScopoli (bugweed) invasion on soil and vegetation in Vhembe Biosphere Reserve, South Africa

“…Although it is not clear how bugweed invasion alters soil properties, there is suspicion that litter deposition and decomposition (Atkinson et al 2014), altered microenvironments underneath bugweed canopy and allelopathy (van den Bosch et al 2004) are driving the observed changes in the soil. The above-mentioned factors have been shown to trigger changes in soil properties following invasion by other alien woody plant, for example Lantana (Ruwanza & Shackleton 2016), Acacia (Yelenik et al 2007) and Eucalyptus species (Tererai et al 2015). Previous studies have shown that invasion by alien plants results in altered soil properties, thereby affecting soil composition and processes (Linders et al 2019), which ultimately result in changes in ecosystem functioning.…”

“…Exchangeable cations were extracted in 1:10 ammonium acetate solution as described by Thomas (1982), before being filtered and measured by atomic absorption spectrometry (SP428; LECO Corporation, St. Joseph, MI, USA). Soil moisture content was measured using the gravimetric soil moisture method (see Ruwanza & Shackleton 2016). Soil penetration resistance levels were measured using a penetrometer (SOILTEST, Inc., Evanston, IL, USA).…”

“…Soil penetration resistance levels were measured using a penetrometer (SOILTEST, Inc., Evanston, IL, USA). Soil water repellency was measured using the Water Droplet Penetration Time (WDPT) method (see Ruwanza and Shackleton (2016) for detailed WDPT method). The WDPT classes used in this study were ‘wettable’ when infiltration was within 5 s, ‘slightly repellent’ when infiltration was 5–60 s, ‘strongly repellent’ when infiltration was 60–600 s, ‘severely repellent’ when infiltration was 600–3600 s, and ‘extremely repellent’ when infiltration was above 3600 s, according to Bisdom et al .…”

“…In total, 30 plots (five plots per patch 9 two invasion condition 9 three sites) were used for soil sampling and vegetation surveys. The experimental design used in the study is similar to the one used by Ruwanza and Shackleton (2016) to examine the effects of Lantana camara on soil properties.…”

“…Soil water repellency was measured using the Water Droplet Penetration Time (WDPT) method (see Ruwanza and Shackleton (2016) for detailed WDPT method). The WDPT classes used in this study were 'wettable' when infiltration was within 5 s, 'slightly repellent' when infiltration was 5-60 s, 'strongly repellent' when infiltration was 60-600 s, 'severely repellent' when infiltration was 600-3600 s, and 'extremely repellent' when infiltration was above 3600 s, according to Bisdom et al (1993) and Ruwanza and Shackleton (2016). It is acknowledged that soil water repellency and compaction are more likely to occur during the dry winter months (when this study was conducted -April to June) than the wet summer months.…”