Using a trait‐based approach for assessing the vulnerability and resilience of hillslope seep wetland vegetation cover to disturbances in the Tsitsa River catchment, Eastern Cape, South Africa

Abstract

Hill slope seep wetlands are ecologically and economically important ecosystems as they supply a variety of ecosystem services to society. In South Africa, livestock grazing is recognized as one of the most important disturbance factors changing the structure and function of hill slope seep wetlands. This study sought to investigate the potential effect of livestock grazing on the resilience and vulnerability of hillslope seep wetland vegetation cover using a trait-based approach (TBA). Changes in vegetation cover were used as a surrogate for indicating grazing intensity. The degree of human disturbances was assessed using the Anthropogenic Activity Index. A TBA was developed using seven plant traits, resolved into 27 trait attributes. Based on the developed approach, plant species were grouped into vulnerable and resilient groups in relation to grazing pressure. It was then predicted that species belonging to the vulnerable group would be less dominant at the highly disturbed sites, as well as in the winter season when grazing pressure is at its peak. The approach developed enabled accurate predictions of the responses of hillslope plant species to grazing pressure seasonally, but spatially, only for the summer season. The predicted responses during the winter season across sites did not match the observed results, which could be attributed to the difficulty in species identification and accurate estimation of vegetation cover during winter. Overall, the approach developed here provides a general framework for applying the TBA and can thus be tested and applied elsewhere. K E Y W O R D Shill slope seep, livestock grazing, traits, vulnerability or resilience

Functional groups of Afrotropical EPT (Ephemeroptera, Plecoptera and Trichoptera) as bioindicators of semi-urban pollution in the Tsitsa River Catchment, Eastern Cape, South Africa

“…Farming in the Tsitsa catchment consists mainly of animal, vegetable, and wood production. The Acacia sp., including grassland and savanna bioregions, are the main vegetation in the area ( Libala, Palmer & Odume, 2020 ).…”

The evaluation of biological indices to assess the condition of hillslope seep wetlands in the Tsitsa River Catchment, South Africa

“…A 100 m transect was established at the centre of each seep wetland in order to avoid the possibility of sampling terrestrial plant species. The very small sizes of hillslope seep wetlands render it important to avoid sampling terrestrial plant species [ 21 ]. Each transect was marked with small steel pegs so that they could be accurately located in the next sampling season.…”

“…A total of 11 hillslope seep wetlands were selected for the study; these are the dominant type of wetland in the catchment. The selection of the wetlands took into account biophysical factors such as slope aspect, soils, and geological characteristics such as sedimentary shale, mudstone and sandstone, as well as the degree of erosion, which was visually assessed ( Table 1 ) [ 21 ]. In the T35D quaternary, three less eroded (LE1, LE2, LE3) wetlands were selected in an area recently changed from communal to private ownership.…”

“…Eight wetlands were selected in T35E, of which four were moderately eroded (ME1, ME2, ME3, ME4) and four were highly eroded (HE1, HE2, HE3, HE4). These wetlands are situated in a communal area where there are no grazing management strategies [ 21 ]. The initial idea was to select 12 seep wetlands, but the level of degradation of wetlands in the catchment made it possible to find only three less eroded sites.…”

Near-surface soil moisture dynamics in a prairie hillslope seep/headwater stream system in Texas, USA

“…Within grassland prairie ecosystems, the beginnings of headwater streams typically form at the convergence of hillslopes that lack riparian woodland canopies and constantly fluctuate between flooding and drying (Dodds et al, 2004). Hillslope seeps, often associated with the upmost reaches of prairie headwater streams, occur along the sides of hills where distinct lateral and vertical changes in subsurface substrate cause infiltrated water to flow laterally (Libala et al, 2020;Vidon & Hill, 2004). During periods of high saturation, excess water can flow downslope toward the base of the hillslope and contribute to surface runoff within headwater channels.…”