DOI: 10.5061/dryad.jm63xsj69
title: Data from: 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

description: 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 recognised 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 (AAI). 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.
description: Developing a trait-based approach (TBA) for assessing the
 vulnerability vegetation cover to livestock grazing in hillslope seep
 wetlands The approach followed in this study was
 largely adapted from Odume et al. (2018) and follows five steps in
 classifying plant species into vulnerability groups: Reviewing the
 literature for reported grazing modes of stress on plant species (more
 details on the manuscript). On the basis of the
 reported grazing modes of stress, select and measure traits that are
 mechanistically linked to the modes of stress (The selected plant traits
 were those that were deemed mechanistically linked to livestock grazing
 disturbances. Seven plant traits resolved into 27 trait attributes were
 selected. The seven plant traits were measured according to the
 standardised world-wide protocol described by Cornelissen et al. (2003)
 and included plant height, specific leaf area, palatability, leaf size,
 leaf dry matter content, longevity (years), and resprouting potential
 (more details on the manuscript). 
 Identifying plant traits deemed mechanistically linked to
 disturbance factors, such as livestock grazing (more details on the
 manuscript) Identifying vulnerable trait attributes
 from the selected trait categories (more details on the
 manuscript). Grouping plant species into three
 vulnerability groups, based on the combination of plant traits (more
 details on the manuscript). Species,
 vegetation cover and AAI Vegetation cover was used as
 a surrogate measure for grazing intensity within each hillslope seep
 wetland. Direct grazing measurement could not be taken but, given that the
 hillslope seeps were situated in a rural catchment where no other major
 activity impact vegetation cover apart from grazing, this measure was
 deemed appropriate. A 100 m transect was established at the centre of each
 seep wetland in order to avoid the possibility of sampling terrestrial
 plant species. This is particular important because of the very small
 sizes of hillslope seep wetlands, and thus care was taken not sample
 terrestrial plant species. However, while care was taken to avoid sampling
 terrestrial plant species, the sampling strategy deployed may also have
 led to under sampling and estimation of edged species. Nevertheless,
 similar sampling strategies have been deployed by (Wardrop et al., 2004).
 Each transect was marked with small steel pegs so that they could be
 accurately located in the next sampling season. The vegetation in each
 site was sampled in two ways. First, the cover was determined following a
 non-destructive method of Flombaum and Sala (2007). Five (0.2 x 1 m)
 quadrats were placed along each transect at intervals of 20, 40, 60, 80,
 and 100 m. In each quadrat, species relative cover and total percentage
 vegetation cover was visually estimated based on the quadrat area covered
 by grass using categories shown in Table 4. Second, all the vascular
 species were identified and recorded along the transect to determine
 species composition using the step-point method (Evans and Love 1957).
 Species used for traits were collected using this approach. To reduce
 potential bias from using cover classes, mid-point of each class was used
 to estimate vegetation cover. The anthropogenic
 Activity Index (AAI) was used to quantify general anthropogenic
 disturbance in the studied hillslope seep wetlands. The index consists of
 five metric, i) surrounding land use intensity, ii) soil disturbance, iii)
 hydrology and habitat alteration, and iv) vegetation community. The five
 metrics were assessed at each wetland, scored and then aggregated to
 provide an AAI value per site. AAI value range between 1 and 15, where
 scores 1-5 indicate least disturbance, 6-10 moderate disturbance and
 &gt; 10 high disturbance (Ervin et al, 2006). Data
 process Species abundance data was captured in excel
 per site. The seven plant traits were measured
 according to the standardised world-wide protocol described by Cornelissen
 et al. (2003), out of those all leaf traits and included plant height,
 were measured specific leaf area, while longevity (years), and resprouting
 potential were derived from literature and expert knowledge. These were
 all typed in excel with their values. Vulnerability scores for each
 species were calculated using percentile distributions.
 Vegetation cover was used as a surrogate measure for grazing
 intensity- the cover collected from each quadrat was then summed to give
 the overall for each site and mid-point of each class was used to estimate
 vegetation cover. AAI data-The five metrics were
 assessed at each wetland, scored and then aggregated to provide an AAI
 value per site. AAI value range between 1 and 15, where scores 1-5
 indicate least disturbance, 6-10 moderate disturbance and &gt; 10 high
 disturbance (Ervin et al, 2006). All scored values of the five metrics
 were summed to obtain the degree of disturbance per site per season and
 then transferred to excel.