Differences in grazing pressure according to good trait-based indicators (PFTs).

<p>Panels A–F compare piosphere and pasture plots across tenure systems (commercial and communal) and biomes (savanna and grassland). All PFTs had a specific response to grazing at least in one biome (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone-0104672-g003" target="_blank">Figure 3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone-0104672-t003" target="_blank">Table 3</a>). Broken lines connect piosphere and pasture plots of a tenure system within a biome, and different letters indicate significant differences (Tukey’s HSD; <i>p</i><0.05). Boxes show medians and 25^th to 75^th percentiles, whiskers stand for the non-outlier ranges of the data. Note the different scaling of the y-axis for panels E and F. HG lin = narrow-leaved perennial grasses, HG lan = broad-leaved perennial grasses, HG = perennial grasses, H = hemicryptophytes, TG = annual grasses, HF = perennial forbs.</p

Response consistency of six PFTs which are good (specific) indicators for grazing pressure at least in one biome.

a<p>PFTs with a sensitive response to grazing had a significant contribution of the grazing-related PC to their final linear models, but other predictor variables had larger effect sizes. PFTs with a specific response to grazing also had a sensitive response, but responded stronger to grazing than to other predictor variables (largest effect size for the grazing-related PC). Insensitive PFTs had a non-significant contribution of grazing-related PC to their final linear models. Arrows indicate the direction of response (↑ positive response to increased grazing pressure, ↓negative response). For details of final linear models refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone.0104672.s002" target="_blank">Tables S2</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone.0104672.s003" target="_blank">S3</a>.</p

Biome and tenure system characteristics, and soil differences between piosphere and pasture plots of the tenure systems in the two biomes.

<p>Climate data: Bloemfontein (29.10°S, 26.30°E), ca. 30–70 km distance to grassland sites; Kuruman (27.43°S, 23.45°E), ca. 35–75 km distance to savanna sites. MAP: mean annual precipitation of hydrological years (July–June); CV: coefficient of variation for MAP. For both meteorological stations, only years without data gaps were used for calculations; data source: <a href="http://climexp.knmi.nl" target="_blank">http://climexp.knmi.nl</a>. Bloemfontein data 1904–2011 (n = 100), Kuruman data 1905–1997 (n = 62). Soil types are given as WRB type <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone.0104672-Brser1" target="_blank">[74]</a>; grassland soils after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone.0104672-Austin1" target="_blank">[50]</a>; savanna soils after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone.0104672-Cowling1" target="_blank">[24]</a>. Vegetation characteristics of the grassland after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone.0104672-Mucina1" target="_blank">[25]</a>; savanna: after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone.0104672-Cowling1" target="_blank">[24]</a>. Herd composition, mobility and farm-specific stocking densities for 2011 were derived from pers. comm. with farmers and provided by C. Naumann. Please note for stocking density that a larger number reflects a lower density. Edaphic conditions are given for the topsoil (0–20 cm) of vegetation plots; letters indicate significant differences within a biome (Tukey’s HSD, <i>p</i><0.05; standardized data).</p

Response of plant aggregations to management and soil conditions in the grassland (A) and in the savanna biome (B).

<p>For each plant aggregation, bars denote the proportion of explained variance (given as effect sizes, η²) in best-fitting linear models, associated with biome-specific principal components and land tenure. Parameters are ordered by their effect sizes, starting with the grazing-related principal component. Arrows facing upwards indicate a positive response to increased grazing, and arrows facing downwards indicate a negative response. Note that negative or positive responses to grazing cannot be assigned to ordination axes. DCA 1 = plot scores on first DCA axis. For abbreviations of PFTs, refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone-0104672-t002" target="_blank">Table 2</a>.</p

Study areas and farms in South Africa’s grassland and savanna biomes.

<p>The large map (A) indicates the position of the two study areas in South Africa. The detailed maps give the position of commercial and communal farms in the savanna biome (B) and in the grassland (C). Communal areas are situated in the former homeland Bophuthatswana.</p

Hierarchical, three-level approach for the definition of plant functional types (PFTs) based on categorical functional traits.

a<p>The percentage of plant species belonging to a certain PFT is given separately for the grassland/for the savanna biome.</p>b<p>PFT acronyms describe the hierarchical combination of traits. For single-trait PFTs, acronyms are based on the first 1–2 letters of Raunkiær’s life form classification <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104672#pone.0104672-Raunkir1" target="_blank">[15]</a>; for two-trait PFTs, acronyms for growth form are added (G = grasses, F = forbs); for three-trait PFTs, acronyms for leaf width are added (lin = linear (narrow-leaved), <5 mm; lan = lanceolate (broad-leaved), 5–10 mm, ov = ovate (very broad-leaved), >10 mm). PFTs which acronyms are in brackets were not included in further analyses due to their low frequency and low relative abundance on plots.</p>c<p>For two- and three-trait PFTs, names are only given if PFTs were retained in subsequent analyses, at least in one biome.</p

Ordination diagrams of herbaceous community composition.

<p>Ordinations are based on two alternative procedures (A, B: detrended correspondence analysis, DCA; and C, D: non-metric multidimensional scaling, NMDS). They visualize differences between piosphere plots and pasture plots on commercial farms and communal farms in South Africa’s grassland biome (A, C) and savanna biome (B, D). Close plots feature a similar species composition, remote plots are more dissimilar. Interpretation of ordination axes follows final linear models with PCA-derived composite variables as predictors. In the grassland biome, a gradient of increasing grazing pressure underlies species turnover along the first ordination axes; in the savanna, it is a gradient of mineral nutrient content in the topsoil (0–20 cm). Note that we refrained from interpreting the second DCA axes due to concerns about their interpretability.</p