Table 1.
Details of the study sites.
Table 2.
ANOVA results of the most parsimonious linear fixed effects model.
Figure 1.
Grass biomass in each of the four MAP values replicated (corresponding to the four different study sites each replicated by four blocks) as a function of distance from the base of the tree (stem) corresponding to 50%, 100%, 150% and 200% of the tree canopy radius.
Biomass values at 100% correspond to the canopy edge or drip line. Bars represent ±2 standard errors. Grass biomass is greater beneath the canopy (50% distance) compared to outside the canopy at the three drier sites, but not at the wettest site.
Figure 2.
Sub-canopy grass biomass (g.m−2) as a function of tree height (m) at each of the four study sites.
Sites are ordered in terms of increasing rainfall from Mopane (a) to Pretoriuskop (d). Sub-canopy grass biomass refers to grass biomass measured at 50% of the canopy radius, i.e. half way between the base of the tree and canopy edge. Solid lines are the best fit regression, dashed lines the 95% confidence interval, and the dotted lines the 95% predicted interval. Removal of the tallest tree in Satara as an outlier does not qualitatively change the outcome of the regression.
Figure 3.
Box and whisker box plots of tree heights in the different study sites (a).
The solid line is the median, and the boxes are defined by the upper and lower quartile (25th and 75th percentiles). The whiskers extend up to 1.5 times the inter-quartile range of the data. The figure indicates that distribution of tree heights was not uneven between study sites. Relationship between average canopy diameter (m) and tree height (m) across all sampled trees (b). Average canopy diameter is the mean of canopy diameters measured along two perpendicular axes. Regression results indicate a tight relationship between canopy diameter and tree height, with taller trees having proportionally larger canopies regardless of species identities (adjusted R2 = 53.8%, p<0.0001. CI: 95% confidence interval, PI: 95% predicted interval).