Species size and light penetration
Light penetration was significantly lower in plots with greater
plot-level mean height (R2 = 0.08, P = 0.025;
Fig. 5) but was unassociated with large species abundance. Mean
intraplot variation in light penetration was significantly positively
correlated with mean light penetration (Spearman correlation, rho= 0.49, P < 0.001; Fig. S2).
Small species abundance and richness in plots were significantly higher
in plots with high light penetration, but not for both definitions of
small species. Small species under the ‘1st quartile’
definition had significantly higher flowering abundance in plots with
higher light penetration (R2 = 0.08, P = 0.027;
Fig. 6A). Median flowering abundance and richness were significantly
higher in plots with increased light penetration (Abundance:
R2=0.1, P = 0.012; Richness: P = 0.014,
R2 = 0.1; Figs. 6B,D). The richness of small species
(1st quartile) did not significantly change with light
penetration (Fig. 6C, Table S1). Within-plot variation in light
penetration was not significantly related to small species abundance or
richness using either definition (Table S1).
The composition of small plant species defined using the median
significantly changed with mean plot-level light penetration (dbRDA1,P = 0.031, pseudo-F 1,47 = 2.06; Fig. 7),
but was unaffected by mean intraplot variation. Mean plot-level light
penetration explained 4.2% of the total variation in plot composition
for ‘median’ small species. Eighteen species had higher abundances
associated with higher light penetration (as demonstrated by positive
loadings along the light penetration axis), while eight species tended
to have lower abundances associated with higher light penetration (as
demonstrated by negative loadings along the light penetration axis; Fig.
7). Conversely, ‘1st quartile’ small species
composition was unaffected by mean light penetration or mean intraplot
variation, and neither were retained as axes.
We performed analyses using both total abundance and flowering
abundance; however, because the analyses of flowering abundance were
more informative, we have focused on these. Half of the analyses using
the total number of individuals demonstrated significant relationships
between light penetration and small species abundance and richness,
compared to two-thirds of analyses using only the number of flowering
individuals. We provide further information on analyses using the total
number of individuals in the supplementary material (Fig. S3-S7).