Liana community structure
Our study showed contrasting edge effects on species diversity in the
two moist semi-deciduous forests. In the Asenanyo Forest Reserve, edge
appeared to have enhanced diversity, while an opposite trend occurred in
the Suhuma Forest Reserve. The trend in the Asenanyo Forest Reserves is
consistent with previous studies that also recorded higher liana
diversity at forest edges in relation to forest interiors (Addo-Fordjour
& Owusu-Baodi 2016; Laurance et al., 2001). It is important to note
that edge effect in our study was observed in edge site in relation to
only deep-interior site. Therefore, we did not observe variation in
species diversity between edge and interior sites. This trend is an
indication that edge effects on liana species diversity penetrated 200 m
into the interior of the forest. The findings of the present study also
indicated that species evenness was poorer in edge site of the Suhuma
Forest Reserve, resulting in a lower species diversity, irrespective of
its higher species richness. The forest edge appears to have influenced
species evenness by exerting differential effects on the abundance of
different species in edge site. Thus, in edge site of Suhuma Forest
Reserve, changes in species abundance mediated edge effects on liana
species diversity. The observed species diversity variation may possibly
relate with edge-related changes in variables such as microclimate, and
tree density and mortality that often characterise forest edges
(Ofosu-Bamfo et al., 2019; Wekesa et al., 2019).
Our study revealed pronounced edge effect on liana abundance at the
community level in the two forest reserves. This pattern is supported by
previous studies which showed that edge effect enhanced liana abundance
in their respective forests (Addo-Fordjour & Owusu-Boadi, 2016;
Campbell et al., 2018; Laurance et al., 2001). Our results showed that
in both forest reserves, edge effects penetrated 200 m from the edge,
and this is in keeping with Laurance et al. (1991) who reported that
edge effects on the abundance of disturbance-adapted plants such as
lianas can penetrate 200 m into forest interior. Forest edges are often
characterised by increased levels of light and desiccation or dryness,
which can promote liana increase (Campbell et al., 2018). Given that
there was a sharp contrast between our forest edges and the surrounding
matrix, we expected the above mentioned conditions to be more pervasive
in edge site. Thus, increased levels of light and dryness at the forest
edge may be associated with the positive response of liana abundance to
edge disturbance in the two forests. At the species level, many liana
species showed diverse responses to edge disturbance in the two forests.
The values of MEI with respect to species abundance varied widely among
the liana species. A similar finding was reported in two rainforests in
Ghana (Ofosu-Bamfo et al., 2019). Our finding implies that although
optimal light and dry conditions may characterise forest edge sites,
they may not enhance the proliferation of some liana species. This may
occur when there is excessive soil desiccation causing liana mortality
(Nepstad et al., 2007). Nevertheless, some of the liana species showed
high positive MEI, indicating that they tended to prefer edge sites.