Edge effects on liana communities in wet evergreen and moist semi-deciduous forest ecosystems
Kwame Nkrumah University of Science and Technology
ABSTRACT Lianas are an important part of forest ecosystems around the world. However, there is insufficient information on their response to edge creation especially in tropical Africa. The current study investigated the effect of forest edge on liana communities in wet evergreen and moist semi-deciduous forest ecosystems in Ghana. The study investigated the effect of edge on liana diversity, species composition, community structure as well as liana–host interactions at edge and non-edge habitats in two wet evergreen forests (Ankasa Conservation Area and Cape Three Points Forest Reserve) and two moist semi-deciduous forests (Asenanyo and Suhuma Forest Reserves). A total of ninety-six 50 m x 50 m plots were surveyed. Two sites were selected in each forest reserve not less than 5 km apart. At each site, 12 plots were randomly and evenly demarcated at distances 0–30 m from the edge, 100–200 m from the edge and >200 m from the edge. Plot distances were kept at not less than 100 m. In each plot liana stems with diameter of ≥1 cm at 1.3 m from the rooting point were identified and enumerated. Liana species richness was comparable among habitats in the wet evergreen ecosystem. Shannon diversity index and Fisher’s diversity index were both significantly higher at the edge habitat than the intermediate habitat but comparable with the interior habitat. In the moist semi-deciduous ecosystem, species richness differed significantly among habitat pairs except the edge versus intermediate habitats. Liana abundance did not differ among habitats in forests of the wet evergreen ecosystem. In the forests of the moist semi-deciduous ecosystem, however, liana abundance was significantly higher at the edge habitat than the interior habitat but comparable with the intermediate habitat. Liana basal area also showed no significant difference among habitats of both wet evergreen and moist semi-deciduous forests except in Cape Three Points. There was generally no separation in the species composition among plots in all forest reserves except between the intermediate and interior habitats of Cape Three Points where some sort of separation was observed. An analysis of similarity further revealed a significant difference in species composition among habitats of Cape Three Points Forest Reserve (R = 0.1987; p = 0.0021). The edge habitat of moist semi-deciduous forest ecosystem seemed to favour the abundance of most liana species relative to the edge habitat of the wet evergreen forest ecosystem. Liana species co-occurrence was positive for the edge and intermediate habitats of the wet evergreen ecosystem but random in the interior habitat. All habitats in the moist semi-deciduous ecosystem showed positive co-occurrence except the intermediate habitat of Asenanyo Forest Reserve. The edge habitat of Ankasa Conservation Area, all habitats of Cape Three Points and Asenanyo Forest Reserves, as well as the edge and interior habitats of Suhuma Forest Reserve showed nested liana-host interaction. Generally, the effect of edge on liana communities was more pronounced in the moist semi-deciduous forest ecosystem than the wet evergreen forest ecosystem.