General Introduction

Abstract

Lianas are woody climbers rooted in soil and are incapable of autonomous vertical growth above a certain height and rely on external support to reach forest canopy (Wyka et al. 2013). Lianas have long attracted the interest of botanists because of the peculiar characteristics associated with this life-form including their climbing mechanisms (Darwin 1865; Isnard and Silk 2009), biomechanical properties (Rowe et al. 2004), anatomical modifications (Bowling and Vaughn 2009), extreme stem hydraulic capacities (Gartner et al. 1990; Ewers et al. 1991) and their extraordinary developmental plasticity (Lee and Richards 1991). Generally, lianas are abundant in tropical forests with a high taxonomic diversity (Schnitzer and Bongers 2002; Mascaro et al. 2004). Although less diverse, they are present in great abundance in many temperate forests as well (Givnish and Vermeij 1976; Putz 1984). Lianas constitute 19–30 % of species diversity in tropical forests (Jongkind and Hawthrone 2005), 9.6–19 % in subtropical forests (Cai and Song 2000) and 5.6–7 % in temperate forests (Gentry 1991). The diversity and abundance of lianas are expected to be explained by abiotic factors such as water, temperature, soil and community structural attributes (Balfour and Bond 1993; Schnitzer and Bongers 2002; Schnitzer et al. 2005). The high diversity of lianas in tropical forests has been assigned to diversity in microhabitats (DeWalt et al. 2006) and the availability of a wide array of dimensions, shapes and morphological features of trees that provide support to them (Clark and Clark 1990). Liana research has been stimulated, especially during the last two decades owing to their increasing presence and dominance in disturbed vegetation and discoveries of the multidimensional role they play in forest dynamics (Schnitzer et al. 2012; Yong et al. 2012). Lianas exhibit a diversity in functional types and ecological strategies (DeWalt et al. 2000; Gerwing 2004; Yuan et al. 2009) and although they have a similar growth form, they do differ in their functional traits including climbing mechanism (Putz 1984; Putz and Holbrook 1991), light requirements (Baars et al. 1998; Gianoli et al. 2010; Putz 1984), flower size and diaspore type (Bullock 1995; Cai et al. 2009; Gentry 1991b).