Structural and nutritional differences between climbers and their supporting trees in a montane rainforest in South-Ecuador

Climbing plants grow fast and have good adaptability to changes in the surrounding conditions. Former studies already indicated good assignment of leaf nitrogen in climbers towards light harvesting by low leaf mass per area and high nitrogen contents. These traits were investigated on climbers and their supporting plants pair wise over an altitude gradient in a montane rainforest in Ecuador, covering a wide range of different forest structures. 80 pairs of climbers and supporters were sampled after assessment of leaf area index, canopy gap fraction and relative photon flux density above each sample pair. The leaf samples were analysed for structural factors, like leaf area, leaf mass per unit area, and carbon content, and element contents, like mass and area based leaf nitrogen and the elements P, K, Ca, MG, Mn and Al. Investment in supporting leaf tissues (i.e. LMA) was lower by climbers than that by their hosts. Climbers built smaller leaves with lower specific leaf mass (LMA) and were better adapted to the prevailing light conditions. Nutrient allocation economy was especially obvious on leaf area basis (Narea). Variations in LMA and Narea values were remarkable lower along the light gradient within the climbers than within their supporters. High contents of leaf phosphorus and potassium enable the climbers not only to allocate nutrients towards shoot growth, but also to respond fast to changes in their environment. This was also evident concerning significant loadings of the variables PFDrel, LMA and Narea in a principal components analysis (PCA). Leaf development also showed different nutrient allocation and LMA patterns between the two growth forms. Optimisation of physiological and morphological traits in their leaves enable climbers to exploit sites that vary greatly in light and other available resources. But the good adaptability of climbing plants is strongly demanding a sufficient nutrient supply, which is mainly given on disturbed sites.