Altitudinal variation of leaf carbon isotope for Dendrosenecio keniensis and Lobelia gregoriana in Mount Kenya alpine zone

Abiotic factors vary along altitudinal gradients, and this may influence plant morphology, physiology and function. This study aimed to test the hypothesis that leaf δ13C,  a common proxy for water use efficiency, was indirectly influenced by morphological adjustments with changing climatic factors along an altitudinal gradient on Mt. Kenya. We sampled leaves of Dendrosenecio keniensis and Lobelia gregoriana using seventy-two 10 × 10 m plots situated every 100 m starting from 3600 to 4300 m. We determined leaf δ13C using stable isotope mass spectrometry. We also quantified the following morphological factors; leaf area, leaf mass per area, specific leaf area and leaf thickness. Climate data included mean annual temperature and precipitation, diurnal temperature range and water vapor pressure. Our results revealed that there was a leaf δ13C enrichment of 1.76 ‰km-1 and 1.62‰ km-1 with altitude for D. keniensis and L. gregoriana respectively. Leaf δ13C was enrichment by 0.01‰ mm-1 with me...