Title：
Altitudinal variation of leaf carbon isotope for Dendrosenecio keniensis and Lobelia gregoriana in Mount Kenya alpine zone
Authors：
Corresponding
Author：
Waigwa, Antony Njogu; Mwangi, Brian Njoroge; Gituru, Robert Wahiti; Omengo, Fred; Zhou, Yadong*; Wang, Qingfeng.
Pubyear：
2021
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Journal：
Biotropica
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Abstract：
Abiotic factors vary along altitudinal gradients, and this may influence plant morphology, physiology and function. This study aimed to test the hypothesis that leaf delta C-13-a common proxy for water use efficiency-was indirectly influenced by morphological adjustments with changing climatic factors along an altitudinal gradient on Mount Kenya. We sampled leaves of Dendrosenecio keniensis and Lobelia gregoriana using seventy-two 10 x 10 m plots situated every 100 m starting from 3600 to 4300 m. We determined leaf delta C-13 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 delta C-13 enrichment of 1.76 parts per thousand km(-1) and 1.62 parts per thousand km(-1) with altitude for D. keniensis and L. gregoriana, respectively. Leaf delta C-13 was enrichment by 0.01 parts per thousand mm(-1) with mean annual precipitation along the altitude gradient for D. keniensis and 0.02 parts per thousand mm(-1) for L. gregoriana. D. keniensis and L. gregoriana have high-water use efficiency, an adaptation for surviving near freezing alpine temperatures and high-diurnal range. Leaf delta C-13 exhibited a depletion of -0.37 parts per thousand per degrees C increase of mean annual temperature along the altitude gradient for D. keniensis and -0.34 parts per thousand per degrees C increase for L. gregoriana. Our results also showed a negative relationship between pCO(2) and leaf delta C-13 and positive relationship between pCO(2) and increment C-13 for both species. Low temperatures led to the increase in leaf thickness and specific leaf area for these two species, factors that influenced leaf delta C-13 and increment C-13. Abstract in Chinese is available with online material
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