Different responses in leaf pigments and leaf mass per area to altitude between evergreen and deciduous woody species

Leaf chlorophyll content is positively associated with photosynthetic capacity and nutrient status, but its functional ecology has seldom been examined thus far. In the present study, we measured leaf chlorophyll and carotenoid concentrations, determined chlorophyll a : chlorophyll b (Chl a : Chl b) and carotenoids : chlorophyll ratios and measured leaf mass per area (LMA) for 63 woody dicot species, including 24 evergreen species and 39 deciduous species, at two altitudes (1800–2400 and 2400–2800 m a.s.l.) of Gongga Mountain, south-west China. The aim of the present study was to determine whether evergreen and deciduous species differ in terms of leaf pigment concentrations and LMA in response to environmental differences associated with changes in elevation. In both life forms, the altitude effect was not significant for chlorophyll and carotenoid concentrations. However, the Chl a : Chl b ratio was significantly higher in evergreen species, whereas LMA was significantly higher in deciduous species, at the high versus low altitude. These observations suggest that evergreen and deciduous species may have different strategies to protect leaf pigments. Mass-based leaf pigment concentrations were lower in evergreen compared with deciduous species, especially at high altitude. LMA was higher in evergreen than deciduous species at both altitudes. Pigment concentrations were negatively correlated with LMA in both life forms at both altitudes. The slope of LMA vs mass-based leaf pigment concentrations was significantly more negative for deciduous than evergreen species, and at low versus high altitude for deciduous species. The findings suggest that deciduous species may invest less photosynthate in leaf pigments but more in inactive components in stressful environments than do evergreens. Thus, the same magnitude of variation in LMA may have different consequences on leaf carbon balance between evergreen and deciduous species, which helps explain why evergreen species are often more likely to occupy more stressful environments than deciduous species.