Leaf trait variation of a dominant neotropical savanna tree across rainfall and fertility gradients

Abstract

The evergreen tree Curatella americana dominates the woody stratum in Venezuelan savannas, along substantial rainfall and soil fertility gradients. This work determines intra-specific variation of leaf traits in Curatella which may account for its extended ecological range. Six Curatella populations, from sites spanning a 1800 mm rainfall and a 5-fold soil fertility range, were selected. Specific leaf area (SLA), N and P content, photosynthesis rate ( A), and the 13δC signature as an indication of long term water use efficiency (WUE lt) were measured at the peak of the rainy season of two years. The sclerophyllous and long-lived Curatella leaves had relatively low SLA, leaf N and P and A which differed among populations but were in the range of other evergreen savanna trees. SLA and A mass were positively related with rainfall whereas 13δC was negatively related. The responses to soil fertility were less clearly defined. There was a marked P limitation in most populations and nutrient resorption accounted for >50% of the leaf N and P budget. The variation in leaf traits of Curatella populations is comparable to inter-specific variation seen in other studies. Multivariate analysis established that the ecophysiological distance among populations of Curatella was mostly accounted by SLA and leaf N differences. The leaf trait response of Curatella to rainfall and fertility position it at the slow end of the global leaf economics spectrum.