How do Light and Water Acquisition Strategies Affect Species Selection during Secondary Succession in Moist Tropical Forests?

Leonie Schönbeck,Frank Sterck,Frans Bongers,Madelon Lohbeck,Miguel Ramos

doi:10.3390/f6062047

Leonie Schönbeck, Frank Sterck + Show 3 more

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https://doi.org/10.3390/f6062047

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Abstract

Pioneer tree species have acquisitive leaf characteristics associated with high demand of light and water, and are expected to be shade and drought intolerant. Using leaf functional traits (specific leaf area, photosynthetic rate, relative water content and stomatal conductance) and tree performance (mortality rate) in the field, we assessed how shade and drought tolerance of leaves are related to the species’ positions along a successional gradient in moist tropical forest in Chiapas, Mexico. We quantified morphological and physiological leaf shade and drought tolerance indicators for 25 dominant species that characterize different successional stages. We found that light demand decreases with succession, confirming the importance of light availability for species filtering during early stages of succession. In addition, water transport levels in the leaves decreased with succession, but high water transport did not increase the leaf’s vulnerability to drought. In fact, late successional species showed higher mortality in dry years than early successional ones, against suggestions from leaf drought tolerance traits. It is likely that pioneer species have other drought-avoiding strategies, like deep rooting systems and water storage in roots and stems. More research on belowground plant physiology is needed to understand how plants adapt to changing environments, which is crucial to anticipate the effects of climate change on secondary forests.

Highlights

It has been proposed that species turnover during secondary succession in wet tropical forests is mainly driven by decreasing light availability [1]
The 25 selected species occurred in 8.3 ± 3.4 out of the 15 plots, with only Luehea speciosa and Trichospermum mexicanum occurring in all plots
In this study we assessed how leaf traits related to light acquisition, shade tolerance, water acquisition, and drought tolerance are associated to secondary succession

Summary

Introduction

It has been proposed that species turnover during secondary succession in wet tropical forests is mainly driven by decreasing light availability [1]. Species composition changes during succession from dominance of species that have an “acquisitive resource capture strategy”, that grow fast and require high light levels, to species that have a “conservative resource capture strategy”, that grow slow and persist in the shaded understory [2,3,4]. Conservative, species persist by having tough leaves that are long-lived and efficiently utilize light. This continuum is in line with the leaf economics spectrum (LES) [5] and the plant economics spectrum [7,8]. The LES highlights the leaf traits associated with light acquisition, critical for leaf carbon balances, but leaf traits associated with water acquisition remain largely undiscussed. It is remarkable that the role of water availability as a driving factor of succession remains poorly studied [11]

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