Abstract
Understanding how trees mediate the effects of chronic anthropogenic disturbance is fundamental to developing forest sustainable management strategies. The role that intraspecific functional diversity plays in such process is poorly understood. Several tree species are repeatedly defoliated at large scale by cattle breeders in Africa to feed livestock. In addition, these tree species are also debarked for medicinal purposes. These human-induced disturbances lead to biomass loss and subsequent decline in the tree growth. The main objective of this work is to investigate how functional traits mediate tree response to chronic anthropogenic disturbance. We used a unique data set of functional traits and growth rate of 503 individual tree of Afzelia africana. We collected data on leaf mass per area (LMA), wood density (WD) and growth rate, and recorded history of human disturbances (debarking, pruning) on individual tree from 12 populations of A. africana distributed in two ecological zones in Benin (West Africa). We tested the effect of disturbances on absolute growth rate across ontogenetic stages, assessed the role of intraspecific trait variability on growth and tested the role of tree functional strategy on the tree growth response to debarking and pruning. We found that debarking did not affect stem growth, suggesting a fast compensatory regrowth of bark wounded. Moreover, tree response to debarking was independent of the functional strategy. By contrast, we found that pruning reduced tree absolute growth; however, trees with low WD were more strongly affected by pruning than trees with high WD. Our results emphasize the importance for plant functioning of the interplay between the availability of leaves for resource acquisition and a resilience strategy by mobilizing stored resources in stem wood to be reinvested for growth under severe disturbances.
Highlights
Functional traits can aid in our understanding of the variation in species response to environment (McGill et al 2006)
When we included the effect of intraspecific functional traits variability in our model (Model 2), we found no significant effect of leaf mass per area (LMA) and Wood density (WD) on growth rate (Table 1, Figs. 4 and 5)
Pruning significantly reduced the growth of A. africana trees by up to 0.35 cm per year, and this negative effect was highest for intermediate aged trees, i.e. around 10 cm with lower WD (Fig. 6)
Summary
Functional traits can aid in our understanding of the variation in species response to environment (McGill et al 2006). With high LMA, leaves exhibit high thickness and toughness that reflect greater resource allocation into defence than into growth (Wright and Cannon 2001). This leads to more robust leaves with long lifespan (Sterck et al 2006) and less damaged from herbivory (Wright and Westoby 2002). Several studies independently demonstrated ontogenetic variation in plant growth/survival and functional traits (Poorter and Bongers 2006; Hérault et al 2011; Iida et al 2014). Recent studies have highlighted the importance of considering ontogenetic shifts in the relationship between functional traits and disturbance (e.g. Herault et al 2010)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
