Evidence of nutrient translocation in response to smoke exposure by the East African ant acacia, Vachellia drepanolobium

Abstract

Fire is a major selective force on arid grassland communities, favoring traits such as the smoke‐induced seed germination response seen in a wide variety of plant species. However, little is known about the relevance of smoke as a cue for plants beyond the seedling stage. We exposed a fire‐adapted savanna tree, Vachellia (=Acacia) drepanolobium, to smoke and compared nutrient concentrations in leaf and root tissues to unexposed controls. Experiments were performed on three age cohorts: 2‐year‐old, 9‐month‐old, and 3‐month‐old plants. For the 2‐year‐old plants exposed to smoke, carbon and nitrogen concentrations were lower in the leaves and higher in the roots than controls. Less pronounced trends were found for boron and magnesium. In contrast, smoke‐exposed 3‐month‐old plants had lower root nitrogen concentrations than controls. No significant differences were found in the 9‐month‐old plants, and no significant shifts in other nutrient concentrations were observed between plant tissues for any of the three age cohorts. Synthesis: Our findings are consistent with smoke‐induced translocation of nutrients from leaves to roots in 2‐year‐old V. drepanolobium. This could represent a novel form of fire adaptation, with variation over the course of plant development. The translocation differences between age cohorts highlight the need to investigate smoke response in older plants of other species. Accounting for this adaptation could better inform our understanding of savanna community structure and nutrient flows under fire regimes altered by anthropogenic land use and climate change.

Automated detection of an insect‐induced keystone vegetation phenotype using airborne LiDAR

“…Quadrats on the western side of the plot were more similar to each other than those on the eastern side (Figure 4b, lower row numbers cluster more closely), while there were no distinguishable patterns along the north–south axis (Figure S3A, no pattern by transect number). These patterns likely reflect a soil nutritional gradient, which is present along the east–west but not the north–south axis of the plot (Childers, 2021; Palmer & Young, 2017). Soil nutrition either directly drives ant species composition and tree use (Farji‐Brener & Werenkraut, 2017; Kenfack et al., 2021; Wagner & Fleur Nicklen, 2010), or affects herbivore use of the landscape, which drives the patterning of ant occupancy (Kaspari, 2020; Palmer et al., 2008).…”