Interspecific facilitation of micronutrient uptake between cluster-root-bearing trees and non-cluster rooted-shrubs in a woodland.

BACKGROUND AND AIMS

Belowground interspecific plant facilitation is supposed to play a key role in enabling species co-existence in hyperdiverse ecosystems in extremely nutrient-poor, semi-arid habitats, such as woodlands in southwestern-Australia. Manganese (Mn) is readily mobilised by cluster root activity in most soils and accumulates in mature leaves of native Australian plant species without significant remobilisation during leaf senescence. We hypothesised that neighbouring shrubs are facilitated in terms of Mn uptake depending on distance to surrounding cluster root-forming trees.

METHODS

We mapped all trees and selected neighbouring shrubs within a study site in Western Australia. Soil samples were collected and analysed for physical properties and nutrient concentrations. To assesses the effect of tree proximity on leaf Mn concentrations [Mn] of non-cluster-rooted woody shrubs, samples of similarly aged leaves were taken. We used multiple linear models to test for factors affecting shrub leaf [Mn].

RESULTS

None of the assessed soil parameters showed a significant correlation with shrub leaf Mn concentrations. However, we observed a significant positive effect of very close trees (2 m) on leaf [Mn] in one of the understorey shrubs. We found additional effects of elevation and shrub size.

CONCLUSIONS

Leaf micronutrient concentrations of understorey shrubs were enhanced when growing within 2 m of tall trees. Our model predictions also indicate that belowground facilitation of Mn uptake was shrub size-dependent. We discuss this result in the light of plant water relations and shrub root system architecture.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11104-023-06092-6.