Mineral Balance Plasticity of Cloudberry (<i>Rubus chamaemorus</i>) in Quebec-Labrador Bogs

Abstract

The “ionome”, or plant elemental signature, is the elemental composition of an organisms, that may vary with genotypic traits and phenotypic plasticity. Cloudberry (Rubus chamaemorus L.) is a circumboreal wild berry naturally growing in oligotrophic oceanic bogs ofQuebecandLabrador. Our objective was to relate cloudberry stand productivity to the ionomes of female ramets and explore the cause of nutrient imbalance in low-performing stands. We analyzed 13 elements in female ramets collected in 86 natural sites where crop productivity varied widely. We computed orthogonally arranged balances reflecting plant stoichiometric rules and soil biogeochemistry. Balances were expressed as isometric log ratios (ilr) between ad hoc sub-compositions. Balances were synthesized into a Mahalanobis distance optimized based on receiving operating characteristics (ROC). The critical Mahalanobis distance was found to be 5.29 for cutoff berry yield of3.8 g.m-2 with test performance of 0.88, as measured by the area under the ROC curve. Although past research on cloudberry focused mainly on the N/P ratio, this exploratory mineral balance analysis indicated that imbalance in the [P,N | S,C] and [Al | Nutrients] partitions appeared to be the factors limiting the most cloudberry productivity in the bogs. Some highly productive stands showed relatively high C fixation and K use efficiency. Due to the complexity of interactions, diagnosis should be conducted computing first a global imbalance index (Mahalanobis distance), then examining in the balance domain binary partitions departing most from reference, and finally appreciating relative shortage, sufficiency or excess of elements in the concentration domain.