Biomass Allocation of Invasive Cenchrus pauciflorus Based on R Package Smatr

Elucidating patterns of plant biomass allocation is an important subject in ecological research. Broadly speaking, two schools of thought are applied to understand it: allometric partitioning theory (APT) and optimal partitioning theory (OPT). Which theory prevails for the highly aggressive invasive weed Cenchrus pauciflorus regarding intraspecific variability in biomass allocation across habitats has never been studied. Using the R package smatr (Standardised Major Axis Estimation and Testing Routines), we report on allometric relationships regarding biomass allocation in four habitats of the Songnen Plain. There is a large body of literature that has generally considered the allometric coefficient. This study further combined the slope, intercept and shift along the common standardized major axis (SMA) to explain biomass partitioning. We found an isometric relationship between aboveground and root biomasses in three habitats and between stem and root biomasses in two habitats, supporting allometric partitioning theory (APT). Significant differences in slopes between habitats were observed for most relationships. Those habitats whose slopes were not significantly different showed significantly different elevations or shifts in location along a common slope, even for isometric relationships. Such inter-habitat variation suggests that the adjustment of biomass allocation may be induced by environmental conditions, supporting optimal partitioning theory (OPT). It has been suggested that phenotypic integration could constrain trait plasticity; whether this is true remains a debated topic with mixed empirical support. We provide one of the few lines of evidence showing that phenotypic integration is positively associated with the phenotypic plasticity magnitude across advantageous and stressful environments. This study provides insights into the adaptive strategies of invasive Cenchrus pauciflorus in heterogeneous habitats and a scientific basis for habitat-specific management and control.