Intraspecific root competition of Caragana microphylla dominates its above-ground population self-thinning: Evidences from GPR

Plant self-thinning power law is regarded as an essential regulation which plays an important role in determining population dynamics and community structure. However, little experimental and theoretical studies on the power law have been developed for shrub, and also little has been done from the perspective of below-ground plant parts to reveal the mechanisms underlying the self-thinning process of natural plant especially in field. Taking the shrub, Caragana microphylla, as example, this study revealed the below-ground root biomass-density relationship of Caragana microphylla and explained how and to what extent do below-ground root competition affect the above-ground self-thinning process. The below-ground root systems were surveyed by Ground- penetrating radar (GPR). The root biomass was estimated based on GPR data. Some of the statistical relationships discussed in this study may be useful for predicting root biomass of shrub community in water-limited ecosystems and will also serve as a frame of reference for future studies.