Allometric scaling relationships of biomass for six common understory species in French temperate forests

Forest ecologists often focus on trees and tend to overlook understory plants. However, understory species, despite representing less aboveground biomass than trees, are essential for forest dynamics and ecosystem functioning. The understory contributes to forest biodiversity, influences the forest microclimate and the availability of water and nutrients, and how disturbances, such as fires and large herbivores, impact the ecosystem. Estimating plant biomass can be difficult and time-consuming, but it is crucial to understanding and managing forest ecosystem services and risks. In this study, we improved biomass measurement methods for six common understory species in European temperate forests and with diverse ecologies and life forms: wood anemone ( Anemone nemorosa ), common heather ( Calluna vulgaris ), common honeysuckle ( Lonicera periclymenum ), purple moor-grass ( Molinia caerulea ), common bracken ( Pteridium aquilinum ) and brambles ( Rubus fruticosus agg.). Based on vegetation samples and measurements from temperate forests in France, mostly on acidic soils, we developed aboveground biomass models. Our findings demonstrate that simple, rapid, non-destructive measurements – like cover and height – enabled us to accurately and precisely estimate the total aboveground ( M T ), leaf ( M L ), and stem ( M S ) biomass. M L and M S scaled isometrically for heather and honeysuckle, and nearly isometrically for bracken, while bramble M L and M S scaled to 0.8 (i.e., varying leaf-to-stem ratio). These allometric scaling relationships are applicable at the scale of temperate acidic French forests and may also be applicable to European forests for the six species studied, thus promising a more complete estimation of forest biomass dynamics.