image: Both APT and OPT influence the biomass allocation among organs during growth. (a) APT, which describes the geometry of the given organism, posits that the scaling exponents between organs, for specific species, are relatively stable, regardless of changes in environmental conditions. Note that it does not imply that scaling exponents are constant values throughout tree growth, but rather suggests that they are a consequence of natural selection optimizing the species' fitness across various environments. (b) OPT emphasizes that plants optimize resource utilization by adjusting the allocation of photosynthetic products, and this strategy applies throughout all the stages of plant growth.
Credit: Man Hu, Hang Shi, Rui He, Nana Wang, Yuzhen Han, Haishan Dang, Quanfa Zhang
A new study published in Forest Ecosystems has shed light on the strategies trees use to allocate biomass among leaves, stems, and roots, revealing a delicate balance between growth rules and environmental adaptation.
The research, led by scientists from the Wuhan Botanical Garden of the Chinese Academy of Sciences, analyzed 239 tree species worldwide, spanning both angiosperms and gymnosperms, to understand how plant size, climate, and soil conditions shape resource distribution. The team tested two long-standing ecological theories: allometric partitioning theory (APT), suggesting growth is ruled by fixed mathematical proportions, and optimal partitioning theory (OPT), proposing trees smartly shift resources to cope with their environment.
The study confirms that trees largely follow universal allometric patterns, and larger trees tend to invest more in stems and roots than in leaves to maintain structural support and storage. However, it also highlights that these rules are not fixed. Allometric constraints provide the basis for biomass allocation, but trees are remarkably flexible, adjusting their growth to environmental conditions.
Beyond size, climate and soil conditions further influence allocation. Angiosperms respond strongly to soil texture and nutrient availability, optimizing root and stem growth, while gymnosperms are particularly sensitive to temperature, often favoring stem growth in warmer conditions.
Also, deciduous angiosperms showed weaker environmental responses compared to evergreen angiosperms and gymnosperms, highlighting the role of evolutionary history and life strategy in shaping allocation patterns.
The results suggest that biomass allocation is governed by both theories, APT and OPT. The study reconciles a long-standing debate in plant ecology. Trees are neither rigidly fixed by growth rules nor entirely plastic. Instead, they operate under a hybrid system that maximizes survival and growth across diverse environments.
The research provides a new lens for predicting how forests might respond to climate change. By quantifying how trees adjust biomass allocation in response to environmental gradients, the study offers insights into carbon storage, forest dynamics, and ecosystem resilience on a global scale.
As the climate continues to shift, understanding these underlying rules and adaptive strategies will be crucial for forest management and conservation planning.
Journal
Forest Ecosystems
Article Title
Tree biomass allocation is governed by allometry but modulated by optimization
Article Publication Date
11-Nov-2025