Does biomass growth increase in the largest trees? Flaws, fallacies and alternative analyses

Abstract

Summary1. The long-standing view that biomass growth in trees typically follows a rise-and-fall unimodal pattern has been challenged by studies concluding that biomass growth increases with size even among the largest stems in both closed forests and in open competition-free environments. We highlight challenges and pitfalls that influence such interpretations. 2. The ability to observe and calibrate biomass change in large stems requires adequate data regarding these specific stems. 3. Data checking and control procedures can bias estimates of biomass growth and generate false increases with stem size. 4. It is important to distinguish aggregate and individual-level trends: a failure to do so results in flawed interpretations. 5. Our assessment of biomass growth in 706 tropical forest stems indicates that individual biomass growth patterns often plateau for extended periods, with no significant difference in the number of stems indicating positive and negative trends in all but one of the 14 species. Nonetheless, when comparing aggregate growth during the most recent five years, 13 out of our 14 species indicate that biomass growth increases with size even among the largest sizes. Thus, individual and aggregate patterns of biomass growth with size are distinct. 6. Claims concerning general biomass growth patterns for large trees remain unconvincing. We suggest how future studies can improve our knowledge of growth patterns in and among large trees.

The limited contribution of large trees to annual biomass production in an old‐growth tropical forest

“…, Sheil et al. ). Different patterns may thus be observed at the tree level, for example by analyzing tree rings (Sheil et al.…”

“…Different patterns may thus be observed at the tree level, for example by analyzing tree rings (Sheil et al. ). Similarly, different patterns are also expected at the forest level, where trees of different size, age and species coexist.…”

“…, Sheil et al. ). Relationships between tree size and tree mortality rates have been proposed but not consensually validated.…”

“…, Sheil et al. ). In other words, the expectation regarding the contribution of large trees to biomass dynamics may vary with the level under consideration, i.e., from individual or species levels to forest level.…”

Nexusing Charcoal in South Mozambique: A Proposal To Integrate the Nexus Charcoal-Food-Water Analysis With a Participatory Analytical and Systemic Tool

“…An empirical observation of the wood piled in the train station in MabalaneSede ready to be sent to Maputo also confirms these numbers. The reason why so many trees are hollow seem to be a common phenomenon in several ecosystems (Ruxton, 2014;Sheil et al, 2017). Studies suggest that this is an adaptation mechanism with microbial or animal consumption of interior wood producing nutrients to feed new growth via the trees roots or, in an alternative explanation, such loss of wood comes at very little cost to the tree and so investment in costly chemical defense of this wood is not economic (Ruxton, 2014).…”