Forest demography and biomass accumulation rates are associated with transient mean tree size vs. density scaling relations

Kailiang Yu*, Han Y H Chen, Arthur Gessler, Thomas A M Pugh, Eric B Searle, Robert B Allen, Hans Pretzsch, Philippe Ciais, Oliver L Phillips, Roel J W Brienen, Chengjin Chu, Shubin Xie, Ashley P Ballantyne

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Linking individual and stand-level dynamics during forest development reveals a scaling relationship between mean tree size and tree density in forest stands, which integrates forest structure and function. However, the nature of this so-called scaling law and its variation across broad spatial scales remain unquantified, and its linkage with forest demographic processes and carbon dynamics remains elusive. In this study, we develop a theoretical framework and compile a broad-scale dataset of long-term sample forest stands (n = 1,433) from largely undisturbed forests to examine the association of temporal mean tree size vs. density scaling trajectories (slopes) with biomass accumulation rates and the sensitivity of scaling slopes to environmental and demographic drivers. The results empirically demonstrate a large variation of scaling slopes, ranging from −4 to −0.2, across forest stands in tropical, temperate, and boreal forest biomes. Steeper scaling slopes are associated with higher rates of biomass accumulation, resulting from a lower offset of forest growth by biomass loss from mortality. In North America, scaling slopes are positively correlated with forest stand age and rainfall seasonality, thus suggesting a higher rate of biomass accumulation in younger forests with lower rainfall seasonality. These results demonstrate the strong association of the transient mean tree size vs. density scaling trajectories with forest demography and biomass accumulation rates, thus highlighting the potential of leveraging forest structure properties to predict forest demography, carbon fluxes, and dynamics at broad spatial scales.
Original languageEnglish
Article numberpgae008
Number of pages9
JournalPNAS nexus
Volume3
Issue number2
DOIs
Publication statusPublished - 17 Feb 2024

Bibliographical note

Funding:
T.A.M.P. and O.L.P. acknowledge funding from the H2020 European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 758873, TreeMort).

Keywords

  • forest demography
  • forest structure and function
  • mean tree size vs. density scaling trajectory
  • biomass accumulation rates

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