Towards a causal understanding of the relationship between structural complexity, productivity and adaptability of forests based on principles of thermodynamics

Abstract

Managing forests for increased structural complexity as well as acknowledging them as ‘complex adaptive systems’ has become a paradigm in modern silviculture. Primary forests usually show greater structural complexity than managed forests since forest management often aims for several reasons at less complex but specific structures, e.g. for the production of desired wood assortments. Therefore, the question why natural forests seem to gravitate towards maximum structural complexity, at least aboveground, remains. Here we argue that the consideration of thermodynamic theory in forest ecosystem research holds great potential for a deeper understanding as to why structural complexity is beneficial to forests when it comes to evolutionary adaptation. We bring together several existing theories and highlight how structural complexity relates to thermodynamic principles and correspondingly forest productivity, potentially also providing us a means to quantify forests’ adaptive capacity.

Leaf trait variation within individuals mediates the relationship between tree species richness and productivity

“…Hence, forest canopies are optimized for light capture (Reich 2012). In particular, a higher structural complexity appears to be linked to greater photosynthetic capacity of the forest (Seidel and Ammer 2023). Optimization for light capture occurs at all organisation levels of the community.…”

Increase in forest structural complexity along a precipitation gradient is mediated by partial harvests in temperate Patagonian forests

“…Recent conceptual advances suggest that such forests are also better able to adapt to a variety of present and future and novel environmental conditions and disturbances 3,5,13 . However, recent advances in scanning technology, specifically ground based LiDAR provide for efficient data collection and quantification of stand structure 14,15 .The concept of forest structural complexity has spurred a productive research area 15 . Efforts began to quantify the distribution of trees and their canopies in three-dimensional space, and to relate this quantification to "standard" forest attributes such as biomass, basal area, volume, leaf area or canopy height [16][17][18][19][20][21] .…”

“…Recent conceptual advances suggest that such forests are also better able to adapt to a variety of present and future and novel environmental conditions and disturbances 3,5,13 . However, recent advances in scanning technology, specifically ground based LiDAR provide for efficient data collection and quantification of stand structure 14,15 .…”

“…forest structural complexity has shown the potential to increase the understanding of the relationships of threedimensional forest structure and ecosystem processes and functions 15,17,25 . However, few empirical studies analyze drivers of variation in forest structural complexity, e.g., rainfall and ecosystem processes, respectively 17,23 , and even less studies refer to silvicultural implications on structural complexity.…”

“…Recent advances in airborne and terrestrial LiDAR (Light detection and ranging) technologies allow quantification of the three-dimensional nature of the forest structure "holistically" (sensu 15,26,27 ) or in a "non-featurecentered" manner (sensu 28 ). Such measures of forest structural complexity, e.g.…”