Individual size inequality links forest diversity and above‐ground biomass

Abstract

Summary Despite the mounting evidence for positive diversity–productivity relationships found in controlled experiments, diversity effects on productivity in natural systems remain hotly debated. Understanding the multivariate links between diversity and productivity in natural systems, in particular natural forests that host the majority of terrestrial biodiversity and provide essential services for humanity, remains a critical challenge for ecologists. We analysed data from 448 plots of varying tree species diversity, stand ages and local nutrient availability in Canada's boreal forest (52°30′–55°24′ N latitude and 102°36′–108° W longitude). We used structural equation models to link multivariate relationships between above‐ground biomass, tree species diversity, stand age and soil nutrient availability. Above‐ground biomass increased with diversity indirectly via increasing tree size inequality, increased with stand age and was higher on sites of medium soil nutrient regime directly as well as indirectly via increased tree size inequality. Synthesis. Our results demonstrate positive diversity effects on above‐ground biomass in natural forests of diverse forest ages and soil resource availability. Furthermore, we show that tree size inequality acts as a mechanism for the positive diversity effects on above‐ground biomass and as a mechanism in regulating above‐ground biomass and species diversity simultaneously via interactions among individuals in natural forests.

Functional composition drives ecosystem function through multiple mechanisms in a broadleaved subtropical forest

“…The relationship between diversity and stem density may be linked with "canopy packing" which optimizes space utilization and, in our example, may lead to increased local biomass. Zhang and Chen (2015) demonstrated that diversity is linked with increased biomass due to increasing tree size inequality in a boreal forest. Similarly, Jucker et al (2015) found that canopy packing was strongly associated with species richness in European permanent forest plots.…”

A Review of Processes Behind Diversity—Productivity Relationships in Forests

“…Indeed, structural diversity was positively correlated with forest productivity (Fig. 3) or above-ground biomass [60] in Canadian forests. Therefore, part of the diversity effects shown in Fig.…”

Linking hypothesized causal factors to aboveground biomass growth in forests of Alabama and the eastern United States

“…Forest structural diversity is one important factor among many that influence productivity (Zhang & Chen, 2015;Ali et al, 2016). A stand with a combination of species differing in characteristics such as shade tolerance, height growth rate, crown structure, leaf phenology, and root depth, can be highly productive because of complementary resource use (Kelty, 1992).…”

“…It has been widely used for exploring complicated causal relationships among variables (Grace, 2008;Paquette & Messier, 2011;Lam & Maguire, 2012;Zuo et al, 2012;Timilsina et al, 2014;Zhang & Chen, 2015;Ali et al, 2016;Dănescu et al, 2016;Grace et al, 2016). SEM models represent hypothesized causeeffect relationship between variables and describe complex interdependencies of the variables (Shipley, 2000).…”

“…In SEM, the causal relationships are described by magnitude of effects, i.e., direct, indirect, and total effects that independent variables have on dependent variables (Pugesek et al, 2003). There is a need of observational studies to enhance our understanding of the multivariate relationships of the ecological and environmental drivers that affect aboveground biomass productivity or carbon storage in natural forests (Zhang & Chen, 2015).…”