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Late-successional unmanaged forests (or old-growth forests) are important terrestrial carbon sinks. Their structurally complex features have been hypothesized to strongly affect forest productivity. However, the mechanisms through which structural complexity influences forest productivity remain unresolved. Here, we report a set of idealised simulations in boreal, sub-boreal, cool-temperate, warm-temperate and tropical forests using a dynamic model of atmosphere and vegetation interactions (Multilayered Integrated Numerical Model of Surface Physics–Growing Plants Interaction, MINoSGI). We aimed to elucidate the effects of tree–size and canopy structural complexity on stand-scale gross primary productivity (GPP) of old-growth forests over 300-year time series. We assumed the tree-size structures of mature old-growth forests as the initial conditions of the simulations. We focused on three different developmental phases of the forests: 29–48 years (phase I), 77–96 years (phase II) and 277–296 years (phase III) from the start of the simulations. Phase I corresponds to an old-growth forest because of our settings of the initial conditions of the simulations, and phase III to a long-term resultant forest without recruitment or mortality. We show that, for a given biome-specific leaf area index (LAI) and individual foliage shape (η), the greatest difference in GPP (ΔGPP) between forests with the most and least structurally complex canopies was 263 g C/m−2(-|-) year−1 in phase I and II when old-growth forests with the most complex canopy structures sustained their complexity, equivalent to almost 13 % of the annual GPP. By contrast, the maximum difference in ΔGPP was reduced to 153 g C/m−2(-|-) year−1 in phase III, equivalent to 8 % of the annual GPP total because the complex canopy structures of old-growth forests without recruitment or mortality approached less multi-layered ones similar to those of less complex and managed forests. Our simulation results indicate that greater tree–size and canopy structural complexity is associated with a broader vertical distribution of foliage, supporting the localisation of leaves in multiple layers. This increases the efficacy of light usage, particularly for shaded leaves receiving only diffuse light within the canopy. As a consequence, for all forest biomes, an increase in in-canopy diffuse light increases GPP in forests with complex canopy structures due to an enhancement of light use efficiency (LUE) of shaded leaves. Overall, our results quantify one of the mechanisms underlying the effects of canopy structural complexity on forest productivity. Moreover, differences in foliage shape between forest biomes can add to uncertainties when predicting GPP based on simulation models. We, therefore, suggest that precise values of the biome-specific factors associated with canopy structure should be employed into simulation models of global carbon budgets.

New (a)biotic conditions, resulting from climate change, are expected to change disturbance dynamics, e.g., wind throw, forest fires and insect outbreaks, and their interactions. Unprecedented natural disturbance dynamics might alter the capability of forest ecosystems to buffer atmospheric CO2 increases in the atmosphere, even leading to the risk that forests transform from sinks into sources of CO2. This study aims to enhance the capability of the ORCHIDEE land surface model to study the impacts of climate change on bark beetle dynamics and subsequent effects on forest functioning. The bark beetle outbreak model is based on previous work by Temperli et al. 2013 for the LandClim landscape model. The new implementation of this model in ORCHIDEE r7791 accounts for the following differences between ORCHIDEE and LandClim: (1) the coarser spatial resolution of ORCHIDEE, (2) the higher temporal resolution of ORCHIDEE, and (3) the pre-existing process representation of wind throw, drought, and forest structure in ORCHIDEE. Qualitative evaluation demonstrated the model’s ability to simulate a wide range of observed post-disturbance forest dynamics: (1) resistance to bark beetle infestation even in the presence of windthrow events; (2) slow transition (3–7 years) from an endemic into an epidemic bark beetle population following medium intensity window events at cold locations; and (3) fast transition (1–3 years) from endemic to epidemic triggered by strong windthrow events. Although all simulated sites eventually recovered from disturbances, the time needed to recover varied from 5 to 10 years depending on the disturbance dynamics. In addition to enhancing the functionality of the ORCHIDEE model, the new bark beetle model represents a fundamental change in the way mortality is simulated, as it replaces a framework in which mortality is conceived as a continuous process by one in which mortality is represented by abrupt events. Changing the mortality framework provided new insights into carbon balance estimates, showing the risk of overestimating the short term sequestration potential under the commonly used continuous mortality framework.

This is a protocol for a systematic map of studies that have examined the impacts of natural disturbances on soil fauna in forest ecosystems. The systematic map aims to characterise these studies, identify opportunities for future quantitative synthesis, and identify knowledge gaps that warrant further primary studies.

This is a protocol for a systematic map of studies that have examined the impacts of natural disturbances on soil fauna in forest ecosystems. The systematic map aims to characterise these studies, identify opportunities for future quantitative synthesis, and identify knowledge gaps that warrant further primary studies.

This is a protocol for an umbrella review to summarise, explore, and appraise the results of existing syntheses of the impacts of natural disturbances on soil properties in forest ecosystems.

This chapter introduces greenhouse gas accounting activities that use “bottom-up” approaches. Bottom-up approaches can be categorized into inventory, bookkeeping, process-based modeling, and data-driven (i.e., remote sensing) methods. Activity data combined with emission factors, gain-loss, or stock-change analyses are the basis of each approach used to carry out the reporting and accounting. Uncertainties stem from data sources, model parameters, type of forcing, reporting level, and uncertainties between methods relate to definitions inherent to reporting requirements by the IPCC and UNFCCC.