Self-thinning tree mortality models that account for vertical stand structure, species mixing and climate

Forrester, David I.; Baker, Thomas; Elms, Stephen; Hobi, Martina L.; Ouyang, Shuai; Wiedemann, John; Xiang, Wenhua; Zell, Jürgen; Pulkkinen, Minna

doi:10.1016/j.foreco.2021.118936

Cited by 20 publications

(18 citation statements)

References 89 publications

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“…Increased carbon stores could supply maintenance respiration in periods of photosynthetic stress 29 , 30 , and increases in water-use efficiency may alleviate the impact of drought 31 , 32 . In contrast, shifts in plant community composition or self-thinning dynamics may increase stand-level mortality 33 . These structural differences lead to no agreement on the direction of Δτ v in the models presented here.…”

Section: Discussionmentioning

confidence: 99%

Process-oriented analysis of dominant sources of uncertainty in the land carbon sink

et al. 2022

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The observed global net land carbon sink is captured by current land models. All models agree that atmospheric CO2 and nitrogen deposition driven gains in carbon stocks are partially offset by climate and land-use and land-cover change (LULCC) losses. However, there is a lack of consensus in the partitioning of the sink between vegetation and soil, where models do not even agree on the direction of change in carbon stocks over the past 60 years. This uncertainty is driven by plant productivity, allocation, and turnover response to atmospheric CO2 (and to a smaller extent to LULCC), and the response of soil to LULCC (and to a lesser extent climate). Overall, differences in turnover explain ~70% of model spread in both vegetation and soil carbon changes. Further analysis of internal plant and soil (individual pools) cycling is needed to reduce uncertainty in the controlling processes behind the global land carbon sink.

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Section: Discussionmentioning

confidence: 99%

Process-oriented analysis of dominant sources of uncertainty in the land carbon sink

et al. 2022

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“…These results are consistent with empirical evidence from Kubiske et al 2019 who reported increasing intercepts of the STLs under higher CO2, with the consequent higher stand biomass levels in the long term. Recent findings also indicate that climatic variables (Brunet-Navarro et al 2016;Forrester et al 2021) influence the STL, although other studies found that it remained constant over time (Pretzsch et al 2014). Importantly, the STL in mixed forests can also change when the relative proportion of species changes (Reyes-Hernandez et al 2013), e.g., due to succession.…”

Section: Interpreting Self-thinning Relationshipsmentioning

confidence: 98%

“…Inventory data from mixed forests were obtained by combining observations from three sources: the Swiss National Forest Inventory (NFI) (Fischer & Traub 2019), the Experimental Forest Management (EFM) network (Forrester et al 2021), and the Swiss Natural Forest Reserves (NFR) (Hobi et al 2020). These data cover a large environmental gradient and a variety of site conditions, making Swiss forests an interesting study case.…”

Section: Forest Datamentioning

confidence: 99%

“…Self-thinning dynamics have also been described in mixed forests (Midgley 2001;Mrad et al 2020) and the application has been generalised to multispecific stands (Rivoire & Le Moguedec 2012;Forrester et al 2021). The self-thinning relationship emerges from densitydriven mortality due to resource competition between individuals, neglecting mortality due to external factors.…”

Section: Interpreting Self-thinning Relationshipsmentioning

confidence: 99%

“…However, the position of the STL is a reflection of site quality (climate and soil properties) and is affected by species identity (Forrester et al 2021). Although temporal changes in the STL are still in doubt (Pretzsch et al 2014), a recent study found that the STL shifted such that forest stands were able to carry higher biomass stocks in a CO2 fertilization experiment (Kubiske et al 2019).…”

Section: Introductionmentioning

confidence: 99%

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Tree growth enhancement drives a persistent biomass gain in unmanaged temperate forests

Marqués

Weng

Bugmann

et al. 2022

Preprint

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While enhanced tree growth over the last decades has been reported in forests across the globe, it remains unclear whether it drives persistent biomass increases of the stands, particularly in mature forests. Enhanced tree growth and stand-level biomass are often linked with a simultaneous increase in density-driven mortality and a reduction in tree longevity. Identifying empirical evidence regarding the balance between these processes is challenging due to the confounding effects of stand history, management, and environmental changes. Here, we investigate the link between growth and biomass via the shift in the negative relationship between average tree size and stand density (tree number). We find increasing stand density for a given tree size in unmanaged closed-canopy forests in Switzerland over the past six decades and a positive relationship between growth and stand density - qualitatively consistent with simulations by a mechanistic, cohort-resolving ecosystem model (LM3-PPA). Model simulations show that, in the absence of other disturbances, enhanced growth persistently increases biomass stocks despite simultaneous decreases in carbon residence time and tree longevity, independent of assumptions about the drivers of tree mortality. However, the magnitude of simulated changes critically depends on the shape of the mortality parameterizations. Our analyses reconcile reports of growth-induced reductions of tree longevity with model predictions of persistent biomass increases, and with our finding of a trend towards denser forests in response to growth - also in mature stands.

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Calibration of the process-based model 3-PG for major central European tree species

et al. 2021

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Process-based forest models are important tools for predicting forest growth and their vulnerability to factors such as climate change or responses to management. One of the most widely used stand-level process-based models is the 3-PG model (Physiological Processes Predicting Growth), which is used for applications including estimating wood production, carbon budgets, water balance and susceptibility to climate change. Few 3-PG parameter sets are available for central European species and even fewer are appropriate for mixed-species forests. Here we estimated 3-PG parameters for twelve major central European tree species using 1418 long-term permanent forest monitoring plots from managed forests, 297 from un-managed forest reserves and 784 Swiss National Forest Inventory plots. A literature review of tree physiological characteristics, as well as regression analyses and Bayesian inference, were used to calculate the 3-PG parameters.The Swiss-wide calibration, based on monospecific plots, showed a robust performance in predicting forest stocks such as stem, foliage and root biomass. The plots used to inform the Bayesian calibration resulted in posterior ranges of the calibrated parameters that were, on average, 69% of the prior range. The bias of stem, foliage and root biomass predictions was generally less than 20%, and less than 10% for several species. The parameter sets also provided reliable predictions of biomass and mean tree sizes in mixed-species forests. Given that the information sources used to develop the parameters included a wide range of climatic, edaphic and management conditions and long time spans (from 1930 to present), these species parameters for 3-PG are likely to be appropriate for most central European forests and conditions.

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Self-thinning tree mortality models that account for vertical stand structure, species mixing and climate

Cited by 20 publications

References 89 publications

Process-oriented analysis of dominant sources of uncertainty in the land carbon sink

Process-oriented analysis of dominant sources of uncertainty in the land carbon sink

Tree growth enhancement drives a persistent biomass gain in unmanaged temperate forests

Calibration of the process-based model 3-PG for major central European tree species

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