Tree demography dominates long‐term growth trends inferred from tree rings

Brienen, Roel; Gloor, Manuel; Ziv, Guy

doi:10.1111/gcb.13410

Cited by 57 publications

(62 citation statements)

References 36 publications

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“…Recovery from past disturbance may induce trends in biomass accumulation and tree growth that cannot be distinguished from those generated by external drivers (Brienen et al, 2016; but see: van der Sleen et al, 2016), like increasing temperatures and increasing atmospheric CO 2 levels (Chave et al, 2008). Our results show that long-term tropical forest dynamics are driven not only by small-scale disturbances resulting from single treefall gaps, but by a complex history of disturbance regimes varying in scale and intensity.…”

Section: Resultsmentioning

confidence: 99%

Tree Age Distributions Reveal Large-Scale Disturbance-Recovery Cycles in Three Tropical Forests

et al. 2017

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Over the past few decades there has been a growing realization that a large share of apparently ‘virgin’ or ‘old-growth’ tropical forests carries a legacy of past natural or anthropogenic disturbances that have a substantial effect on present-day forest composition, structure and dynamics. Yet, direct evidence of such disturbances is scarce and comparisons of disturbance dynamics across regions even more so. Here we present a tree-ring based reconstruction of disturbance histories from three tropical forest sites in Bolivia, Cameroon, and Thailand. We studied temporal patterns in tree regeneration of shade-intolerant tree species, because establishment of these trees is indicative for canopy disturbance. In three large areas (140–300 ha), stem disks and increment cores were collected for a total of 1154 trees (>5 cm diameter) from 12 tree species to estimate the age of every tree. Using these age estimates we produced population age distributions, which were analyzed for evidence of past disturbance. Our approach allowed us to reconstruct patterns of tree establishment over a period of around 250 years. In Bolivia, we found continuous regeneration rates of three species and a peaked age distribution of a long-lived pioneer species. In both Cameroon and Thailand we found irregular age distributions, indicating strongly reduced regeneration rates over a period of 10–60 years. Past fires, windthrow events or anthropogenic disturbances all provide plausible explanations for the reported variation in tree age across the three sites. Our results support the recent idea that the long-term dynamics of tropical forests are impacted by large-scale disturbance-recovery cycles, similar to those driving temperate forest dynamics.

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Section: Resultsmentioning

confidence: 99%

Tree Age Distributions Reveal Large-Scale Disturbance-Recovery Cycles in Three Tropical Forests

et al. 2017

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“…In the models, the positive trends were to a large extent attributable to the increasing tree size, which is well known to be a major determinant for tree growth rates (MacFarlane & Kobe, ; Lapointe‐Garant et al., ). However, attributing these types of changes in growth trends to specific drivers with statistical modelling is notoriously difficult (Brienen, Gloor, & Ziv, ). They are confounded with covarying effects of other trend‐like changes in the 20th century, such as the fertilization effects from the globally increasing CO 2 concentration, and spring warming, earlier snowmelt and N deposition that have been shown have occurred in the current study area or in the larger region (Hari et al., ; Irannezhad, Ronkanen, Kiani, Chen, & Kløve, ; Palviainen et al., ).…”

Section: Discussionmentioning

confidence: 99%

The roles of competition and climate in tree growth variation in northern boreal old‐growth forests

Aakala

Berninger

Starr

2018

J Vegetation Science

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Questions How have tree growth and growth trends varied in structurally complex old‐growth forests? What determines this variation and how this differs among species? Location Natural boreal old‐growth forests, northern Finland. Methods We sampled trees over 10‐cm diameter on 48 randomly located 0.1‐ha plots in three landscapes and compiled a data set of 1,565 trees including all three main species, and a full range of sizes and competitive states in northern boreal old‐growth forests. We extracted tree ring samples from every tree and used ring widths to reconstruct tree sizes and their neighbourhood for the past 50 years for Pinus sylvestris and Picea abies, and 30 years for Betula pubescens. We used mixed‐effects models to study variation in tree growth. In the models, we used annually varying environmental variables, forest and tree structural variables and site variables as predictors. We also measured soil hydraulic properties for a water balance model to specifically include soil moisture deficits as predictors. Results Tree growth rates had increased during the analysis period for all three species, with the highest increases for P. sylvestris and B. pubescens. All three species grew well during warm summers, but P. sylvestris and P. abies growth was also negatively influenced by soil moisture deficits. Competition in these sparse forests had a small influence on growth. However, its influence increased over time. Conclusions The trees showed positive growth trends, but the increasing competition means that such strong positive trends are unlikely to continue over the long term. For year‐to‐year variability, negative influence of droughts implied that increasing temperatures are not only beneficial to tree growth even in these high‐latitude forests. Overall, the findings demonstrate the site‐ and species‐dependent complexity in tree responses to environmental and structural changes we may expect in the future.

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“…Brienen et al 2010;Vlam et al 2017) and potentially to monitor forest responses to climate change (e.g. van der Sleen et al 2015;Zuidema et al 2012, but also see Brienen et al 2016a). With such important applications, it is vital to understand what drives ring formation and thus how growth dynamics might vary between sites, even within a single species.…”

Section: Introductionmentioning

confidence: 99%

Does Cedrela always form annual rings? Testing ring periodicity across South America using radiocarbon dating

Baker

Santos

Gloor

et al. 2017

Trees

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Key Message Radiocarbon dating shows that Cedrela trees from Bolivia, Ecuador and Venezuela form one ring per year but Cedrela trees from Suriname form two rings per year. Abstract Tropical tree rings have the potential to yield valuable ecological and climate information, on the condition that rings are annual and accurately dated. It is important to understand the factors controlling ring formation, since regional variation in these factors could cause trees in different regions to form tree rings at different times. Here, we use 'bomb-peak' radiocarbon ( 14 C) dating to test the periodicity of ring formation in Cedrela trees from four sites across tropical South America. We show that trees from Bolivia, Ecuador and Venezuela have reliably annual tree rings, while trees from Suriname regularly form two rings per year. This proves that while tree rings of a particular species may be demonstrably annual at one site, this does not imply that rings are formed annually in other locations. We explore possible drivers of variation in ring periodicity and find that Cedrela growth rhythms are most likely caused by precipitation seasonality, with a possible degree of genetic control. Therefore, tree-ring studies undertaken at new locations in the tropics require independent validation of the annual nature of tree rings, irrespective of how the studied species behaves in other locations.

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Tree demography dominates long‐term growth trends inferred from tree rings

Cited by 57 publications

References 36 publications

Tree Age Distributions Reveal Large-Scale Disturbance-Recovery Cycles in Three Tropical Forests

Tree Age Distributions Reveal Large-Scale Disturbance-Recovery Cycles in Three Tropical Forests

The roles of competition and climate in tree growth variation in northern boreal old‐growth forests

Does Cedrela always form annual rings? Testing ring periodicity across South America using radiocarbon dating

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