Dendrochronology of a fir wave

Standard analyses in dendrochronology were combined with estimates of wood production efficiency to clarify patterns of tree mortality in wave-regenerated fir forests (Abiesbalsamea (L.) Mill.). Results revealed important differences in radial growth and wood production per unit foliage area between dieback stands of young (37 years) and old (74 years) wave sites, indicating that wave mortality is not related to age nor restricted to trees of low vigor. Overstory trees in both young and old dieback areas are characterized by a high frequency of missing or partial rings in late years without significant change in wood production efficiency, suggesting that the primary cause for a decline at the wave edge is a mechanical loss of foliage rather than a decrease in photosynthetic efficiency. This is supported by a highly significant reduction (P = 0.005) in projected leaf area for dieback-zone trees. Tree-ring characteristics reported here are symptomatic of a carbon balance problem which may lead to tree death through a number of secondary causes.

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A synthesis of radial growth patterns preceding tree mortality

Global Change Biology ◽

10.1111/gcb.13535 ◽

2016 ◽

Vol 23 (4) ◽

pp. 1675-1690 ◽

Cited By ~ 179

Author(s):

Maxime Cailleret ◽

Steven Jansen ◽

Elisabeth M. R. Robert ◽

Lucía Desoto ◽

Tuomas Aakala ◽

...

Keyword(s):

Radial Growth ◽

Tree Mortality ◽

Growth Patterns

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Architectural differences in saplings of temperate versus tropical angiosperms; consequences of the deciduous habit?

Canadian Journal of Botany ◽

10.1139/b05-109 ◽

2005 ◽

Vol 83 (11) ◽

pp. 1391-1401 ◽

Cited By ~ 4

Author(s):

David A. King

Keyword(s):

High Frequency ◽

Plant Architecture ◽

Tropical Species ◽

Deciduous Species ◽

Evergreen Species ◽

Crown Shape ◽

Temperate Deciduous ◽

Lower Height ◽

Filtering Effect ◽

Overstory Trees

The architecture of saplings of temperate deciduous species of the southeastern United States was compared with that of tropical evergreen species of Central America, Borneo, and northeastern Australia. The deciduous species were more planar in the understory than were the tropical species, because of (i) more planar leaf displays within branches, (ii) a high frequency of arching, plagiotropic main stems (associated with greater plasticity in crown symmetry in relation to light), and (iii) a lower height of first branching. The deciduous species also had more planar branches than did subtropical and temperate evergreen angiosperms. This greater planarity in temperate deciduous understories may be associated with the simultaneous positioning of most leaves during a single flush in the spring. In contrast, saplings in tropical understories typically bear multiple leaf cohorts and position new leaves at the peripheries of existing leaf displays. These results and those of other studies suggest that there are adaptive links between plant architecture and phenology. Other factors, such as latitudinal variation in sun angles, may influence crown shape in overstory trees, but did not seem to be involved here, possibly because the filtering effect of the canopy results in smaller latitudinal shifts in understory illumination angles during the growing season. Thus, by favouring the deciduous habit, the cold winters and warm, humid summers of the eastern deciduous biome of North America appear to have had a notable influence on sapling architecture.

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Does forest growth acceleration lead to denser stands? Insights from Swiss forests and mechanistic modelling

10.5194/egusphere-egu21-8832 ◽

2021 ◽

Author(s):

Laura Marques ◽

Ensheng Weng ◽

Harald Bugmann ◽

David I. Forrester ◽

Martina Hobi ◽

...

Keyword(s):

Tree Growth ◽

Carbon Balance ◽

Tree Mortality ◽

Forest Growth ◽

Growth Enhancement ◽

Carbon Sinks ◽

Terrestrial Carbon ◽

Model Simulations ◽

Leaf Level ◽

Use Efficiency

Forest demographic processes - growth, recruitment and mortality - are being altered by global change. The changing balance between growth and mortality strongly influences forest dynamics and the carbon balance. Elevated atmospheric carbon dioxide (eCO2) has been reported to enhance photosynthesis and tree growth rates by increasing both light-use efficiency (LUE) and water-use efficiency (WUE). Tree growth enhancement could be translated into an increase in biomass stocks or could be associated with a reduction in the longevity of trees, thus reducing the ability of forest ecosystems to act as carbon sinks over long timescales. These links between growth and mortality, and the implications for forest stand density and self-thinning relationships are still debated. Scarce empirical evidence exists for how changing drivers affect tree mortality due to existing data and modelling limitations. Understanding the causes of observed mortality trends and the mechanisms underlying these processes is critical for accurate projections of global terrestrial carbon storage and its feedbacks to anthropogenic climate change.Here, we combine a mechanistic model with empirical forest data to better understand the causes of changes in tree mortality and the implications for past and future trends in forest tree density. Specifically, we test the Grow-Fast-Die-Young hypothesis to investigate if a leaf-level CO2 fertilization effect may lead to an increase in the biomass stock in forest stands. We use a novel vegetation demography model (LM3-PPA) which includes vegetation dynamics with biogeochemical processes allowing for explicit representation of individuals and a mechanistic treatment of tree mortality. The key links between leaf-level assimilation and stand dynamics depend on the carbon turnover time. In this sense, we investigate alternative mortality assumptions about the functional dependence of mortality on tree size, tree carbon balance or growth rate. These formulations represent typical approaches to simulate mortality in mechanistic forest models. Model simulations show that increasing photosynthetic LUE leads to higher biomass stocks, with contrasting behavior among mortality assumptions. Empirical data from Swiss forest inventories support the results from the model simulations showing a shift upwards in the self-thinning relationships, with denser stands and bigger trees. This data-supported mortality-modelling helps to identify links between forest responses and environmental changes at the leaf, tree and stand levels and yields new insight into the causes of currently observed terrestrial carbon sinks and future responses.

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Radial Growth Patterns Associated with Tree Mortality in Nothofagus pumilio Forest

Forests ◽

10.3390/f10060489 ◽

2019 ◽

Vol 10 (6) ◽

pp. 489 ◽

Cited By ~ 2

Author(s):

Milagros Rodríguez-Catón ◽

Ricardo Villalba ◽

Ana Srur ◽

A. Park Williams

Keyword(s):

Growth Rate ◽

Growth Rates ◽

Forest Dynamics ◽

Radial Growth ◽

Tree Mortality ◽

Growth Patterns ◽

Severe Drought ◽

Nothofagus Pumilio ◽

Total Size ◽

Growth Trends

Tree mortality is a key process in forest dynamics. Despite decades of effort to understand this process, many uncertainties remain. South American broadleaf species are particularly under-represented in global studies on mortality and forest dynamics. We sampled monospecific broadleaf Nothofagus pumilio forests in northern Patagonia to predict tree mortality based on stem growth. Live or dead conditions in N. pumilio trees can be predicted with high accuracy using growth rate as an explanatory variable in logistic models. In Paso Córdova (CO), Argentina, where the models were calibrated, the probability of death was a strong negative function of radial growth, particularly during the six years prior to death. In addition, negative growth trends during 30 to 45 years prior to death increased the accuracy of the models. The CO site was affected by an extreme drought during the summer 1978–1979, triggering negative trends in radial growth of many trees. Individuals showing below-average and persistent negative trends in radial growth are more likely to die than those showing high growth rates and positive growth trends in recent decades, indicating the key role of droughts in inducing mortality. The models calibrated at the CO site showed high verification skill by accurately predicting tree mortality at two independent sites 76 and 141 km away. Models based on relative growth rates showed the highest and most balanced accuracy for both live and dead individuals. Thus, the death of individuals across different N. pumilio sites was largely determined by the growth rate relative to the total size of the individuals. Our findings highlight episodic severe drought as a triggering mechanism for growth decline and eventual death for N. pumilio, similar to results found previously for several other species around the globe. In the coming decades, many forests globally will be exposed to more frequent and/or severe episodes of reduced warm-season soil moisture. Tree-ring studies such as this one can aid prediction of future changes in forest productivity, mortality, and composition.

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Effects of Spruce Budworm Outbreaks on the Productivity and Stability of Balsam Fir Forests

The Forestry Chronicle ◽

10.5558/tfc60273-5 ◽

1984 ◽

Vol 60 (5) ◽

pp. 273-279 ◽

Cited By ~ 96

Author(s):

David A. MacLean

Keyword(s):

Tree Mortality ◽

Choristoneura Fumiferana ◽

Spruce Budworm ◽

Balsam Fir ◽

Wood Production ◽

Ecological Stability ◽

Short Term ◽

Eastern Canada ◽

Feasible Method ◽

Human Usage

Effects of spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks on the productivity and stability of forests in eastern Canada are reviewed and discussed. Defoliation results in reduced growth of trees, widespread tree mortality, and loss of wood production, and thereby causes major forest management problems. At present, the only feasible method for limiting damage and losses from budworm outbreaks over large areas is to apply chemical or biological insecticides periodically to kill larvae and protect the forest from defoliation and tree mortality. Although budworm outbreaks definitely disrupt the wood-producing capacity of forests (or the short-term "stability of forests for human usage"), in terms of overall ecological stability, outbreaks apparently act as a cycling mechanism that allows advance fir-spruce regeneration to succeed the fir-spruce overstory.

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Local forest structure variability increases resilience to wildfire in dry western U.S. coniferous forests

10.32942/osf.io/k72ye ◽

2019 ◽

Cited By ~ 1

Author(s):

Michael J Koontz ◽

Malcolm P. North ◽

Chhaya M. Werner ◽

Stephen E. Fick ◽

Andrew M. Latimer

Keyword(s):

Sierra Nevada ◽

Forest Structure ◽

Tree Mortality ◽

Forest Ecosystems ◽

Fire Suppression ◽

Fire Severity ◽

Fire Behavior ◽

Dry Forest ◽

Structural Variability ◽

Overstory Trees

A “resilient” forest endures disturbance and is likely to persist. Resilience to wildfire may arise from feedback between fire behavior and forest structure in dry forest systems. Frequent fire creates fine-scale variability in forest structure, which may then interrupt fuel continuity and prevent future fires from killing overstory trees. Testing the generality and scale of this phenomenon is challenging for vast, long-lived forest ecosystems. We quantify forest structural variability and fire severity across >30 years and >1,000 wildfires in California’s Sierra Nevada. We find that greater variability in forest structure increases resilience by reducing rates of fire-induced tree mortality and that the scale of this effect is local, manifesting at the smallest spatial extent of forest structure tested (90 x 90m). Resilience of these forests is likely compromised by structural homogenization from a century of fire suppression, but could be restored with management that increases forest structural variability.

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Tree mortality and radial growth losses caused by the western spruce budworm in a Douglas-fir stand in British Columbia

Canadian Journal of Forest Research ◽

10.1139/x82-117 ◽

1982 ◽

Vol 12 (4) ◽

pp. 780-787 ◽

Cited By ~ 71

Author(s):

R. I. Alfaro ◽

G. A. Van Sickle ◽

A. J. Thomson ◽

E. Wegwitz

Keyword(s):

Radial Growth ◽

Tree Mortality ◽

Small Diameter ◽

Basal Area ◽

Spruce Budworm ◽

Douglas Fir ◽

Radial Increment ◽

Western Spruce Budworm ◽

Number Of Stems ◽

The Relationship

The effects of defoliation by western spruce budworm (Choristoneuraoccidentalis (Freeman)), on Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) radial growth at breast height and tree mortality are given. Four hundred and twenty trees were marked in an 81-year-old stand, and their defoliation levels were recorded annually from 1970 to 1980 in an outbreak that lasted from 1970 to 1974, inclusive. Forty-one trees were felled and dissected in 1977, 3 years after recovery began. The number of stems per hectare was reduced by 39.3% and basal area by 11.6% through mortality, most occurring among the small diameter, suppressed, and intermediate trees. Relationships were established between mortality and defoliation. Radial increments were examined, and the presence of four outbreaks during the life of the stand was detected. The combined effect of these infestations amounted to a loss of about 12% of the estimated potential diameter had not the insects been active. The most recent outbreak (1970–1974) caused a total of 10 years of subnormal growth, including 5 years due to defoliation and 5 years of recovery. The relationship between radial increment losses and defoliation intensity and duration is studied and quantified.

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