Detecting trends in tree growth: not so simple

Bowman, David M. J. S.; Brienen, Roel J. W.; Gloor, Emanuel; Phillips, Oliver L.; Prior, Lynda D.

doi:10.1016/j.tplants.2012.08.005

Cited by 257 publications

(239 citation statements)

References 48 publications

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“…Ontogenetic factors strongly influence tree growth and may lead to wrong conclusions if not treated appropriately (Bowman et al, 2013). When the BAI data was modeled accounting for the influence of tree age on growth, we found that declining individuals show important legacy effects of drought on growth represented by a negative growth trend after the drought period ( Figure 5C).…”

Section: Long-term Effects Of Drought On Growth: Legacy Effectsmentioning

confidence: 93%

Forest Growth Responses to Drought at Short- and Long-Term Scales in Spain: Squeezing the Stress Memory from Tree Rings

et al. 2018

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Drought-triggered declines in forest productivity and associated die-off events have increased considerably due to climate warming in the last decades. There is an increasing interest in quantifying the resilience capacity of forests against climate warming and drought to uncover how different stands and tree species will resist and recover after more frequent and intense droughts. Trees form annual growth rings that represent an accurate record of how forest growth responded to past droughts. Here we use dendrochronology to quantify the radial growth of different forests subjected to contrasting climatic conditions in Spain during the last half century. Particularly, we considered four climatically contrasting areas where dominant forests showed clear signs of drought-induced dieback. Studied forests included wet sites dominated by silver fir (Abies alba) in the Pyrenees and beech (Fagus sylvatica) stands in northern Spain, and drought-prone sites dominated by Scots pine (Pinus sylvestris) in eastern Spain and black pine (Pinus nigra) in the semi-arid south-eastern Spain. We quantified the growth reduction caused by different droughts and assessed the short-and long-term resilience capacity of declining vs. non-declining trees in each forest. In all cases, drought induced a marked growth reduction regardless tree vigor. However, the capacity to recover after drought (resilience) at short-and long-term scales varied greatly between declining and non-declining individuals. In the case of beech and silver fir, non-declining individuals presented greater growth rates and capacity to recover after drought than declining individuals. For Scots pine, the resilience to drought was found to be lower in recent years regardless the tree vigor, but the growth reduction caused by successive droughts was more pronounced in declining than in non-declining individuals. In the black pine forest an extreme drought induced a marked growth reduction in declining individuals when accounting for age effects on growth rates. We demonstrate the potential of tree-ring data to record short-and long-term impacts of drought on forest growth and to quantify the resilience capacity of trees.

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Section: Long-term Effects Of Drought On Growth: Legacy Effectsmentioning

confidence: 93%

Forest Growth Responses to Drought at Short- and Long-Term Scales in Spain: Squeezing the Stress Memory from Tree Rings

et al. 2018

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“…Structural reconstruction requires an assumption that tree size is generally related to tree age, and size-class structure and disturbance severity are linked' . However, determining the strength of an age-size relationship in a tree species would require site-specific empirical data (Bowman et al, 2013), and complex natural regeneration dynamics confound simplified interpretations of past regeneration events.The assumption that tree diameter distributions can be used to reliably reconstruct past fire regimes at patch to landscape scales bs_bs_banner Global Ecology and Biogeography, (Global Ecol. Biogeogr.)…”

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confidence: 99%

Unsupported inferences of high‐severity fire in historical dry forests of the western United States: response to Williams and Baker

Fulé

Swetnam

Brown

et al. 2013

Global Ecology and Biogeography

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Reconstructions of dry western US forests in the late 19th century in Arizona, Colorado and Oregon based on General Land Office records were used by Williams & Baker (2012; Global Ecology and Biogeography, 21, 1042-1052; hereafter W&B) to infer past fire regimes with substantial moderate and high-severity burning. The authors concluded that present-day large, high-severity fires are not distinguishable from historical patterns. We present evidence of important errors in their study. First, the use of tree size distributions to reconstruct past fire severity and extent is not supported by empirical age-size relationships nor by studies that directly quantified disturbance history in these forests. Second, the fire severity classification of W&B is qualitatively different from most modern classification schemes, and is based on different types of data, leading to an inappropriate comparison. Third, we note that while W&B asserted 'surprising' heterogeneity in their reconstructions of stand density and species composition, their data are not substantially different from many previous studies which reached very different conclusions about subsequent forest and fire behaviour changes. Contrary to the conclusions of W&B, the preponderance of scientific evidence indicates that conservation of dry forest ecosystems in the western United States and their ecological, social and economic value is not consistent with a present-day disturbance regime of large, high-severity fires, especially under changing climate. KeywordsFire regime, fire severity, General Land Office survey, historical range of variability, ponderosa pine, wildfire. INTRODUCTIONA recent study in Global Ecology and Biogeography (Williams & Baker, 2012, hereafter W&B) applied historical data from General Land Office (GLO) surveys c. 1880 to reconstruct historical dry forests on four large landscapes in Arizona, Colorado and Oregon (USA). W&B described forest composition as characterized by 'abundant ponderosa pine (Pinus ponderosa C. Lawson), with lesser amounts of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), white fir (Abies concolor (Gord. & Glend.) Lindl. ex Hildebr.), grand fir (Abies grandis (Douglas ex D. Don) Lindl.), juniper (Juniperus L.), western larch (Larix occidentalis Nutt.) and lodgepole pine (Pinus contorta Douglas ex Louden)' . W&B infer that the presence of a certain proportion of trees below a site-specific diameter threshold is evidence of 'higher'-severity fire, a term they use to indicate a combination of 'mixed-plus high-severity fire' . They then compare the proportion of plots with evidence of 'higher'-severity fire to the distribution of fire severities estimated from satellite imagery of recent large wildfires in the western United States, concluding that modern fires are within the historical range of variability (HRV) of fire severity. They also found it 'surprising' that dry forests 'commonly thought to have been open and parklike' were heterogeneous and relatively dense. W&B conclude that current management pr...

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“…This is because of an initial very rapid decline in RGRs with increasing tree size, which is caused by accumulation of non-photosynthetic material such as stems, branches, and roots (Bowman et al 2013). Trees that suffered reduction in crown diameter (hereafter crown shrinkage) from 1984 to 2008 were analyzed separately from those that exhibited growth.…”

Section: Discussionmentioning

confidence: 99%

Conifer demography in forest–grassland mosaics: a landscape-scale study over a 24-year period

Souza

2017

Botany

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Survivorship was higher in forest patches than in grasslands, where it showed densitydependence. In forest patches, survivorship was positively related to both patch area and distance from forest edge. Crown breakage was more common in the grassland than in forest patches. In forest patches, it was positively related to crown size, number of conspecific neighbours, and patch area. Adult Araucaria seem to benefit from angiosperm-dominated neighbourhoods relative to isolation in grasslands. Densitydependent effects, known to be widespread among seeds and seedlings, were shown to be important to adult trees as well.

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Detecting trends in tree growth: not so simple

Cited by 257 publications

References 48 publications

Forest Growth Responses to Drought at Short- and Long-Term Scales in Spain: Squeezing the Stress Memory from Tree Rings

Forest Growth Responses to Drought at Short- and Long-Term Scales in Spain: Squeezing the Stress Memory from Tree Rings

Unsupported inferences of high‐severity fire in historical dry forests of the western United States: response to Williams and Baker

Conifer demography in forest–grassland mosaics: a landscape-scale study over a 24-year period

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