The paradox of defoliation: Declining tree water status with increasing soil water content

Balducci, Lorena; Fierravanti, Angelo; Rossi, Sergio; Delzon, Sylvain; Grandpré, Louis De; Kneeshaw, Daniel; Deslauriers, Annie

doi:10.1016/j.agrformet.2020.108025

Cited by 19 publications

(10 citation statements)

References 92 publications

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“…However, under different stress conditions such as defoliation, needles damage or loss after larval feeding had a minimal or no effect on water loss (Quentin et al, 2011;Bouzidi et al, 2019). An increased leaf water content and reduced evapotranspiration (Balducci et al, 2020) are required to counteract the reduction of turgor pressure due to needle removal. Therefore, in the case of defoliation, increased water uptake and stem growth could take place until carbon remobilization from plants parts could act also as a safety buffer for stem growth in the first years of consecutive defoliation.…”

Section: Discussion Defoliation Effects On Stem Radius Variationmentioning

confidence: 99%

“…Before 2016, when SBW was not observed in our site, the duration of xylogenesis (irreversible radial growth) and number of enlarging cells were also similar between the species (Chen et al, 2019), suggesting that water availability in wood tissues and turgor pressure process (cell expansion) were adequate. However, when defoliation started, balsam fir showed a smaller hydraulic safety margin compared to black spruce (Balducci et al, 2020). This suggests that these species have different behavior of daily radial variation over time to sustain growth waterdriven process.…”

Section: Species Contrasting Response To Defoliationmentioning

confidence: 97%

“…However, during and after severe defoliation of apical shoots, a higher transpiration demand is generally combined with a decrease in midday water potential (Eyles et al, 2013;Salmon et al, 2015). Yet the reduction of leaf area due to defoliation, even if it constrains transpiration, was not enough to significantly reduce the relative water content (RWC) (Balducci et al, 2020). Previous works support the idea that RWC reflects the balance between leaf tissue water supply and transpiration rate (Meinzer et al, 2003(Meinzer et al, , 2014.…”

Section: Modulation Of Diurnal Contraction and Expansion Fluctuationsmentioning

confidence: 99%

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Variation of Stem Radius in Response to Defoliation in Boreal Conifers

Balducci

Rozenberg

Deslauriers

2021

Front. For. Glob. Change

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In the long term, defoliation strongly decreases tree growth and survival. Insect outbreaks are a typical cause of severe defoliation. Eastern spruce budworm (Choristoneura fumiferana Clem.) outbreaks are one of the most significant disturbances of Picea and Abies boreal forests. Nevertheless, in boreal conifers, a 2-year defoliation has been shown to quickly improve tree water status, protect the foliage and decrease growth loss. It suggests that defoliation effects are time-dependent and could switch from favorable in the short term to unfavorable when defoliation duration exceeds 5–10 years. A better understanding of the effect of defoliation on stem radius variation during the needle flushing time-window could help to elucidate the relationships between water use and tree growth during an outbreak in the medium term. This study aims to assess the effects of eastern spruce budworm (Choristoneura fumiferana Clem.) defoliation and bud phenology on stem radius variation in black spruce [Picea mariana (Mill.) B.S.P.] and balsam fir [Abies balsamea (L.) Mill.] in a natural stand in Quebec, Canada. We monitored host and insect phenology, new shoot defoliation, seasonal stem radius variation and daytime radius phases (contraction and expansion) from 2016 to 2019. We found that defoliation significantly increased stem growth at the beginning of needle flushing. Needles flushing influenced the amplitude and duration of daily stem expansion and contraction, except the amplitude of stem contraction. Over the whole growing season, defoliation increased the duration of stem contraction, which in turn decreased the duration of stem expansion. However, the change (increase/decrease) of the duration of contraction/expansion reflects a reduced ability of the potential recovery from defoliation. Black spruce showed significantly larger 24-h cycles of stem amplitude compared to balsam fir. However, both species showed similar physiological adjustments during mild stress, preventing water loss from stem storage zones to support the remaining needles’ transpiration. Finally, conifers react to defoliation during a 4-year period, modulating stem radius variation phases according to the severity of the defoliation.

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Section: Discussion Defoliation Effects On Stem Radius Variationmentioning

confidence: 99%

Section: Species Contrasting Response To Defoliationmentioning

confidence: 97%

Section: Modulation Of Diurnal Contraction and Expansion Fluctuationsmentioning

confidence: 99%

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Variation of Stem Radius in Response to Defoliation in Boreal Conifers

Balducci

Rozenberg

Deslauriers

2021

Front. For. Glob. Change

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“…According to these observations, the risks of reduction in tree growth due to combined drought and pest defoliation might be minimal during relatively short term and mild droughts. Conversely, considerable damage due to insect defoliation in areas, where relatively longer and more intense droughts are predicted cannot be ruled out (Balducci et al, 2020).…”

Section: The Effect Of Combined Biotic and Abiotic Stresses On The Grmentioning

confidence: 99%

The Threat of the Combined Effect of Biotic and Abiotic Stress Factors in Forestry Under a Changing Climate

2020

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Plants encounter several biotic and abiotic stresses, usually in combination. This results in major economic losses in agriculture and forestry every year. Climate change aggravates the adverse effects of combined stresses and increases such losses. Trees suffer even more from the recurrence of biotic and abiotic stress combinations owing to their long lifecycle. Despite the effort to study the damage from individual stress factors, less attention has been given to the effect of the complex interactions between multiple biotic and abiotic stresses. In this review, we assess the importance, impact, and mitigation strategies of climate change driven interactions between biotic and abiotic stresses in forestry. The ecological and economic importance of biotic and abiotic stresses under different combinations is highlighted by their contribution to the decline of the global forest area through their direct and indirect roles in forest loss and to the decline of biodiversity resulting from local extinction of endangered species of trees, emission of biogenic volatile organic compounds, and reduction in the productivity and quality of forest products and services. The abiotic stress factors such as high temperature and drought increase forest disease and insect pest outbreaks, decrease the growth of trees, and cause tree mortality. Reports of massive tree mortality events caused by “hotter droughts” are increasing all over the world, affecting several genera of trees including some of the most important genera in plantation forests, such as Pine, Poplar, and Eucalyptus. While the biotic stress factors such as insect pests, pathogens, and parasitic plants have been reported to be associated with many of these mortality events, a considerable number of the reports have not taken into account the contribution of such biotic factors. The available mitigation strategies also tend to undermine the interactive effect under combined stresses. Thus, this discussion centers on mitigation strategies based on research and innovation, which build on models previously used to curb individual stresses.

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“…A recent study by Itter et al [ 131 ] of two outbreaking defoliators found that both drought and defoliators have immediate and lagged effects on tree growth but that there was no interaction between drought and defoliation. To illustrate the complexity of the relationships, one study on tree mortality suggested that climate stress occurring before an outbreak may have been a contributing factor to insect-caused mortality of trees [ 132 ], whereas another study showed that insect defoliation, by reducing photosynthetic and transpiring surfaces, may protect trees from drought [ 133 ]. The temporal sequence of events and the measurement of effect (growth loss and/or mortality) are thus factors that need to be considered.…”

Section: Global Change As a Driver Of Increased Insect Outbreaksmentioning

confidence: 99%

The Vision of Managing for Pest-Resistant Landscapes: Realistic or Utopic?

et al. 2021

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Purpose of Review Forest managers have long suggested that forests can be made more resilient to insect pests by reducing the abundance of hosts, yet this has rarely been done. The goal of our paper is to review whether recent scientific evidence supports forest manipulation to decrease vulnerability. To achieve this goal, we first ask if outbreaks of forest insect pests have been more severe in recent decades. Next, we assess the relative importance of climate change and forest management–induced changes in forest composition/structure in driving these changes in severity. Recent Findings Forest structure and composition continue to be implicated in pest outbreak severity. Mechanisms, however, remain elusive. Recent research elucidates how forest compositional and structural diversity at neighbourhood, stand, and landscape scales can increase forest resistance to outbreaks. Many recent outbreaks of herbivorous forest insects have been unprecedented in terms of duration and spatial extent. Climate change may be a contributing factor, but forest structure and composition have been clearly identified as contributing to these unprecedented outbreaks. Summary Current research supports using silviculture to create pest-resistant forest landscapes. However, the precise mechanisms by which silviculture can increase resistance remains uncertain. Further, humans tend to more often create pest-prone forests due to political, economic, and human resistance to change and a short-sighted risk management perspective that focuses on reactive rather than proactive responses to insect outbreak threats. Future research efforts need to focus on social, political, cultural, and educational mechanisms to motivate implementation of proven ecological solutions if pest-resistant forests are to be favoured by management.

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The paradox of defoliation: Declining tree water status with increasing soil water content

Cited by 19 publications

References 92 publications

Variation of Stem Radius in Response to Defoliation in Boreal Conifers

Variation of Stem Radius in Response to Defoliation in Boreal Conifers

The Threat of the Combined Effect of Biotic and Abiotic Stress Factors in Forestry Under a Changing Climate

The Vision of Managing for Pest-Resistant Landscapes: Realistic or Utopic?

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