Defoliation reduces growth but not carbon reserves in Mediterranean Pinus pinaster trees

Puri, Elena; Hoch, Günter; Körner, Christian

doi:10.1007/s00468-015-1199-y

Cited by 48 publications

(41 citation statements)

References 52 publications

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“…Decreased leaf area may be a risk factor reducing tree growth under drought and is also an indicator for mortality (Dobbertin & Brang, ; Eilmann et al ., ). The negative influence of defoliation on growth has been reported from several other natural and experimental studies (Galiano et al ., ; Piper et al ., ; Puri et al ., ) and is supported by the growth efficiency theory of Waring (). Here, we show that decreasing leaf area not only negatively affects growth, but also C storage.…”

Section: Discussionmentioning

confidence: 74%

Homeostatic levels of nonstructural carbohydrates after 13 yr of drought and irrigation inPinus sylvestris

et al. 2018

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Nonstructural carbohydrates (NSCs) are important for the growth and survival of trees. Drought may lead to a decrease in tree growth and to NSC depletion, whereas increased soil moisture in otherwise dry ecosystems may increase growth and NSC concentrations. A long-term (13 yr) irrigation experiment was conducted in a Pinus sylvestris-dominated forest located at the dry margin of the species in southern Switzerland. We measured the relative leaf area, growth, NSCs, needle δ C, [N] and [P] in trees on control and irrigated plots. Irrigation resulted in higher growth rates and carbon isotope discrimination, but did not alter NSC levels. Growth and NSC decreased with decreasing leaf area in both treatments, but NSC did not correlate with leaf-level gas exchange indices, such as foliar δ C, [N] or [P]. A legacy effect was shown, as trees with initially low leaf area had limited ability to respond to prolonged irrigation. The NSC constancy across treatments provides evidence that carbohydrate storage may stay constant when climate changes are sufficiently slow to allow acclimation. Moreover, we speculate that total leaf area, rather than leaf gas exchange per unit leaf area, drives the variation in whole-tree carbohydrate dynamics in this system.

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Section: Discussionmentioning

confidence: 74%

Homeostatic levels of nonstructural carbohydrates after 13 yr of drought and irrigation inPinus sylvestris

et al. 2018

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“…At the beginning of August, 11 wk after defoliation, starch concentrations were strongly decreased only in the evergreen Q. ilex , and not in the deciduous Q. petraea , probably because of the low C costs for leaf formation and the fast transition of new formed leaves from C sinks to sources in winter‐deciduous species (Keel & Schädel, ; Landhäusser, ). The observed reductions of starch with defoliation are consistent with other defoliation studies on different species (Li et al ., ; Palacio et al ., , ; Landhäusser & Lieffers, ; Puri et al ., ). However, during the second half of the season, defoliated saplings of both species showed a stronger increase in starch concentrations than undefoliated saplings at all three CO 2 concentrations.…”

Section: Discussionmentioning

confidence: 97%

“…Consequently, these findings suggest that the C shortage is only transient and of short duration (Palacio et al ., , ), and the observed severe and sustained growth reductions after defoliation are not attributable to a persistent C limitation, but to other factors such as a critical loss of nutrients other than C (e.g. nitrogen (N) or phosphorus (P); Millard et al ., ), or a down‐regulation of cambial activity as a direct consequence of the reduced water demand from leaves (Puri et al ., ). Further pieces of evidence might come from experiments that combine defoliation treatments with simultaneous changes of the trees’ C supply, for example via elevated or decreased atmospheric CO 2 treatments.…”

Section: Introductionmentioning

confidence: 97%

Growth reduction after defoliation is independent ofCO₂supply in deciduous and evergreen young oaks

2017

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Reduced productivity of trees after defoliation might be caused by limited carbon (C) availability. We investigated the combined effect of different atmospheric CO concentrations (160, 280 and 560 ppm) and early season defoliation on the growth and C reserves (nonstructural carbohydrates (NSC)) of saplings of two oak species with different leaf habits (deciduous Quercus petraea and evergreen Quercus ilex). In both species, higher CO supply significantly enhanced growth. Defoliation had a strong negative impact on growth (stronger for Q. ilex), but the relative reduction of growth caused by defoliation within each CO treatment was very similar across all three CO concentrations. Low CO and defoliation led to decreased NSC tissue concentrations mainly in the middle of the growing season in Q. ilex, but not in Q. petraea. However, also in Q. ilex, NSC increased in woody tissues in defoliated and low-CO saplings towards the end of the growing season. Although the saplings were C limited under these specific experimental conditions, growth reduction after defoliation was not directly caused by C limitation. Rather, growth of trees followed a strong allometric relationship between total leaf area and conductive woody tissue, which did not change across species, CO concentrations and defoliation treatments.

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“…Limiting plant C availability via defoliation or reductions of atmospheric [CO 2 ] may indicate allocation priorities and several recent studies have tracked how such limitations affect C reserves. For example, maintenance of NSC concentrations (used as measure of storage) during concomitant reductions of growth occurred even when the supply of new C had been constrained via defoliation (Wiley et al ., ; Puri et al ., ) or in trees strongly affected by drought (Klein, ). These studies are clever attempts to tackle C storage regulatory dynamics.…”

Section: Studies On the Use Of Nsc In Plant Functioning – Progress Tomentioning

confidence: 99%

Understanding the roles of nonstructural carbohydrates in forest trees – from what we can measure to what we want to know

2016

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Summary Carbohydrates provide the building blocks for plant structures as well as versatile resources for metabolic processes. The nonstructural carbohydrates (NSC), mainly sugars and starch, fulfil distinct functional roles, including transport, energy metabolism and osmoregulation, and provide substrates for the synthesis of defence compounds or exchange with symbionts involved in nutrient acquisition or defence. At the whole‐plant level, NSC storage buffers the asynchrony of supply and demand on diel, seasonal or decadal temporal scales and across plant organs. Despite its central role in plant function and in stand‐level carbon cycling, our understanding of storage dynamics, its controls and response to environmental stresses is very limited, even after a century of research. This reflects the fact that often storage is defined by what we can measure, that is, NSC concentrations, and the interpretation of these as a proxy for a single function, storage, rather than the outcome of a range of NSC source and sink functions. New isotopic tools allow direct quantification of timescales involved in NSC dynamics, and show that NSC‐C fixed years to decades previously is used to support tree functions. Here we review recent advances, with emphasis on the context of the interactions between NSC, drought and tree mortality.

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Defoliation reduces growth but not carbon reserves in Mediterranean Pinus pinaster trees

Abstract: Key message Reduced growth but high NSC after severe defoliation of evergreen trees can be explained by three, non-exclusive processes: critical loss of non-C reserves, hormonal changes, and prioritisation of C storage over growth.

Cited by 48 publications

References 52 publications

Homeostatic levels of nonstructural carbohydrates after 13 yr of drought and irrigation inPinus sylvestris

Homeostatic levels of nonstructural carbohydrates after 13 yr of drought and irrigation inPinus sylvestris

Growth reduction after defoliation is independent ofCO₂supply in deciduous and evergreen young oaks

Understanding the roles of nonstructural carbohydrates in forest trees – from what we can measure to what we want to know

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Defoliation reduces growth but not carbon reserves in Mediterranean Pinus pinaster trees

Abstract: Key message Reduced growth but high NSC after severe defoliation of evergreen trees can be explained by three, non-exclusive processes: critical loss of non-C reserves, hormonal changes, and prioritisation of C storage over growth.

Cited by 48 publications

References 52 publications

Homeostatic levels of nonstructural carbohydrates after 13 yr of drought and irrigation inPinus sylvestris

Homeostatic levels of nonstructural carbohydrates after 13 yr of drought and irrigation inPinus sylvestris

Growth reduction after defoliation is independent ofCO2supply in deciduous and evergreen young oaks

Understanding the roles of nonstructural carbohydrates in forest trees – from what we can measure to what we want to know

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Growth reduction after defoliation is independent ofCO₂supply in deciduous and evergreen young oaks