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Two simplifying hypotheses have been proposed for whole‐plant respiration. One links respiration to photosynthesis; the other to biomass. Using a first‐principles carbon balance model with a prescribed live woody biomass turnover, applied at a forest research site where multidecadal measurements are available for comparison, we show that if turnover is fast the accumulation of respiring biomass is low and respiration depends primarily on photosynthesis; while if turnover is slow the accumulation of respiring biomass is high and respiration depends primarily on biomass. But the first scenario is inconsistent with evidence for substantial carryover of fixed carbon between years, while the second implies far too great an increase in respiration during stand development – leading to depleted carbohydrate reserves and an unrealistically high mortality risk. These two mutually incompatible hypotheses are thus both incorrect. Respiration is not linearly related either to photosynthesis or to biomass, but it is more strongly controlled by recent photosynthates (and reserve availability) than by total biomass.
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... An increase in total stemwood NSCs from November to March has been previously observed in other temperate forests, being attributed to remobilization of sugars from storage compartments in coarse roots in advance of the C demands associated with springtime growth (Hoch et al. 2003 Thus, the spring programmed activation of starch synthesis in wood can occur even when C resources are very limited by the absence of a photosynthesizing crown. This strongly supports the debated hypothesis of an active control of the accumulation and buffering role of NSCs in wood (Sala et al. 2012, Collalti, Tjoelker, et al. 2020). ...
... The absence of a strong depletion of NSCs at the end of two sequential years characterised by extreme weather events that strongly reduced C supply and increased C demand for sustaining stress-recovery (frost) and stress-tolerance (drought) processes further support the hypothesis that C reserves in plants can be actively managed by trees. In this view, wood NSC synthesis, cleavage, interconversion, mobilisation, and allocation are likely tightly controlled at the physiological, biochemical and molecular level to optimize long-term growth and survival (Sala et al. 2012, Collalti et al. 2018, Merganičová et al. 2019, Collalti, Tjoelker, et al. 2020). ...
... The warm drought of 2017 had a strong effect on NSC dynamics and led to starch hydrolysis and accumulation of soluble sugars in woody tissue. As drought induces a partial stomatal closure that reduces C uptake, trees depend more on NSC storage to sustain metabolic activities, defence mechanisms against pathogens, and osmoregulation processes(McDowell 2011, Hartmann and Trumbore 2016, Collalti, Tjoelker, et al. 2020. The observed increase of wood soluble sugar concentration during July-August 2017 agrees with the key role of these non-structural compounds as solutes for osmoregulation(Chaves et al. 2003). ...
Article
Extreme weather events are increasing in frequency and intensity due to global climate change. We hypothesized that tree carbon reserves are crucial for resilience of beech, buffering the source-sink imbalance due to late frosts and summer droughts, and that different components of non-structural carbohydrates (NSCs) play specific roles in coping with stressful situations. To assess the compound effects on mature trees of two extreme weather events, first a late frost in spring 2016 and then a drought in summer 2017, we monitored the phenology, radial growth and the dynamics of starch and soluble sugars in a Mediterranean beech forest. A growth reduction of 85% was observed after the spring late frost, yet not after the drought event. We observed a strong impact of late frost on starch, which also affected its dynamic at the beginning of the subsequent vegetative season. In 2017, the increase of soluble sugars, associated with starch hydrolysis, played a crucial role in coping with the severe summer drought. NSCs helped to counteract the negative effects of both events, supporting plant survival and buffering source-sink imbalances under stressful conditions. Our findings indicate a strong trade-off between growth and NSC storage in trees. Overall, our results highlight the key role of NSCs on beech trees response to extreme weather events, confirming the resilience of this species to highly stressful events. These insights are useful for assessing how forests may respond to the potential impacts of climate change on ecosystem processes in the Mediterranean area.
... R m is computed, for each functional-structural tree C pool (i.e. live wood, leaves and fine roots), using a temperature-acclimated Q 10 relationship (for details on thermal acclimation see Tjoelker et al., 2001;Atkin and Tjoelker, 2003;Smith and Dukes, 2012;Collalti et al., 2018) and a N-based maintenance respiration (m R ) rate for living tissues of 0.218 g C g N -1 day -1 (Ryan et al., 1991;Amthor and Baldocchi, 2001;Oleson et al., 2013;Drake and Tjoelker, 2016, Collalti et al., 2016, 2020a. R g is considered a fixed fraction (i.e. ...
... Allocation of NPP among tree C pools is performed daily, with preference to a non-structural carbon pool (NSC, i. e. storage in starch and sugars), which is used directly to fuel R m , up to a minimum NSC threshold level. The minimum NSC-threshold level is a fraction (a model parameter) of the live wood C-content (Collalti et al., 2020a). Once (and if) the minimum NSC threshold is reached, C is allocated preferentially for biomass growth for the different tree structural C-pools depending on the phenological phase as formerly described in Collalti et al. (2016). ...
... The only phenological phase during which NSC has no priority in allocation is during bud break (D'Andrea et al., 2020(D'Andrea et al., , 2021, when recent GPP is completely allocated for growth of leaves up to a maximum annual leaf area index (LAI, m 2 m -2 ), which is computed at the beginning of each year of simulation through the pipe-model (Shinozaki et al., 1964;Mäkelä, 1997), and growth of fine roots. This NSC allocation scheme reflects a quasi-active role of NSC, with NSC usually having priority over growth of new structural tissues, as described by Sala (2011), Merganičová et al. (2019 and Collalti et al. (2020a). This implies that any asynchrony between C-demand (i.e. ...
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Forest management practices might act as nature-based methods to remove CO2 from the atmosphere and slow anthropogenic climate change and thus support an EU forest-based climate change mitigation strategy. However, the extent to which diversified management actions could lead to quantitatively important changes in carbon sequestration and stocking capacity at the tree level remains to be thoroughly assessed. To that end, we used a state-of-the-science bio-geochemically based forest growth model to simulate effects of multiple forest management scenarios on net primary productivity (NPP) and potential carbon woody stocks (pCWS) under twenty scenarios of climate change in a suite of observed and virtual forest stands in temperate and boreal European forests. Previous modelling experiments indicated that the capacity of forests to assimilate and store atmospheric CO2 in woody biomass is already being attained under business-as-usual forest management practices across a range of climate change scenarios. Nevertheless, we find that on the long-term, with increasing atmospheric CO2 concentration and warming, managed forests show both higher productivity capacity and a larger potential pool size of stored carbon than unmanaged forests as long as thinning and tree harvesting are of moderate intensity.
... In addition, current leaf respiration models generally do not take into account changes in the vertical gradient of light availability within the forest, which is known to greatly influence plant metabolism (Weerasinghe et al., 2014;Heskel and Tang, 2018). Respiratory rates have also been associated with morphological and nutrient variation of leaves, such as leaf mass per area (LMA), nitrogen, and phosphorus concentration (Meir et al., 2001;Atkin et al., 2015;Crous et al., 2017;Rowland et al., 2017), and can be regulated by the availability of respiratory substrates, such as non-structural carbohydrates including soluble sugars and starch (Collalti et al., 2019). ...
... The degree of light suppression was higher for species in the understory and lower for species in the canopy (Figures 3F, 4B). Respiratory activity throughout the day is regulated, in part, by the demand for energy and the production of respiratory substrates during photosynthesis (Lambers et al., 2008;Tcherkez and Ghashghaie, 2017;Collalti et al., 2019). In this study, we found that the degree of light suppression of leaf respiration is lower in species that have higher dark respiration and an overall greater metabolic activity. ...
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Leaf respiration in the dark (Rdark) and light (Rday) is poorly characterized in diverse tropical ecosystems, and little to no information exists on the degree of light suppression in common tree species within the Amazon basin, and their dependences upon plant functional traits and position within the canopy. We quantified Rdark and apparent Rday using the Kok method and measured key leaf traits in 26 tree individuals of different species distributed in three different canopy positions: canopy, lower canopy, and understory. To explore the relationships between the leaf traits we used the standardized major axis (SMA). We found that canopy trees had significantly higher rates of Rdark and Rday than trees in the understory. The difference between Rdark and Rday (the light suppression of respiration) was greatest in the understory (68 ± 9%, 95% CI) and lower canopy (49 ± 9%, 95% CI) when compared to the canopy (37 ± 10%, 95% CI). We also found that Rday was significantly and strongly correlated with Rdark (p < 0.001) for all the canopy positions. Also, leaf mass per area (LMA) and leaf Phosphorus concentration (P) had a significant relationship with Rdark (p < 0.001; p = 0.003), respectively. In addition, a significant relationship was found for LMA in the canopy and lower canopy positions (p = 0.009; p = 0.048) while P was only significant in the canopy (p = 0.044). Finally, no significant relationship was found between Rdark and nitrogen, sugars, and starch. Our results highlight the importance of including representation of the light suppression of leaf respiration in terrestrial biosphere models and also of accounting for vertical gradients within forest canopies and connections with functional traits.
... Furthermore, the model allows the simulation of different management scenarios by defining the intensity and the interval of removals, as well as the length of rotation periods and artificial replanting schemes, which can be varied through the simulation time. For a full description of key model principles and theoretical framework see also Collalti et al. (2014Collalti et al. ( , 2016Collalti et al. ( , 2018Collalti et al. ( , 2019Collalti et al. ( , 2020a, Dalmonech et al. (2022), Engel et al. (2021), and Marconi et al. (2017). ...
... Indeed, the simulation included a thinning of 25 % of stand BA that took place in 1993, which was reflected by the reduction in tree density in that year and a slight increase in the growth rate of mean stand DBH in the following years (0.6 cm y −1 after the thinning vs. 0.3 cm y −1 before the thinning). Furthermore, the model was able to reproduce the mean seasonal cycle of daily GPP as obtained by the eddy covariance tower with sufficient accuracy, supporting previous assessments of model performance (Collalti et al., , 2018(Collalti et al., , 2020aDalmonech et al., 2022;Engel et al., 2021;Mahnken et al., 2022;Marconi et al., 2017). The R 2 of 0.69 is in line with previous evaluations of simulated daily GPP across northern European forest sites (average R 2 across three sites = 0.73; Collalti et al., 2018), while the ME of 0.61 is within the range found for daily GPP simulated with other process-based models (0.42-0.84 in Bagnara et al., 2015;0.61-0.98 in Minunno et al., 2016). ...
Article
Mediterranean pine plantations provide several ecosystem services but are vulnerable to climate change. Forest management might play a strategic role in the adaptation of Mediterranean forests, but the joint effect of climate change and diverse management options have seldom been investigated together. Here, we simulated the development of a Laricio pine (Pinus nigra subsp. laricio) stand in the Bonis watershed (southern Italy) from its establishment in 1958 up to 2095 using a state-of-the-science process-based forest model. The model was run under three climate scenarios corresponding to increasing levels of atmospheric CO2 concentration and warming, and six management options with different goals, including wood production and renaturalization. We analysed the effect of climate change on annual carbon fluxes (i.e., gross and net primary production) and stocks (i.e., basal area, standing and harvested carbon woody stocks) of the autotrophic compartment, as well as the impact of different management options compared to a no management baseline. Results show that higher temperatures (+3 to +5°C) and lower precipitation (−20 % to −22 %) will trigger a decrease in net primary productivity in the second half of the century. Compared to no management, the other options had a moderate effect on carbon fluxes over the whole simulation (between −14 % and +11 %). While standing woody biomass was reduced by thinning interventions and the shelterwood system (between −5 % and −41 %), overall carbon stocks including the harvested wood were maximized (between +41 % and +56 %). Results highlight that management exerts greater effects on the carbon budget of Laricio pine plantations than climate change alone, and that climate change and management are largely independent (i.e., no strong interaction effects). Therefore, appropriate sil-vicultural strategies might enhance potential carbon stocks and improve forest conditions, with cascading positive effects on the provision of ecosystem services in Mediterranean pine plantations.
... Plant size is one of the most important factors that explain the relationship between carbon supply and demand at the whole-plant to ecosystem scales (Collalti et al. 2019;O'Leary et al. 2019). The respiration rate of terrestrial plants scales with plant body mass, and the scaling relationship is generally modelled by a simple power function on log-log coordinates. ...
... The scaling of respiration of individual shoots and each organ will provide fundamental clues for comparing carbon dynamics and the development of shoots between bamboos and trees (Collalti et al. 2019;O'Leary et al. 2019;Salomón et al. 2020). To clarify the differences in scaling, we measured the respiration rate of 58 individual Moso bamboo shoots and their total organs. ...
Article
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Both Moso bamboo ( Phyllostachys pubescens ) and tree forests have a large biomass; they are considered to play an important role in ecosystem carbon budgets. The scaling relationship between individual whole-shoot (i.e., aboveground parts) respiration and whole-shoot mass provides a clue for comparing the carbon budgets of Moso bamboo and tree forests. However, nobody has empirically demonstrated whether there is a difference between these forest types in the whole-shoot scaling relationship. We developed whole-shoot chambers and measured the shoot respiration of 58 individual mature bamboo shoots from the smallest to the largest in a Moso bamboo forest, and then compared them with that of 254 tree shoots previously measured. For 30 bamboo shoots, we measured the respiration rate of leaves, branches, and culms. We found that the scaling exponent of whole-shoot respiration of bamboo fitted by a simple power function on a log–log scale was 0.843 (95 % CI 0.797–0.885), which was consistent with that of trees, 0.826 (95 % CI 0.799–0.851), but higher than 3/4, the value typifying the Kleiber’s rule. The respiration rates of leaves, branches, and culms at the whole-shoot level were proportional to their mass, revealing a constant mean mass-specific respiration of 1.19, 0.224, and 0.0978 µmol CO 2 kg − 1 s − 1 , respectively. These constant values suggest common traits of organs among physiologically integrated ramets within a genet. Additionally, the larger the shoots, the smaller the allocation of organ mass to the metabolically active leaves, and the larger the allocation to the metabolically inactive culms. Therefore, these shifts in shoot-mass partitioning to leaves and culms caused a negative metabolic scaling of Moso bamboo shoots. The observed convergent metabolic scaling of Moso bamboo and trees may facilitate comparisons of the ecosystem carbon budgets of Moso bamboo and tree forests.
... Source-driven modelling of leaf photosynthesis cascades down to C-dependent estimates of R S . However, it is still unclear whether plant respiration is controlled by respiratory substrate (source-driven) or by the plant demand to satisfy metabolic requirements (sink-driven) (Collalti et al., 2020;Körner, 2015;Schiestl-Aalto et al., 2015). Moreover, costs of growth and maintenance respiratory metabolism under the GMRP are commonly assumed constant over time and among species (Amthor, 2000). ...
... This approach is similarly suggested for plant growth (Körner, 2015;Schiestl-Aalto et al., 2015) and proposed in TReSpire, calibrated against measurements of ΔD and E A . We further speculate that relatively constant photosynthesisto-respiration ratios, commonly reported at the whole tree level (Collalti et al., 2020;Dusenge et al., 2019;Gifford, 2003;Waring et al., 1998), results from the long-term interannual balance between C gain, loss and storage during plant development (Schiestl-Aalto et al., 2015; and feedback effects of the respiratory demand on the C gain, rather than from direct control of photosynthesis on woody tissue respiration, as might be the case in photosynthetic tissues. ...
Article
Stem respiration (RS) plays a crucial role in plant carbon budgets. However, its poor understanding limits our ability to model woody tissue and whole-tree respiration. A biophysical model of stem water and carbon fluxes (TReSpire) was calibrated on cedar, maple, and oak trees during spring and late summer. For this, stem sap flow, water potential, diameter variation, temperature, CO2 efflux, allometry and biochemistry were monitored. Shoot photosynthesis (PN) and non-structural carbohydrates (NSC) were additionally measured to evaluate source-sink relations. The highest RS and stem growth was found in maple and oak during spring, both being seasonally decoupled from PN and [NSC]. Temperature largely affected maintenance respiration (RM) in the short term, but temperature-normalized RM was highly variable on a seasonal timescale. Overall, most of the respired CO2 radially diffused to the atmosphere (> 87 %) while the remainder was transported upward with the transpiration stream. The modelling exercise highlights the sink driven behaviour of RS and the significance of overall metabolic activity on nitrogen (N) allocation patterns and N-normalized respiratory costs to capture RS variability over the long term. These insights should be considered when modelling plant respiration, whose representation is currently biased towards a better understanding of leaf metabolism. This article is protected by copyright. All rights reserved.
... At the whole-plant scale, growth is dependent on the difference between net carbon assimilation by the leaves and the respiration of whole-plant nonphotosynthetic tissues (Collalti et al. 2019;Impa et al. 2019). When light availability is very low, plants can consume carbon stocks to maintain their metabolism (Givnish 1988). ...
Article
Aims Screening tree species in tropical rainforest according to their shade tolerance is important to efficiently manage the native trees of economic significance in secondary forest enrichment regimes. The objective of this study was to determine the whole-plant light compensation point (WPLCP) and compare the phenotypic plasticity in relation to growth and carbon allocation of Cariniana legalis and Gallesia integrifolia seedlings under low light availability. Methods Seedlings were cultivated for 77 days under conditions of five photosynthetically active radiation (PAR) (0.02, 1.1, 2.3, 4.5 and 5.9 mol photons m -2 day -1) in three replicates. Growth and carbon allocation variables were determined. Important Findings Growth rates of C. legalis were higher and lower than those of G. integrifolia under 1.1 and 5.9 mol photons m -2 day -1, respectively. The WPLCP differed significantly between the two species. In accordance with the criteria of the shade tolerance classification for these two tropical tree species, our results showed that C. legalis had lower WPLCP and phenotypic plasticity in terms of higher growth rates and greater shade tolerance than G. integrifolia. From a practical point of view, we demonstrated that the differential linkage between growth and changing PAR between the two species can become a useful tool for comparing and selecting tree species in forest enrichment projects.
... The stem cutting performed better than rooted stump or terminal cutting on number of leaves, leaf fresh weight, leaf dry weight, root length and root dry weight, and accumulated more essential nutrients than other planting materials. The accumulated nutrients included nitrogen and carbohydrates required for further growth (Otiende et al. 2017, Cavalcante et al. 2019, respiration process (Collalti et al. 2020) and producing energy for other metabolic processes (O'Leary et al. 2019). Sun et al. (2019 reported that a higher photosynthetic pigment in cucumber leaf was linearly associated with photosynthetic capacity. ...
Article
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Alternanthera sissoo is currently propagated using stem or terminal cuttings, since it does not produce fertile seeds. This research aimed to identify the most effective propagation planting material among rooted stump, stem cutting and terminal cutting, as well as their response to the application of NPK fertilizer. The results showed a better performance for stem cutting than for rooted stump or apical cutting. The canopy area was positively related to the longest diameter (R² = 0.92) and the average of two-way cross-sectional diameter (R² = 0.89). The number of branches, branch fresh weight, leaf fresh and dry weights did not vary among the planting materials; however, the total number of leaves, branch and root dry weights were higher for stem cutting. Stem cutting is also available in a larger quantity than the other two planting materials when collected from each mother plant. Therefore, it is recommended for optimizing leaf yield in A. sissoo. The species positively responded to NPK fertilization, as shown by the increase of the SPAD value for 6 to 12 days after the initial application. Therefore, for maximizing yield, it should be regularly fertilized with NPK every 3 weeks, coinciding with the time that the SPAD index falls back to pre-NPK application levels. KEYWORDS: Infertile seeds; perennial vegetables; stem cutting; vegetative propagation
... BVOCs are closely related to the amount of carbon accumulating in the growing period which depends on the balance (net primary production, NPP) of photosynthesis (gross primary production, GPP) and respiration (R) (Collalti et al., 2020). Empirical models have been widely adopted to estimate BVOC emissions based on vegetation factors, emission factors, and environmental factors (Cai et al., 2021). ...
Article
As a volatile organic compound existing in the atmosphere, methanol plays a key role in atmospheric chemistry due to its comparatively high abundance and long lifetime. Croplands are a significant source of biogenic methanol, but there is a lack of systematic assessment for the production and emission of methanol from crops in various phases. In this study, methanol emissions from spring wheat during the growing period were estimated using a developed emission model. The temporal and spatial variations of methanol emissions of spring wheat in a Canadian province were investigated. The averaged methanol emission of spring wheat is found to be 37.94 ± 7.5 μg·m-2·h-1, increasing from north to south and exhibiting phenological peak to valley characteristics. Moreover, cold crop districts are projected to be with higher increase in air temperature and consequent methanol emissions during 2020-2099. Furthermore, the seasonality of methanol emissions is found to be positively correlated to concentrations of CO, filterable particulate matter, and PM10 but negatively related to NO2 and O3. The uncertainty and sensitivity analysis results suggest that methanol emissions show a Gamma probabilistic distribution, and growth length, air temperature, solar radiation and leafage are the most important influencing variables. In most cases, methanol emissions increase with air temperature in the range of 3-35 °C while the excessive temperature may result in decreased methanol emissions because of inactivated enzyme activity or increased instant methanol emissions due to heat injury. Notably, induced emission might be the major source of biogenic methanol of mature leaves. The results of this study can be used to develop appropriate strategies for regional emission management of cropping systems.
... However, as the heartwood is not contributing to sap transport, diameters along the trunk cannot be understood based on sap transport only, unless heartwood is considered a waste produced, e.g. due to ageing (Collalti et al. 2019) or difficulties in using the same sapwood when branches die and grow (Chiba et al. 1988). Phloem transport down the trunk may be similarly limiting tree height due to path length (Woodruff 2013), but again, does not explain diameters, unless trunk circumference needs to be increased to increase transport capacity. ...
Article
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Key message Spruce trunk tapering corresponds closely to tapering required to resist bending forces caused by wind and gravity. Abstract Understanding why trunks (tree stems) are the size that they are is important. However, this understanding is fragmented into isolated schools of thought and has been far from complete. Realistic calculations on minimum trunk diameters needed to resist bending moments caused by wind and gravity would be a significant step forward. However, advancements using this biomechanical approach have been delayed by difficulties in modelling bending of trunks and wind gusts. We felled and measured five Norway spruces (Picea abies) in an unthinned monoculture in southeastern Finland planted 67 years earlier. We then focused on forces working on storm-bent (maximally bent) trees caused by gravity and the strongest gust in a 1-h simulation with a large-eddy simulation model. The weakest points along the trunks of the three largest trees resisted mean above-canopy wind speeds ranging from 10.2 to 12.7 m s⁻¹ (3.3-fold in the strongest gust), but the two smallest were well protected by a dense layer of leaves from the bending tops of larger trees, and could have resisted stronger winds. Gravity caused approximately one quarter of the critical bending moments. The wind that breaks the trunks in their weakest points is close to breaking them in other points, supporting the importance of bending moments caused by wind and gravity in the evolution of trunk taper.
... (e.g., Fisher et al., 2006;Fleischer et al., 2019;Langan et al., 2017;Lovenduski & Bonan, 2017;Morin et al., 2021;Sakschewski et al., 2016). For example, using different versions of the same forest model, Collalti, Tjoelker, et al., (2020) tested two ecological theories about plant respiration. Models can thus also prove useful to pinpoint data and knowledge gaps and hence further guide the design of new experiments and empirical studies (Medlyn et al., 2016;Norby et al., 2016;Rykiel, 1996;Van Nes & Scheffer, 2005). ...
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1. Understanding the processes that shape forest functioning, structure, and diversity remains challenging, although data on forest systems are being collected at a rapid pace and across scales. Forest models have a long history in bridging data with ecological knowledge and can simulate forest dynamics over spatio-temporal scales unreachable by most empirical investigations. 2. We describe the development that different forest modelling communities have followed to underpin the leverage that simulation models offer for advancing our understanding of forest ecosystems. 3. Using three widely applied but contrasting approaches –­ species distribution models, individual-­based forest models, and dynamic global vegetation models –­ as examples, we show how scientific and technical advances have led models to transgress their initial objectives and limitations. We provide an overview of recent model applications on current important ecological topics and pinpoint ten key questions that could, and should, be tackled with forest models in the next decade. 4. Synthesis. This overview shows that forest models, due to their complementarity and mutual enrichment, represent an invaluable toolkit to address a wide range of fundamental and applied ecological questions, hence fostering a deeper understanding of forest dynamics in the context of global change.
... The genetic and chemical manipulation of the mitochondrial activity may be a useful tool to improve the AsA synthesis and eventually the tolerance of plants to abiotic and biotic stress. Modifying AsA synthesis and respiratory activity might be a strategy for the conservation of plant products, particularly in the case of products of commercial interest (Dusenge et al., 2018;Collalti et al., 2019;Jalali et al., 2020). In conclusion, the involvement of AsA in regulating multiple plant functions goes beyond simply its roles as antioxidant and co-factor molecule. ...
Article
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The molecule vitamin C, in the chemical form of ascorbic acid (AsA), is known to be essential for the metabolism of humans and animals. Humans do not produce AsA, so they depend on plants as a source of vitamin C for their food. The AsA synthesis pathway occurs partially in the cytosol, but the last oxidation step is physically linked to the respiratory chain of plant mitochondria. This oxidation step is catalyzed by L-galactono-1,4-lactone dehydrogenase (L-GalLDH). This enzyme is not considered a limiting step for AsA production; however, it presents a distinguishing characteristic: the L-GalLDH can introduce electrons directly into the respiratory chain through cytochrome c (Cytc) and therefore can be considered an extramitochondrial electron source that bypasses the phosphorylating Complex III. The use of Cytc as electron acceptor has been debated in terms of its need for AsA synthesis, but little has been said in relation to its impact on the functioning of the respiratory chain. This work seeks to offer a new view about the possible changes that result of the link between AsA synthesis and the mitochondrial respiration. We hypothesized that some physiological changes related to low AsA may be not only explained by the deficiency of this molecule but also by the changes in the respiratory function. We discussed some findings showing that respiratory mutants contained changes in AsA synthesis. Besides, recent works that also indicate that the excessive electron transport via L-GalLDH enzyme may affect other respiratory pathways. We proposed that Cytc reduction by L-GalLDH may be considered as alternative respiratory pathway that is active during AsA synthesis. Also, it is proposed that possible links of this pathway with other pathways of alternative electron transport in plant mitochondria may exist. The review suggests possible implications of this relationship, particularly for situations of stress. We hypothesized that the L-GalLDH may be part of a pathway of alternative electron transport that would serve as a strategy for adaptation of plant respiration to changing conditions.
... As droughts and wildfires are expected to become more frequent, the time of occurrence between these disturbances may even get shorter than forest recovery time, determining permanently damaged ecosystems and widespread degradation [95]. Although forest growth models are powerful tools that can be applied in simulating the C dynamics in forests [98,99], our results are subject to some uncertainty and a number of caveats [100,101]. In this study, we modeled vegetation recovery time as a function of climate only. ...
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In recent decades, droughts, deforestation and wildfires have become recurring phenomena that have heavily affected both human activities and natural ecosystems in Amazonia. The time needed for an ecosystem to recover from carbon losses is a crucial metric to evaluate disturbance impacts on forests. However, little is known about the impacts of these disturbances, alone and synergistically, on forest recovery time and the resulting spatiotemporal patterns at the regional scale. In this study, we combined the 3-PG forest growth model, remote sensing and field derived equations, to map the Amazonia-wide (3 km of spatial resolution) impact and recovery time of aboveground biomass (AGB) after drought, fire and a combination of logging and fire. Our results indicate that AGB decreases by 4%, 19% and 46% in forests affected by drought, fire and logging + fire, respectively, with an average AGB recovery time of 27 years for drought, 44 years for burned and 63 years for logged + burned areas and with maximum values reaching 184 years in areas of high fire intensity. Our findings provide two major insights in the spatial and temporal patterns of drought and wildfire in the Amazon: (1) the recovery time of the forests takes longer in the southeastern part of the basin, and, (2) as droughts and wildfires become more frequent-since the intervals between the disturbances are getting shorter than the rate of forest regeneration-the long lasting damage they cause potentially results in a permanent and increasing carbon losses from these fragile ecosystems.
... A gradual ontogenetic transition occurs when fine roots grow into coarse roots (> 2 mm in diameter). This transition is also seen in the scaling of respiration with body size for young seedling growing into larger mature trees (Enquist et al. 2007;Mori et al. 2010;Starko and Martone 2016;Ogawa 2019;Collalti et al. 2020). Our findings support the idea that there is not a unified and single constant scaling exponent for metabolismbiomass relationships in terrestrial plants, consistent with the hypothesis by White (2010), which argues that no universal scaling exponent can be applied to animals and plants. ...
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Background Metabolic scaling theory predicts that plant productivity and biomass are both size-dependent. However, this theory has not yet been tested in plant roots. Methods In this study, we tested how metabolic scaling occurs in plants using a comprehensive plant root dataset made up of 1016 observations from natural habitats. We generated metabolic scaling exponents by log-transformation of root productivity versus biomass. Results Results showed that the metabolic scaling exponents of fine root (< 2 mm in diameter) productivity versus biomass were close to 1.0 for all ecosystem types and functional groups. Scaling exponents decreased in coarse roots (> 2 mm in diameter). Conclusions We found isometric metabolic scaling in fine roots, a metabolically active organ similar to seedlings or saplings. Our findings also indicate a shift in metabolic scaling during plant development. Overall, our study supports the absence of any unified single constant scaling exponent for metabolism-biomass relationships in terrestrial plants, especially for forests with woody species.
... Trees passively transport sap (water) up in the sapwood, and the resistance caused by length 66 of the path or height difference has been used as the basis for modelling maximum tree height 67 (Koch et al. 2004) and growth deceleration in plantations (Ryan and Yoder 1997). However, 68 as the heartwood is not contributing to sap transportation, diameters along the trunk cannot be 69 understood based on sap transportation only, unless heartwood is considered a waste 70 4 produced e.g. because of ageing (Collalti et al. 2019) or difficulties in using the same 71 sapwood when branches die and grow (Chiba et al. 1988). Phloem transportation down the 72 trunk may be similarly limiting tree height due to path length (Woodruff 2013), but does not 73 explain diameters, unless trunk circumference needs to be increased to increase transport 74 capacity. ...
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Background: Understanding why trunks (tree stems) are the size that they are is important. However, this understanding is fragmented into isolated schools of thought and has been far from complete. Realistic calculations on minimum trunk diameters needed to resist bending moments caused by wind and gravity would be a significant step forward. However, advancements using this biomechanical approach have been delayed by difficulties in modelling wind gusts. We felled and measured five Norway spruces (Picea abies) in an unthinned monoculture in southeastern Finland planted 67 years earlier. We focused on forces working on storm-bent (maximally bent) trees caused by gravity and the strongest gust in a one-hour simulation with a large-eddy simulation model. Results: The three largest trees resisted mean above-canopy wind speeds ranging from 10.2 m s⁻¹ to 12.7 m s⁻¹ (3.3-fold in the gust), but the two smallest were well protected by a dense layer of leaves from the bending tops of larger trees, and could have resisted stronger winds. Gravity caused approximately one quarter of the critical bending moments. Conclusions: Our biomechanical modelling of trunk taper based on wind and gravity leads to diameters close to those measured, and we discuss the potential causes of the deviations. This approach could also be used to model tree biomasses and how those may change with changing climate.
... Moreover, part of respired CO 2 can be fixed in xylem storage pools (DeRoo, Salomón, & Steppe, 2020). ES is influenced by many factors, such as air temperature (Yang et al., 2016), growth rate (Damesin, Ceschia, le Goff, Ottorini, & Dufrêne, 2002), distribution and turnover of living cells (Collalti et al., 2020) and tree social status (Guidolotti, Rey, D'Andrea, Matteucci, & de Angelis, 2013). RS can be separated in growth respiration (R G ), which provides the energy for synthesizing new tissues; and by maintenance respiration (R M ), which maintains existing living cells (Amthor, 2000;Thornley, 1970). ...
Article
The effects of short‐term extreme events on tree functioning and physiology are still rather elusive. European beech is one of the most sensitive species to late frost and water shortage. We investigated the intra‐annual C dynamics in stems under such conditions. Wood formation and stem CO2 efflux were monitored in a Mediterranean beech forest for three years (2015–2017), including a late frost (2016) and a summer drought (2017). The late frost reduced radial growth and, consequently, the amount of carbon fixed in the stem biomass by 80%. Stem carbon dioxide efflux in 2016 was reduced by 25%, which can be attributed to the reduction of effluxes due to growth respiration. Counter to our expectations, we found no effects of the 2017 summer drought on radial growth and stem carbon efflux. The studied extreme weather events had various effects on tree growth. Even though late spring frost had a strong impact on beech radial growth in the current year, trees fully recovered in the following growing season, indicating high resilience of beech to this stressful event. This article is protected by copyright. All rights reserved.
... Moreover, part of respired CO 2 can be fixed in xylem storage pools (DeRoo, Salomón, & Steppe, 2020). ES is influenced by many factors, such as air temperature (Yang et al., 2016), growth rate (Damesin, Ceschia, le Goff, Ottorini, & Dufrêne, 2002), distribution and turnover of living cells (Collalti et al., 2020) and tree social status (Guidolotti, Rey, D'Andrea, Matteucci, & de Angelis, 2013). RS can be separated in growth respiration (R G ), which provides the energy for synthesizing new tissues; and by maintenance respiration (R M ), which maintains existing living cells (Amthor, 2000;Thornley, 1970). ...
Article
The effects of short-term extreme events on tree functioning and physiology are still rather elusive. European beech is one of the most sensitive species to late frost and water shortage. We investigated the intra-annual C dynamics in stems under such conditions. Wood formation and stem CO2 efflux were monitored in a Mediterranean beech forest for 3 years (2015-2017), including a late frost (2016) and a summer drought (2017). The late frost reduced radial growth and, consequently, the amount of carbon fixed in the stem biomass by 80%. Stem carbon dioxide efflux in 2016 was reduced by 25%, which can be attributed to the reduction of effluxes due to growth respiration. Counter to our expectations, we found no effects of the 2017 summer drought on radial growth and stem carbon efflux. The studied extreme weather events had various effects on tree growth. Even though late spring frost had a strong impact on beech radial growth in the current year, trees fully recovered in the following growing season, indicating high resilience of beech to this stressful event.
... This indicates that warming induced a fast growth rate or photosynthesis rate. Plants, therefore, could have a higher biomass and generate more recent photosynthates for higher maintenance and growth respiration during the early phenophases (Molau 1993, Körner 2003, Ernakovich et al. 2014, Collalti et al. 2020), such as the flowering stage (Körner 2003). Our result also supports our hypothesis that Re in the reproductive stage (i.e., DB) would have a higher temperature sensitivity than at other stages (Fig 2). ...
Article
Phenology has a great effect on the carbon cycle. Significant relationships have been well demonstrated between phenology and photosynthesis. However, few studies have been undertaken to characterize relationships between phenology and ecosystem respiration (Re). We conducted a reciprocal transplant experiment among three elevations for two-years to measure Re over six phenological sequences throughout the growing seasons. Our results showed that changes in phenological duration were mainly determined by the onset of phenology, as one day advance of phenological onset could lengthen 0.13 days of phenological duration. Advances in early spring phenophases (i.e., first leaf-out, first bud/boot-set and first flowering) under warming strengthened the temperature sensitivity of Re. However, the late phenophases (i.e., first seeding-set, first post-fruiting vegetation and first leaf-coloring) had non-significant relationships with Re. In total, after pooling all the data, one day advance of phenophases would increase Re by 2.23% under warming. In particular, Re would increase by 29.12% with an advance of phenophases by 8.46 days of under a 1.5 °C warming scenario. Our analysis of the coupling between temperature/moisture–phenology–Re may further supplement evidence that warmer spring temperature increases carbon emission by advancing early phenophases. This points to a faster and easier way to investigate how aboveground functional traits (phenology) affect unseen functional traits (Re) on the Tibetan Plateau.
... UV radiation can change cell membrane characteristics that may not only result in changes in membrane permeability and ionic balance, but may also be ultimately responsible for the partial inhibition of photosynthesis and respiratory changes [8]. Respiration depends primarily on photosynthesis, as the respiration process consumes the carbons that are produced from photosynthesis [9]. ...
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Pure polyethylene (PE) is enriched with several additives to make it a smart application material in protected cultivation, as a cover material for either greenhouses or screenhouses. When this material completely or partially absorbs ultraviolet (UV) solar radiation, then it is called UV blocking material. The current work presents a review on the effects of the UV blocking covering materials on crop growth and development. Despite the passage of several years and the evolution of the design technology of plastic greenhouse covers, UV blocking materials have not ceased to be a rather interesting technique for the protection of several vegetable and ornamental species. Much of the research on UV blocking materials focuses on their indisputable effect on reducing the activity of pests and viral-related diseases, rather than on the effects on the crop physiology itself. In the present paper, representative studies dealing with the effect of the UV blocking materials on the agronomic factors of different crops are presented and discussed. The results reveal that UV blocking materials have mainly positive effects on the different plant physiological functions, such as photosynthesis and transpiration rate, and on growth characteristics, while they might have a negative effect on the production and content of secondary compounds, as anthocyanins and total phenolics.
... This perspective suggests that both processes (GEP and Reco) decrease as forest ages, with GEP decreasing faster than Reco (Tang et al., 2014). For instance, maintenance respiration costs may increase as forest stand develops and biomass accumulates (Collalti et al., 2020), which will then represent a large fraction of Reco. However, the assumption that the relative contribution of respiration for growth or maintenance to Reco is a constant proportion of GEP has been recently challenged since biomass accumulation during forest aging, climate, and soil properties likely affect the Reco/GEP ratio (Collalti & Prentice, 2019). ...
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Resumen El bosque tropical seco (BTS) es una de las coberturas terrestres más ampliamente distribuidas en México, pero su contribución regional y global a los ciclos del carbono y del agua es aún muy incierta. Medimos los flujos de CO2 y vapor de agua entre el ecosistema y la atmósfera utilizando la técnica de covarianza de vórtices entre 2016 y 2018 en un BTS maduro en el noroeste de México. Primero, investigamos la magnitud y la estacionalidad de la evapotranspiración (ET), la producción neta del ecosistema (NEP) y sus flujos contribuyentes, la producción bruta del ecosistema (GEP) y la respiración del ecosistema (Reco). En segundo lugar, exploramos los principales factores ambientales que controlan los flujos de carbono y de agua, y probamos si este ecosistema actuó como fuente o sumidero neto de carbono. Durante el período de estudio, la precipitación que recibió el ecosistema regresó a la atmósfera a través de ET (738.9 ± 58.26 mm y⁻¹). La respiración del ecosistema (2203.16 ± 244.2 g C m⁻² y⁻¹) fue consistentemente mayor que la GEP (1,975.32 ± 295.52 g C m⁻² y‐1), determinando una NEP anual (−227.6 ± 59.4 g C m⁻² y⁻¹) que resultó en pérdidas netas anuales de carbono. Este bosque mantuvo su eficiencia en el uso del agua (WUE; GEP / ET) a lo largo de los años (2.53–3.24), pero la disponibilidad de agua restringió el uso de la luz y las tasas máximas de asimilación de carbono. Nuestros resultados dan relevancia a la retroalimentación entre el contenido de agua del suelo y la radiación neta como las principales variables ambientales que controlan los flujos del ecosistema en este bosque tropical seco maduro.
... First, the longer transport pathway for water in taller trees can result in more closed stomata (to avoid xylem cavitation) and therefore reduced GPP 26 , with no corresponding reduction in R a , at least in the short-term 27 . Second, larger trees may respire more because of their greater sapwood volume and mass per unit leaf area 8,28,29 , leading to increased R a (for the maintenance of living sapwood tissues) and reduced NPP relative to GPP. Third, soil fertility declines due to nutrient immobilization as stands age 30 ; this is consistent with observations of an increased ratio of fine-root-to-leaf-carbon, and reduced nitrogen concentration in soils 10,31 . ...
Article
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Forest production efficiency (FPE) metric describes how efficiently the assimilated carbon is partitioned into plants organs (biomass production, BP) or-more generally-for the production of organic matter (net primary production, NPP). We present a global analysis of the relationship of FPE to stand-age and climate, based on a large compilation of data on gross primary production and either BP or NPP. FPE is important for both forest production and atmospheric carbon dioxide uptake. We find that FPE increases with absolute latitude, precipitation and (all else equal) with temperature. Earlier findings-FPE declining with age-are also supported by this analysis. However, the temperature effect is opposite to what would be expected based on the short-term physiological response of respiration rates to temperature, implying a top-down regulation of carbon loss, perhaps reflecting the higher carbon costs of nutrient acquisition in colder climates. Current ecosystem models do not reproduce this phenomenon. They consistently predict lower FPE in warmer climates, and are therefore likely to overestimate carbon losses in a warming climate.
... In addition to temperature rise, changes in precipitation, elevated CO 2 and nitrogen deposition, and other environmental variables, e.g. soil nutrient availability, forest biodiversity, forest age and recent photosynthates (Collalti et al., 2020), were also important determinants for RA soil . For example, vegetation would allocate more carbon to roots during the seedling stages, and the carbon allocation to shoot would increase with vegetation ages (Qi et al., 2019). ...
Article
Belowground autotrophic respiration (RAsoil) depends on carbohydrates from photosynthesis flowing to roots and rhizospheres, and is one of the most important but least understood components in forest carbon cycling. Carbon allocation plays an important role in forest carbon cycling and reflects forest adaptation to changing environmental conditions. However, carbon allocation to RAsoil has not been fully examined at the global scale. To fill this knowledge gap, we first used a Random Forest algorithm to predict the spatio-temporal patterns of RAsoil from 1981 to 2017 based on the most updated Global Soil Respiration Database (v5) with global environmental variables; calculated carbon allocation from photosynthesis to RAsoil (CAB) as a fraction of gross primary production; and assessed its temporal and spatial patterns in global forest ecosystems. Globally, mean RAsoil from forests was 8.9 ± 0.08 Pg C yr⁻¹ (mean ± standard deviation) from 1981 to 2017 and increased significantly at a rate of 0.006 Pg C yr⁻², paralleling broader soil respiration changes and suggesting increasing carbon respired by roots. Mean CAB was 0.243 ± 0.016 and decreased over time. The temporal trend of CAB varied greatly in space, reflecting uneven responses of CAB to environmental changes. Combined with carbon use efficiency, our CAB results offer a completely independent approach to quantify global aboveground autotropic respiration spatially and temporally, and could provide crucial insights into carbon flux partitioning and global carbon cycling under climate change.
... -/ is the change rate of B 2 partial pressure modified by initial moisture (Collalti et al., 2020). The calculation formula of the change rate of partial pressure is: ...
... Both physiological and biochemical parameters influence leaf photosynthesis, which ultimately determines the biomass accumulation in plants [56,57]. Any disruption in these parameters by single or multiple stresses can cause a significant reduction in biomass production [14,58]. ...
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Upland cotton encounters biotic and abiotic stresses during the growing season, which significantly affects the genetic potential of stress tolerance and productivity. The root-knot nematode (RKN) (Meloidogyne incognita) is a soilborne roundworm affecting cotton production. The occurrence of abiotic stress (drought stress, DS) can alter the plant–disease (RKN) interactions by enhancing host plant sensitivity. Experiments were conducted for two years under greenhouse conditions to investigate the effect of RKN and DS and their combination using nematode-resistant (Rk-Rn-1) and nematode susceptible (M8) cotton genotypes. These genotypes were subjected to four treatments: control (100% irrigation with no nematodes), RKN (100% irrigation with nematodes), DS (50% irrigation with no nematodes), and DS + RKN (50% irrigation with nematodes). We measured treatments-induced changes in cotton (i) leaf reflectance between 350 and 2500 nm; and (ii) physiology and biomass-related traits for diagnosing plant health under combined biotic and abiotic stresses. We used a maximum likelihood classification model of hyperspectral data with different dimensionality reduction techniques to learn RKN and DS stressors on two cotton genotypes. The results indicate (i) the RKN stress can be detected at an early stage of 10 days after infestation; (ii) RKN, DS, and DS + RKN can be detected with an accuracy of over 98% using bands from 350–1000 nm and 350–2500 nm. The genotypes ‘Rk-Rn-1’and ‘M8’ showed differential responses to DS, RKN, and DS + RKN. With a few exceptions, all three stressors reduced the pigments, physiology, and biomass traits and the magnitude of reduction was higher in ‘M8’ than ‘Rk-Rn-1’. Observed impact of stressors on plant growth followed DS + RKN > DS > RKN. Similarly, leaf reflectance properties exhibited a significant difference between individual stress treatments indicating that the hyperspectral sensor data can be used to discriminate RKN-infected plants from drought-stressed plants. Thus, our study reveals that hyperspectral and physiological changes in response to RKN and DS could help diagnose plant health before visual symptoms.
... For instance, larger trees can exhibit higher levels of self-shading and may have larger carbohydrate reserves which together would contribute to a stronger compensatory response. On the other hand, respiration of non-photosynthetic tissue as a fraction of photosynthesis tends to increase with tree size (Collalti et al., 2020) which would imply a more negative effect of leaf loss for larger trees. We also expect that variation in competition will change the effects of pruning on yield. ...
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In cocoa cultivation pruning is considered an essential yield-enhancing practice but its effects on cocoa tree growth and yield, and how these are mediated by tree size and competition are poorly understood. Here, we evaluate the impact of experimental pruning on: light interception, leaf flushing and the number of flowers and of developing, wilted and harvested pods. The pruning treatment removed an average 26.4% of cocoa tree aboveground biomass and was aimed to create an open cup-shaped crown. Stem basal area and sum of neighbor tree basal area were used as proxies for tree size and tree competition, respectively. All response variables were analysed at tree level as a function of pruning, tree size and tree competition using generalized linear mixed effect models. After one year, pruned trees recovered initial losses in whole-canopy light interception but maintained a more uniform distribution of light in the canopy. Pruning directly increased flushing activity, while the effect on the other variables was mediated by the interaction with tree size and competition. Pruning increased the positive effect of tree size and competition on flower number and similar effects were found for small pod number. The latter effect was counterbalanced by an increase of pod wilting in pruned trees under high competition, resulting in similar numbers of large and harvested pods on the stem in pruned and unpruned trees. For pods in the canopy, pruning did enhance the positive effect of tree size and strongly reduced the negative effect of competition on pod number. As canopy pods made up 60% of the total, similar pruning effects were found for the total number of harvested pods. The predicted net effect of pruning on the number of harvested pods varied greatly with tree size and competition, ranging from -58% for small trees under low competition, to +150% for large trees under high competition. This large variability stresses the importance of individual-level analysis to quantify pruning effects and calls for more attention to individual tree characteristics in training and practice of cocoa pruning. The pruning-induced reduction of negative competition effects suggests that pruning can contribute to realizing high-density cocoa stands.
... An increasing trend in the fine root to foliage ratio with latitude has been observed (Helmisaari et al. 2007, Lehtonen et al. 2016b which could contribute to a declining northward trend in E, provided that an opposite trend did not exist in the sapwood to foliage ratio. Maintenance respiration rates have been related to temperature and tissue N content (Ryan et al. 1996, Collalti et al. 2020) but have also been found to vary in parallel with photosynthesis (Dewar et al. 1999, Wertin andTeskey 2008), rendering E relatively insensitive to the environment. If CUE really has a declining trend with latitude, some key elements seem to be missing from our conventional description of the production and consumption processes in forest ecosystems. ...
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There is evidence that carbon fluxes and stocks decrease with increasing latitude in boreal forests, suggesting a reduction in carbon use efficiency. While vegetation and soil carbon dynamics have been widely studied, the empirical finding that ectomycorrhizal fungi (ECM) become more abundant towards the north has not been quantitatively linked to carbon use efficiency. We formulated a conceptual model of combined fine-root and ECM carbon use efficiency (CUE) as NPP/GPP (net primary production/gross primary production). For this, we included the mycorrhiza as gains in plant NPP but considered the extramatrical hyphae as well as exudates as losses. We quantified the carbon processes across a latitudinal gradient using published eco-physiological and morphological measurements from boreal coniferous forests. In parallel, we developed two CUE models using large-scale empirical measurements amended with established models. All models predicted similar latitudinal trends in vegetation CUE and net ecosystem production (NEP). CUE in the ECM model declined on average by 0.1 from latitude 60 to 70 with overall mean 0.390 ± 0.037. NEP declined by 200 g m⁻² yr⁻¹ with mean 171 ± 79.4 g m⁻² yr⁻¹. ECM had no significant effect on predicted soil carbon. Our findings suggest that ECM can use a significant proportion of the carbon assimilated by vegetation and hence be an important driver of the decline in CUE at higher latitudes. Our model suggests the quantitative contribution of ECM to soil carbon to be less important but any possible implications through litter quality remain to be assessed. The approach provides a simple proxy of ECM processes for regional C budget models and estimates.
... Nonstructural carbohydrates (NSCs) are used not only for growth, energy metabolism (e.g. respiration) and C storage (Hartmann & Trumbore, 2016;Martínez-Vilalta et al., 2016;Schiestl-Aalto et al., 2019;Collalti et al., 2020), but also for other purposes in trees. For example, soluble sugars (mainly glucose, fructose and sucrose) are used to regulate water and osmotic potential in plant cells (Hartmann & Trumbore, 2016). ...
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In warming climates, soil water content (SWC) may act as an important factor in determining belowground carbon dynamics in boreal forests. Here, we estimated the respiration and nonstructural carbohydrate (NSC) concentrations of tree roots in a mature Scots pine (Pinus sylvestris L.) stand in southern Finland during two growing seasons with contrasting weather conditions. Root respiration was estimated with four different methods: 1) incubating excised roots, 2) partitioning forest floor respirations with root exclusion, or 3) based on temperature response functions and 4) modelling with the whole-tree carbon model ‘CASSIA’. In addition, we conducted a drought experiment in a greenhouse to determine the effect of reduced soil-water availability on respiration by incubating soil and roots of Scots pine saplings. We observed that the respiration of incubated roots of Scots pine saplings and soil decreased with drying after excluding the effect of temperature on respiration (RRES), soil being more sensitive to drought than roots. Similarly, RRES of incubated roots in the field was significantly decreased by lowered SWC, whereas respiration of the entire root system estimated with other methods was clearly higher in dryer and warmer than moister and cooler year. Nevertheless, incubated roots excavated from the topsoil are most affected by drying soil, which might not reflect the response of the entire root system. RRES of incubated roots was negatively associated with root fructose and glucose concentrations. At the same time, root fructose, glucose and sucrose concentrations were negatively associated with SWC due to their role in osmoregulation. Thereby it seems that RRES does not directly follow the changes in NSCs despite the apparent correlation. Our study highlights the responsive nature of root carbon dynamics in varying weather events that should be taken into account in estimating and modelling the impacts of warming climate.
... En el tercer y cuarto inventario, México reportó que los bosques (sector uso del suelo, cambio de uso del suelo y forestería) fueron emisores netos de gases efecto invernadero (GEI) (de Jong et al., 2006(de Jong et al., , 2009, aunque posteriormente (INECC y SEMARNAT, 2015 reportó que los bosques fueron sumideros de carbono, argumentando que la categoría "Bosques que permanecen como Bosques" incrementó sus almacenes, lo que se ha empleado para establecer la necesidad de modificar el mecanismo REDD para considerar esta situación (Skutsch et al., 2017(Skutsch et al., , 2018. Existe controversia sobre el estado de los bosques maduros, donde algunos autores con base en la tesis de los costos de respiración asociados a la asimilación de carbono (Odum, 1969), han planteado que los bosques maduros están en equilibrio (no incrementan ni reducen la captura de carbono); sin embargo, los costos de respiración de mantenimiento pueden aumentar a medida que se desarrolla la masa forestal y se acumula biomasa (Collalti et al., 2020). Sin embargo, la suposición de que la contribución relativa de la respiración al crecimiento o mantenimiento es una proporción constante de la productividad bruta del ecosistema debe considerar la edad del bosque, el clima y las propiedades del suelo (Collalti y Prentice, 2019). ...
Article
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Los almacenes y flujos de carbono en los bosques y selvas de México plantean retos importantes para caracterizarlos y modelarlos. En el contexto de trabajos hacia el Segundo Reporte del Estado del Ciclo del Carbono en México del Programa Mexicano del Carbono, se plantea una hoja de ruta de la estrategia general y elementos constitutivos orientados a los boques y selvas. En particular, se discute las incertidumbres y parametrizaciones de los modelos dinámicos del carbono para la generación de escenarios para evaluar políticas públicas y acciones de intervención para analizar los impactos en la sociedad. Se discute una propuesta para un modelo generalizado de alometría, incluida su extensión para considerar la incertidumbre, en las estimaciones de los almacenes de carbono. Asimismo, se plantea el desarrollo de modelos dinámicos del carbono simplificados y fáciles de parametrizar, incluidos los modelos de estados y transiciones. El problema de imputación de los almacenes a la escala de país, se discute con relación a los métodos geoestadísticos y de aprendizaje de máquina. Finalmente, se presenta evidencia experimental con relación a la discusión sobre si los bosques que permanecen como bosques incrementan o disminuyen sus almacenes de carbono, concluyéndose que la evidencia plantea que los bosques y selvas son emisores neto y no sumideros. Palabras clave: estimaciones de C; modelos alométricos; modelos dinámicos; permanencia de bosques.
... Sapwood area senescence (i.e., conversion to heartwood) is assumed to occur with aging, although evidence points towards a plant-controlled developmental process (Spicer, 2005). Most process-based forest models assume a fixed rate of sapwood 11 240 245 250 255 turnover (Collalti et al., 2020). Like in eq. ...
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Regional-level applications of dynamic vegetation models are challenging because they need to accommodate the variation in plant functional diversity, which requires moving away from broadly-defined functional types. Different approaches have been adopted in the last years to incorporate a trait-based perspective into modeling exercises. A common parametrization strategy involves using trait data to represent functional variation between individuals while discard taxonomic identity, but this strategy ignores the phylogenetic signal of trait variation and cannot be employed when predictions for specific taxa are needed, as in applications to inform forest management planning. An alternative strategy involves adapting the taxonomic resolution of model entities to that of the data source employed for large-scale initialization and estimating functional parameters from available plant trait databases while adopting alternative solutions for missing data and non-observable parameters. Here we report the advantages and limitations of this second strategy according to our experience in the development of MEDFATE (v. 2.8.1), a novel cohort-based and trait-enabled model of forest dynamics, for its application over a region in the Western Mediterranean Basin. First, 217 taxonomic entities were defined according to woody species codes of the Spanish National Forest Inventory. While forest inventory data were used to obtain some empirical parameter estimates, a large proportion of physiological, morphological, and anatomical parameters were mapped to measured plant traits, with estimates extracted from multiple databases and averaged at the required taxonomic level. Estimates for non-observable key parameters were obtained using meta-modeling and calibration exercises. Missing values were filled using imputation procedures based on trait coordination, taxonomic averages or both. The model properly simulated observed historical basal area changes, with a performance similar to an empirical model trained for the same region. While strong efforts are still required to parameterize trait-enabled models for multiple taxa, estimation procedures can be progressively refined, transferred to other regions or models and iterated following data source changes by employing automated workflows. We advocate for the adoption of trait-enabled population-structured models for regional-level projections of forest function and dynamics.
... Firstly, different types of land-use may influence the biogeochemical effects of land on climate change. The land is considered to have a significant impact on climate change and the greenhouse effect, including through the carbon sequestration of plants attached to the land , carbon dioxide release through respiration by plants, animals, and microorganisms (Collalti et al., 2020), and greenhouse gases released permafrost temperatures rise (Brentrup et al., 2021). Land-use type and land-use structure are key factors affecting climate change and the greenhouse effect (Dirmeyer et al., 2010). ...
Article
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Studies have shown that land and climate interact in complex ways through multiple biophysical and biogeochemical feedbacks. In this interaction mechanism, the carbon fixation effect among different land-use types and objective conditions among different regions have significant gaps, leading to the heterogeneous impact of land-use on climate change. This study takes temperature change as the observation index to reflect climate change, and analyzes the process of land use type adjustment affecting vegetation cover and climate change. Based on the data of 214 countries from 1990 to 2018, this paper uses the spatial Durbin model with temperature lag to verify the heterogeneous impact of land-use on climate change in two dimensions of land-use type (Agriculture, forestry and their subdivision structure) and region (latitude and land-sea difference). The following conclusions are drawn: 1) The impact of different land-use types on climate change is heterogeneous. The impact of agricultural land on climate change is not significant, but the increase of the forest land proportion will help to restrain the rise of national temperature. 2) The impact of land-use on climate change has regional heterogeneity. There is heterogeneity in the impact on climate change among sample countries of different latitudes. The geographical differences make the mechanism of land-use affecting climate change between island countries and mainland countries also have heterogeneity, mainly in that island countries are not affected by the land-use structure adjustment of neighboring countries. 3) A country's climate change is affected by both its own land-use structure and the land-use structure of neighboring countries, and the latter is more critical. The conclusions in this study provide helpful supplementary evidence for the importance of international climate cooperation and provide a reference for proposing international initiatives to address climate change or establishing an international convention to address climate change.
... Primary production indicators, such as gross primary production (GPP) and net primary production (NPP), have been widely modelled in carbon cycle-related studies at the global scale as they are climate-sensitive (Huang et al., 2019;Tang et al., 2019;Stocker et al., 2019). GPP is the total amount of carbon stored by plants, which takes into account autotrophic respiration (Collalti and Prentice, 2019;Collalti et al., 2020). Subtraction of autotrophic respiration gives us the net carbon transformed into biomass (NPP). ...
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Background Cork oak agroforestry systems (AFS) have been managed for centuries by humans to produce cork and other goods and services and have recently been recognised as an important reservoir for biodiversity improvement and conservation. However, despite having recently been included as a natural habitat of community-wide interest within the EU Habitats Directive, these systems are in a critical situation of decline. Among other factors, they are strongly threatened by climate change, the effects of which are also expected to be particularly severe in the Mediterranean region. In this study, we aimed to evaluate the influence of climate variability by examining primary production indicators and also to analyse whether the geographical location may have a role in the incidence of the adverse effects of climate. Methods Cork oak AFS were identified in the Forest Map of Spain and the Land use map of Portugal and categorized on the basis of canopy cover. Seasonal climate data from 2001 to 2020 were used to model relationships with climate predictors and proximity to the coast. Hotspot analysis was conducted to identify significant spatial clusters of high- and low-efficiency areas. Results The responses to the influence of climatic conditions differed among the various cork oak AFS categories, particularly in the forest category, which was less dependent on climate variations. Relative humidity and water availability were the main drivers of net primary production (NPP). Carbon use efficiency (CUE) was limited by relative humidity and spring temperature in open ecosystems. Proximity to the coast proved beneficial, especially in years with adverse weather conditions, but was not a limiting factor for survival of the ecosystem. Finally, the results of the hotspot analysis supported the other findings, highlighting high-efficiency areas close to the coast and cold spots grouped in specific areas or dispersed inland. Conclusions Canopy plays a key role in the influence of climatic conditions, particularly in forest categories in which a high density seems to generate microclimate conditions. Water availability, both via the soil and air moisture, is the main driver of primary production, reflecting different adaptive strategies. The oceanic atmosphere may act as a buffer in years of extreme drought.
... Respiration is involved in the carbon catabolic process that metabolizes carbon substrates to produce high energy molecules for fueling the entire metabolism. There is a reciprocal relationship between the respiration level and cellular biomass biosynthesis (Collalti et al., 2020). Hurry et al. (2005) showed a decrease in plant dry matter production under intensive respiration. ...
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Increasing cassava production could mitigate one of the global food insecurity challenges by providing a sustainable food source. To improve the yield potential, physiological strategies (i.e., the photosynthetic efficiency, source-to-sink carbon partitioning, and intracellular carbon metabolism) can be applied in breeding to screen for superior genotypes. However, the influences of source-to-sink carbon partitioning and carbon metabolism on the storage root development of cassava are relatively little understood. We hypothesized that carbon partitioning and utilization vary modulating the distinctive storage root yields of high and low-yielding cassava varieties, represented in this study by varieties Kasetsart 50 (KU50) and Hanatee (HN), respectively. Plant growth, photosynthesis measurements, soluble sugars, and starch contents of individual tissues were analyzed at different developmental stages. Also, the diurnal patterns of starch accumulation and degradation in leaves were investigated through iodine staining. Despite a comparable photosynthetic rate, KU50 grew better and yielded greater storage roots than HN. Interestingly, both varieties differed in their carbon partitioning strategies. KU50 had a high photosynthetic capacity and was better efficient in converting photoassimilates to carbon substrates and allocating them to sink organs for their growth. In contrast, HN utilized the photoassimilates at a high metabolic cost, in terms of respiration, and inefficiently allocated carbon to stems rather than storage roots. These results highlighted that carbon assimilation and allocation are genetic potential characteristics of individual varieties, which in effect determine plant growth and storage root yield of cassava. The knowledge gained from this study sheds light on potential strategies for developing new high-yielding genotypes in cassava breeding programs.
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Micro (Nano)plastics are ubiquitous in the environment and can potentially affect the toxic effects of other chemicals, such as heavy metals. Although the interaction of micro (nano)plastics and heavy metals as well as their effects on aquatic organisms have been widely investigated, studies on their influence on terrestrial plants are limited. Therefore, in this study, the effects of polystyrene (PS), carboxy-modified PS (CPS) and amino-modified PS (APS) nanoparticles on the accumulation and toxicity of Pb on dandelion (Taraxacum asiaticum Dahlst) were investigated using hydroponic cultivation. The presence of the three PS caused cell damage and destroyed the tertiary structure of the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and dehydrogenase (DHA) enzymes, thereby inhibiting Rubisco and root activities, which hindered nutrient uptake and photosynthesis. The inhibition of APS on the biomass of dandelion was greater than that of PS and CPS. Confocal laser scanning microscope and transmission electron microscopy analysis showed that APS was more likely to enter the roots of dandelion than PS and CPS. The presence of Pb induced more PS, CPS, and APS to enter dandelion roots, and Pb aggravated PS and CPS toxicities on dandelion rather than APS toxicity. This is because the complex formed by CPS and Pb can affect the structure of Rubisco and DHA through covalent and coordination bonds, and Pb increased the surface positive charge on CPS, according to Gaussian analysis. The presence of both PS and CPS significantly reduced Pb uptake by dandelion, and they did not exacerbate the toxicity of Pb. In contrast, APS slightly inhibited Pb accumulation, but aggravated Pb toxicity in dandelion. Our findings revealed that the changes in the uptake of nanoplastics and Pb by dandelion potentially resulted in a cascade of events that increased the toxicity and inhibited the growth of dandelion seedlings.
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The growth and reproduction of plants are highly size-dependent and markedly affected by light intensity. Vallisneria spinulosa S.Z.Yan is a common submersed macrophyte and is widely used in current lake restoration projects. The size of plants to be used to get optimal restoration results is not known, however, and may vary with water clarity. In this study, the effects of different plant sizes (large, medium and small, i.e. approximately 2.40 g, 1.01 g and 0.27 g per plant) on the growth and reproduction of V. spinulosa were tested under three light intensities (high, medium, low, i.e. 25%, 6% and 1% of full sunlight, respectively). Both plant size and light intensity were found to be of great significance for plant growth and reproduction. The relative growth rate (RGR) of biomass was higher for small than for large plants at both high and low light, while the absolute growth rate (AGR) of biomass was higher for large-sized plants at medium and high light intensity. Asexual reproduction of V. spinulosa was positively correlated with plant size and more affected by plant size than by light intensity, while sexual reproduction was most affected by light intensity. RGR and AGR of plant height were highest for medium-sized plants at moderate light intensity. Therefore, the size of submersed macrophytes should be considered when using this species in connection with lake restoration. Verification of our results under field conditions is needed, though, before firm conclusions can be reached about the optimal plant size of V. spinulosa to be used in lake restoration as also other factors like, e.g. periphyton shading and wave actions may play a role.
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Extreme weather events are increasing in frequency and intensity due to global climate change. We hypothesized that thesehave a strong impact on the stem radial growth and the dynamic of non-structural carbohydrates (NSCs). In order to assessthe effects on mature trees of a late frost occurred in spring 2016 and a drought event characterizing the summer 2017, wemonitored the phenology, the radial growth and the dynamic of starch and soluble sugars in a Mediterranean beech forest.Growth was much more reduced by spring late frost than by summer drought, while NSCs dynamic was deeply involved incounteracting the negative effects of both events, supporting plant survival and buffering source-sink imbalances under suchstressful conditions, resulting in a strong trade-off between growth and NSCs dynamic in trees. Overall, our results highlightthe key role of NSCs on trees resilience to extreme weather events, confirming the relevant adaptability to stressful conditions.Such an insight is useful to assess how forests may respond to the potential impacts of climate change on ecosystem processesand to define how future management strategies can help adaptation of beech forests in the Mediterranean area.
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Mediterranean pine plantations provide several ecosystem services but are particularly sensitive to climate change. Forest management practices might play a strategic role in the long-term adaptation of Mediterranean forests, however the joint effect of climate change and alternative management options together in the near and far future must be investigated. Here, we developed a management options portfolio and simulated the development of a Laricio pine (Pinus nigra subsp. laricio) stand in the Bonis watershed (southern Italy) from its establishment in 1958 up to 2095 using a state-of-the-science process-based forest model. The model was run under three climate change scenarios corresponding to increasing levels of atmospheric CO2 concentration, and seven management options with different goals, including post-disturbance management, wood production and renaturalization purposes. We analyzed the effect of climate change on annual carbon fluxes (i.e., gross and net primary production) and stocks (i.e., basal area and potential carbon woody stocks), as well as the impact of different management options compared to no management. Results show that, while climate change (i.e. warming and enriched atmospheric CO2 concentration) seems to increase carbon fluxes and stocks in the first half of the century, both show a substantial decrease in the second half, along with higher temperatures (+3 to +5 °C) and lower precipitation (–20% to –22%). When compared to no management, alternative options had a moderate effect on carbon fluxes over the whole simulation (between –6% and +7%) but overall carbon stocks were maximized by thinning interventions and the shelterwood system (+54% to +55%). We demonstrate that the choice of management exerts greater effects on the features of Laricio pine plantations than climate change alone. Therefore, silvicultural strategies might enhance potential stocks and improve forest conditions, with cascading positive effects on the provision of ecosystem services in Mediterranean pine plantations.
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Even after complete stomatal closure, plants lose water through the leaf cuticles and bark. This residual water conductance of leaves (gleaf‐res) and stems (gbark) can negatively impact plant water balance and affect plant survival in seasonally dry environments. However, little is known about the costs and benefits associated with such water leaks, especially on stem level. Here, we characterized the structural and functional determinants of the variability in gbark across tropical savanna species to elucidate how variations in this trait are related to contrasting growth strategies. The high variability in gbark across species was associated with morphoantomical properties of the outer bark (thickness, density, and lenticel investment), and such characteristics influenced both stem transpiration and respiration, suggesting the existence of a trade‐off between water conservation and oxygen permeability, which reflected contrasting growth and dehydration tolerance strategies. For instance, species with higher gbark and gleaf‐res presented a fast resource acquisition strategy but were more prone to drought‐induced mortality by hydraulic failure. However, model simulations revealed that the relative contribution of gleaf‐res and gbark to overall water balance depended on whether leaves were less or more resistant to cavitation than the stems. Synthesis. By combining correlative studies, experimental results, and a modeling exercise, we provide a new understanding of the costs and benefits associated with the variability in gbark across tropical savanna species, and a new perspective for studies of water relations and carbon economics in species from a hyperdiverse savanna.
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Root respiration (Rr) plays a crucial role in the global carbon balance, because Rr accounts for about a half of soil respiration in typical forest ecosystems. Plant roots are different in metabolism and functions according to size. Fine roots, which are typically defined as roots < 2 mm in diameter, perform important ecosystem functions and consequently govern belowground carbon cycles mainly because of their high turnover rates. However, the phenological variation of fine root functions is not well understood yet. To quantitatively examine the fine root functions, we adopted an approach to partition Rr into growth respiration (Rg) and maintenance respiration (Rm) using a modified traditional model, in which Rg was proportional to root production, and Rm was proportional to root biomass and exponentially related to soil temperature. We conducted a field experiment on soil respiration and fine root biomass and production over a year in a larch‑dominated young forest developing on the bare ground after removing surface organic soil to parameterize the model. The model was significantly parameterized using the field data measured in such simplified field conditions, because we could control spatial variation in heterotrophic respiration and contamination from roots other than fine roots. The annual Rr of all roots was 94 g C m‑2 yr‑1 and accounted for 25% of total soil respiration on average. The annual Rr was partitioned into fine root Rg, fine root Rm and coarse root Rm by 30, 44 and 26%, respectively; coarse root Rg was presumed to be negligible. Fine root Rg and Rm varied according to the seasonal variations of fine root production and soil temperature, respectively; the contribution of fine root biomass was minor because of its small seasonality. The contribution of Rg to total fine root respiration was lower in the cold season with low production.
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This study aimed to simulate oak and beech forest growth under various scenarios of climate change and to evaluate how the forest response depends on site properties and particularly on stand characteristics using the individual process-based model HETEROFOR. First, this model was evaluated on a wide range of site conditions. We used data from 36 long-term forest monitoring plots to initialize, calibrate, and evaluate HETEROFOR. This evaluation showed that HETEROFOR predicts individual tree radial growth and height increment reasonably well under different growing conditions when evaluated on independent sites. In our simulations under constant CO2 concentration ([CO2]cst) for the 2071-2100 period, climate change induced a moderate net primary production (NPP) gain in continental and mountainous zones and no change in the oceanic zone. The NPP changes were negatively affected by air temperature during the vegetation period and by the annual rainfall decrease. To a lower extent, they were influenced by soil extractable water reserve and stand characteristics. These NPP changes were positively affected by longer vegetation periods and negatively by drought for beech and larger autotrophic respiration costs for oak. For both species, the NPP gain was much larger with rising CO2 concentration ([CO2]var) mainly due to the CO2 fertilisation effect. Even if the species composition and structure had a limited influence on the forest response to climate change, they explained a large part of the NPP variability (44% and 34% for [CO2]cst and [CO2]var, respectively) compared to the climate change scenario (5% and 29%) and the inter-annual climate variability (20% and 16%). This gives the forester the possibility to act on the productivity of broadleaved forests and prepare them for possible adverse effects of climate change by reinforcing their resilience.
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Introductory paragraph We present a global analysis of the relationship of forest production efficiency (FPE) to stand age and climate, based on a large compilation of data on gross primary production and either biomass production or net primary production. FPE is important for both forest production and atmospheric carbon dioxide uptake. Earlier findings – FPE declining with age – are supported by this analysis. However, FPE also increases with absolute latitude, precipitation and (all else equal) with temperature. The temperature effect is opposite to what would be expected based on the short-term physiological response of respiration rates to temperature. It implies top-down regulation of forest carbon loss, perhaps reflecting the higher carbon costs of nutrient acquisition in colder climates. Current ecosystem models do not reproduce this phenomenon. They consistently predict lower FPE in warmer climates, and are therefore likely to overestimate carbon losses in a warming climate.
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Process-based vegetation models are widely used to predict local and global ecosystem dynamics and climate change impacts. Due to their complexity, they require careful parameterization and evaluation to ensure that projections are accurate and reliable. The PROFOUND Database (PROFOUND DB) provides a wide range of empirical data on European forests to calibrate and evaluate vegetation models that simulate climate impacts at the forest stand scale. A particular advantage of this database is its wide coverage of multiple data sources at different hierarchical and temporal scales, together with environmental driving data as well as the latest climate scenarios. Specifically, the PROFOUND DB provides general site descriptions, soil, climate, CO2, nitrogen deposition, tree and forest stand level, and remote sensing data for nine contrasting forest stands distributed across Europe. Moreover, for a subset of five sites, time series of carbon fluxes, atmospheric heat conduction and soil water are also available. The climate and nitrogen deposition data contain several datasets for the historic period and a wide range of future climate change scenarios following the Representative Concentration Pathways (RCP2.6, RCP4.5, RCP6.0, RCP8.5). We also provide pre-industrial climate simulations that allow for model runs aimed at disentangling the contribution of climate change to observed forest productivity changes. The PROFOUND DB is available freely as a “SQLite” relational database or “ASCII” flat file version (at https://doi.org/10.5880/PIK.2020.006/; Reyer et al., 2020). The data policies of the individual contributing datasets are provided in the metadata of each data file. The PROFOUND DB can also be accessed via the ProfoundData R package (https://CRAN.R-project.org/package=ProfoundData; Silveyra Gonzalez et al., 2020), which provides basic functions to explore, plot and extract the data for model set-up, calibration and evaluation.
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Carbon allocation plays a key role in ecosystem dynamics and plant adaptation to changing environmental conditions. Hence, proper description of this process in vegetation models is crucial for the simulations of the impact of climate change on carbon cycling in forests. Here we review how carbon allocation modelling is currently implemented in 31 contrasting models to identify the main gaps compared with our theoretical and empirical understanding of carbon allocation. A hybrid approach based on combining several principles and/or types of carbon allocation modelling prevailed in the examined models, while physiologically more sophisticated approaches were used less often than empirical ones. The analysis revealed that, although the number of carbon allocation studies over the past 10 years has substantially increased, some background processes are still insufficiently understood and some issues in models are frequently poorly represented, oversimplified or even omitted. Hence, current challenges for carbon allocation modelling in forest ecosystems are (i) to overcome remaining limits in process understanding, particularly regarding the impact of disturbances on carbon allocation, accumulation and utilization of nonstructural carbohydrates, and carbon use by symbionts, and (ii) to implement existing knowledge of carbon allocation into defence, regeneration and improved resource uptake in order to better account for changing environmental conditions.
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Current process-based vegetation models are complex scientific tools that require proper evaluation of the different processes included in the models to prove that the models can be used to integrate our understanding of forest ecosystems and project climate change impacts on forests. The PROFOUND database (PROFOUND DB) described here aims to bring together data from a wide range of data sources to evaluate vegetation models and simulate climate impacts at the forest stand scale. It has been designed to fulfill two objectives: - Allow for a thorough evaluation of complex, process-based vegetation models using multiple data streams covering a range of processes at different temporal scales - Allow for climate impact assessments by providing the latest climate scenario data. Therefore, the PROFOUND DB provides general a site description as well as soil, climate, CO2, Nitrogen deposition, tree-level, forest stand-level and remote sensing data for 9 forest stands spread throughout Europe. Moreover, for a subset of 5 sites, also time series of carbon fluxes, energy balances and soil water are available. The climate and nitrogen deposition data contains several datasets for the historic period and a wide range of future climate change scenarios following the Representative Emission Pathways (RCP2.6, RCP4.5, RCP6.0, RCP8.5). In addition, we also provide pre-industrial climate simulations that allow for model runs aimed at disentangling the contribution of climate change to observed forest productivity changes. The PROFOUND Database is available freely but we incite users to respect the data policies of the individual datasets as provided in the metadata of each data file. The database can also be accessed via the PROFOUND R-package, which provides basic functions to explore, plot and extract the data. The data (PROFOUND DB) are provided in two different versions (ProfoundData.sqlite download as ProfoundData.zip, ProfoundData_ASCII.zip) and documented by the following three documents: (1) PROFOUNDdatabase.pdf: describes the structure, organisation and content of the PROFOUND DB. (2) PROFOUNDsites.pdf: displays the main data of the PROFOUND DB for each of the 9 forest sites in tables and plots. (3) ProfoundData.pdf: explains how to use the PROFOUND R-Package "ProfoundData" to access the PROFOUND DB and provides example scripts on how to apply it.
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Photosynthesis is not entirely synchronized with carbon sinks, implying that trees are capable of storing non-structural carbohydrates (NSC), such as soluble sugars and starch. These storages provide a buffer between carbohydrate supply and demand and also allow trees to resist drought through osmoregulation. However, estimates of the total pool size and seasonal dynamics of the NSC storage of mature trees are still rare. Part of NSC is allocated outside roots, mainly to symbiotic, root-associated mycorrhizal fungi. The quantity and dynamics of this allocation are difficult to estimate in field conditions due to the close interaction between the symbionts. The aims of this study were to (1) determine the temporal development of NSC concentrations in tree organs, (2) upscale the storage compounds to whole-tree level and (3) analyse the significance of NSC allocation to belowground symbionts as part of the carbon balance in mature pines in a boreal Scots pine stand in southern Finland. We took samples every 2-4 weeks of needles, fine roots, stem wood, shoot wood and phloem from 1 to 3 trees in 2015. Concentrations of soluble sugars and starch were analyzed from the samples and upscaled to tree level. For quantifying the third aim, we used a whole-tree carbon balance model CASSIA that incorporates daily photosynthesis, respiration and organ-specific growth as functions of environmental factors. In this study, we included the allocation to belowground symbionts as an additional carbon sink and scaled the flux using the NSC pool over the whole tree. We observed that organ-specific NSC concentrations were highest in phloem, needles and fine roots. Total NSC increased in spring, peaked during midsummer and decreased again in autumn without any notable decrease during the most intensive growth period at midsummer. In the model analysis, 6% of yearly photosynthesis was allocated to the root-associated symbionts. The study highlights the applicability of the carbon balance approach in evaluating the importance of processes that cannot yet be directly measured.