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Context: It has been proposed that the distribution of resprouter and seeder Erica in the Cape Floristic Region (CFR) of South Africa is determined by drought rather than by fire frequency. Seedlings of Erica seeders are predicted to withstand the mild droughts of the southwest CFR better than those of Erica resprouters, which would account for the abundance of seeders in this region. Aims: This study aimed to test this hypothesis using Erica coccinea (L.), which contains both a resprouter and a seeder form. Methods: One-year-old seedlings of both forms were subjected to a progressively severe 50-day drought in the greenhouse. Key results: Contrary to expectations, seeder seedlings had 67% higher mortality than resprouters during the initial phase of drought (30% vs 18% after 32 days). However, both forms were unable to survive as the drought progressed, resulting in 95% mortality by Day 50. There were limited differences between the forms in gas exchange and water potential, and no difference in root:shoot ratios. However, resprouters had significantly higher soluble carbohydrates than did seeders, which may have aided in delaying mortality. Conclusions: Our results showed no evidence of resprouter seedlings being more vulnerable to mild drought than seeders in E. coccinea. Implications: Our findings challenge the hypothesis that the distribution of this species can be explained by the vulnerability of resprouter seedlings to mild drought. We tested drought sensitivity in reseeder and resprouter seedlings of E. coccinea , a species that contains both reseeder and resprouter morphs. Contrary to expectations, seeder seedlings were more drought sensitive than were resprouter seedlings. Our results challenge the drought-distribution hypothesis for Erica in the Cape Floristic region. [ABSTRACT FROM AUTHOR]

Survival of tree seedlings at high elevations has been shown to be limited by thermal constraints on carbon balance, but it is unknown if carbon relations also limit seedling survival at lower elevations, where water relations may be more important. We measured and modeled carbon fluxes and water relations in first-year Pinus flexilis seedlings in garden plots just beyond the warm edge of their natural range, and compared these with dry-mass gain and survival across two summers. We hypothesized that mortality in these seedlings would be associated with declines in water relations, more so than with carbon-balance limitations. Rather than gradual declines in survivorship across growing seasons, we observed sharp, large-scale mortality episodes that occurred once volumetric soil-moisture content dropped below 10%. By this point, seedling water potentials had decreased below -5 MPa, seedling hydraulic conductivity had decreased by 90% and seedling hydraulic resistance had increased by >900%. Additionally, non-structural carbohydrates accumulated in aboveground tissues at the end of both summers, suggesting impairments in phloem-transport from needles to roots. This resulted in low carbohydrate concentrations in roots, which likely impaired root growth and water uptake at the time of critically low soil moisture. While photosynthesis and respiration on a leaf area basis remained high until critical hydraulic thresholds were exceeded, modeled seedling gross primary productivity declined steadily throughout the summers. At the time of mortality, modeled productivity was insufficient to support seedling biomass-gain rates, metabolism and secondary costs. Thus the large-scale mortality events that we observed near the end of each summer were most directly linked with acute, episodic declines in plant hydraulic function that were linked with important changes in whole-seedling carbon relations.

Non-structural carbohydrates (NSCs) facilitate plant adaptation to drought stress, characterize tree growth and survival ability, and buffer against external disturbances. Previous studies have focused on the distribution and dynamics of NSCs among different plant organs under drought conditions. However, discussion about the NSC levels of fine roots in different root branch orders is limited, especially the relationship between fine root trait variation and NSC content. The objective of the study was to shed light on the synergistic variation in fine root traits and NSC content in different root branch orders under different drought and soil substrate conditions. The 2-year-old Fraxinus mandshurica Rupr. potted seedlings were planted in three different soil substrates (humus, loam, and sandy–loam soil) and subjected to four drought intensities (CK, mild drought, moderate drought, and severe drought) for 2 months. With increasing drought intensity, the biomass of fine roots decreased significantly. Under the same drought intensity, seedlings in sandy–loam soil had higher root biomass, and the coefficient of variation of 5th-order roots (37.4, 44.5, and 53% in humus, loam, and sandy–loam soil, respectively) was higher than that of lower-order roots. All branch order roots of seedlings in humus soil had the largest specific root length (SRL) and specific root surface area (SRA), in addition to the lowest diameter. With increasing drought intensity, the SRL and average diameter (AD) of all root branch orders increased and decreased, respectively. The fine roots in humus soil had a higher soluble sugar (SS) content and lower starch (ST) content compared to the loam and sandy–loam soil. Additionally, the SS and ST contents of fine roots showed decreasing and increasing tendencies with increasing drought intensities, respectively. SS and ST explained the highest degree of the total variation in fine root traits, which were 32 and 32.1%, respectively. With increasing root order, the explanation of the variation in root traits by ST decreased (only 6.8% for 5th-order roots). The observed response in terms of morphological traits of different fine root branch orders of F. mandshurica seedlings to resource fluctuations ensures the maintenance of a low cost-benefit ratio in the root system development.

The definition of stress comes from the physical sciences and refers to the ability of a force applied to a material to induce a deformation (strain). Unlike materials, living organisms and biological systems react to stress with responses to prevent or repair the damage. Plants exposed to stressful conditions move from an optimal (non-stressed) to sub-optimal state, until they reach a new equilibrium with the changed environmental conditions, through physiological, biochemical, and genetic pathways to cope with the new environmental conditions. Multiple fluctuating environmental pressures often act simultaneously, then the effects of individual stresses cannot be isolated. In natural ecosystems, plants, and plant communities, naturally adapted to harsh environments, are in equilibrium with their environment. This equilibrium can be considered as “optimal” albeit in relative terms (i.e., for a specific genotype at a specific site). The mechanisms of acclimatization and adaptation are important especially in trees, which are sessile long-living organisms, unable to escape from the worsening of the environmental conditions. Rapid climate change, with severe drought and heat waves, can have different effects in relation to their level of equilibrium before the impact (starting point). The new equilibrium can be defined in terms of fitness (capacity of individuals to grow and reproduce) and resilience (capacity to cope to stress and restore the condition prior to the disturbing factor). Field studies suggest that the photosynthetic efficiency can be preserved or restored in short time after the stress event, but resilience (measured in terms of dynamic of non-structural carbohydrates at tree level) may be more severely affected. The conservation and management activities of natural resources require monitoring the stress conditions of vegetation and predicting the possible changes in species composition and structure of communities and ecosystems. This is desirable to maintain and optimise the ecosystem services in a new environmental and future climate scenario.

Non-structural carbohydrates (NSCs) are labile components in forest litter that can be released quickly at the early stage of litter decomposition and accelerate the metabolic turnover of soil microorganisms, which is essential for the formation of forest soil organic matter. Therefore, understanding the NSCs response mechanisms to forest litter at different altitudes is critical for understanding nutrient cycling in the forest soil under climate change conditions. In this study, we used the net bag decomposition method to observe the dynamics of NSCs release in Chinese fir topsoil and canopy litter at four altitudes for 360 days based on the climatic zone characteristics distributed vertically along the elevation of Wuyi Mountain. The release of NSCs in Chinese fir litter rise gradually with height increases during the decomposition. The difference of the cumulative release percentage of soluble sugar between different altitudes is more significant than that of starch. The response of the NSC content in different treatment groups at four altitudes are different. The release of NSCs in the leaf canopy litter is higher than that in the leaf topsoil litter. On the contrary, the release of NSCs in the mixture of leaf and twig topsoil litter is higher than that in the mixture of leaf and twig canopy litter. Taken together, this study is of great significance for a comprehensive understanding of the effect of climate change on NSCs during the decomposition of Chinese fir litter.

Background and Aims Carbon reserves are a critical source of energy and substrates that allow trees to cope with periods of minimal carbon gain and/or high carbon demands, conditions which are prevalent in high-latitude forests. However, we have a poor understanding of carbon reserve dynamics at the whole-tree level in mature boreal trees. We therefore sought to quantify the seasonal changes in whole-tree and organ-level carbon reserve pools in mature boreal Betula papyrifera. Methods Non-structural carbohydrate (NSC; soluble sugars and starch) tissue concentrations were measured at key phenological stages throughout a calendar year in the roots, stem (inner bark and xylem), branches and leaves, and scaled up to estimate changes in organ and whole-tree NSC pool sizes. Fine root and stem growth were also measured to compare the timing of growth processes with changes in NSC pools. Key Results The whole-tree NSC pool increased from its spring minimum to its maximum at bud set, producing an average seasonal fluctuation of 0.96 kg per tree. This fluctuation represents a 72 % change in the whole-tree NSC pool, which greatly exceeds the relative change reported for more temperate conspecifics. At the organ level, branches accounted for roughly 48–60 % of the whole-tree NSC pool throughout the year, and their seasonal fluctuation was four to eight times greater than that observed in the stemwood, coarse roots and inner bark. Conclusions Branches in boreal B. papyrifera were the largest and most dynamic storage pool, suggesting that storage changes at the branch level largely drive whole-tree storage dynamics in these trees. The greater whole-tree seasonal NSC fluctuation in boreal vs. temperate B. papyrifera may result from (1) higher soluble sugar concentration requirements in branches for frost protection, and/or (2) a larger reliance on reserves to fuel new leaf and shoot growth in the spring. [ABSTRACT FROM AUTHOR]

Carbon starvation posits that defoliation‐ and drought‐induced mortality results from drawing down stored non‐structural carbohydrates (NSCs), but evidence is mixed, and few studies evaluate mortality directly. We tested the relationships among defoliation severity, NSC drawdown and tree mortality by measuring NSCs in mature oak trees defoliated by an invasive insect, Lymantria dispar, across a natural gradient of defoliation severity.We collected stem and root samples from mature oaks (Quercus rubra and Q. alba) in interior forests (n = 34) and forest edges (n = 47) in central Massachusetts, USA. Total NSC (TNC; sugar + starch) stores were analysed with respect to tree size, species and defoliation severity, which ranged between 5% and 100%.TNC stores declined significantly with increasingly severe defoliation. Forest edge trees had higher TNC stores that were less sensitive to defoliation than interior forest trees, although this may be a result of differing defoliation history. Furthermore, we observed a mortality threshold of 1.5% dry weight TNC.Our study draws a direct link between insect defoliation and TNC reserves and defines a TNC threshold below which mortality is highly likely. These findings advance understanding and improve model parametrization of tree response to insect outbreaks, an increasing threat with globalization and climate change. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Predicted increases in forest drought mortality highlight the need for predictors of incipient drought‐induced mortality (DIM) risk that enable proactive large‐scale management. Such predictors should be consistent across plants with varying morphology and physiology. Because of their integrative nature, indicators of water status are promising candidates for real‐time monitoring of DIM, particularly if they standardize morphological differences among plants. We assessed the extent to which differences in morphology and physiology between Pinus ponderosa populations influence time to mortality and the predictive power of key indicators of DIM risk. Time to incipient mortality differed between populations but occurred at the same relative water content (RWC) and water potential (WP). RWC and WP were accurate predictors of drought mortality risk. These results highlight that variables related to water status capture critical thresholds during DIM and the associated dehydration processes. Both WP and RWC are promising candidates for large‐scale assessments of DIM risk. RWC is of special interest because it allows comparisons across different morphologies and can be remotely sensed. Our results offer promise for real‐time landscape‐level monitoring of DIM and its global impacts in the near term. Relative water content (RWC) predicts drought‐induced mortality risk in morphologically and physiologically distinct Pinus ponderosa seedling populations. Mortality curves based on RWC show incipient mortality thresholds close to turgor loss point that are consistent across organs and populations. [ABSTRACT FROM AUTHOR]

Plant ecosystem structure is understood to be a result of complex multitrophic interactions. Most multitrophic studies focus on plant aboveground adaptations to aboveground herbivore pressures, neglecting belowground adaptations in response to aboveground damage. Differential investment in root structures may allow plants to compensate for tissue loss or damage due to herbivores. Furthermore, phylogeny may constrain a plant's ability to adapt belowground. We examined the belowground responses of 12 species of oak Quercus to varying locations and intensities of simulated herbivore damage. We first established that oak belowground traits responded to aboveground herbivory by measuring patterns of investment in coarse versus fine root structures and re‐allocation of non‐structural carbohydrates (NSC) to root storage. We then tested whether phylogeny could explain variations in investment patterns using phylogenetic independent contrasts. Plant adaptations to aboveground herbivory included allocating biomass and carbon reserves to root structures, depending on the location and intensity of herbivore damage. NSC re‐allocation to root storage was observed when oak species experienced any type of damage, but damage to lateral tissues caused a greater re‐allocation than apical damage or control treatments. We found that most belowground responses to aboveground herbivory are species‐specific and may be adapted for environmental conditions or type of herbivory. Some responses to herbivore damage, such as changes in fine‐root mass and root sugar concentrations, were phylogenetically constrained. Phylogenetic constraints generally occur when there is severe damage at the apical meristem. Plants may adapt to aboveground tissue loss due to varying herbivore pressures (i.e. varying location and intensity of damage) by differentially investing in root types and NSC re‐allocation to root storage. Understanding linkages between and phylogenetic constraints of plant belowground responses to aboveground herbivory will improve our understanding of the ecological processes involved in multitrophic interactions. [ABSTRACT FROM AUTHOR]

Carbon sequestration is a key ecosystem service provided by forests. Inventory data based on individual trees are considered to be the most accurate method for estimating forest productivity. However, the estimations of forest photosynthesis from inventory data remain understudied, particularly when considering the growth and development of individual trees under the background of global change.Here, we used the leaf growth process with phenology and non‐structural carbohydrates (NSC) storage to revise an individual‐tree‐based carbon model, FORCCHN. This model couples leaf development and biomass to quantify gross primary productivity (GPP) in the forests, where growth is decoupled from photosynthesis in daily step. The model was initialized with inventory‐based forest data rather than the more widely used satellite‐based data.We tested the model against measured above‐ground woody biomass, growth of leaf biomass, daily gross ecosystem exchange (GEE) and yearly GEE at five representative forest sites in the Northern Hemisphere. We also compared the results from the original model and the revised model at five forest sites. Including leaf growth dynamics and inventory‐based initialization improved the predicted performance (r2) of GPP by an average of 33%.Synthesis and applications. Our results suggest that the appropriate vegetation data sources (i.e. inventory or satellite selection) and the effective predictions of the growth process should be considered when developing future carbon cycle models and forest carbon estimation options. Applying and improving such carbon models to evaluate carbon sequestration is an important part of forest carbon sink management. [ABSTRACT FROM AUTHOR]

Worldwide drought events have been reported to cause tree growth decline and mortality, thus altering the carbon (C) balance of forest ecosystems. While most of the attention has been focused on the physiological mechanisms associated with drought‐induced tree responses of a few species at specific locations, the ecological attributes of these species, like their niche breadth, may be also important in determining species' sensitivity or resilience to drought. We postulated that wide‐niche breadth tree species should be more drought‐resilient than narrow‐niche breadth species.Using the most severe 2015–2016 El Niño drought event in the last 70 years in Patagonia, we determined pre‐ and post‐drought growth (BAI, basal area increment), C reserves in the form of non‐structural carbohydrate concentrations (NSCs = starch and soluble sugars), wood isotope (δ13C, iWUE and δ18O) signalling and xylem anatomy (mean vessel diameter, mvd) in eight angiosperm tree species of contrasting niche breadth across a sharp precipitation gradient in southern Chile.All species responded in unison after the drought with a non‐water‐conservative response, maintaining BAI and NSCs, decreasing δ13C, and increasing both mvd and the soluble sugars:NSCs ratio relative to pre‐drought time. Contrary to previous results reporting species‐specific drought responses, our results show unequivocally a functional coordination of organisms' vital traits associated with a non‐water‐conservative strategy, and a drought‐induced acclimation based on starch conversion into soluble sugars in all of the tree species we examined, regardless of their niche breadth and habitat preference.We state that abiotic drivers such as drought may have selected similar interspecific responses provided that they operate at the community level rather than at the species level. These findings mark the need to revise current views about the ultimate interspecific functional coordination of organisms' vital traits when facing more frequent and intensive drought events. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Roots are plant organs that absorb nutrients and water. While roots serve as sink organs for nutrients in perennial and woody plant species, the dynamics of nutrient accumulation in roots for annual plant species, particularly in crop species like Oryza sativa L. (rice), are not well understood. Japanese rice cultivars bred for whole-crop silage exhibit large aboveground biomass and a notably small number of spikelets. This sink-source imbalance leads to the accumulation of non-structural carbohydrates (NSC) in stems after heading. It is hypothesized that rice cultivars with substantial aboveground biomass might also develop significant belowground biomass. Consequently, the sink-source imbalance may result in NSC accumulation in roots. This study aims to test two hypotheses: firstly, that newly developed small-panicle rice cultivars accumulate NSC in roots post-heading, and secondly, that this post-heading NSC accumulation in roots can be influenced by cultural practices affecting spikelet number per panicle. Two small-panicle cultivars, Tachisuzuka and Tachiayaka, and two large-panicle cultivars, Kusanohoshi and Hoshiaoba, were grown using different methods of three cultural practices: nitrogen application, transplanting season, and planting density. Measurements of dry matter, NSC (starch and sugars), and nitrogen in each plant part (panicle, leaf, stem, and roots) were taken over time after heading. The spikelet number per panicle was also counted. Post-heading, the small-panicle cultivars exhibited NSC accumulation in roots, a phenomenon not observed in the large-panicle cultivars. Although the three cultural practices altered the spikelet number per panicle and thus the sink capacity of the small-panicle cultivars, root NSC accumulation remained unaffected. Additionally, nitrogen weight per unit field area increased with increases in root weight in the small-panicle cultivars. The imbalance in the sink-source relationship is likely responsible for the post-heading NSC accumulation in roots observed in small-panicle cultivars. However, the lack of root response in NSC accumulation to changes in panicle sink capacity suggests other mechanisms might be involved in root NSC accumulation. Notably, significant amounts of NSC and nitrogen remain in the roots of small-panicle cultivars after harvest. The accumulation of NSC and nitrogen in roots post-heading could potentially enhance crop growth in subsequent years. • First clear evidence of post-heading non-structural carbohydrate (NSC) accumulation in rice roots. • Small-panicle cultivars accumulate significantly more NSC and nitrogen in roots than large-panicle cultivars. • Root starch content increased up to 20–25 % in small-panicle cultivars after heading. • Cultivation practices affecting sink capacity did not significantly alter root NSC accumulation. • Accumulated root NSC and nitrogen may contribute to soil fertility and growth of subsequent crops. [ABSTRACT FROM AUTHOR]

Abstract Background Carbohydrate partitioning and utilization is a key determinant of growth rate and of yield in plants and crops. There are few studies on crops in field conditions. In Arabidopsis, starch accumulation in leaves is a negative indicator of growth rate. Results Here, we wished to establish if starch accumulation in leaves could potentially be a marker for growth rate and yield in crops such as maize. We characterized daily patterns of non-structural carbohydrate (NSC) at different growth stages over two seasons for maize hybrids in the field. In 27 commercial hybrids, we found a significant negative relationship between residual starch in leaves and plant growth, but not with final yield and biomass. We then focused on three typical hybrids and established a method for calculation of C turnover in photosynthetic leaves that took into account photosynthesis, leaf area and NSC accumulation. The ratios of stored NSC decreased from approximately 15% to less than 4% with ongoing ontogeny changes from V7 to 28 days after pollination. Conclusion The proportion rather than absolute amount of carbon partitioned to starch in leaves at all stages of development related well with yield and biomass accumulation. It is proposed that screening plants at an early vegetative growth stage such as V7 for partitioning into storage may provide a prospective method for maize hybrid selection. Our study provides the basis for further validation as a screening tool for yield.

Abstract Background Understanding the mechanisms of crops in response to elevated CO2 concentrations is pivotal to estimating the impacts of climate change on the global agricultural production. Based on earlier results of the “doubling-CO2 concentration” experiments, many current climate models may overestimate the CO2 fertilization effect on crops, and meanwhile, underestimate the potential impacts of future climate change on global agriculture ecosystem when the atmospheric CO2 concentration goes beyond the optimal levels for crop growth. Results This study examined the photosynthetic response of soybean (Glycine max (L.) Merr.) to elevated CO2 concentration associated with changes in leaf structure, non-structural carbohydrates and nitrogen content with environmental growth chambers where the CO2 concentration was controlled at 400, 600, 800, 1000, 1200, 1400, 1600 ppm. We found CO2-induced down-regulation of leaf photosynthesis as evidenced by the consistently declined leaf net photosynthetic rate (A n) with elevated CO2 concentrations. This down-regulation of leaf photosynthesis was evident in biochemical and photochemical processes since the maximum carboxylation rate (V cmax) and the maximum electron transport rate (J max) were dramatically decreased at higher CO2 concentrations exceeding their optimal values of about 600 ppm and 400 ppm, respectively. Moreover, the down-regulation of leaf photosynthesis at high CO2 concentration was partially attributed to the reduced stomatal conductance (G s) as demonstrated by the declines in stomatal density and stomatal area as well as the changes in the spatial distribution pattern of stomata. In addition, the smaller total mesophyll size (palisade and spongy tissues) and the lower nitrogen availability may also contribute to the down-regulation of leaf photosynthesis when soybean subjected to high CO2 concentration environment. Conclusions Down-regulation of leaf photosynthesis associated with the changes in stomatal traits, mesophyll tissue size, non-structural carbohydrates, and nitrogen availability of soybean in response to future high atmospheric CO2 concentration and climate change.

Trees that grow in urban areas are confronted with a wide variety of stresses that undermine their long-term survival. These include mechanical damage to the crown, root reduction and stem injury, all of which remove significant parts of plant tissues. The single or combined effects of these stresses generate a complex array of growth and ecophysiological responses that are hard to predict. Here we evaluated the effects of different individual and combined damage on the dynamics of non-structural carbohydrates (NSC, low weight sugars plus starch) concentration and new tissue growth (diameter increment) in young trees. We hypothesized that (i) tissue damage will induce larger reductions in diameter growth than in NSC concentrations and (ii) combinations of stress treatments that minimally alter the “functional equilibrium” (e.g., similar reductions of leaf and root area) would have the least impact on NSC concentrations (although not on growth) helping to maintain tree health and integrity. To test these hypotheses, we set up a manipulative field experiment with 10-year-old trees of common urban species (Celtis occidentalis, Fraxinus pennsylvanica, and Tilia cordata). These trees were treated with a complete array of mechanical damage combinations at different levels of intensity (i.e., three levels of defoliation and root reduction, and two levels of stem damage). We found that tree growth declined in relation to the total amount of stress inflicted on the trees, i.e., when the combined highest level of stress was applied, but NSC concentrations were either not affected or, in some cases, increased with an increasing level of stress. We did not find a consistent response in concentration of reserves in relation to the combined stress treatments. Therefore, trees appear to reach a new “functional equilibrium” that allows them to adjust their levels of carbohydrate reserves, especially in stems and roots, to meet their metabolic demand under stressful situations. Our results provide a unique insight into the carbon economy of trees facing multiple urban stress conditions in order to better predict long-term tree performance and vitality.

Trees that grow in urban areas are confronted with a wide variety of stresses that undermine their long-term survival. These include mechanical damage to the crown, root reduction and stem injury, all of which remove significant parts of plant tissues. The single or combined effects of these stresses generate a complex array of growth and ecophysiological responses that are hard to predict. Here we evaluated the effects of different individual and combined damage on the dynamics of non-structural carbohydrates (NSC, low weight sugars plus starch) concentration and new tissue growth (diameter increment) in young trees. We hypothesized that (i) tissue damage will induce larger reductions in diameter growth than in NSC concentrations and (ii) combinations of stress treatments that minimally alter the "functional equilibrium" (e.g., similar reductions of leaf and root area) would have the least impact on NSC concentrations (although not on growth) helping to maintain tree health and integrity. To test these hypotheses, we set up a manipulative field experiment with 10-year-old trees of common urban species (Celtis occidentalis, Fraxinus pennsylvanica , and Tilia cordata). These trees were treated with a complete array of mechanical damage combinations at different levels of intensity (i.e., three levels of defoliation and root reduction, and two levels of stem damage). We found that tree growth declined in relation to the total amount of stress inflicted on the trees, i.e., when the combined highest level of stress was applied, but NSC concentrations were either not affected or, in some cases, increased with an increasing level of stress. We did not find a consistent response in concentration of reserves in relation to the combined stress treatments. Therefore, trees appear to reach a new "functional equilibrium" that allows them to adjust their levels of carbohydrate reserves, especially in stems and roots, to meet their metabolic demand under stressful situations. Our results provide a unique insight into the carbon economy of trees facing multiple urban stress conditions in order to better predict long-term tree performance and vitality. [ABSTRACT FROM AUTHOR]

Non‐structural carbohydrate (NSC) storage may be under strong selection in woody plant species that occur across broad environmental gradients. We therefore investigated carbon (C) allocation strategies in a widespread non‐native woody plant, Tamarix. We predicted that genotypes with exposure to episodic freeze events would show elevated NSC concentrations compared to warm‐adapted genotypes with the trade‐off of reduced growth and reproduction relative to warm‐adapted populations.We established an experimental common garden using genotypes of Tamarix, sourced across a strong thermal gradient within the introduced range. We measured seasonal NSC storage in coarse roots and stems, above‐ground growth and flower production.Autumn NSC concentrations were 50% higher in genotypes from sites with episodic spring freeze events compared to genotypes from warmer sites. These cold‐adapted genotypes also had a 2.3‐fold higher starch to soluble sugar ratio than warm‐adapted genotypes. Across all genotypes and seasons, NSC storage was inversely correlated with growth and reproduction.Results suggest that Tamarix from colder locations cope with freeze events by maintaining large storage pools to support tissue regrowth, but with the trade‐off of overall reduced growth and reproduction. Our results are consistent with rapid selection in C allocation strategies in response to climate in introduced woody species. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Trees' total amount of non‐structural carbohydrate (NSC) stores and the proportion of these stores residing as insoluble starch are vital traits for individuals living in variable environments. However, our understanding of how stores vary in response to environmental stress is poorly understood as the genetic component of storage is rarely accounted for in studies. Here, we quantified variation in NSC traits in branch samples taken from over 600 clonally transplanted black cottonwood (Populus trichocarpa) trees grown in two common gardens. We found heritable variation in both total NSC stores and the proportion of stores in starch (H2TNC = 0.19, H2PropStarch = 0.31), indicating a substantial genetic component of variation. In addition, we found high amounts of plasticity in both traits in response to cold temperatures and significant genotype‐by‐environment (GxE) interactions in the total amount of NSC stored (54% of P is GxE). This finding of high GxE indicates extensive variation across trees in their response to environment, which may explain why previous studies of carbohydrate stores' responses to stress have failed to converge on a consistent pattern. Overall, we found high amounts of environmental and genetic variation in NSC storage concentrations, which may bolster species against future climate change. Black cottonwood (Populus trichocarpa) exhibits substantial genetic and environmental variation in the storage of non‐structural carbohydrates (NSC). Noticeably, plasticity in total NSC stores is largely attributable to genotype‐by‐environment interactions, which may explain why the literature on NSC storage response to stress is equivocal. [ABSTRACT FROM AUTHOR]

Purpose: Plant belowground storage traits are important for mediating environmental stress, but their role in response to water availability and their coordination with above-ground traits is largely unknown. We predicted a coordination of conservative above- and belowground traits and preferential storage of water-soluble carbohydrates in the drier grassland and acquisitive traits and preferential storage of starch in the wetter grassland. Methods: We examined the relationship between plant preference/response for water availability (habitat preference, intrinsic water use efficiency, and leaf relative water content deficit) and the traits of belowground storage organs (morphological, anatomical, and storage carbohydrate concentration) in 37 perennial herbs from a wet and a dry temperate grassland in the Czech Republic. Results: Species from the dry grassland preferred lower moisture, had greater water use efficiency than those from the wet grassland, and were also more conservative in their morphological and leaf traits. Although dry grassland plants preferentially stored oligo- and polysaccharides, their water-use efficiency increased with greater concentrations of starch. Leaf relative water content deficit did not vary significantly between the grasslands and additionally, the relationship to plant economy was not always in accord with other measures of preference for water availability. Conclusion: Our results imply that belowground storage organs play a role in the response to reduced water availability. The strategies employed are further dependent upon the habitat and phylogeny of the species. [ABSTRACT FROM AUTHOR]

The long-term increases in average temperature and intensification of droughts which characterise the current state of the Earth’s climate system have a negative impact on forest ecosystems and can lead to a decrease in their area and deterioration of the living conditions of their components. In the conditions of the Ukrainian Steppe an important environmental, antierosion, water-protective and soil-protective role belongs to the ravine forests. The most valuable component of the ravine forests is presented by natural populations of common oak (Quercus robur L.), which are able to tolerate the arid climate typical of the steppe region. But with global warming, the endurance of this species is changing. It is believed that a significant role in plant adaptation to drought and high temperatures may belong to non-structural carbohydrates. Therefore, it is important to study changes in the concentration of these substances in the leaves of this leading species under the action of adverse hydrothermal conditions. The article analyzes the content and dynamics of soluble sugars (glucose, fructose, sucrose) and starch in the leaves of Quercus robur L. under different forest growth conditions of the ravine forest (hygromesophilic (CL2–3), mesoxerophilic (CL1) and xerophilic (CL0)). The research was conducted in the forest in the Viyskove area (steppe zone of Ukraine) in the thalweg and at different levels of slope of southern exposure. Content of glucose, fructose, sugar and starch in Quercus roburleaves was determined. It was found that when exposed to high temperatures and increasing water stress during the vegetation period in xerophilic (CL0–1) and mesoxerophilic (CL1) forest growth conditions, the concentration of both glucose and sucrose in the leaves of Q. robur increases and it becomes much higher than in conditions of more optimal water supply. At the same time, the disaccharide content increases more significantly than that of monosaccharide. The greatest amount of these sugars is observed in the driest months (July, August), when conditions for providing plants with water are the most stressful. When water stress grows the increase in concentration of glucose and sucrose is correlated with reduction of starch content. It has been found that the concentration of fructose in Q. robur leaves in droughty conditions of growing was comparable to more favourable conditions of moisture. In September, there is a decline in the content of all forms of non-structural carbohydrates in the leaves of plants of all variants compared to the previous month, especially in conditions of adverse water supply. Therefore, forest growth conditions do not affect the nature of the dynamics of soluble sugars and starch in the leaves of Q.robur, although they change their quantitative indicators. Based on the protective function of sugars under the action of stressors on plants, we can assume that in conditions of significant lack of moisture in the soil their accumulation in the leaves in areas with mesoxerophilic and xerophilic hygrotopes plays an important role in increasing Q. robur drought resistance. [ABSTRACT FROM AUTHOR]

There is a need to better understand and promote formation of ' Jiang Xiang ', the highly valuable heartwood of Dalbergia odorifera T. Chen. Plant growth regulators are the most widely used and generally most effective promoters of heartwood formation. However, to date no method has been proved effective for D. odorifera as little is known about biochemical and physiological change during heartwood development. Four potential heartwood induction substances viz. ethephon, methyl jasmonate, salicylic acid and abscisic acid solutions were injected into the trunk of D. odorifera to determine the effect on heartwood formation and related physiological responses. Non-structural carbohydrates, wood properties, essential oil and histochemical and structural observation were assessed in the post-treatment period. As also observed in the formation of natural heartwood, growth regulator-induced Jiang Xiang production was accompanied by sapwood dehydration, non-structural carbohydrates consumption and synthesis of heartwood specific substances. These substances were synthesized in the ray and axial parenchyma and than transported into the vessels through the pits. As the heartwood substances accumulated, basic density and essential oil content increased gradually, thereby Jiang Xiang was finally produced. In this process, physiological parameters of discoloured sapwood gradually evolved to resemble those of natural heartwood. Ethephon-induced Jiang Xiang was closest to natural heartwood and its density, essential oil content, composition and relative amounts met the standards for high-quality Jiang Xiang , while the other inducers had unsatisfactory induction effects. This study supports the hypothesis that ethephon could be applied to induce formation of Jiang Xiang in D. odorifera. [ABSTRACT FROM AUTHOR]

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Fine roots are vital for water and nutrient uptake in plants. Understanding the responses of metabolic traits to changing environmental conditions is critical, but little is known. In this study, the carbohydrate content of fine roots was characterized for six soil layers and three diameter classes in a Schrenk spruce (Picea schrenkiana) forest on the Tianshan Mountains of China. Soil nitrogen addition can influence carbohydrate content, but the degree is related to soil layer and fine root diameter. Specifically, as nitrogen (N) levels increased, the soluble sugar, cellulose, lignin and structural carbohydrate content (SC) all increased and then decreased; the starch and non-structural carbohydrate content (NSC) decreased gradually. In addition, N addition had significant effects on starch and cellulose content, as well as total carbohydrates. The interaction between root diameter and N addition also influenced soluble sugars, cellulose and NSC, while the three-way interaction among N addition, soil layer and diameter only affected cellulose content and NSC/SC. In the control treatment (no nitrogen addition), the following soil factors influenced fine root metabolism in order of decreasing importance: C:N, C:P, N:P, C, N, water content, bulk density, pH, conductivity, and P. In the N addition treatments, the soil conductivity, pH, and N content were strongly correlated with root metabolic characteristics. [ABSTRACT FROM AUTHOR]

When exploring the impact of resource availability on perennial plants, artificial treatments often apply conditions homogeneously across space and time, even though this rarely reflects conditions in natural systems. To investigate the effects of spatially heterogeneous soil moisture on morphological and physiological responses, trembling aspen (Populus tremuloides) saplings were used in a split-pot experiment. Following the division of the root systems, saplings were established for a full year and then subjected to either heterogeneous (portion of the root system exposed to non-lethal drought) or homogeneous (whole root system exposed to non-lethal drought or well-watered) treatments. Above- and belowground growth and non-structural carbohydrate (NSC) reserves (soluble sugars and starch) were measured to determine how allocation of reserves and mass between and within organs changed in response to variation in soil moisture availability. In contrast to saplings in the homogeneous drought treatment, which experienced reduced shoot growth, leaf abscission and fine root loss, saplings exposed to the heterogeneous conditions maintained similar aboveground growth and increased root system allocation compared to well-watered saplings. Interestingly under heterogeneous soil moisture conditions, the portion of the root system that was resource limited had no root dieback and increased carbon reserve concentrations, while the portion of the root system that was not resource limited added new roots (30% increase). Overall, saplings subjected to the heterogeneous soil moisture regime over-compensated belowground, both in mass and NSC reserves. These results indicate that the differential allocation of mass or reserves between above- and belowground organs, but also within the root system can occur. While the mechanisms and processes involved in these patterns are not clear, these responses could be interpreted as adaptations and acclimations to preserve the integrity of the entire sapling and suggests that different portions of plant organs might respond autonomously to local conditions. This study provides further appreciation of the complexity of the mechanisms by which plants manage heterogeneous conditions and offers evidence that spatial and temporal variability of resource availability, particularly belowground, needs to be accounted for when extrapolating and modeling stress responses at larger temporal and spatial scales.

Storage carbon (C) pools are often assumed to contribute to respiration and growth when assimilation is insufficient to meet the current C demand. However, little is known of the age of stored C and the degree to which it supports respiration in general. We used bomb radiocarbon ((14)C) measurements to determine the mean age of carbon in CO2 emitted from and within stems of three tropical tree species in Peru. Carbon pools fixed >1 year previously contributed to stem CO2 efflux in all trees investigated, in both dry and wet seasons. The average age, i.e., the time elapsed since original fixation of CO2 from the atmosphere by the plant to its loss from the stem, ranged from 0 to 6 years. The average age of CO2 sampled 5-cm deep within the stems ranged from 2 to 6 years for two of the three species, while CO2 in the stem of the third tree species was fixed from 14 to >20 years previously. Given the consistency of (14)C values observed for individuals within each species, it is unlikely that decomposition is the source of the older CO2. Our results are in accordance with other studies that have demonstrated the contribution of storage reserves to the construction of stem wood and root respiration in temperate and boreal forests. We postulate the high (14)C values observed in stem CO2 efflux and stem-internal CO2 result from respiration of storage C pools within the tree. The observed age differences between emitted and stem-internal CO2 indicate an age gradient for sources of CO2 within the tree: CO2 produced in the outer region of the stem is younger, originating from more recent assimilates, whereas the CO2 found deeper within the stem is older, fueled by several-year-old C pools. The CO2 emitted at the stem-atmosphere interface represents a mixture of young and old CO2. These observations were independent of season, even during a time of severe regional drought. Therefore, we postulate that the use of storage C for respiration occurs on a regular basis challenging the assumption that storage pools serve as substrates for respiration only during times of limited assimilation.

Objectives: Carbon fixed during photosynthesis is exported from leaves towards sink organs as non-structural carbohydrates (NSC), that are a key energy source for metabolic processes in trees. In xylem, NSC are mostly stored as soluble sugars and starch in radial and axial parenchyma. The multi-functional nature of xylem means that cells possess several functions, including water transport, storage and mechanical support. Little is known about how NSC impacts xylem multi-functionality, nor how NSC vary among species and climates. We collected leaves, stem and root xylem from tree species growing in three climates and estimated NSC in each organ. We also measured xylem traits linked to hydraulic and mechanical functioning. Data description: The paper describes functional traits in leaves, stems and roots, including NSC, carbon, nitrogen, specific leaf area, stem and root wood density and xylem traits. Data are provided for up to 90 angiosperm species from temperate, Mediterranean and tropical climates. These data are useful for understanding the trade-offs in resource allocation from a whole-plant perspective, and to better quantify xylem structure and function related to water transportation, mechanical support and storage. Data will also give researchers keys to understanding the ability of trees to adjust to a changing climate. [ABSTRACT FROM AUTHOR]

When exploring the impact of resource availability on perennial plants, artificial treatments often apply conditions homogeneously across space and time, even though this rarely reflects conditions in natural systems. To investigate the effects of spatially heterogeneous soil moisture on morphological and physiological responses, trembling aspen (Populus tremuloides) saplings were used in a split-pot experiment. Following the division of the root systems, saplings were established for a full year and then subjected to either heterogeneous (portion of the root system exposed to non-lethal drought) or homogeneous (whole root system exposed to non-lethal drought or well-watered) treatments. Above- and belowground growth and non-structural carbohydrate (NSC) reserves (soluble sugars and starch) were measured to determine how allocation of reserves and mass between and within organs changed in response to variation in soil moisture availability. In contrast to saplings in the homogeneous drought treatment, which experienced reduced shoot growth, leaf abscission and fine root loss, saplings exposed to the heterogeneous conditions maintained similar aboveground growth and increased root system allocation compared to well-watered saplings. Interestingly under heterogeneous soil moisture conditions, the portion of the root system that was resource limited had no root dieback and increased carbon reserve concentrations, while the portion of the root system that was not resource limited added new roots (30% increase). Overall, saplings subjected to the heterogeneous soil moisture regime over-compensated belowground, both in mass and NSC reserves. These results indicate that the differential allocation of mass or reserves between above- and belowground organs, but also within the root system can occur. While the mechanisms and processes involved in these patterns are not clear, these responses could be interpreted as adaptations and acclimations to preserve the integrity of the entire sapling and suggests that different portions of plant organs might respond autonomously to local conditions. This study provides further appreciation of the complexity of the mechanisms by which plants manage heterogeneous conditions and offers evidence that spatial and temporal variability of resource availability, particularly belowground, needs to be accounted for when extrapolating and modeling stress responses at larger temporal and spatial scales. [ABSTRACT FROM AUTHOR]

Background and Aims Although the plant economic spectrum seeks to explain resource allocation strategies, carbohydrate storage is often omitted. Belowground storage organs are the centre of herb perennation, yet little is known about the role of their turnover, anatomy and carbohydrate storage in relation to the aboveground economic spectrum. Methods We collected aboveground traits associated with the economic spectrum, storage organ turnover traits, storage organ inner structure traits and storage carbohydrate concentrations for ~80 temperate meadow species. Key Results The suites of belowground traits were largely independent of one another, but there was significant correlation of the aboveground traits with both inner structure and storage carbohydrates. Anatomical traits diverged according to leaf nitrogen concentration on the one hand and vessel area and dry matter content on the other; carbohydrates separated along gradients of leaf nitrogen concentration and plant height. Conclusions Contrary to our expectations, aboveground traits and not storage organ turnover were correlated with anatomy and storage carbohydrates. Belowground traits associated with the aboveground economic spectrum also did not fall clearly within the fast–slow economic continuum, thus indicating the presence of a more complicated economic space. Our study implies that the generally overlooked role of storage within the plant economic spectrum represents an important dimension of plant strategy. [ABSTRACT FROM AUTHOR]

In order to explore the variation characteristics of the non-structural carbohydrate concentration of dominant tree species in the coniferous and broad-leaved natural secondary forest in the Xiaoxing’an Mountains with tree species, organs and thinning intensity, and to understand the distribution pattern, growth status, adaptation strategies and recovery potential of the NSC after the forest belt thinning, the coniferous and broad-leaved natural secondary forest in the mixed natural secondary forest with 6 kinds of thinning intensity(0%, 15%, 20%, 25%, 30%, 35%), select 5 main tree species, collect tree branches, trunks and leaves, and determine their soluble sugar and starch concentration, analyze the variation characteristics of NSC components with tree species, organs and thinning intensity. The results showed that there were significant differences in the concentration of soluble sugar, starch and total NSC among different tree species. All NSC components have high variation in different tree species. The coefficients of variation of the NSC components of Picea asperata, Acermono, Acer tegmentosum and Pinus koraiensis were all greater than 30%, and the highest was 88%. There were significant differences in NSC concentration among different organs. Among them, the concentration of soluble sugar was the highest in the leaves and the lowest in the trunk. The concentration of starch and total NSC was the highest in the trunk and the lowest in the branches. The various components of NSC had low variation in different organs, all of which were less than 35%. The intensity of thinning also had a significant effect on each NSC component. All NSC components had high variation in different. [ABSTRACT FROM AUTHOR]

Copyright of Forest Research is the property of Forest Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: To restore secondary forests (major forest resources worldwide), it is essential to accelerate the natural regeneration of dominant trees by altering micro-environments. Forest gaps are products of various disturbances, ranging from natural storms or wildfires to anthropogenic events like logging and slashing-and-burning, and sprouts of most tree species with non-structural carbohydrates (NSCs) storage can regenerate from stumps after gap formation. However, how the stump sprouts with diverse NSCs storages and stump sizes (i.e., diameters) adapt to various micro-environments of within-gap positions remains unclear. Therefore in this study, we monitored the stump sprout regeneration (density, survival, and growth) and NSCs concentrations of three dominant tree species with different shade tolerances and varying stump diameters at five within-gap positions for the first two consecutive years after gap formation. Results: Stump diameter was positively correlated with sprout density, growth, and survival of all three tree species, but insignificantly related with sprout NSCs concentrations at the early stage after gap formation. The effect of within-gap position on sprout NSCs concentrations was different among species. After an environmental adaptation of two growing seasons, the north of gap (higher light availability and lower soil moisture habitat) was the least conducive for shade-intolerant Quercus mongolica to accumulate leaf NSCs, and the east of gap (shadier and drier habitat) was conducive to increasing the leaf NSCs concentrations of shade-tolerant Tilia mandshurica. Conclusions: Within-gap position significantly affected leaf NSCs concentrations of all three tree species, but most of the sprout growth, survival, and stem NSCs concentrations were independent of the various within-gap positions. Besides stump diameter, the NSCs stored in stump and root systems and the interspecific differences in shade tolerance also contributed more in sprout regeneration at the early stage (2 years) of gap formation. A prolonged monitoring (> 10 years) is needed to further examine the long-term effects of stump diameter and within-gap position on sprout regeneration. All of these findings could be applied to gap-based silviculture by promoting sprout regeneration of dominant tree species with different shade tolerances, which would help accelerate the restoration of temperate secondary forests. [ABSTRACT FROM AUTHOR]

Key message: Pathogen-induced defoliation resulted in a reduction in transpiration, an upregulation of photosynthesis in the early growing season, and no change in NSC reserves across stem, root, and foliar tissues. The defoliation of eastern white pine (Pinus strobus L.) by native fungi associated with white pine needle damage (WPND) can substantially reduce foliar area for much of the growing season in the northeastern United States. Chronic defoliations in the region are known to have slowed growth rates in symptomatic stands, but the physiological impacts of WPND as it relates to tree water use and carbon assimilation are largely unresolved. We investigated how the severity of WPND defoliation influences transpiration throughout the course of a growing season. We also assessed leaf-level gas exchange between defoliation severity classes and needle age over time. Finally, we compared concentrations of non-structural carbohydrates (NSC) between defoliation severity classes in five different tissue types over time. We found that trees experiencing a high-severity defoliation had 20% lower sap flux density compared to low-severity individuals. We found that rates of photosynthesis were significantly influenced by the needle age class and time of year, while instantaneous water use efficiency was higher across all needle age classes late in the growing season. Our findings suggest that the residual current-year foliage of high-severity defoliated trees compensated for the loss of mature second- and third-year foliage in the early portion of the growing season. This study found that soluble sugars and starch varied significantly over time and by tissue type, but defoliation severity had little effect on NSC concentrations. Together with reduced basal area increment in high-severity trees relative to low-severity trees, this indicates that WPND-affected trees are prioritizing NSC storage over secondary growth. [ABSTRACT FROM AUTHOR]

Climate change has a large influence on plant functional and phenotypic traits including plant primary and secondary metabolites. One well-established approach to investigating the variation in plant metabolites involves studying plant populations along elevation and latitude gradients. We considered how two space-for-time climate change gradients (elevation and latitude) influence carbohydrate reserves (soluble sugars, starches) and secondary metabolites (monoterpenes, diterpene resin acids) of lodgepole pine trees in western Canada. We were particularly interested in the relationship of terpenes and carbohydrates with a wide range of tree, site, and climatic factors. We found that only elevation had a strong influence on the expression of both terpenes and carbohydrates of trees. Specifically, as elevation increased, concentrations of monoterpenes and diterpenes generally increased and soluble sugars (glucose, sucrose, total sugars) decreased. In contrast, latitude had no impact on either of terpenes or carbohydrates. Furthermore, we found a positive relationship between concentrations of starch and total terpenes and diterpenes in the elevation study; whereas neither starches nor sugars were correlated to terpenes in the latitude study. Similarly, both terpenes and carbohydrates had a much greater number of significant correlations to site characteristics such as slope, basal area index, and sand basal area, in the elevational than in the latitude study. Overall, these results support the conclusion that both biotic and abiotic factors likely drive the patterns of primary and secondary metabolite profiles of lodgepole pine along geographical gradients. Also, presence of a positive relationship between terpenes and starches suggests an interaction between primary ad secondary metabolites of lodgepole pine trees. [ABSTRACT FROM AUTHOR]

Plant sugars serve to balance nutrition, regulate development, and respond to biotic and abiotic stresses, whereas non-structural carbohydrates (NSCs) are essential energy sources that facilitate plant growth, metabolism, and environmental adaptation. To better elucidate the mechanisms of NSCs in red maple, ultrahigh-performance liquid chromatograph Q extractive mass spectrometry (UHPLC-QE-MS) and high-throughput RNA-sequencing were performed on green, red, and yellow leaves from a selected red maple mutant. In green leaves, the fructose phosphorylation process exhibited greater flux. In yellow leaves, sucrose and starch had a stronger capacity for synthesis and degradation, whereas in red leaves, there was a greater accumulation of trehalose and manninotriose. ArTPS5 positively regulated amylose, which was negatively regulated by ArFBP2, whereas ArFRK2 and ArFBP13 played a positive role in the biosynthesis of Sucrose-6P. Sucrose-6P also regulated anthocyanins and abscisic acid in red maple by affecting transcription factors. The results of this paper can assist with the control and optimization of the biosynthesis of NSCs in red maple, which may ultimately provide the foundation for influencing sugar production in Acer. [ABSTRACT FROM AUTHOR]

It is widely accepted that a tight coordination between carbon (C) utilization in the sink and C assimilation and metabolism in the source exists in higher plants. However, much of our current understanding is based on research from herbaceous plants, where the source and sink interaction is less sophisticated compared to woody perennials with a significant sink presence. Apple (Malus x domestica Borkh.) is a good representative of the latter category, and its production and transport of sorbitol, in addition to sucrose, adds complexity to C regulation. In this study, fouryear- old "Gala"/"M.26" apple trees were subjected to crop load levels at 2.5, 7.5, and 15 fruits/cm2 trunk cross-sectional area. Low crop load trees exhibited reduced leaf C assimilation and extra accumulation of non-structural carbohydrates (NSC). This was primarily a result of reduced activity of Rubisco and increased activities of key enzymes that synthesize starch, sucrose, and sorbitol. Among the NSC, leaf starch was found to be most sensitive to crop load and could function as a leading indicator for source--sink balance in apple. However, even the high crop load trees still retained a significant amount of NSC in leaves at dawn, demonstrating that apple is fundamentally different from herbaceous plants in the way it balances leaf carbon inventories at dawn with carbon export at night for sink growth. [ABSTRACT FROM AUTHOR]

The distribution of vegetation in coastal wetlands is significantly influenced by soil properties. However, the mechanisms of how soil characteristics impact the physiological processes of Tamarix chinensis forests remain underexplored. This study examined changes in the soil physicochemical properties and structural attributes of natural T. chinensis forests in the Yellow River Delta with increasing distance from the shoreline. T. chinensis trees were classified into healthy, intermediate, and dying categories based on growth potential, and dynamic changes in salt ions and non-structural carbohydrates (NSCs) were investigated. Results indicated that increasing distance from the shoreline corresponded to decreased soil salinity and pH, and increased soil moisture. T. chinensis mortality rate decreased, while tree height and ground diameter increased with distance. Soil salt content was positively correlated with T. chinensis mortality, but negatively correlated with tree height and ground diameter. Trees with lower growth potential had higher Na + but lower K + and K + /Na + ratio. Soil salt content was positively correlated with root and stem Na + , while soil moisture was positively correlated with leaf NSCs. These findings suggest that soil salt content and moisture significantly influence T. chinensis ion absorption and NSC accumulation, with sodium toxicity being a key factor in the spatial distribution of T. chinensis forests.

In a tropical savanna climate like Thailand, cassava can be planted all year round and harvested at 8 to 12 months after planting (MAP). However, it is not clear how water limitation during the dry season without rain affects carbon assimilation, partitioning, and yield. In this field investigation, six cassava genotypes were planted in the rainy season (August 2021) under continuous irrigation (control) or subjected to drought for 60 days from 3MAP to 5MAP during the dry season (November 2021 to January 2022) with no irrigation and rainfall. After that, the plants were rewatered and continued growing until harvest at 12MAP. After 60 days of stress, there were significant reductions in the mean net photosynthesis rate (Pn), petiole, and root dry weight (DW), and slight reductions in leaf, stem, and tuber DW. The mean starch concentrations were reduced by 42% and 16% in leaves and tubers, respectively, but increased by 12% in stems. At 6MAP after 30 days of rewatering, Pn fully recovered, and stem starch was remobilized resulting in a dramatic increase in the DW of all the organs. Although the mean tuber DW of the drought plants at 6MAP was significantly lower than that of the control, it was significantly higher at 12MAP. Moreover, the mean tuber starch concentration at 12MAP of the drought plants (18.81%) was also significantly higher than that of the controls (16.46%). In the drought treatment, the high-yielding varieties, RY9, RY72, KU50, and CMR38-125-77 were similarly productive in terms of tuber DW and starch concentration while the breeding line CM523-7 produced the lowest tuber biomass and significantly lower starch content. Therefore, for cassava planted in the rainy season in the tropical savanna climate, the exposure to drought during the early growth stage was more beneficial than the continuous irrigation.

Introduction: Salinity and droughts are severe abiotic stress factors that limit plant growth and development. However, the differences and similarities of non-structural carbohydrates (NSCs) responses patterns of trees under the two stress conditions remain unclear., Methods: We determined and compared the growth, physiology, and NSCs response patterns and tested the relationships between growth and NSCs concentrations (or pool size) of Eucommia ulmoides seedlings planted in field under drought and salt stress with different intensities and durations., Results and Discussion: We found that drought and salt stress can inhibit the growth of E. ulmoides , and E. ulmoides tended to enhance its stress resistance by increasing proline concentration and leaf thickness or density but decreasing investment in belowground biomass in short-term stress. During short-term drought and salt stress, the aboveground organs showed different NSCs response characteristics, while belowground organs showed similar change characteristics: the starch (ST) and NSCs concentrations in the coarse roots decreased, while the ST and soluble sugar (SS) concentrations in the fine roots increased to enhance stress resistance and maintain water absorption function. As salt and drought stress prolonged, the belowground organs represented different NSCs response patterns: the concentrations of ST and SS in fine roots decreased as salt stress prolonged; while ST in fine roots could still be converted into SS to maintain water absorption as drought prolonged, resulting in an increase of SS and a decrease of ST. Significant positive relationships were found between growth and the SS and total NSCs concentrations in leaves and branches, however, no significant correlations were found between growth and below-ground organs. Moreover, relationships between growth and NSCs pool size across organs could be contrast., Conclusion: Our results provide important insights into the mechanisms of carbon balance and carbon starvation and the relationship between tree growth and carbon storage under stress, which were of great significance in guiding for the management of artificial forest ecosystem under the context of global change., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhang, Qin, Kan, Liu, Wang, Fan and Jiang.)

Knowledge of the physiological mechanisms underlying species vulnerability to drought is critical for better understanding patterns of tree mortality. Investigating plant adaptive strategies to drought should thus help to fill this knowledge gap, especially in tropical rainforests exhibiting high functional diversity. In a semi-controlled drought experiment using 12 rainforest tree species, we investigated the diversity in hydraulic strategies and whether they determined the ability of saplings to use stored non-structural carbohydrates during an extreme imposed drought. We further explored the importance of water- and carbon-use strategies in relation to drought survival through a modelling approach. Hydraulic strategies varied considerably across species with a continuum between dehydration tolerance and avoidance. During dehydration leading to hydraulic failure and irrespective of hydraulic strategies, species showed strong declines in whole-plant starch concentrations and maintenance, or even increases in soluble sugar concentrations, potentially favouring osmotic adjustments. Residual water losses mediated the trade-off between time to hydraulic failure and growth, indicating that dehydration avoidance is an effective drought-survival strategy linked to the 'fast-slow' continuum of plant performance at the sapling stage. Further investigations on residual water losses may be key to understanding the response of tropical rainforest tree communities to climate change., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Non-structural carbohydrates (NSCs), as the labile fraction and dominant carbon currency, are essential mediators of plant adaptation to environments. However, whether and how NSC coordinates with plant economic strategy frameworks, particularly the well-recognized leaf economics spectrums (LES) and root economics space (RES), remains unclear. We examined the relationships between NSC and key plant economics traits in leaves and fine roots across 90 alpine coniferous populations on the Tibetan Plateau, China. We observed contrasting coordination of NSC with economics traits in leaves and roots. Leaf total NSC and soluble sugar aligned with the leaf economic spectrum, conveying a trade-off between growth and storage in leaves. However, NSC in roots was independent of the root economic spectrum, but highly coordinated with root foraging, with more starch and less sugar in forage-efficient, thinner roots. Further, NSC-trait coordination in leaves and roots was, respectively, driven by local temperature and precipitation. These findings highlight distinct roles of NSC in shaping the above- and belowground multidimensional economics trait space, and NSC-based carbon economics provides a mechanistic understanding of how plants adapt to heterogeneous habitats and respond to environmental changes., (© 2024 The Authors. New Phytologist © 2024 New Phytologist Foundation.)

Root foraging strategies of plants may be critical to the competition for nutrient resources in the nutrient patches, but little is known about these of co-existing tree species in subtropical regions. This study aimed to elucidate root foraging strategies of three co-existing tree species in nutrient heterogeneous soils by exploring their root distribution, root morphology, photosynthates allocation and nutrient accumulation. Seedlings of the three tree species [moso bamboo (Phyllostachys edulis), Chinese fir (Cunninghamia lanceolata), and masson pine (Pinus massoniana)] were grown for 8months under one homogeneous soil [uniform nitrogen (N) plus phosphorus (P)] and three heterogeneous soils (localized N supply, localized P supply, or localized N plus P supply). The biomass, root morphological parameters (i.e., root length and root surface area), specific root length (SRL), non-structural carbohydrates (NSCs, i.e., mobile sugar and starch) in roots, total N and total P of plants were measured. The plasticity and distribution of root system were analyzed by calculating the root response ratio (RRR) and root foraging precision (FP), respectively. The results are as follows (i) Chinese fir tended to forage more N by promoting root proliferation in the N-rich patch, while root proliferation of bamboo and pine did not change. For P, bamboo absorbed more P by promoting root proliferation in the P-rich patch. The total P content of Pine and Chinese fir under localized P supply treatment remain the same despite the fact that the root length in the P-rich patch and the FP increased. (ii) Chinese fir foraged more N by increasing root length and decreasing SRL in the NP-rich patch; bamboo foraged more N and P by increasing root length and SRL in the NP-rich patch. The FP and foraging scale (FS) of both bamboo and Chinese fir were significantly improved under localized N plus P treatment. (iii) The concentrations of NSC were positively correlated with root morphological plasticity for moso bamboo and Chinese fir. Our results indicated that higher morphological plasticity is exhibited in moso bamboo and Chinese fir than masson pine in nutrient heterogeneous soils, allowing them to successfully forage for more nutrients.

Drought represents the most important limiting factor controlling performance of subtropical plants, leading to reduced growth and die-offs. However, the mechanisms underlying growth and physiological responses of subtropical woody plants to different types of drought are poorly understood. Here, potted seedlings of a typical evergreen shrub species Ardisia lindleyana D. Dietr. in subtropical China, were exposed to three water regimes: well watered (WW), fast drought (FD) and slow drought (SD) until death. Leaf gas exchange and water potential were measured over the experimental period. Dry mass production and allocation, leaf nitrogen and carbon isotopic composition, and non-structural carbohydrates (NSC) were measured at mortality. Results showed that growth, leaf water potential and photosynthesis were significantly reduced in both drought regimes. FD induced significant increase of root soluble sugars, but promoted significant depletion of leaf and root starch, finally displaying depletion of root NSC. By contrast, SD led to significant depletion of stem and root starch, whereas the accumulation of soluble sugars in stem and root was significantly higher than that of WW, thereby resulting in no significant change of NSC. Neither FD nor SD has affected leaf carbon isotopic composition or nitrogen concentration at mortality. Our results demonstrate the divergent effects of two different drought treatments on carbon and water economy of A. lindleyana, which may have implications for understanding the mortality mechanism of understory plants in subtropical forests in China.

The highly valuable heartwood of Dalbergia odorifera T. Chen, known as Jiang Xiang in traditional Chinese medicine, is formed very slowly, and there is a need to better understand the process and promote heartwood formation. Chemical induction is considered to be one of the promising methods to induce heartwood formation. However, to date no method has been proved effective for D. odorifera as little is known about biochemical and physiological changes during heartwood development. Three potential heartwood induction substances viz. acetic acid, sodium chloride, and hydrogen peroxide solutions were injected into the trunk of D. odorifera to determine the effect on heartwood formation and physiological activity. Non-structural carbohydrates, lipids, wood properties, and essential oil were assessed in the post-treatment period. As also observed in the formation of natural heartwood, chemical-induced Jiang Xiang production was accompanied by sapwood dehydration, non-structural carbohydrates consumption, and synthesis of heartwood substances. As the heartwood substances accumulated, basic density and essential oil content increased gradually, thereby Jiang Xiang was finally produced. In this process, physiological parameters of discolored sapwood gradually evolved to resemble those of natural heartwood. Hydrogen peroxide-induced Jiang Xiang was closest to natural heartwood, and the essential oil components met the standards for high-quality Jiang Xiang, while the induction effects of acetic acid and sodium chloride were unsatisfactory. Thus, this study indicates that hydrogen peroxide has the potential to induce Jiang Xiang production in Dalbergia odorifera.

There is an ongoing debate on whether a drought induced carbohydrate limitation (source limitation) or a direct effect of water shortage (sink limitation) limit growth under drought. In this study, we investigated the effects of the two driest summers recorded in southern Chile in the last seven decades, on the growth and non-structural carbohydrates (NSC) concentrations of the slow-growing conifer Fitzroya cupressoides. Specifically, we studied the seasonal variation of NSC in saplings and adults one and two years after the occurrence of a 2 year-summer drought at two sites of contrasting precipitation and productivity (mesic-productive vs. rainy-less productive). We also evaluated radial growth before, during and after the drought, and predicted that drought could have reduced growth. If drought caused C source limitation, we expected that NSCs will be lower during the first than the second year after drought. Conversely, similar NSC concentrations between years or higher NSC concentrations in the first year would be supportive of sink limitation. Also, due to the lower biomass of saplings compared with adults, we expected that saplings should experience stronger seasonal NSC remobilization than adults. We confirmed this last expectation. Moreover, we found no significant growth reduction during drought in the rainy site and a slightly significant growth reduction at the mesic site for both saplings and adults. Across organs and in both sites and age classes, NSC, starch, and sugar concentrations were generally higher in the first than in the second year following drought, while NSC seasonal remobilization was generally lower. Higher NSC concentrations along with lower seasonal NSC remobilization during the first post-drought year are supportive of sink limitation. However, as these results were found at both sites while growth decreased slightly and just at the mesic site, limited growth only is unlikely to have caused NSC accumulation. Rather, these results suggest that the post-drought dynamics of carbohydrate storage are partly decoupled from the growth dynamics, and that the rebuild of C reserves after drought may be a priority in this species.

The success of invasive alien species (IAS) is often linked to differences in functional traits in relation to other, either native or non-invasive, species. Two of the most problematic IAS in the Mediterranean area belong to Hakea and Acacia genera that often invade pine plantations. Therefore, the aim of this study was to assess the seasonal variations in photosynthetic pigments, total phenolics, and non-structural carbohydrates (NSC), including total soluble sugars (SS) and starch (St), and lipid peroxidation, in terms of malondialdehyde (MDA) in the leaves of evergreen species, two IAS (Hakea sericea and Acacia melanoxylon) and one native (Pinus pinaster), throughout 2019. All parameters showed a pronounced seasonal variability while also differing across species. Generally, the lowest contents of photosynthetic pigments, phenolics and SS were noted in early spring, along with the highest St and NSC values. On the other hand, higher photosynthetic pigment and lower NSC contents were measured in early autumn and early winter. When these parameters were compared across the three species, the IAS had significantly higher content of photosynthetic pigments, mainly chlorophyll b and total chlorophyll, and lower total phenolics and MDA concentrations in their leaves than Pinus pinaster. Differences in seasonal patterns were also observed. Hakea sericea and Acacia melanoxylon had considerably higher chlorophyll, SS and NSC contents in the early autumn, while Pinus pinaster had higher St and MDA contents in early summer. Overall, the biochemical characteristics of leaves of the studied IAS can explain their success in the Mediterranean area, in terms of tolerance to stressful environmental conditions.

Citrus trees are a very important crops that are cultivated worldwide, but not much knowledge is known about the ecophysiological responses to climatic changes in trees under natural conditions. The aim of this study was to investigate their adaptive capacity in response to seasonal phenological and environmental changes. The trial included Citrus trees (sweet orange, bitter orange, lemon, mandarin) growing under non-regular cropping conditions in a Monumental Charterhouse in Tuscany, in a subtropical Mediterranean climate with hot summer conditions. During a 1-year field trial, we determined the variations in chlorophyll fluorescence parameters and leaf biochemical traits (content of chlorophylls and carotenoids, total phenolic content (TPC), total antioxidant capacity (TAC), and total non-structural carbohydrates). In all Citrus spp., interspecific mean values of photochemical efficiency peaked during the summer, while a marked photoinhibition occurred in the winter in concomitance with higher interspecific mean values of leaf TPC, TAC, and non-structural carbohydrates. The trees showed the pivotal role played by photosynthetic acclimation as a survival strategy to tolerate abiotic stress in the climate change hotspot of Mediterranean environment. This study is included in a wider project aimed at a new valorization of Citrus trees as genetic resource and its by-products with added-value applications for innovative functional foods.

Remobilization is an important mechanism of resource conservation in plants. However, our understanding of whether the responses of resource remobilization to global warming differ between deciduous and evergreen trees remains unclear. We assessed resource remobilization from leaves to 1-year-old shoots in a deciduous (Betula ermanii) and an evergreen (Quercus aquifolioides) species along elevational gradients (i.e., temperature gradient) at the end of growing season. We aimed to test the hypotheses that the reallocation rate increased with increasing elevation and that more resources were reallocated from leaves to storage tissues in deciduous species than in evergreen species. We analyzed the concentrations of non-structural carbohydrates (NSC), nitrogen (N) and phosphorus (P), and compared the differences in remobilization efficiency of NSC, N, and P between leaves and shoots within each species and between the two species along the elevational gradients. Due to the different strategies of evergreen and deciduous species in nutrients use, the deciduous species had higher N and P remobilization rate, but lower remobilization rate of sugars, starch, and NSC than the evergreen species at the end of growing season. The remobilization rate of NSC, N, and P was significantly higher in trees at their upper limits compared to lower elevations. Our results suggest that trees reallocate resources from leaves to storage tissues before leaf senescence or at the end of growing season, to increase the resource use efficiency and to adapt to the harsh alpine environments. These results contribute to better understanding of the alpine treeline phenomenon in a changing world.

Drought‐induced tree mortality is expected to occur more frequently under predicted climate change. However, the extent of a possibly mitigating effect of simultaneously rising atmospheric [CO2] on stress thresholds leading to tree death is not fully understood, yet. Here, we studied the drought response, the time until critical stress thresholds were reached and mortality occurrence of Pinus halepensis (Miller). In order to observe a large potential benefit from eCO2, the seedlings were grown with ample of water and nutrient supply under either highly elevated [CO2] (eCO2, c. 936 ppm) or ambient (aCO2, c. 407 ppm) during 2 years. The subsequent exposure to a fast or a slow lethal drought was monitored using whole‐tree gas exchange chambers, measured leaf water potential and non‐structural carbohydrates. Using logistic regressions to derive probabilities for physiological parameters to reach critical drought stress thresholds, indicated a longer period for halving needle starch storage under eCO2 than aCO2. Stomatal closure, turgor loss, the duration until the daily tree C balance turned negative, leaf water potential at thresholds and time‐of‐death were unaffected by eCO2. Overall, our study provides for the first‐time insights into the chronological interplay of physiological drought thresholds under long‐term acclimation to elevated [CO2]. Water savings on the leaf‐level are annulled by increases in leaf area under highly elevated [CO2] limiting [CO2] benefits for Aleppo pine to mild drought conditions. Critical thresholds, time‐to‐mortality and mortality risk under extreme drought conditions are not affected by [CO2]. [ABSTRACT FROM AUTHOR]