Search

Tree species that close stomata early in response to drought are likely to suffer from an imbalance between limited carbohydrate supply due to reduced photosynthesis and metabolic demand. Our objective was to clarify the dynamic responses of non-structural carbohydrates to drought in a water-saving species, the hinoki cypress (Chamaecyparis obtusa Sieb. et Zucc.). To this end, we pulse-labeled young trees with 13CO2 10 days after the beginning of the drought treatment. Trees were harvested 7 days later, early during drought progression, and 86 days later when they had suffered from a long and severe drought. The labeled carbon (C) was traced in phloem extract, in the organic matter and starch of all the organs, and in the soluble sugars (sucrose, glucose and fructose) of the most metabolically active organs (foliage, green branches and fine roots). No drought-related changes in labeled C partitioning between belowground and aboveground organs were observed. The C allocation between non-structural carbohydrates was altered early during drought progression: starch concentration was lower by half in the photosynthetic organs, while the concentration of almost all soluble sugars tended to increase. The preferential allocation of labeled C to glucose and fructose reflected an increased demand for soluble sugars for osmotic adjustment. After 3 months of a lethal drought, the concentrations of soluble sugars and starch were admittedly lower in drought-stressed trees than in the controls, but the pool of non-structural carbohydrates was far from completely depleted. However, the allocation to storage had been impaired by drought; photosynthesis and the sugar translocation rate had also been reduced by drought. Failure to maintain cell turgor through osmoregulation and to refill embolized xylem due to the depletion in soluble sugars in the roots could have resulted in tree mortality in hinoki cypress, though the total pool of carbohydrate was not completely depleted.

Why this research Matters The inner bark plays important roles in tree stems, including radial exchange of water with the xylem and translocation of carbohydrates. Both processes affect the water content and the thickness of the inner bark on a diurnal basis. For the first time, we simultaneously measured the diurnal variations in the inner bark thickness of hinoki cypress (Chamaecyparis obtusa) by using point dendrometers and those of local xylem potential by using stem psychrometers located next to the dendrometers to determine how these variations were related to each other, to phloem turgor and carbohydrate transport. We also estimated the axial hydrostatic pressure gradient by measuring the osmolality of the sap extracted from the inner bark. The inner bark shrunk during the day and swelled during the night with an amplitude related to day‐to‐day and seasonal variations in climate. The relationship between changes in xylem water potential and inner bark thickness exhibited a hysteresis loop during the day with a median lag of 2 h. A phloem turgor‐related signal can be retrieved from the diurnal variations in the inner bark thickness, which was higher at the upper than at the lower position along the trunk. However, a downward hydrostatic pressure gradient was only observed at dawn, suggesting diurnal variations in the phloem sap flow velocity.

Seasonal variations in microbial biomass and metabolic quotient within the litter layer and the microorganism-mediated mechanisms causing seasonal variation in litter heterotrophic respiration in w...

Introduction to the invited issue on phloem function and dysfunction

On-going climate change is increasing the risk of drought stress across large areas worldwide. Such drought events decrease ecosystem productivity and have been increasingly linked to tree mortality. Understanding how trees respond to water shortage is key to predicting the future of ecosystem functions. Phloem is at the core of the tree functions, moving resources such as non-structural carbohydrates, nutrients, and defence and information molecules across the whole plant. Phloem function and ability to transport resources is tightly controlled by the balance of carbon and water fluxes within the tree. As such, drought is expected to impact phloem function by decreasing the amount of available water and new photoassimilates. Yet, the effect of drought on the phloem has received surprisingly little attention in the last decades. Here we review existing knowledge on drought impacts on phloem transport from loading and unloading processes at cellular level to possible effects on long-distance transport and consequences to ecosystems via ecophysiological feedbacks. We also point to new research frontiers that need to be explored to improve our understanding of phloem function under drought. In particular, we show how phloem transport is affected differently by increasing drought intensity, from no response to a slowdown, and explore how severe drought might actually disrupt the phloem transport enough to threaten tree survival. Because transport of resources affects other organisms interacting with the tree, we also review the ecological consequences of phloem response to drought and especially predatory, mutualistic and competitive relations. Finally, as phloem is the main path for carbon from sources to sink, we show how drought can affect biogeochemical cycles through changes in phloem transport. Overall, existing knowledge is consistent with the hypotheses that phloem response to drought matters for understanding tree and ecosystem function. However, future research on a large range of species and ecosystems is urgently needed to gain a comprehensive understanding of the question.

Drought-induced tree death has become a serious problem in global forest ecosystems. Two nonexclusive hypotheses, hydraulic failure and carbon starvation, have been proposed to explain tree die-offs. To clarify the mechanisms, we investigated the physiological processes of drought-induced tree death in saplings with contrasting Huber values (sapwood area/total leaf area). First, hydraulic failure and reduced respiration were found in the initial process of tree decline, and in the last stage carbon starvation led to tree death. The carbohydrate reserves at the stem bases, low in healthy trees, accumulated at the beginning of the declining process due to phloem transport failure, and then decreased just before dying. The concentrations of non-structural carbohydrates at the stem bases are a good indicator of tree damage. The physiological processes and carbon sink-source dynamics that occur during lethal drought provide important insights into the adaptive measures underlying forest die-offs under global warming conditions., 乾燥を受けた樹木が枯死に至る生理過程を解明 --地球温暖化の森林への影響を高精度に予測する道を開く成果--. 京都大学プレスリリース. 2019-01-28.

The extent of damage to Pinus thunbergii trees in coastal forests resulting from the tsunami caused by the Great East Japan Earthquake in 2011 differed depending on the local environment. The height (H) of P. thunbergii was generally limited in stands closer to the coastline and these trees could fail due to the force of the tsunami. The resistance forces of coastal forests to tsunamis are expressed as critical turning moments and measured by tree-pulling experiments. However, few studies have focused on the differences in the critical turning moment between stands with locally different environmental conditions among P. thunbergii coastal forests. We determined the differences in the critical turning moments of P. thunbergii in two contrasting sites having different distances from the coastline. We also estimated the tolerance of P. thunbergii in the two sites against loading from tsunami. Two experimental plots, sea-side and land-side, in a coastal P. thunbergii forest were established with different depths of the water table belowground and wind forces. In both plots, the aboveground traits, including the diameter at breast height (DBH), and H × DBH2 of P. thunbergii, were positively correlated with the critical turning moments. In particular, when P. thunbergii had the same H × DBH2 between the plots, there were no differences in the critical turning moments. This result suggested that P. thunbergii at the sea-side had acclimated for 50 years to their environment by changing shallow tap roots for shallower belowground water and developing horizontal roots for strong winds. The depth of the center point of rotation was significantly deeper and was positively correlated with moments in the land-side plot, suggesting changes from a tap root system to a plate root system in the sea-side plot with a shallower water table. The estimated loading from the tsunami with a 2 m wave height was over the critical turning moments for both plots. P. thunbergii trees at the sea-side plot could be more susceptible to overturning by lower-height waves than at the land-side plot because of differences in aboveground traits of H × DBH. We propose that the practical management of coastal forests is to create an embankment by raising the ground level to develop tree growth with capable of enhanced resilience to tsunamis.

L929 cell supernatant is commonly used to differentiate murine macrophages from bone marrow. The supernatant and its effect on macrophage phenotype was characterised by proteomics and the authors identified novel immunoregulatory proteins., BMDMs are a key model system to study macrophage biology in vitro. Commonly used methods to differentiate macrophages from BM are treatment with either recombinant M-CSF or the supernatant of L929 cells, which secrete M-CSF. However, little is known about the composition of L929 cell-conditioned media (LCCM) and how it affects the BMDM phenotype. Here, we used quantitative mass spectrometry to characterise the kinetics of protein secretion from L929 cells over a 2-wk period, identifying 2,193 proteins. Whereas M-CSF is very abundant in LCCM, we identified several other immune-regulatory proteins such as macrophage migration inhibitory factor (MIF), osteopontin, and chemokines such as Ccl2 and Ccl7 at surprisingly high abundance levels. We therefore further characterised the proteomes of BMDMs after differentiation with M-CSF, M-CSF + MIF, or LCCM, respectively. Interestingly, macrophages differentiated with LCCM induced a stronger anti-inflammatory M1 phenotype that those differentiated with M-CSF. This resource will be valuable to all researchers using LCCM for the differentiation of BMDMs.

Use of ground-penetrating radar (GPR) can non-destructively estimate diameter and distribution of coarse roots in Cryptomeria japonica in weathered granite soils under field conditions. Ground-penetrating radar (GPR) has been used as an assessment tool for non-destructive detection of tree root biomass, but few studies have estimated root diameter under forest field conditions. The aim of this study was to clarify whether coarse root diameter of C. japonica in weathered granite soils can be estimated using GPR in a forest. Roots of mature C. japonica were scanned using a 900 MHz GPR antenna before being excavated. The diameter and distribution of excavated roots were compared with those identified by GPR, and the relationships between the diameter and waveform indices in radar profiles were also examined. The detection frequency of the number of roots larger than 5 mm in diameter was 47.7%. Limiting factors affecting root detection using GPR in forest field conditions were small root diameter, increasing root depth, and number of adjacent roots. Only one waveform index, using the sum of time intervals between zero crossings (ΣT, ns) of all reflection waveforms of GPR within the range from the first break time at the root top to the delay point time at the root bottom, had a significant relationship with excavated root diameters. A linear regression model was constructed to estimate root diameter using ΣT, and a significant positive relationship in diameter between GPR-estimated and excavated roots was confirmed. The results in this study indicate that the diameter and distribution of C. japonica coarse roots under forest field conditions could be estimated using GPR and this technique could contribute to future evaluation of slope stability by evaluating tree roots under vulnerable soils, such as weathered granite.

In temperate and boreal forest, the production of extraradical mycorrhizal hyphae (EMH) is a major pathway for the plant – soil carbon (C) flux. For warm-temperate forest, however, scarcely available field data provide inconclusive evidence for the drivers of EMH production dynamics. In this study, we measured the seasonal variation in EMH production in Japanese warm-temperate Chamaecyparis obtusa (arbuscular mycorrhizal evergreen) and Quercus serrata forest (ectomycorrhizal broad-leaf), and assessed the relationship of EMH production to air temperature, global solar radiation, and soil water content. EMH productions of six consecutive two-month periods were estimated from hyphal lengths (HLs) and hyphal carbon masses (HCs) in 360 hyphal in-growth mesh bags and corrected for non-mycorrhizal HLs and HCs in 72 control bags from root-trenched areas. Seasonal variations in HL and HC productions of EMH were significant in both forest types. HL and HC productions of EMH were significantly related to air temperature which drives plant C assimilation in both forest types. We, thus, present evidence for coupling of EMH production to plant C assimilation in warm-temperate forest, regardless of the dominating mycorrhizal type.

The different root systems of Pinus thunbergii observed after the tsunami in 2011 were possibly influenced by different groundwater levels before the tsunami. The aims of this study were to quantify the tap and horizontal root structure and evaluate their relationship with the above-ground parts under different groundwater levels in a coastal P. thunbergii forest. Two plots, sea- and land-side, with different groundwater levels, in a P. thunbergii stand, were established, and the entire root-systems of three select trees each were harvested to evaluate the biomass, lengths, and cross-sectional areas of the tap and horizontal roots. In the sea-side plot, which had a shallower groundwater level, plate root systems with thicker and longer horizontal roots, but fewer tap roots were observed, whereas tap root systems were well developed in the land-side plots, where the groundwater level was deeper. The root-to- shoot ratio was significantly higher in the sea-side plot than in the land-side plot. We confirmed that quantitative contrasting root systems of P. thunbergii develop under different groundwater levels and higher biomass allocation to horizontal roots occur under shallower groundwater depths, emphasizing the need for management practices that promote the development of tap root systems to enhance resistance to tsunamis.

Phloem failure has recently been recognized as one of the mechanisms causing tree mortality under drought, though direct evidence is still lacking. We combined 13C pulse-labelling of 8-year-old beech trees (Fagus sylvatica L.) growing outdoors in a nursery with an anatomical study of the phloem tissue in their stems to examine how drought alters carbon transport and phloem transport capacity. For the six trees under drought, predawn leaf water potential ranged from -0.7 to -2.4 MPa, compared with an average of -0.2 MPa in five control trees with no water stress. We also observed a longer residence time of excess 13C in the foliage and the phloem sap in trees under drought compared with controls. Compared with controls, excess 13C in trunk respiration peaked later in trees under moderate drought conditions and showed no decline even after 4 days under more severe drought conditions. We estimated higher phloem sap viscosity in trees under drought. We also observed much smaller sieve-tube radii in all drought-stressed trees, which led to lower sieve-tube conductivity and lower phloem conductance in the tree stem. We concluded that prolonged drought affected phloem transport capacity through a change in anatomy and that the slowdown of phloem transport under drought likely resulted from a reduced driving force due to lower hydrostatic pressure between the source and sink organs.

Regeneration by sprouting in secondary forests is a necessary technique not only for the utilization of forest resources, but also for maintaining forest health by regrowth and avoiding slope instability caused by over-sized aboveground biomass. The strength of soil reinforcement by roots generally decreases during the tree death process in deforestation, such as clear-cutting, whereas root system strength temporarily decreases in trees that regenerate sprouting after cutting. However, quantitative evaluation of decreasing soil reinforcement by roots and slope stability has not been conducted during regeneration. In this study, we evaluated changes in the number of roots and root distribution up to 3 years after cutting in the regeneration process of Quercus serrata, a major dominant species of secondary forests in warm and cool temperate zones in Japan. We also estimated soil reinforcement by roots: additional cohesion from roots using the root bundle model, and slope stability based on a factor of safety by dividing the effect of the tree root system into vertical and horizontal cohesion with soil physical properties. After cutting at the height of approximately 0.2 m, the aboveground sprouting branches immediately regenerated, whereas the belowground root system gradually decayed. The additional cohesion from roots in trees before cutting was calculated as 34.6 kPa, whereas it decreased significantly to 21.7 kPa in living stumps 3 years after cutting. The value for the factor of safety with a saturated soil thickness of 0.7 m was calculated as 1.20 in soil under trees before cutting, whereas it decreased significantly to 1.11 in soil under living stumps in the 3 years after cutting. The safety factor's value to 0.99 in soil under dead stumps, which did not regenerate sprouts within 3 years after cutting. We concluded that the probability of slope failure was significantly greater in the dead stumps than in the living stumps and could vary depending on the dynamics of above- and below-ground parts, including fine roots.

Tree root diameter and root distribution are crucial factors for root reinforcement in forest soils and can be estimated using nondestructive ground-penetrating radar (GPR). However, no studies on estimating root reinforcement have been performed using GPR. The aim of this study was to evaluate root reinforcement using GPR in thinned and unthinned stands of Cryptomeria japonica in Andisols. Roots in each stand were detected using a 900 MHz GPR and the diameter and horizontal distribution of roots were estimated. Roots were also excavated to compare their GPR estimates. The relationships between root diameter and tensile force were established through field pullout tests. Finally, root reinforcements in each stand were estimated using the recently proposed root bundle model (RBM). There were no significant differences in the diameter frequency distribution of roots estimated between thinned and unthinned stands, determined using either the GPR or excavation methods. The detection frequency of the number of roots >5 mm in diameter using GPR was 27.2%, but it increased to 58.7% for roots >10 mm. The waveform indexes, determined using the sum of time intervals between zero crossings (ΣT) of all reflection waveforms of GPR, had a significant linear relationship with the diameters of excavated roots, indicating that waveform index could be used to estimate root diameter using the GPR index in these stands. Furthermore, the relationship between the root tensile force (F) and- root diameter (d) was estimated as F = 15.69 d1.75 (R2 = 0.87). The root reinforcements at the center of gaps between individual trees were estimated to be 23.4–32.9 kPa in the thinned stand and 8.8–23.9 kPa in the unthinned stand using GPR. These values ranged from 31.9% to 170.7% of those obtained by using the excavation method. There were no significant differences in root reinforcement between thinned and unthinned stands, regardless of the method used. This study revealed that GPR, together with diameter-tensile force relationships, can nondestructively estimate root reinforcement in managed forests. This protocol can be applied to manage forests to evaluate the effects of management on belowground roots.

We developed simple algorithms for reconstructing tree root system architecture using only the root point coordinate and diameter, which can be systematically obtained without digging up the root systems. Root system architecture (RSA) is strongly related to various root functions of the tree. The aim of this study was to develop a three-dimensional (3D) RSA model using systematically obtained information on root locations and root diameters at the locations. We excavated root systems of Cryptomeria japonica and systematically obtained XYZ coordinates and root diameters using a 10-cm grid. We clarified the patterns of the root point connections and developed a reconstructed root system model. We found that the root diameters farther from the stump centre are smaller. Additionally, we found that the root lengths of the segments running between the base and the connected root point were smaller than those of other root segments, and the inner angle between the base and the stump and between the base and the connected root point was narrower than for the other pairs. The new RSA model developed according to these results had average accuracies of 0.64 and 0.80 for estimates of total volume and length, respectively. The developed model can estimate 3D RSA using only root point data, which can be obtained without digging up root systems. This suggests a wide applicability of this model in root function evaluation.

(13) CO2 pulse-labelling experiments were performed in situ on adult beeches (Fagus sylvatica) and pines (Pinus pinaster) at different phenological stages to study seasonal and interspecific short-term dynamics and partitioning of recently assimilated carbon (C) in leaves. Polar fraction (PF, including soluble sugars, amino acids and organic acids) and starch were purified from foliage sampled during a 10-d chase period. C contents, isotopic compositions and (13) C dynamics parameters were determined in bulk foliage, PF and starch. Decrease in (13) C amount in bulk foliage followed a two-pool exponential model highlighting (13) C partitioning between 'mobile' and 'stable' pools, the relative proportion of the latter being maximal in beech leaves in May. Early in the growing season, new foliage acted as a strong C sink in both species, but although young leaves and needles were already photosynthesizing, the latter were still supplied with previous-year needle photosynthates 2 months after budburst. Mean (13) C residence times (MRT) were minimal in summer, indicating fast photosynthate export to supply perennial organ growth in both species. In late summer, MRT differed between senescing beech leaves and overwintering pine needles. Seasonal variations of (13) C partitioning and dynamics in field-grown tree foliage are closely linked to phenological differences between deciduous and evergreen trees.

Understanding how extraradical mycorrhizal fungal hyphae (EMH) regulate the cycling and retention of plant-assimilated carbon (C) in forest soils requires estimation of the production, mortality, and decomposition of EMH. To do this, the use of mass-balance models in combination with hyphal in-growth mesh bags (“in-growth bags”) was proposed in recent studies. However, poor knowledge on the decomposition of field-grown EMH prevents confirmation of assumed EMH decomposition dynamics. In this study, we determined the decrease in hyphal length density of field-grown EMH of arbuscular mycorrhizal fungi (AM) over eight months in in-growth bags incubated in a warm-temperate Chamaecyparis obtusa forest, to study EMH decomposition under field conditions. We used exponential decay models to describe the changes in the decomposition rate of EMH over the incubation time, between EMH diameter classes, and between seasons. A rapid decrease of the decomposition rate of EMH within two months from 2.5 to 0.1 month−1 was estimated, corresponding to an increase in half-life from 0.3 to 7 months. Furthermore, significant differences in the initial maximum decomposition rate were estimated between fine (1.6 month−1; minimum half-life: 0.4 months) and coarse EMH (3.1 month−1; minimum half-life: 0.2 months) and between incubations during spring-summer (April and August; 2.7 month−1; minimum half-life: 0.3 months) and autumn-winter (October and February; 1.1 month−1; minimum half-life: 0.6 months). This large variability in the decomposition rates of EMH of AM fungi has to be considered in mass-balance models to estimate C fluxes between plants, soil, and the atmosphere.

Background: Snaclecs affect the hemostasis of snakebite victims upon envenomation. Results: Rhinocetin, a novel snaclec, inhibits integrin α2β1-dependent functions of human platelets and endothelial cells. Conclusion: The actions of rhinocetin are consistent with hemorrhagic symptoms upon envenomation. Significance: Due to its inhibitory actions on integrin α2β1, rhinocetin may have potential diagnostic and therapeutic values., Snaclecs are small non-enzymatic proteins present in viper venoms reported to modulate hemostasis of victims through effects on platelets, vascular endothelial, and smooth muscle cells. In this study, we have isolated and functionally characterized a snaclec that we named “rhinocetin” from the venom of West African gaboon viper, Bitis gabonica rhinoceros. Rhinocetin was shown to comprise α and β chains with the molecular masses of 13.5 and 13 kDa, respectively. Sequence and immunoblot analysis of rhinocetin confirmed this to be a novel snaclec. Rhinocetin inhibited collagen-stimulated activation of human platelets in a dose-dependent manner but displayed no inhibitory effects on glycoprotein VI (collagen receptor) selective agonist, CRP-XL-, ADP-, or thrombin-induced platelet activation. Rhinocetin antagonized the binding of monoclonal antibodies against the α2 subunit of integrin α2β1 to platelets and coimmunoprecipitation analysis confirmed integrin α2β1 as a target for this venom protein. Rhinocetin inhibited a range of collagen-induced platelet functions such as fibrinogen binding, calcium mobilization, granule secretion, aggregation, and thrombus formation. It also inhibited integrin α2β1-dependent functions of human endothelial cells. Together, our data suggest rhinocetin to be a modulator of integrin α2β1 function and thus may provide valuable insights into the role of this integrin in physiological and pathophysiological scenarios, including hemostasis, thrombosis, and envenomation.

Pulse-labelling of trees with stable or radioactive carbon (C) isotopes offers the unique opportunity to trace the fate of labelled CO(2) into the tree and its release to the soil and the atmosphere. Thus, pulse-labelling enables the quantification of C partitioning in forests and the assessment of the role of partitioning in tree growth, resource acquisition and C sequestration. However, this is associated with challenges as regards the choice of a tracer, the methods of tracing labelled C in tree and soil compartments and the quantitative analysis of C dynamics. Based on data from 47 studies, the rate of transfer differs between broadleaved and coniferous species and decreases as temperature and soil water content decrease. Labelled C is rapidly transferred belowground-within a few days or less-and this transfer is slowed down by drought. Half-lives of labelled C in phloem sap (transfer pool) and in mature leaves (source organs) are short, while those of sink organs (growing tissues, seasonal storage) are longer. (13)C measurements in respiratory efflux at high temporal resolution provide the best estimate of the mean residence times of C in respiratory substrate pools, and the best basis for compartmental modelling. Seasonal C dynamics and allocation patterns indicate that sink strength variations are important drivers for C fluxes. We propose a conceptual model for temperate and boreal trees, which considers the use of recently assimilated C versus stored C. We recommend best practices for designing and analysing pulse-labelling experiments, and identify several topics which we consider of prime importance for future research on C allocation in trees: (i) whole-tree C source-sink relations, (ii) C allocation to secondary metabolism, (iii) responses to environmental change, (iv) effects of seasonality versus phenology in and across biomes, and (v) carbon-nitrogen interactions. Substantial progress is expected from emerging technologies, but the largest challenge remains to carry out in situ whole-tree labelling experiments on mature trees to improve our understanding of the environmental and physiological controls on C allocation.

Aims Tree roots in forest soils can be detected using nondestructive ground-penetrating radar (GPR). However, few studies have investigated root detection frequency; i.e., how many and which roots are identified in a radar profile out of the total quantity of roots present in a forest stand. The objective of this study was to quantify root detection frequency and uncertainty, including relationships between root detection and radar parameters using 1.5 GHz GPR in a Pinus thunbergii forest on sandy soils.

Soil CO2 efflux is the main source of CO2 from forest ecosystems and it is tightly coupled to the transfer of recent photosynthetic assimilates belowground and their metabolism in roots, mycorrhiza and rhizosphere microorganisms feeding on root-derived exudates. The objective of our study was to assess patterns of belowground carbon allocation among tree species and along seasons. Pure 13CO2 pulse labelling of the entire crown of three different tree species (beech, oak and pine) was carried out at distinct phenological stages. Excess 13C in soil CO2 efflux was tracked using tuneable diode laser absorption spectrometry to determine time lags between the start of the labelling and the appearance of 13C in soil CO2 efflux and the amount of 13C allocated to soil CO2 efflux. Isotope composition (δ13C) of CO2 respired by fine roots and soil microbes was measured at several occasions after labelling, together with δ13C of bulk root tissue and microbial carbon. Time lags ranged from 0.5 to 1.3 days in beech and oak and were longer in pine (1.6–2.7 days during the active growing season, more than 4 days during the resting season), and the transfer of C to the microbial biomass was as fast as to the fine roots. The amount of 13C allocated to soil CO2 efflux was estimated from a compartment model. It varied between 1 and 21 % of the amount of 13CO2 taken up by the crown, depending on the species and the season. While rainfall exclusion that moderately decreased soil water content did not affect the pattern of carbon allocation to soil CO2 efflux in beech, seasonal patterns of carbon allocation belowground differed markedly between species, with pronounced seasonal variations in pine and beech. In beech, it may reflect competition with the strength of other sinks (aboveground growth in late spring and storage in late summer) that were not observed in oak. We report a fast transfer of recent photosynthates to the mycorhizosphere and we conclude that the patterns of carbon allocation belowground are species specific and change seasonally according to the phenology of the species.

We separately examined the temporal patterns of root production by Japanese oak (Quercus crispula) and dwarf bamboo (Sasa veitchii), which is a major understory species in cool temperate forests. We grew Japanese oak seedlings and Sasa stocks (i.e., the rhizome and connected culms) in organic‐free sand in rhizoboxes and then scanned roots that were visible through the sides of the rhizoboxes to measure the length of each root in images. Japanese oak root production peaked in July, but Sasa root production peaked in both July and October. Soil temperature was highly correlated with root production of Japanese oak, but less so with Sasa root. Leaves of Sasa expanded in late summer, and the photosynthetic rate of Sasa was highest in September, suggesting that the aboveground phenology influences the extensive root production of Sasa in October due to the supply of carbohydrate. These results demonstrate different temporal patterns of root production by Japanese oak seedlings and understory species (Sasa), even under similar environmental conditions.

It has been reported that ground-penetrating radar (GPR) is a nondestructive tool that can be used to detect coarse roots in forest soils. However, successful GPR application for root detection has been site-specific and numerous factors can interfere with the resolution of the roots. We evaluated the effects of root diameter, root volumetric water content, and vertical and horizontal intervals between roots on the root detection of Cryptomeria japonica in sand using 900-MHz GPR. We found that roots greater than 19 mm in diameter were clearly detected. Roots having high volumetric water content were easily detected, but roots with less than 20% water content were not detected. Two roots that were located closely together were not individually distinguished. These results confirm that root diameter, root water content, and intervals between roots are important factors when using GPR for root detection and that these factors lead to an underestimation of root biomass.

Coarse tree roots, which are responsible for most root carbon storage, are usually measured by destructive methods such as excavation and coring. Ground penetrating radar (GPR) is a non-destructive tool that could be used to detect coarse roots in forest soils. In this study, we examined whether the roots of Cryptomeria japonica, a major plantation species in Japan, can be detected with GPR. We also looked for factors that impact the analysis and detection of roots. Roots and wooden dowels of C. japonica were buried 30 cm deep in sandy granite soil. From GPR measurements with a 900 MHz antenna, the distribution and diameter of samples in several transects were recorded. The buried roots were detected clearly and could be distinguished at diameters of 1.1–5.2 cm. There were significant positive relationships between root diameter and parameters extracted from the resultant GPR waveform. The difference in water content between roots and soil is a crucial factor impacting the ability to detect roots...

We measured the rates of respiration from snags and logs (“coarse woody debris”, CWD) of Japanese red pine ( Pinus densiflora Sieb. et Zucc.) to examine the rate of decomposition and CO 2 efflux from these materials in a temperate secondary broad-leaved forest in Japan. At this site, a high quantity of CWD of P. densiflora had accumulated as a result of pine wilt disease during the 1970s. Respiration rates were measured using a dynamic closed chamber method combined with an infrared gas analyzer. We measured the respiration rate of 7 samples of snags and 10 samples of logs from August 2003 to January 2004. The responses of the respiration rates of snags ( R snag ) and logs ( R log ) to changing temperature were both exponential and the responses to water content were quadratic, and the same function could be used to estimate annual values of both R snag and R log . Intensive measurements of water contents of snags and logs showed a marked difference in water content. The mean water content of snags was 20% of log water content. This difference was likely responsible for the observed difference in annual R snag and R log . The decay rate constants estimated from the respiration rates measurement of snags and logs were 0.019 and 0.081 year −1 , respectively. Despite being lower than R log , R snag was a significant compartment of the CWD carbon budget at this site.

Made available in DSpace on 2022-04-28T19:03:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-11 Potassium (K) is an important limiting factor of tree growth, but little is known of the effects of K supply on the long-distance transport of photosynthetic carbon (C) in the phloem and of the interaction between K fertilization and drought. We pulse-labelled 2-year-old Eucalyptus grandis L. trees grown in a field trial combining K fertilization (+K and -K) and throughfall exclusion (+W and -W), and we estimated the velocity of C transfer by comparing time lags between the uptake of 13CO2 and its recovery in trunk CO2 efflux recorded at different heights. We also analysed the dynamics of the labelled photosynthates recovered in the foliage and in the phloem sap (inner bark extract). The mean residence time of labelled C in the foliage was short (21-31 h). The time series of 13C in excess in the foliage was affected by the level of fertilization, whereas the effect of throughfall exclusion was not significant. The velocity of C transfer in the trunk (0.20-0.82mh-1) was twice as high in +K trees than in -K trees, with no significant effect of throughfall exclusion except for one +K-W tree labelled in the middle of the drought season that was exposed to a more pronounced water stress (midday leaf water potential of -2.2MPa). Our results suggest that besides reductions in photosynthetic C supply and in C demand by sink organs, the lower velocity under K deficiency is due to a lower cross-sectional area of the sieve tubes, whereas an increase in phloem sap viscosity is more likely limiting phloem transport under drought. In all treatments, 10 times less 13C was recovered in inner bark extracts at the bottom of the trunk when compared with the base of the crown, suggesting that a large part of the labelled assimilates has been exported out of the phloem and replaced by unlabelled C. This supports the 'leakage-retrieval mechanism' that may play a role in maintaining the pressure gradient between source and sink organs required to sustain high velocity of phloem transport in tall trees. UMR 1137 Ecologie et Ecophysiologie Forestières Facult des Sciences Universit de Lorraine INRA UMR 1137 Ecologie et Ecophysiologie Forestières Centre de Nancy CIRAD UMR Ecoandsols Ecologie Fonctionnelle and Biogochimie des Sols and Agro-cosystèmes Embrapa Meio Ambiente Universidade Estadual de São Paulo Departamento de Ciências Florestais ESALQ Universidade de São Paulo ESALQ Laboratory of Forest Utilization Department of Forest and Biomaterial Science Graduate School of Agriculture Kyoto University Centro de Energia Nuclear Na Agricultura Universidade de São Paulo Departamento de Ciências Atmosfricas IAG Universidade de São Paulo ESALQ Universidade Estadual de São Paulo

Our objective was to quantify the production of ectomycorrhizal (ECM) hyphae throughout the growing season. For this purpose, we used ingrowth mesh bags (30 μm mesh filled with 40 g sand) in top soils of Fagus sylvatica , Quercus petraea and Pinus pinaster forests in France. Installations were done at three or four different growth phases at each site and mesh bags were retrieved after one to three months. Ingrowing ECM hyphae measured 250–2257 mm bag −1 on average after one to three months. Specific hyphal length was 14.6–42.9 km g −1 of hyphal mass and differed among sites. Hyphal colonization was generally greater after three months than after one month regardless of season or species. Ingrowth was lower in autumn relative to the growth in summer ( Fagus ) or in spring and summer ( Quercus ). In Pinus , growth in winter was lower than in other seasons. These differences in ingrowth may relate to differences in seasonal carbon allocation, but may also result from differences between soils and/or climate such as the prolonged summer drought, affecting in particular the Pinus site.

Root respiration was separated from total soil respiration in this study. Experiments were carried out in September 2003 at Yamashiro Experimental Forest located in Kyoto Prefecture. It is a secondary forest of broad-leaf trees including some conifer species. The root system was dug out and divided into several classes by size. The respiration rate of each size was measured by the closed-chamber method consisting of an IRGA, a pump, and a chamber made of acrylic. Temperature in the chamber was measured by thermo couple. The results showed that the smaller the diameter of the root was, the higher the respiration rate per unit weight was. A Mmuch higher rate was found in fine roots in comparison with other classes. From the relationships between basal diameter and root mass of each size for sample trees, root mass of each size per area was estimated. By combining the respiration rate and root mass of each size per area, root respiration could be calculated at 0.0707 mg CO2 m-2 s-1 as a total. More than the half was occupied by fine root respiration. Mean total soil respiration was 0.19 mg CO2 m-2 s-1 during this experiments. Therefore, the contribution of root respiration to soil respiration was estimated at 37.2%.

The root systems of forest trees are composed of different diameters and heterogeneous physiological traits. However, the pattern of root respiration rates from finer and coarser roots across various tropical species remains unknown. To clarify how respiration is related to the morphological traits of roots, we evaluated specific root respiration and its relationships to mean root diameter (D) of various diameter and root tissue density (RTD; root mass per unit root volume; gcm(-3)) and specific root length (SRL; root length per unit root mass; mg(-1)) of the fine roots among and within 14 trees of 13 species from a primary tropical rainforest in the Pasoh Forest Reserve in Peninsular Malaysia. Coarse root (2-269mm) respiration rates increased with decreasing D, resulting in significant relationships between root respiration and diameter across species. A model based on a radial gradient of respiration rates of coarse roots simulated the exponential decrease in respiration with diameter. The respiration rate of fine roots (

Studies of fine root phenology and respiration in forest ecosystems are reviewed. Direct, nondestructive observation methods, such as the minirhizotron imaging system and the root window, provide simultaneous quantitative measurements of root production and mortality. Temporal patterns are discussed, as well as endogenous and exogenous factors (e.g., soil temperature and moisture) controlling fine root dynamics. Both root respiration and microbial respiration release CO2 from the soil to the atmosphere; methods that distinguish them are evaluated. Finally, factors controlling root respiration, such as root age and diameter and soil nitrogen concentration, are reviewed, and approaches for scaling up root respiration to stand level are discussed.

International audience; Phloem is the main pathway for transferring photosynthates belowground. In situ13C pulse labelling of trees 8–10 m tall was conducted in the field on 10 beech (Fagus sylvatica) trees, six sessile oak (Quercus petraea) trees and 10 maritime pine (Pinus pinaster) trees throughout the growing season. Respired 13CO2 from trunks was tracked at different heights using tunable diode laser absorption spectrometry to determine time lags and the velocity of carbon transfer (V). The isotope composition of phloem extracts was measured on several occasions after labelling and used to estimate the rate constant of phloem sap outflux (kP). Pulse labelling together with high-frequency measurement of the isotope composition of trunk CO2 efflux is a promising tool for studying phloem transport in the field. Seasonal variability in V was predicted in pine and oak by bivariate linear regressions with air temperature and soil water content. V differed among the three species consistently with known differences in phloem anatomy between broadleaf and coniferous trees. V increased with tree diameter in oak and beech, reflecting a nonlinear increase in volumetric flow with increasing bark cross-sectional area, which suggests changes in allocation pattern with tree diameter in broadleaf species. Discrepancies between V and kP indicate vertical changes in functional phloem properties.

Fine root respiration is a significant component of carbon cycling in forest ecosystems. Although fine roots differ functionally from coarse roots, these root types have been distinguished based on arbitrary diameter cut-offs (e.g., 2 or 5 mm). Fine root morphology is directly related to physiological function, but few attempts have been made to understand the relationships between morphology and respiration of fine roots. To examine relationships between respiration rates and morphological traits of fine roots (0.15-1.4 mm in diameter) of mature Quercus serrata Murr., we measured respiration of small fine root segments in the field with a portable closed static chamber system. We found a significant power relationship between mean root diameter and respiration rate. Respiration rates of roots

International audience; The study of the fate of assimilated carbon in respiratory fluxes in the field is needed to resolve the residence and transfer times of carbon in the atmosphere– plant–soil system in forest ecosystems, but it requires high frequency measurements of the isotopic composition of evolved CO2.We developed a closed transparent chamber to label the whole crown of a tree and a labelling system capable of delivering a 3-h pulse of 99% 13CO2 in the field. The isotopic compositions of trunk and soil CO2 effluxes were recorded continuously on two labelled and one control trees by a tuneable diode laser absorption spectrometer during a 2-month chase period following the late summer labelling. The lag times for trunk CO2 effluxes are consistent with a phloem sap velocity of about 1 m h_1. The isotopic composition (d13C) of CO2 efflux from the trunk was maximal 2–3 days after labelling and declined thereafter following two exponential decays with a half-life of 2–8 days for the first and a half-life of 15– 16 days for the second. The isotopic composition of the soil CO2 efflux was maximal 3–4 days after labelling and the decline was also well fitted with a sum of two exponential functions with a half-life of 3–5 days for the first exponential and a half-life of 16–18 days for the second. The amount of label recovered in CO2 efflux was around 10–15% of the assimilated 13 CO2 for soil and 5–13% for trunks. As labelling occurred late in the growing season, substantial allocation to storage is expected.

Understanding how plants are constructed—i.e., how key size dimensions and the amount of mass invested in different tissues varies among individuals—is essential for modeling plant growth, carbon stocks, and energy fluxes in the terrestrial biosphere. Allocation patterns can differ through ontogeny, but also among coexisting species and among species adapted to different environments. While a variety of models dealing with biomass allocation exist, we lack a synthetic understanding of the underlying processes. This is partly due to the lack of suitable data sets for validating and parameterizing models. To that end, we present the Biomass And Allometry Database (BAAD) for woody plants. The BAAD contains 259 634 measurements collected in 176 different studies, from 21 084 individuals across 678 species. Most of these data come from existing publications. However, raw data were rarely made public at the time of publication. Thus, the BAAD contains data from different studies, transformed into standard units and variable names. The transformations were achieved using a common workflow for all raw data files. Other features that distinguish the BAAD are: (i) measurements were for individual plants rather than stand averages; (ii) individuals spanning a range of sizes were measured; (iii) plants from 0.01–100 m in height were included; and (iv) biomass was estimated directly, i.e., not indirectly via allometric equations (except in very large trees where biomass was estimated from detailed sub-sampling). We included both wild and artificially grown plants. The data set contains the following size metrics: total leaf area; area of stem cross-section including sapwood, heartwood, and bark; height of plant and crown base, crown area, and surface area; and the dry mass of leaf, stem, branches, sapwood, heartwood, bark, coarse roots, and fine root tissues. We also report other properties of individuals (age, leaf size, leaf mass per area, wood density, nitrogen content of leaves and wood), as well as information about the growing environment (location, light, experimental treatment, vegetation type) where available. It is our hope that making these data available will improve our ability to understand plant growth, ecosystem dynamics, and carbon cycling in the world's vegetation.

Background & Aims: Abetalipoproteinemia and Anderson's disease are hereditary lipid malabsorption syndromes. In abetalipoproteinemia, lipoprotein assembly is defective because of mutations in the microsomal triglyceride transfer protein. Here, we evaluated the intracellular transport of apolipoprotein B48 to localize the defect in Anderson's disease. Methods: Asparagine-linked oligosaccharide processing of apolipoprotein B48 in normal and affected individuals was determined by the endoglycosidase H and F sensitivities of the protein after metabolic labeling of intestinal explants in organ culture. Cell ultrastructure was evaluated with electron microscopy. Results: In Anderson's disease as in normal individuals, there was a time-dependent transformation of high mannose endoglycosidase H–sensitive oligosaccharides, of endoplasmic reticulum origin, to complex endoglycosidase H–resistant oligosaccharides, added in the Golgi network. In contrast, despite the translocation of apolipoprotein B48 into the endoplasmic reticulum in patients with abetalipoproteinemia and in biopsies treated with Brefeldin A, which blocks anterograde transport between the endoplasmic reticulum and the Golgi network, there was no transformation of endoglycosidase H–sensitive oligosaccharides. Conclusions: In abetalipoproteinemia and Anderson's disease, apolipoprotein B48 is completely translocated into the endoplasmic reticulum, but only in Anderson's disease is the protein transported to the Golgi apparatus. This suggests that Anderson's disease is caused by a post-Golgi cargo-specific secretion defect. GASTROENTEROLOGY 2001;121:1101-1108