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In the indigenous southern taiga fern-forb fir forests on the Tom-Yaya interfluve (Tomsk Oblast), the characteristics of tree stands, underbrush, undergrowth, coarse woody debris, ground cover, soils and their contribution to carbon sequestration were studied. The average stock of the forest stand for the type of biogeocenosis was 315.8 ± 56.1 m3 /ha, the average stock of the Siberian fir (Abies sibirica Ledeb.) in different stands varied from 99.2 to 201.4 m3 /ha. In terms of forest health condition, the forest stands are weakened to varying degrees, the fir elements of the forest stands are stronger, which is largely due to their damage by the invasive four-eyed fir bark beetle (Polygraphus proximus Blandford). The underbrush is sparse or of medium density (880–2720 pieces/ha), formed mainly by red raspberry (Rubus idaeus L.) and rowan (Sorbus sibirica Hedl.). Undergrowth with an absolute predominance of fir, its number (800–920 trees/ha) characterizes unsatisfactory regeneration in all studied stands. The average volume of deadfall for the type of biogeocenosis was 2.1 ± 0.5 m3 /ha, stumps 3.3 ± 0.8 m3 /ha, brushwood – 9.2 ± 5.3 m3 /ha. The features of the phytocenosis include high values of floristic diversity (131 species), species richness of the grass cover (105 species) and species richness of plant communities (57 species per 400 m2 ). The increased participation of ferns in the composition of the grass stand is due to the presence of windows occupying from 5 to 30 % of the area of the phytocenosis, formed in stands at the site of fallouts and dead trees, mainly due to the drying out of fir damaged by the four-eyed fir bark beetle.. For the first time, data have been obtained on the phytomass of the ground cover of southern taiga fir forests in Western Siberia, estimated on average at 0.88 t/ha, with a wide variation of this indicator due to the peculiarities of the horizontal structure of the ground cover and different illumination in sub canopy parcels and windows. The features of the composition, structure and thermal regime of the soils of the studied biogeocenoses are shown. Data are presented on changes in the productivity of phytocenoses, soil humus and carbon reserves in various components of the studied forests.

The primary aim of the current study was to develop a model capable of predicting the spatial distribution patterns of soil organic carbon (SOC) in mangrove forests (Avicennia marina) affected by camel grazing along the southern coast of the Red Sea. Four protected locations within mangrove forests were selected along the southern coast of the Saudi Red Sea, while eight other locations were selected under the influence of camel grazing. Three equations—allometric, exponential, and sigmoid—were employed on soil carbon data obtained from 40 soil cores, which equated to 600 soil samples. The goal was to develop models that could forecast how the cumulative SOC stocks (SOCc) and volumetric SOC densities (SOCv) would be distributed throughout the respective soil profiles in protected and grazed locations of mangroves, in order to predict how soil carbon changes when mangroves are under grazing stress. The sigmoid and exponential equations proved to be most effective in predicting SOCv distribution, with average R2 values of 0.956681 and 0.893894 for protected and grazed locations, respectively. For protected locations, all three equations effectively predicted the SOCc, with the sigmoid equation (R2 = 0.999942) exhibiting the best performance. In grazed locations, all equations were applicable, with the allometric equation demonstrating superior accuracy (R2 = 0.999910). The study found that grazing activities in mangrove forests resulted in a loss of SOC stock of 7.0 kg C/m2, accounting for 54% of the initial stock. These findings will significantly enhance our comprehension of SOC distribution in mangrove ecosystems under the grazing effect, allowing us to quantify the impact of camel grazing on SOC dynamics in coastal ecosystems.

Interspecific variations in phenotypic plasticity of trees that are affected by climate change may alter the ecosystem function of forests. Seedlings of four common tree species (Castanopsis fissa , Michelia macclurei , Dalbergia odorifera and Ormosia pinnata) in subtropical plantations of southern China were grown in the field under rainout shelters and subjected to changing precipitation (48 L of water every 4 days in the dry season, 83 L of water every 1 day in the wet season; 4 g m−2 year−1 of nitrogen (N)), low N deposition (48 L of water every 2 days in the dry season, 71 L of water every 1 day in the wet season; 8 g m−2 year−1 N), high N deposition (48 L of water every 2 days in the dry season, 71 L of water every 1 day in the wet season; 10 g m−2 year−1 N) and their interactive effects. We found that the changes in seasonal precipitation reduced the light-saturated photosynthetic rate (A sat) for C. fissa due to declining area-based foliar N concentrations (Na). However, we also found that the interactive effects of changing precipitation and N deposition enhanced A sat for C. fissa by increasing foliar Na concentrations, suggesting that N deposition could alleviate N limitations associated with changing precipitation. Altered precipitation and high N deposition reduced A sat for D. odorifera by decreasing the maximum electron transport rate for RuBP regeneration (J max) and maximum rate of carboxylation of Rubisco (V cmax). Ormosia pinnata under high N deposition exhibited increasing A sat due to higher stomatal conductance and V cmax. The growth of D. odorifera might be inhibited by changes in seasonal precipitation and N deposition, while O. pinnata may benefit from increasing N deposition in future climates. Our study provides an important insight into the selection of tree species with high capacity to tolerate changing precipitation and N deposition in subtropical plantations. [ABSTRACT FROM AUTHOR]

This paper evaluates the potential effects of farmers' species preferences on carbon stock in cocoa-based agroforestry systems (CAFS) in the Central Region of Cameroon. To achieve this goal, the species composition and structural variables of two land-use systems were investigated using 26 plots of 30 m × 30 m each, of which 20 were distributed in CAFS and 6 in adjacent secondary forests. Allometric models were used to estimate the species aboveground and root carbon stock. Ordination analysis indicated three types of species management systems: high-density timber and fruit trees; high-density Musaceae, palms and other shading trees; and low-density timber and fruit trees. The average densities of cocoa shading trees and shrubs were 234 ± 136 and 843 ± 360 individuals' ha−1, respectively. Thus, the average potential carbon stock of the sampled CAFS was estimated at 186.97 ± 86.06 Mg C ha−1, 22% representing the root carbon stock. The transformation of secondary forest into various species management systems decreased the aboveground carbon by 18–34%. The annual rate of carbon accumulation estimated based on ring analyses was within the range 2.32–13.74 Mg C ha−1 year−1. The monetary value of the total carbon stored and the carbon accumulation rate were US$4042 ha−1and US$159 ha−1year−1, respectively. [ABSTRACT FROM AUTHOR]

Nonstructural carbohydrates (NSCs) mediate plant survival when the plant's carbon (C) balance is negative, suggesting that NSCs could predict plant survival under C stress. To examine this possibility, we exposed saplings of six temperate tree species to diverse levels of C stress created by the combination of two light conditions (full light availability and deep shade) and two defoliation levels (severe defoliation and nondefoliation). We then measured survival, biomass and total NSCs and soluble sugars (SSs) concentrations in different organs of both dead and live saplings.We estimated mean NSCs and SSs contents and concentrations per sapling and fitted logistic generalized mixed‐effects models to determine if NSCs and SSs predict survival. Using inverse prediction modelling, we also determined whether there is a common NSCs and SSs threshold across species at the time of sapling's death.Defoliation and shade reduced the mean sapling's NSCs and SSs contents, indicating C stress. Mean sapling NSCs and SSs contents and concentrations predicted survival and the robustness of the models improved with the inclusion of species. At death, saplings of the exotic deciduous tree species Acer pseudoplatanus exhibited significantly lower mean NSCs and SSs contents than saplings of the evergreen conifer species Podocarpus nubigenus and lower stem NSCs and SSs concentrations than the broadleaf evergreen species Drimys winteri.The energetic role that NSCs and SSs play in plants under C stress was evidenced by the capacity of these compounds to predict sapling survival under C stress. No common threshold of NSCs and SSs contents or concentrations for sapling survival amongst species was found, indicating that the level of these compounds may not be good proxies for interspecific comparisons of tolerance to C stress. Presumably, there are species‐specific limits for the mobilization and use of NSCs and SSs in metabolism.Our results anticipate that the inclusion of NSCs and SSs in modelling will improve predictions regarding tree responses to ongoing climate change. Nonetheless, a better understanding of the many roles that carbohydrates play in plant survival under C stress is required to scale predictions up to the community level. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Nonstructural carbon (NSC) reserves act as buffers to sustain tree activity during periods when carbon (C) assimilation does not meet C demand, but little is known about their age and accessibility; we designed a controlled girdling experiment in the Amazon to study tree survival on NSC reserves. We used bomb-radiocarbon (14 C) to monitor the time elapsed between C fixation and release ('age' of substrates). We simultaneously monitored how the mobilization of reserve C affected δ13 CO2 . Six ungirdled control trees relied almost exclusively on recent assimilates throughout the 17 months of measurement. The Δ14 C of CO2 emitted from the six girdled stems increased significantly over time after girdling, indicating substantial remobilization of storage NSC fixed up to 13-14 yr previously. This remobilization was not accompanied by a consistent change in observed δ13 CO2 . These trees have access to storage pools integrating C accumulated over more than a decade. Remobilization follows a very clear reverse chronological mobilization with younger reserve pools being mobilized first. The lack of a shift in the δ13 CO2 might indicate a constant contribution of starch hydrolysis to the soluble sugar pool even outside pronounced stress periods (regular mixing).

Studying the response relationship and spatial distribution characteristics of carbon reserve and land use change and predicting the change trend of carbon reserve caused by the change of land use type in the future can provide some reference for watershed policy formulation, land use structure adjustment, and the realization of the "two-carbon" goal. Based on the land use data from 2000, 2010, and 2020, the InVEST model was used to calculate carbon reserves and analyze the change characteristics and to simulate the land use change and its impact on carbon reserves in natural development, urban development, and ecological protection in 2030 with the help of the PLUS model. The study found that ① the main land types in the Shiyang River Basin from 2000 to 2020 were cultivated land, grassland, and unused land. The area of cultivated land, water area, and construction land in the Shiyang River Basin showed a significant increasing trend, and the construction land area increased the most. ② In the natural development scenario of 2030, cultivated land, water area, and construction all increased by 6.15%, 9.56%, and 29.9%, respectively. In the urban development scenario, the area of construction land increased the most. Compared with that in the other two scenarios, the area of forest land and grassland increased in the ecological protection scenarios. ③ The carbon reserves of the Shiyang River Basin from 2000 to 2020 showed a steady increase, with an overall increase of 0.035×10 8 t. The increased carbon reserves were mainly due to the increase in cultivated land area. ④ In 2030, the carbon reserves of the Shiyang River Basin showed an increasing trend in all three scenarios. The carbon reserves in the three scenarios were 5.65×10 8 , 5.64×10 8 ,and 5.73×10 8 t, respectively, with the largest increase in carbon reserves in the ecological conservation scenario, mainly due to the increase in grassland and woodland. The results showed that the expansion of construction land was the main cause of the loss of carbon reserves. If effective ecological protection measures are taken, the carbon reserves in the Shiyang River Basin will be improved, and the problem of the loss of carbon reserves caused by economic development can be solved.

The accumulated aerial biomass was evaluated at the level of botanical families in an evergreen montane forest subject to different degrees of intervention in the upper Puyo river watershed. In five transects of 0.1 ha, species with diameter at breast height (DBH) = 10 cm were recorded. Fewer families were found in sites with a high degree of disturbance. The aerial biomass varied from 161.84 to 339.70 Mg.ha-1, with greater accumulation in individuals of smaller diametric class. The families with the highest biomass importance value index were Moraceae, Arecaceae and Euphorbiaceae, recognized for their potential in terms of structure and carbon. Detrended correspondence analysis (DCA) indicated variation in the contribution of biomass for each site, having a small number of families to maintain carbon stocks. This provides relevant information that facilitates decision making for restoration in disturbed sites. [ABSTRACT FROM AUTHOR]

In temperate evergreen conifers, growth occurs mostly in summer but photosynthesis precedes year-round; thus, nonstructural carbohydrates (NSC) increase in winter but decrease in summer. Given that mild drought reduces growth but not photosynthesis, a drought in summer should increase NSCs more than one in winter. However, the active regulation hypothesis suggests that to increase future drought resilience, plants might downregulate growth to increase NSCs after a winter drought even if NSCs do not increase during the drought. To test if so, potted Pinus taeda saplings (age $< 1$ yr) were subjected to six-month droughts in a greenhouse with one treatment receiving drought during winter (Sep-Mar), and another during summer (Mar-Sep). Both treatments were compared to a control. To measure dry biomass and NSCs, we harvested plants monthly following each drought, while to assess changes in growth rates, we measured height and diameter monthly. While we observed seasonal variation and an overall increase during the study, we found no drought-related changes in NSC dynamics; however, drought did reduce growth. Furthermore, drought in winter did reduce growth during the following summer, but the reduction was less than for a drought in summer. We conclude that the effect of drought on NSCs was too small to detect in our plants. While better control of soil water would have reduced a major source of uncertainty, plants with larger NSC reserves or more intense stress would also yield easier-to-detect effects. Although not definitive, our results suggest that water stress does not lead to dramatic changes in seasonal NSC dynamics in its aftermath, despite what one might expect under the active regulation hypothesis., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)

The article is aimed at suggesting directions of formation of institutional support for introduction of the innovative financial-economic instrument of the internal carbon market (ICM) of the sector of agricultural land use and highlighting aspects of development of its legislative provision. The relevance of the suggested instrument is underlined by the necessity for Ukraine to fulfill the obligations under the Framework Convention on Climate Change of the UN, the Kyoto Protocol, the Paris Agreement, which are aimed at counteracting climate changes and adapting to their consequences. Through the use of the method of statistical analysis together with the analysis of dynamics of land-use categories in terms of farmlands, it has been proved that existing approaches to agricultural land use have a negative impact on the level of agri-ecological and food security of the State, lead to the loss of fertility and contribute to the increase of carbon emissions from the reservoir of mineral soils. The proposed approach forms the bases of further scientific and methodological developments for elaboration of the theoretical, normative-legislative, organizational and economic directions of development of the ICM of the sector of land use. The aspects of further improvement of legislation and of positive influence of ICM on the associated economic sectors are displayed.

Wetland can maintain the stability of natural ecological environment and carbon cycle. With the acceleration of urbanization and the development of marine aquaculture, the wetland ecosystem of Liaohe River estuary has been damaged to a certain extent. Based on the analysis of measured biomass of natural vegetation and normalized vegetation index extracted from remote sensing images, the biomass regression model based on remote sensing image was established. Through comparative analysis, the binomial function was the optimal model. The carbon reserves of natural vegetation in Liaohe River estuary wetland is 969 323. 100 t, which is 10% compared with the measured value of 1077 146.0181. Using remote sensing image to retrieve vegetation biomass, we can get more accurate carbon reserves of natural vegetation in Liaohe River estuary wetland. [ABSTRACT FROM AUTHOR]

In this study, we explore how a hurricane disturbance influenced carbon allocation for the production of new fine roots. Before and after a hurricane, we measured the age of carbon (time since fixation from the atmosphere) in fine root structural tissues using natural abundance radiocarbon (14C) measured by accelerator mass spectrometry. Roots were sampled from five seasonally dry tropical forests ranging in age from 6 yr to a mature forest. Structural carbon in combined live + dead roots picked from soil cores sampled 1 month before the hurricane had mean ages ranging from 4 to 11 yr, whereas live roots alone had ages of 1-2 yr. Structural carbon in new live fine roots produced over a period lasting from 3 wk before the hurricane to 2 months after the event had mean ages of between 2 and 10 yr. Contrary to expectations, our results showed that plants allocate long-lived storage carbon pools to the production of new fine roots after canopy defoliation and root mortality. The age of the carbon allocated for new roots increased with forest age and forest above-ground biomass, suggesting an adaptation of plants to survive and recover from severe disturbances.

Cone development in conifer species is crucial to ensure sexual regeneration. A better understanding of carbon (C) source-sink relations at the branch level can guide strategies for improving resource allocation to reproduction. In particular, the evaluation of C relations between vegetative and reproductive branches is helpful to test whether tree branches are carbon autonomous. With this aim, we integrated girdling and defoliation treatments with 13C pulse labeling in situ to evaluate C autonomy in cone-bearing branches of P. koraiensis during the growing season. Girdling significantly reduced branch volumetric development, branch biomass, and non-structural carbohydrates across foliar, twig, and cone tissues; it also arrested cone development. Defoliation effects on these variables were minor, although they tended to increase with defoliation intensity. In addition, 13C increased by 4.5% and 45.4% after 4 h and 24 h of 13C labeling in unlabeled cone-bearing branches, respectively, indicating the C translocation from labeled vegetative branches. These results indicate that the cone-bearing branches are not C autonomous and that the development of female cones relies to a great extent on C import from neighboring branches. However, the amount of C translocated was largely dependent on manipulative alterations of the source-sink balance, thereby denoting extensive plasticity in the degree of branch C autonomy. These results shed light on the reproductive physiology of P. koraiensis.

The implementation of new practices and their results to prevent or mitigate soil degradation and increase carbon capture were presented in this paper. The study was made on "Los Barzaga" farm, in the province of Guantanamo, where poor drainage conditions, low soil fertility and erosion affect 90% of the area, causing greater degradation and reduction of production. Several soil preservation and improvement procedures were established, considering the limiting factors identified. The physical and chemical indexes were evaluated, and the carbon reserves were monitored. The practices implemented (live and dead barriers, rill and reservoir correction), contributed to a 62 t. ha-1 reduction of soil loss, with positive changes in apparent density, infiltration and compacting velocity, and nutrient contents. Additionally, soil carbon increased to 20.67%.

Nonstructural carbohydrate (NSC) remobilization remains poorly understood in trees. In particular, it remains unclear (i) which tissues (e.g. living bark or xylem) and compounds (sugars or starch) in woody plants are the main sources of remobilized carbon, (ii) to what extent these NSC pools can be depleted and (iii) whether initial NSC mass or concentration is a better predictor of regrowth potential following disturbance. To address these questions, we collected root segments from a large mature trembling aspen stand; we then allowed them to resprout (sucker) in the dark and remobilize NSC until all sprouts had died. We found that initial starch mass, not concentration, was the best predictor of subsequent sprout mass. In total, more NSC mass (~4×) was remobilized from the living inner bark than the xylem of the roots. After resprouting, root starch was generally depleted to <0.6% w/w in both tissues. In contrast, a large portion of sugars appear unavailable for remobilization: sugar concentrations were only reduced to 12% w/w in the bark and 2% in the xylem. These findings suggest that in order to test whether plant processes like resprouting are limited by storage we need to (i) measure storage in the living bark, not just the xylem, (ii) consider storage pool size—not just concentration—and (iii) carefully determine which compounds are actually components of the storage pool. [ABSTRACT FROM AUTHOR]

Highlights • Many analytical methods are used to measure seagrass non-structural carbohydrate content, however, these are non-comparable. • Carbohydrates estimates by high performance liquid chromatograph assays are more precise than colorimetric assays. • Solvents commonly used for sugar extraction and starch gelatinization result in significantly different estimations. • We present an optimized 5-step protocol for the quantitation of seagrass non-structural carbohydrates. Abstract Non-structural carbohydrate (NSC) content provides a quantitative measure of seagrass response to environmental stress and recovery. A review of the literature shows that numerous analytical methods are used to measure seagrass NSC. Colorimetric methods are most commonly used; however, these methodologies lack precision and provide no insights with respect to individual monosaccharides released by hydrolysis. We determined experimentally that assays by high performance liquid chromatograph (HPLC) are more precise and capable of estimating carbohydrates to within 1.1% of expected carbohydrate levels, compared to a greater than 15.0% deviation by colorimetric assays (phenol-sulfuric acid). Furthermore, solvents used for soluble sugar extraction (ethanol/water, methanol/water and water) and starch gelatinization (hydrochloric acid and sodium hydroxide) result in significantly different NSC estimations. Thus, estimation of seagrass NSC by different analytical protocols are non-comparable. We present an optimized 5-step protocol for the quantitation of seagrass soluble NSC and starch using HPLC that identifies individual mono- and oligosaccharides. Creating and using a standardised protocol for NSC quantitation will create a more cogent bio-indicator that enables comparisons of estimates between studies. Additionally, quantitation of individual sugars by HPLC will enable detailed investigation of seagrass metabolic responses to environmental stress. [ABSTRACT FROM AUTHOR]

Seagrass meadows form highly productive and valuable ecosystems in the marine environment. Throughout the year, seagrass meadows are exposed to abiotic and biotic variations linked to (i) seasonal fluctuations, (ii) short-term stress events such as, e.g., local nutrient enrichment, and (iii) small-scale disturbances such as, e.g., biomass removal by grazing. We hypothesized that short-term stress events and small-scale disturbances may affect seagrass chance for survival in temperate latitudes. To test this hypothesis we focused on seagrass carbon reserves in the form of starch stored seasonally in rhizomes, as these have been defined as a good indicator for winter survival. Twelve Zostera noltei meadows were monitored along a latitudinal gradient in Western Europe to firstly assess the seasonal change of their rhizomal starch content. Secondly, we tested the effects of nutrient enrichment and/or biomass removal on the corresponding starch content by using a short-term manipulative field experiment at a single latitude in the Netherlands. At the end of the growing season, we observed a weak but significant linear increase of starch content along the latitudinal gradient from south to north. This agrees with the contention that such reserves are essential for regrowth after winter, which is more severe in the north. In addition, we also observed a weak but significant positive relationship between starch content at the beginning of the growing season and past winter temperatures. This implies a lower regrowth potential after severe winters, due to diminished starch content at the beginning of the growing season. Short-term stress and disturbances may intensify these patterns, because our manipulative experiments show that when nutrient enrichment and biomass loss co-occurred at the end of the growing season, Z. noltei starch content declined. In temperate zones, the capacity of seagrasses to accumulate carbon reserves is expected to determine carbon-based regrowth after winter. Therefore, processes affecting those reserves might affect seagrass resilience. With increasing human pressure on coastal systems, short- and small-scale stress events are expected to become more frequent, threatening the resilience of seagrass ecosystems, particularly at higher latitudes, where populations tend to have an annual cycle highly dependent on their storage capacity.

Non-structural carbohydrates (NSCs) form a fundamental yet poorly quantified carbon pool in trees. Studies of NSC seasonality in forest trees have seldom measured whole-tree NSC stocks and allocation among organs and are not representative of all tree functional types. Non-structural carbohydrate research has primarily focussed on broadleaf deciduous and coniferous evergreen trees with distinct growing seasons, while broadleaf evergreen trees remain under-studied despite their different growth phenology. We measured whole-tree NSC allocation and temporal variation in Eucalyptus obliqua L'Hér., a broadleaf evergreen tree species typically occurring in mixed-age temperate forests, which has year-round growth and the capacity to resprout after fire. Our overarching objective was to improve the empirical basis for understanding the functional importance of NSC allocation and stock changes at the tree- and organ-level in this tree functional type. Starch was the principal storage carbohydrate and was primarily stored in the stem and roots of young (14-year-old) trees rather than the lignotuber, which did not appear to be a specialized starch storage organ. Whole-tree NSC stocks were depleted during spring and summer due to significant decreases in starch mass in the roots and stem, seemingly to support root and crown growth but potentially exacerbated by water stress in summer. Seasonality of stem NSCs differed between young and mature trees and was not synchronized with stem basal area increments in mature trees. Our results suggest that the relative magnitude of seasonal NSC stock changes could vary with tree growth stage and that the main drivers of NSC fluctuations in broadleaf evergreen trees in temperate biomes could be periodic disturbances such as summer drought and fire, rather than growth phenology. These results have implications for understanding post-fire tree recovery via resprouting and for incorporating NSC pools into carbon models of mixed-age forests. [ABSTRACT FROM AUTHOR]

Seagrass meadows form highly productive and valuable ecosystems in the marine environment. Throughout the year, seagrass meadows are exposed to abiotic and biotic variations linked to (i) seasonal fluctuations, (ii) short-term stress events such as, e.g., local nutrient enrichment, and (iii) small-scale disturbances such as, e.g., biomass removal by grazing. We hypothesized that short-term stress events and smallscale disturbances may affect seagrass chance for survival in temperate latitudes. To test this hypothesis we focused on seagrass carbon reserves in the form of starch stored seasonally in rhizomes, as these have been defined as a good indicator for winter survival. Twelve Zostera noltei meadows were monitored along a latitudinal gradient in Western Europe to firstly assess the seasonal change of their rhizomal starch content. Secondly, we tested the effects of nutrient enrichment and/or biomass removal on the corresponding starch content by using a short-term manipulative field experiment at a single latitude in the Netherlands. At the end of the growing season, we observed a weak but significant linear increase of starch content along the latitudinal gradient from south to north. This agrees with the contention that such reserves are essential for regrowth after winter, which is more severe in the north. In addition, we also observed a weak but significant positive relationship between starch content at the beginning of the growing season and past winter temperatures. This implies a lower regrowth potential after severe winters, due to diminished starch content at the beginning of the growing season. Short-term stress and disturbances may intensify these patterns, because our manipulative experiments show that when nutrient enrichment and biomass loss co-occurred at the end of the growing season, Z. noltei starch content declined. In temperate zones, the capacity of seagrasses to accumulate carbon reserves is expected to determine carbon-based regrowth after winter. Therefore, processes affecting those reserves might affect seagrass resilience. With increasing human pressure on coastal systems, short- and small-scale stress events are expected to become more frequent, threatening the resilience of seagrass ecosystems, particularly at higher latitudes, where populations tend to have an annual cycle highly dependent on their storage capacity. [ABSTRACT FROM AUTHOR]

Soil is a main component of the terrestrial ecosystem, and soil carbon research is significant in the carbon cycle and global change. Using the geochemical survey data from Poyang Lake in Jiangxi province and the surrounding economic zone multi-target regional, the total carbon and organic carbon from the surface, middle and deep soil in research area was studied and the organic carbon reserves and organic carbon density distribution characteristics analyzed. The results indicate that the overall carbon in the study area consists mainly of organic carbon. The reserve of organic carbon is 138 million tons and organic carbon density is 3512 t/km2 in the surface soil (0-0.2 m), 439 million tons and 11156 t/km2 in the middle soil (0-1.0 m) and 614 hundred million tons and 15617 t/km2 in the deep soil (0-1.8 m). Compared with the national agricultural geological survey data, organic carbon density of surface soil in the study area is 10.86% higher than that of the national agricultural geology survey, however, organic carbon density of middle and deep soil is close to the results of national agricultural geology. It shows that the research area has huge reserves of organic carbon. Further studies were conducted to uncover the distribution and the distribution characteristics of organic carbon in soil by using the organic carbon density and organic carbon reserves for different soil types, different land utilization types, different geomorphic units and different administrative units. Research results suggest that each layers of soil possesses the same organic carbon density spatial distribution characteristics, which is closely related to the geological background and the vegetation coverage. A high value area of carbon density is located in hilly areas and mountainous regions, such as the paleozoic carbonaceous rock and coal strata from the north of Fengcheng City, the south of Gaoan City and the surrounding of Leping City. The highest organic carbon density occurred in the topsoil of Leping city. Low organic carbon density is located in lake and river valley areas. The results of this study provide reliable data for studying the carbon cycle and carbon emissions in the Jiangxi countryside.

Reduced productivity of trees after defoliation might be caused by limited carbon (C) availability., We investigated the combined effect of different atmospheric CO2 concentrations (160, 280 and 560 ppm) and early season defoliation on the growth and C reserves (nonstructural carbohydrates ( NSC)) of saplings of two oak species with different leaf habits (deciduous Quercus petraea and evergreen Quercus ilex)., In both species, higher CO2 supply significantly enhanced growth. Defoliation had a strong negative impact on growth (stronger for Q. ilex), but the relative reduction of growth caused by defoliation within each CO2 treatment was very similar across all three CO2 concentrations. Low CO2 and defoliation led to decreased NSC tissue concentrations mainly in the middle of the growing season in Q. ilex, but not in Q. petraea. However, also in Q. ilex, NSC increased in woody tissues in defoliated and low- CO2 saplings towards the end of the growing season., Although the saplings were C limited under these specific experimental conditions, growth reduction after defoliation was not directly caused by C limitation. Rather, growth of trees followed a strong allometric relationship between total leaf area and conductive woody tissue, which did not change across species, CO2 concentrations and defoliation treatments. [ABSTRACT FROM AUTHOR]

Plants that store nonstructural carbohydrates (NSC) may rely on carbon reserves to survive carbon-limiting stress, assuming that reserves can be mobilized. We asked whether carbon reserves decrease in resource stressed seedlings, and if NSC allocation is related to species' relative stress tolerances. We tested the effects of stress (shade, drought, and defoliation) on NSC in seedlings of five temperate tree species (Acer rubrum Marsh., Betula papyrifera Marsh., Fraxinus americana L., Quercus rubra L., and Quercus velutina Lam.). In a greenhouse experiment, seedlings were subjected to combinations of shade, drought, and defoliation. We harvested seedlings over 32-97 days and measured biomass and NSC concentrations in stems and roots to estimate depletion rates. For all species and treatments, except for defoliation, seedling growth and NSC accumulation ceased. Shade and drought combined caused total NSC decreases in all species. For shade or drought alone, only some species experienced decreases. Starch followed similar patterns as total NSC, but soluble sugars increased under drought for drought-tolerant species. These results provide evidence that species deplete stored carbon in response to carbon limiting stress and that species differences in NSC response may be important for understanding carbon depletion as a buffer against shade- and drought-induced mortality. [ABSTRACT FROM AUTHOR]

Target of rapamycin (TOR) is a master regulator that controls growth and metabolism by integrating external and internal signals. Although there was a great progress in the study of TOR in plants and in the model alga Chlamydomonas, scarce data are available in other green algae. Thus, in this work we studied TOR signaling in Ostreococcus tauri , the smallest free-living eukaryote described to date. This picoalga is particularly important because it has a key site at the base of the green lineage and is part of the marine phytoplankton, contributing to global photosynthesis. We investigated OtTOR complex in silico and experimentally, by using first- and second-generation TOR inhibitors, such as rapamycin and PP242. We analyzed the effect of TOR down-regulation on cell growth and on the accumulation of carbon reserves. The results showed that O. tauri responds to TOR inhibitors more similarly to plants than to Chlamydomonas, being PP242 a valuable tool to study this pathway. Besides, Ot tor expression analysis revealed that the kinase is dynamically regulated under nutritional stress. Our data indicate that TOR signaling is conserved in O. tauri and we propose this alga as a good and simple model for studying TOR kinase and its regulation. [Display omitted] • TOR signaling is conserved in the green alga Ostreococcus tauri. • TOR signaling is involved in cell growth, chlorophyll homeostasis and nutritional stress response. • Second generation TOR inhibitor PP242 is an effective tool to downregulate TOR pathway. • TOR inhibition induces starch and neutral lipid excretion like nitrogen stress condition. • O. tauri is a good and simple model for studying TOR and its regulation in photosynthetic organisms. [ABSTRACT FROM AUTHOR]

Nonstructural carbohydrates (NSCs) buffer differences in plant carbon supply (photosynthesis) and demand (respiration, growth, etc.) but the regulation of their dynamics remains unresolved. Seasonal variations in NSCs are well-documented, but differences in the time-average, amplitude, phase, and other characteristics across ecosystems and functional types lack explanation; furthermore, observed dynamics do not always match expectations. The failure to match observed and expected dynamics has stimulated debate on whether carbon supply or demand drives NSC dynamics. To gain insight into how carbon supply and demand drive seasonal NSC dynamics, we derive a simple model of NSC dynamics based on carbon mass balance and linearizing the NSC demand to determine how supply-driven and demand-driven seasonal NSC dynamics differ. We find that supply-driven and demand-driven dynamics yield distinct timings of seasonal extrema, and supply overrides demand when carbon supply is low in winter (e.g., at high latitudes). Our results also suggest that NSC dynamics often lag changes carbon mass balance. We also predict differences in NSC dynamics across mass, suggesting saplings are more dynamics and respond faster to the environment than mature trees. Our findings suggest substrate-dependent regulation with environmental variation is sufficient to generate complex NSC dynamics., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background and Aims Developing a conceptual and functional framework for simulating annual long-term carbohydrate storage and mobilization in trees has been a weak point for virtually all tree models. This paper provides a novel approach for solving this problem using empirical field data and details of structural components of simulated trees to estimate the total carbohydrate stored over a dormant season and available for mobilization during spring budbreak. Methods The seasonal patterns of mobilization and storage of non-structural carbohydrates in bark and wood of the scion and rootstock crowns of the trunks of peach (Prunus persica) trees were analysed subsequent to treatments designed to maximize differences in source–sink behaviour during the growing season. Mature peach trees received one of three treatments (defruited and no pruning, severe pruning to 1·0 m, and unthinned with no pruning) in late winter, just prior to budbreak. Selected trees of each treatment were harvested at four times (March, June, August and November) and slices of trunk and root crown tissue above and below the graft union were removed for carbohydrate analysis. Inner bark and xylem tissues from the first to fifth rings were separated and analysed for non-structural carbohydrates. Data from these experiments were then used to estimate the amount of non-structural carbohydrates available for mobilization and to parameterize a carbohydrate storage sub-model in the functional–structural L-PEACH model. Key Results The mass fraction of carbohydrates in all sample tissues decreased from March to June, but the decrease was greatest in the severely pruned and unthinned treatments. November carbohydrate mass fractions in all tissues recovered to values similar to those in the previous March, except in the older xylem rings of the severely pruned and unthinned treatment. Carbohydrate storage sink capacity in trunks was empirically estimated from the mean maximum measured trunk non-structural carbohydrate mass fractions. The carbohydrate storage source available for mobilization was estimated from these maximum mass fractions and the early summer minimum mass fractions remaining in these tissues in the severe treatments that maximized mobilization of stored carbohydrates. The L-PEACH sink–source carbohydrate distribution framework was then used along with simulated tree structure to successfully simulate annual carbohydrate storage sink and source behaviour over years. Conclusions The sink–source concept of carbohydrate distribution within a tree was extended to include winter carbohydrate storage and spring mobilization by considering the storage sink and source as a function of the collective capacity of active xylem and phloem tissue of the tree, and its annual behaviour was effectively simulated using the L-PEACH functional–structural plant model. [ABSTRACT FROM AUTHOR]

Abstract: In temperate regions, climatic factors impose a general seasonal pattern on seagrass growth that can be observed in leaf growth rates and, in small species, also in shoot density. Large variations in shoot density suggest a strong temporal uncoupling between shoot recruitment and shoot mortality, and the dependence of each of these processes on different drivers. Here we examine seasonal patterns of recruitment and mortality in the seagrass Cymodocea nodosa, one of the species most sensitive to seasonal forcing in the Mediterranean. We sampled two local populations submitted to different nutrient availability in Alfacs Bay (NW Mediterranean) and determined recruitment and mortality rates, as well as other plant traits, on a monthly basis. Our results confirm the hypothesized uncoupling, with maximum mortality 2 months after maximum recruitment. Whereas timing of recruitment was associated with light availability, and was supported by carbohydrate remobilisation, mortality was related to high water temperatures and probably also to light limitation in late summer due to self-shading. In the high-nutrient population, algal overgrowth caused further light deprivation, with mortality rates higher than in the low-nutrient population. It is emphasised that the demographic balance of the studied populations was negative for most of the year, with the exception of August and September. Therefore, caution is necessary when overall population trends are inferred from single annual sampling events. [Copyright &y& Elsevier]

There is no consensus about how stresses such as low water availability and temperature limit tree growth. Sink limitation to growth and survival is often inferred if a given stress does not cause non-structural carbohydrate (NSC) concentrations or levels to decline along with growth. However, trees may actively maintain or increase NSC levels under moderate carbon stress, making the pattern of reduced growth and increased NSCs compatible with carbon limitation. To test this possibility, we used full and half defoliation to impose severe and moderate carbon limitation on 2-year-old Quercus velutina Lam. saplings grown in a common garden. Saplings were harvested at either 3 weeks or 4 months after treatments were applied, representing short- and longer-term effects on woody growth and NSC levels. Both defoliation treatments maintained a lower total leaf area than controls throughout the experiment with no evidence of photosynthetic up-regulation, and resulted in a similar total biomass reduction. While fully defoliated saplings had lower starch levels than controls in the short term, half defoliated saplings maintained control starch levels in both the short and longer term. In the longer term, fully defoliated saplings had the greatest starch concentration increment, allowing them to recover to near-control starch levels. Furthermore, between the two harvest dates, fully and half defoliated saplings allocated a greater proportion of new biomass to starch than did controls. The maintenance of control starch levels in half defoliated saplings indicates that these trees actively store a substantial amount of carbon before growth is carbon saturated. In addition, the allocation shift favouring storage in defoliated saplings is consistent with the hypothesis that, as an adaptation to increasing carbon stress, trees can prioritize carbon reserve formation at the expense of growth. Our results suggest that as carbon limitation increases, reduced growth is not necessarily accompanied by a decline in NSC concentrations. Therefore, a lack of NSC decline may not be evidence that reduced tree growth under cold or water stress is caused by sink limitation. [ABSTRACT FROM AUTHOR]

Winter-drought induced forest diebacks in the low-latitude margins of species' distribution ranges can provide new insights into the mechanisms (carbon starvation, hydraulic failure) underlying contrasting tree reactions. We analysed a winter-drought induced dieback at the Scots pine's southern edge through a dual-isotope approach (Δ13 C and δ18 O in tree-ring cellulose). We hypothesized that a differential long-term performance, mediated by the interaction between CO2 and climate, determined the fates of individuals during dieback. Declining trees showed a stronger coupling between climate, growth and intrinsic water-use efficiency ( WUEi) than non-declining individuals that was noticeable for 25 years prior to dieback. The rising stomatal control of water losses with time in declining trees, indicated by negative Δ13 C- δ18 O relationships, was likely associated with their native aptitude to grow more and take up more water (suggested by larger tracheid lumen widths) than non-declining trees and, therefore, to exhibit a greater cavitation risk. Freeze-thaw episodes occurring in winter 2001 unveiled such physiological differences by triggering dieback in those trees more vulnerable to hydraulic failure. Thus, WUEi tightly modulated growth responses to long-term warming in declining trees, indicating that co-occurring individuals were differentially predisposed to winter-drought mortality. These different performances were unconnected to the depletion of stored carbohydrates. [ABSTRACT FROM AUTHOR]

Seasonal and inter-annual dynamics of growth, non-structural carbohydrates (NSC) and carbon isotope composition (δ13C) of NSC were studied in a beech forest of Central Italy over a 2-year period characterized by different environmental conditions. The net C assimilated by forest trees was mainly used to sustain growth early in the season and to accumulate storage carbohydrates in trunk and root wood in the later part of the season, before leaf shedding. Growth and NSC concentration dynamics were only slightly affected by the reduced soil water content (SWC) during the drier year. Conversely, the carbon isotope analysis on NSC revealed seasonal and inter-annual variations of photosynthetic and post-carboxylation fractionation processes, with a significant increase in δ13C of wood and leaf soluble sugars in the drier summer year than in the wetter one. The highly significant correlation between δ13C of leaf soluble sugars and SWC suggests a decrease of the canopy C isotope discrimination and, hence, an increased water-use efficiency with decreasing soil water availability. This may be a relevant trait for maintaining an acceptable plant water status and a relatively high C sink capacity during dry seasonal periods. Our results suggest a short- to medium-term homeostatic response of the Collelongo beech stand to variations in water availability and solar radiation, indicating that this Mediterranean forest was able to adjust carbon–water balance in order to prevent C depletion and to sustain plant growth and reserve accumulation during relatively dry seasons. [ABSTRACT FROM AUTHOR]

Heat waves and droughts are expected to increase in frequency and severity in many regions with future climate change, threatening the survival of a number of forest ecosystems. However, our understanding of the physiological processes and mechanisms underlying drought-induced tree mortality is incomplete. Here, we present results on the physiological response of young Norway spruce trees exposed to lethal drought stress., We applied three levels of drought treatment (control, drying-rewetting, complete drought) and monitored relevant physiological functions and processes of carbon and water relations at high temporal resolution until tree death occurred., Only trees subjected to continuous drought died in our experiment. Trees subjected to drying-rewetting cycles consistently recovered in their ability to transport water, indicating that these trees do not suffer permanent damage to the hydraulic system. In all cases, drought reduced carbon assimilation, caused changes in carbon allocation and appeared to have severely reduced phloem functioning and carbon translocation. Structural growth was sacrificed for carbon investment in maintenance respiration and osmoprotection. Severe drought caused trees to rely on stored carbon reserves but, in contrast to above-ground tissues, only root carbon pools were strongly reduced when trees died., Our results indicate that drought-induced changes in carbon allocation, use and transport differ between above- and below-ground tissues in trees. While root death may have been caused by carbon depletion, this was definitely not the case in above-ground tissues. Our findings indicate that mortality mechanisms are not defined at the organism level but rather within tree compartments. [ABSTRACT FROM AUTHOR]

Fine roots play a key role in the forest carbon balance, but their carbon dynamics remain largely unknown., We pulse labelled 50 m2 patches of young boreal forest by exposure to 13CO2 in early and late summer. Labelled photosynthates were traced into carbon compounds of < 1 and 1-3 mm diameter roots (fine roots), and into bulk tissue of these and first-order roots (root tips)., Root tips were the most strongly labelled size class. Carbon allocation to all size classes was higher in late than in early summer; mean residence times (MRTs) in starch increased from 4 to 11 months. In structural compounds, MRTs were 0.8 yr in tips and 1.8 yr in fine roots. The MRT of carbon in sugars was in the range of days., Functional differences within the fine root population were indicated by carbon allocation patterns and residence times. Pronounced allocation of recent carbon and higher turnover rates in tips are associated with their role in nutrient and water acquisition. In fine roots, longer MRTs but high allocation to sugars and starch reflect their role in structural support and storage. Accounting for heterogeneity in carbon residence times will improve and most probably reduce the estimates of fine root production. [ABSTRACT FROM AUTHOR]

Severe droughts may increase physiological stress on long-lived woody vegetation, occasionally leading to rapid defoliation and progressive increase in mortality of overstorey trees. Over the last few years, episodes of drought-induced tree dieback have been documented in a variety of woodlands and forests around the world. However, the factors determining tree survival and subsequent recovery are still poorly understood, especially in resprouter species. We have studied the effects of a single drought episode on crown condition in a holm oak (Quercus ilex L.) forest located in NE Spain 7 years after the drought event. Generalized linear models were used to study the environmental correlates of forest crown condition 7 years after the drought event. Additionally, we evaluated the association between crown condition and the carbon and nutrient reserves stored in lignotubers 7 years after the drought. Our study reveals the multifactor nature of a drought-driven forest dieback in which soil depth and the characteristics of individual trees, particularly their number of stems, determined a complex spatial pattern of tree-level responses. This dieback was associated with a depletion of the carbon reserves in lignotubers 7 years after the episode, representing a reduction of up to 60% in highly drought-damaged trees. Interestingly, in the absence of new acute droughts, successive surveys in 2007–11 showed a direct association between carbon reserves depletion and further deterioration of crown condition. More frequent droughts, as predicted by climate change projections, may lead to a progressive depletion of carbon reserves and to a loss of resilience in Mediterranean resprouter species. [ABSTRACT FROM PUBLISHER]

• Severe drought may increase physiological stress on long-lived woody vegetation, occasionally leading to mortality of overstory trees. Little is known about the factors determining tree survival and subsequent recovery after drought. • We used structural equation modeling to analyse the recovery of Scots pine (Pinus sylvestris) trees 4 yr after an extreme drought episode occurred in 2004– 2005 in north-east Spain. Measured variables included the amount of green foliage, carbon reserves in the stem, mistletoe (Viscum album) infection, needle physiological performance and stem radial growth before, during and after the drought event. • The amount of green leaves and the levels of carbon reserves were related to the impact of drought on radial growth, and mutually correlated. However, our most likely path model indicated that current depletion of carbon reserves was a result of reduced photosynthetic tissue. This relationship potentially constitutes a feedback limiting tree recovery. In addition, mistletoe infection reduced leaf nitrogen content, negatively affecting growth. Finally, successive surveys in 2009–2010 showed a direct association between carbon reserves depletion and droughtinduced mortality. • Severe drought events may induce long- term physiological disorders associated with canopy defoliation and depletion of carbon reserves, leading to prolonged recovery of surviving individuals and, eventually, to delayed tree death. [ABSTRACT FROM AUTHOR]

Current knowledge on tree carbon (C) allocation to wood is particularly scarce in plants subjected to disturbance factors, such as browsing, which affects forest regeneration worldwide and has an impact on the C balance of trees. Furthermore, quantifying the degree to which tree rings are formed from freshly assimilated vs. stored carbohydrates is highly relevant for our understanding of tree C allocation. We used 13C labelling to quantify seasonal allocation of stored C to wood formation in two species with contrasting wood anatomy: Betula pubescens Ehrh. (diffuse-porous) and Quercus petraea [Matt.] Liebl. (ring-porous). Clipping treatments (66% shoot removal, and unclipped) were applied to analyse the effect of browsing on C allocation into tree rings, plus the effects on tree growth, architecture, ring width and non-structural carbohydrates (NSCs). The relative contribution of stored C to wood formation was greater in the ring-porous (55–70%) than in the diffuse-porous species (35–60%), although each species followed different seasonal trends. Clipping did not cause a significant depletion of C stores in either species. Nonetheless, a significant increase in the proportion of stored C allocated to earlywood growth was observed in clipped birches, and this could be explained through changes in tree architecture after clipping. The size of C pools across tree species seems to be important in determining the variability of seasonal C allocation patterns to wood and their sensibility to disturbances such as browsing. Our results indicate that the observed changes in C allocation to earlywood in birch were not related to variations in the amount or concentration of NSC stores, but to changes in the seasonal availability of recently assimilated C caused by modifications in tree architecture after browsing. [ABSTRACT FROM AUTHOR]

The effects of dehydration and subsequent rehydration on photosynthetic parameters and carbon reserves were investigated in the resurrection plant Reaumuria soongorica. Dehydration was imposed by withholding water and covering plants with a PVC sheet when it rained, over a period of 53 days, by which time all leaves had been shed. Thereafter, plants were watered at 7-day intervals. The diurnal course of the net photosynthetic rate (Pn) was bimodal under well-watered conditions. After a period of withholding water, the second peak disappeared, and Pn, instantaneous water use efficiency (WUE), stomatal conductance (gs) and intercellular CO2 concentration (Ci) decreased, but sugar, starch and non-structural carbohydrate (NSC) reserves increased. It was concluded that under the conditions of high temperature and dehydration, the reduction of Pn should be mainly attributed to gs. On rehydration Pn, gs, Ci and WUE increased slightly in the stem. Accompanying new leaf production, carbon reserves in the stem decreased. This indicated that carbon reserves in the stem have two important ecological roles, survival during dormant periods and support of vegetative regrowth following rehydration. [ABSTRACT FROM AUTHOR]

Abstract: The growing stock more than doubled from 1.6 to 3.4millionm3 between 1912 and 2005 in forests on an area of 387km2 in southern Finland. The stock expansion continued for 93 years noting interim results, which were available for 1959, 1982, 1994 and 1999. Forested area in the region hardly changed. Carbon sequestration was mainly a result of a long-term recovery from forest degradation, a legacy of land use in the 18th and 19th centuries. Tree demography responded to management change especially of mature stands: Average tree size and stocking density of stands increased. On average the expanding biomass stock sequestered 18tons C annually per km2 (18g C per m2). In comparison, the emissions of fossil carbon in the region were estimated at 12tons C per km2 (12g C per m2) on average. However, fossil CO2 emissions exceeded biomass sequestration in recent decades. The powerful and persistent expansion of the carbon stock was an unintended co-benefit of forestry, which was motivated by the intention to improve timber yield. On the more negative side the change in management introduced clear-cuts, and a loss of diverse elements of the pre-industrial biota. [Copyright &y& Elsevier]

Abstract: The net gain of carbon in European Union (EU) forest vegetation during 1990–2005 was estimated at 360–400Tg CO2 year−1 by analysing international data. This amount is at low end of the range of recent corresponding estimates, but greater than earlier estimates published for the period 1971–1990. The sequestration took place almost exclusively in areas which were already forested in 1990. In 2005, new plantations, established after 1990, contributed only about 8% to the estimated net gain. The sequestration was estimated to be the greatest in Germany, France, Italy, Finland and Poland regardless of data source and method of estimation. On a per capita basis, the sequestration was estimated to be the greatest in Finland and Latvia. Carbon sequestration in forests is an important component of the long-term carbon balance of the EU. Carbon sequestration in forests is partly driven by a recovery of the ecosystems from human-induced degradation in the 19th century and the first half of the 20th century. Forest management has affected carbon sequestration and merits attention in climate policy presuming that new policies and measures are reconciled with those already in place for the promotion of the diverse goals of land management in Europe. [Copyright &y& Elsevier]

Background and Aims: Rubus chamaemorus (cloudberry) is a herbaceous clonal peatland plant that produces an extensive underground rhizome system with distant ramets. Most of these ramets are non-floral. The main objectives of this study were to determine: (a) if plant growth was source limited in cloudberry; (b) if the non-floral ramets translocated carbon (C) to the fruit; and (c) if there was competition between fruit, leaves and rhizomes for C during fruit development. [ABSTRACT FROM PUBLISHER]

Characterizing the use of carbon (C) reserves in trees is important for understanding regional and global C cycles, stress responses, asynchrony between photosynthetic activity and growth demand, and isotopic exchanges in studies of tree physiology and ecosystem C cycling. Using an inadvertent, whole-ecosystem radiocarbon (14C) release in a temperate deciduous oak forest and numerical modeling, we estimated that the mean age of stored C used to grow both leaf buds and new roots is 0.7 years and about 55% of new-root growth annually comes from stored C. Therefore, the calculated mean age of C used to grow new-root tissue is ∼0.4 years. In short, new roots contain a lot of stored C but it is young in age. Additionally, the type of structure used to model stored C input is important. Model structures that did not include storage, or that assumed stored and new C mixed well (within root or shoot tissues) before being used for root growth, did not fit the data nearly as well as when a distinct storage pool was used. Consistent with these whole-ecosystem labeling results, the mean age of C in new-root tissues determined using ‘bomb-14C’ in three additional forest sites in North America and Europe (one deciduous, two coniferous) was less than 1–2 years. The effect of stored reserves on estimated ages of fine roots is unlikely to be large in most natural abundance isotope studies. However, models of root C dynamics should take stored reserves into account, particularly for pulse-labeling studies and fast-cycling roots (<1 years). [ABSTRACT FROM AUTHOR]

Question: Are there hot spots of algal mat deposition in space and time at the marsh scale and, if so, how does this affect the coexistence of a dominant (Spartina anglica) and gap dependent (Salicornia europaea) species? Location: The Rattekaai salt marsh in the Scheldt estuary in the southwestern Netherlands (NW Europe). Methods: Mat cover and the abundance of the gap dependent species Salicornia europaea were monitored at the scale of a marsh. The effects of mat cover on the vegetation structure were studied by applying three mat removal treatments over three growing seasons. Results: The low marsh border was found to be a hot spot of algal mat deposition during the growing season, which had a correlated spatial pattern between two successive years at a 20 m × 20 m scale. The combination of duration, timing and repetition of mat cover determined growth inhibition of the competitive dominant Spartina anglica, and thereby the abundance of subordinates such as Salicornia europaea. Mat cover reduced the storage of carbon reserves in Spartina and our results imply that repetition of non-lethal mat cover can lead to ‘gap creation’. Gaps gave only temporary habitat to less dominant species since Spartina quickly re-invaded them. The gap dependent annual Salicornia was most abundant at intermediate levels of disturbance measured as a function of both space and time. Conclusions: In addition to disturbance level, the spatial and temporal distribution of disturbance are important in creating and maintaining habitat for gap dependent species. Relatively small disturbances will have a large effect on diversity if the spatial and temporal distribution of the disturbances leads to ‘disturbance hot spots’. [ABSTRACT FROM AUTHOR]

Abstract Previous evidence indicates that differences in the concentration of underground organic reserves can drive the survival and growing ability of lucerne under cold and defoliation stresses. In order to provide the selection process with further information on compounds that may influence plant performance under grazing, we assessed variations in cold-season concentrations of nitrogen and carbon reserves on genotypes that had been identified for morphological features that possibly enhance grazing tolerance. The selected genotypes encompassed distinct morphological patterns (defined as ‘models’) and different taxa within the Medicago sativa complex, as shown by different flower colours. Crown concentrations of reserves were determined on 90 genotypes, whereas root concentrations were measured on a subsample of 15 genotypes. Wide intergenotypic variation was observed for all reserve substances. Comparisons among models and among flower colour classes highlighted the high concentrations of crown carbohydrates and root and crown-soluble proteins of the model coded as ‘D1’, characterized by prostrate, rhizomatous habit and long dormancy, which largely corresponded to plants with yellow or variegated flowers, typical of ssp. falcata and × varia , respectively. There was a strong ‘flower colour × storage organ’ interaction for sugar concentration, and the results suggested a preferential compartment of sugars in the roots of purple-flowered genotypes that belonged to the ssp. sativa . A rank correlation analysis indicated a positive relationship between persistence after two years under grazing of half-sib progenies deriving from 19 genotypes out of the 90 and crown concentrations of carbohydrates of the 19 mother plants. [ABSTRACT FROM AUTHOR]

Cone development in conifer species is crucial to ensure sexual regeneration. A better understanding of carbon (C) source-sink relations at the branch level can guide strategies for improving resource allocation to reproduction. In particular, the evaluation of C relations between vegetative and reproductive branches is helpful to test whether tree branches are carbon autonomous. With this aim, we integrated girdling and defoliation treatments with 13C pulse labeling in situ to evaluate C autonomy in cone-bearing branches of P. koraiensis during the growing season. Girdling significantly reduced branch volumetric development, branch biomass, and non-structural carbohydrates across foliar, twig, and cone tissues; it also arrested cone development. Defoliation effects on these variables were minor, although they tended to increase with defoliation intensity. In addition, 13C increased by 4.5% and 45.4% after 4 h and 24 h of 13C labeling in unlabeled cone-bearing branches, respectively, indicating the C translocation from labeled vegetative branches. These results indicate that the cone-bearing branches are not C autonomous and that the development of female cones relies to a great extent on C import from neighboring branches. However, the amount of C translocated was largely dependent on manipulative alterations of the source-sink balance, thereby denoting extensive plasticity in the degree of branch C autonomy. These results shed light on the reproductive physiology of P. koraiensis. [ABSTRACT FROM AUTHOR]

The seasonal patterns in concentrations of both soluble (NSC-S) and insoluble (NSC-I) non-structural carbohydrates, in 3-year-old peach trees (Prunus persica L. Batsch) grown in sand culture are described. The ability of trees to mobilize their carbohydrate reserves in response to scion-trunk girdling, which prevents photosynthate transport toward the roots, was tested at four phenological stages. Girdling induces a NSC-I depletion in roots and rootstock-trunk bark and a NSC-I accumulation in leaves and shoots. On the contrary, the NSC-S concentrations of the organs located both above and below girdling were not significantly affected by the treatment. Consequently, when phloem transport breaks down, trees, whatever their growing stage, mobilize carbohydrate reserves below the girdle to maintain the soluble sugar contents at the same level as in control trees. [ABSTRACT FROM PUBLISHER]

Tree growth is generally considered to be temperature limited at upper elevation treelines, yet climate factors controlling tree growth at semiarid treelines are poorly understood. We explored the influence of climate on stem growth and stable isotopes for Polylepis tarapacana Philipi, the world's highest elevation tree species, which is found only in the South American Altiplano. We developed tree-ring width index (RWI), oxygen (δ18O) and carbon (δ13C) chronologies for the last 60 years at four P. tarapacana stands located above 4400 m in elevation, along a 500 km latitude aridity gradient. Total annual precipitation decreased from 300 to 200 mm from the northern to the southern sites. We used RWI as a proxy of wood formation (carbon sink) and isotopic tree-ring signatures as proxies of leaf-level gas exchange processes (carbon source). We found distinct climatic conditions regulating carbon sink processes along the gradient. Current growing-season temperature regulated RWI at northern-wetter sites, while prior growing-season precipitation determined RWI at arid southern sites. This suggests that the relative importance of temperature to precipitation in regulating tree growth is driven by site water availability. By contrast, warm and dry growing seasons resulted in enriched tree-ring δ13C and δ18O at all study sites, suggesting that similar climate conditions control carbon-source processes along the gradient. Site-level δ13C and δ18O chronologies were significantly and positively related at all sites, with the strongest relationships among the southern drier stands. This indicates an overall regulation of intercellular carbon dioxide via stomatal conductance for the entire P. tarapacana network, with greater stomatal control when aridity increases. This manuscript also highlights a coupling (decoupling) between physiological processes at leaf level and wood formation as a function of similarities (differences) in their climatic sensitivity. This study contributes to a better understanding and prediction of the response of high-elevation Polylepis woodlands to rapid climate changes and projected drying in the Altiplano., (© The Author(s) 2021. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)