Leaf Mass Research Articles

Lower grass stomatal conductance under elevated CO2 can decrease transpiration and evapotranspiration rates despite carbon fertilization.

Anthropogenic increase in carbon dioxide (CO2) affects plant physiology. Plant responses to elevated CO2 typically include: (1) enhanced photosynthesis and increased primary productivity due to carbon fertilization and (2) suppression of leaf transpiration due to CO2-driven decrease in stomatal conductance. The combined effect of these responses on the total plant transpiration and on evapotranspiration (ET) has a wide range of implications on local, regional, and global hydrological cycles, and thus needs to be better understood. Here, we investigated the net effect of CO2-driven perennial ryegrass (Lolium perenne) physiological responses on transpiration and evapotranspiration by integrating physiological and hydrological (water budget) methods, under a controlled environment. Measurements of the net photosynthetic rate, stomatal conductance, transpiration rate, leaf mass per area, aboveground biomass, and water balance components were recorded. Measured variables under elevated CO2 were compared with those of ambient CO2. As expected, our results show that elevated CO2 significantly decreases whole-plant transpiration rates (38% lower in the final week) which is a result of lower stomatal conductance (57% lower in the final week) despite a slight increase in aboveground biomass. Additionally, there was an overall decline in evapotranspiration (ET) under elevated CO2, indicating the impact of CO2-mediated suppression of transpiration on the overall water balance. Although studies with larger sample sizes are needed for more robust conclusions, our findings have significant implications for global environmental change. Reductions in ET from ryegrass-dominated grasslands and pastures could increase soil moisture and groundwater recharge, potentially leading to increased surface runoff and flooding.

Plant Morphological and Leaf Anatomical Traits in Coffea arabica L. Cultivars Cropped in Gorongosa Mountain, Mozambique

Studies on the genetic diversity of coffee trees are important, considering their role in the maximization of productivity and quality. However, the success of a breeding program depends on the existence of genetic variability in the population under study. Our study aimed to evaluate the genetic diversity of the morpho-agronomic and anatomical leaf traits of different cultivars of Coffea arabica grown in the Gorongosa mountain region, in the area of Gorongosa National Park, Mozambique. The experiment assessed nine coffee cultivars based on their morpho-agronomic and anatomical traits. The plagiotropic branch diameter, leaf dry mass, leaf mass per area, number of epidermal cells + stomata, and stomatal form indicated differences among the studied cultivars. Among the nine C. arabica cultivars grown in the mountainous region of Gorongosa National Park, Mozambique, low genetic variability in morpho-agronomic traits was detected, while the genetic variability in leaf anatomical traits was higher. The nine cultivars were segregated into two groups, one consisting of Catucaí Amarelo 2SL and Catuaí Vermelho IAC 81, and the second consisting of Catuaí Amarelo IAC 39, Catucaí Vermelho 19/8, Acauã, Catucaí 785-15, Costa Rica, Catimor 128, and Catuaí Vermelho IAC 44. The cultivar segregation into the two groups indicated that the morpho-anatomical traits can be considered during the selection stages in breeding programs.

Growing at the arid edge: Anatomical variations in leaves are more extensive than in stems of five Mediterranean species across contrasting moisture regimes.

Increasing aridity in the Mediterranean region affects ecosystems and plant life. Various anatomical changes in plants help them cope with dry conditions. This study focused on anatomical differences in leaves and xylem of five co-occurring Mediterranean plant species namely Quercus calliprinos, Pistacia palaestina, Pistacia lentiscus, Rhamnus lycioides, and Phillyrea latifolia in wet and dry sites. Stomatal density, stomatal length, leaf mass area, lamina composition, percentage of intercellular air spaces, and mesophyll cell area in leaves of plants in wet and dry sites were analyzed. Xylem anatomy was assessed through vessel length and area in branches. In the dry site, three species had increased stomatal density and decreased stomatal length. Four species had increased palisade mesophyll and reduced air space volume. In contrast, phenotypic changes in the xylem were less pronounced; vessel length was unaffected by site conditions, but vessel diameter decreased in two species. Intercellular air spaces proved to be the most dynamic anatomical feature. Quercus calliprinos had the most extensive anatomical changes; Rhamnus lycioides had only minor changes. All these changes were observed in comparison to the species in the wet site. This study elucidated variations in anatomical responses in leaves among co-occurring Mediterranean plant species and identified the most dynamic traits. Understanding these adaptations provides valuable insights into the ability of plants to thrive under changing climate conditions.

Performance and Evaluation of Hanski 227 Oriental Tobacco in Dak Lak Region, Vietnam from 2022 - 2024

With the results of selecting Oriental tobacco varieties suitable for natural conditions in Vietnam, with potential for raw material quality and raw material production capacity in Vietnam, from 6 oriental tobacco varieties originating from Bulgaria, the Tobacco Institute has been testing in Ninh Thuan province from 2019 to 2021, and Dak Lak from 2021 to 2022. The results of the trial planting show that oriental tobacco varieties are good growth, and are quite suitable for the soil and climate conditions in Ninh Thuan and Dak Lak provinces, and have selected 2 the best oriental tobacco varieties as Basma 16 and Hanski 227. In which, Hanski 227 variety is evaluated to have outstanding prospects due to its good growth ability, high yield, characteristic aroma and good smoking properties. The Hanski 227 variety has less harvested leaves, larger leaf size and mass than Basma 16 variety, so the labor costs for cultivation, harvesting and preliminary processing are lower. To evaluate the ability to expand the oriental area in Vietnam, we continue to trial planting the Hanski 227 oriental variety in Dak Lak in 2023 - 2024, with a fertilizer level and a planting density corresponding to 50N + 30P2O5 + 80K2O (N: NH4NO3, P: (Ca(H2PO4)2 and K: K2SO4) and 110,000 plants/ha. The experimental trial results show the Hanski 227 variety has good growth, high yield, and good quality, with yield fluctuating 1.52 - 1.66 tons/ha, nicotine content: 0.81 - 1.38%, and reducing sugar content: 8.9 - 12.1%, and the oriental material has a characteristic aroma and good smoking properties. Based on the trial results shows that the quality of Hanski 227 grown in Dak Lak are the same the oriental tobacco importing from Bulgaria, Türkiye and Greece. Therefore, the Dak Lak province is the most suitbale region for producing good quality oriental tobacco in Vietnam compared to Ninh Thuan region. Because materials in Ninh Thuan has the high clorua content reducing material quality. In 2025, we continue to grow the Hanski 227 oriental tobacco variety in Dak Lak region on a large area and complete the preliminary processing process, with the goal of producing Oriental tobacco raw materials domestically, with appropriate production costs.

Contrasting regulation of leaf gas exchange of semi-arid tree species under repeated drought.

Predicting how plants respond to drought requires an understanding of how physiological mechanisms and drought response strategies occur, as these strategies underlie rates of gas exchange and productivity. We assessed the response of 11 plant traits to repeated experimental droughts in four co-occurring species of central Australia. The main goals of this study were to: (i) compare the response to drought between species; (ii) evaluate whether plants acclimated to repeated drought; and (iii) examine the degree of recovery in leaf gas exchange after cessation of drought. Our four species of study were two tree species and two shrub species, which field studies have shown to occupy different ecohydrological niches. The two tree species (Eucalyptus camaldulensis Dehnh. and Corymbia opaca (D.J.Carr & S.G.M.Carr) K.D.Hill & L.A.S.Johnson) had large reductions in stomatal conductance (gs) values, declining by 90% in the second drought. By contrast, the shrub species (Acacia aptaneura Maslin & J.E.Reid and Hakea macrocarpa A.Cunn. ex R.Br.) had smaller reductions gs in the second drought of 52 and 65%, respectively. Only A. aptaneura showed a physiological acclimatation to drought due to small declines in gs versus ᴪpd (0.08 slope) during repeated droughts, meaning they maintained higher rates of gs compared with plants that only experienced one final drought (0.19 slope). All species in all treatments rapidly recovered leaf gas exchange and leaf mass per area following drought, displaying physiological plasticity to drought exposure. This research refines our understanding of plant physiological responses to recurrent water stress, which has implications for modelling of vegetation, carbon assimilation and water use in semi-arid environments under drought.

Global patterns of plant functional traits and their relationships to climate

Plant functional traits (FTs) determine growth, reproduction and survival strategies of plants adapted to their growth environment. Exploring global geographic patterns of FTs, their covariation and their relationships to climate are necessary steps towards better-founded predictions of how global environmental change will affect ecosystem composition. We compile an extensive global dataset for 16 FTs and characterise trait-trait and trait-climate relationships separately within non-woody, woody deciduous and woody evergreen plant groups, using multivariate analysis and generalised additive models (GAMs). Among the six major FTs considered, two dominant trait dimensions—representing plant size and the leaf economics spectrum (LES) respectively—are identified within all three groups. Size traits (plant height, diaspore mass) however are generally higher in warmer climates, while LES traits (leaf mass and nitrogen per area) are higher in drier climates. Larger leaves are associated principally with warmer winters in woody evergreens, but with wetter climates in non-woody plants. GAM-simulated global patterns for all 16 FTs explain up to three-quarters of global trait variation. Global maps obtained by upscaling GAMs are broadly in agreement with iNaturalist citizen-science FT data. This analysis contributes to the foundations for global trait-based ecosystem modelling by demonstrating universal relationships between FTs and climate.

Soil fungi lead to stronger ‘diminishing returns’ in fine‐root length versus mass allometry towards earlier successional tropical forests

Abstract Decreasing returns in resource acquisition ability with increasing leaf mass investment is called ‘diminishing returns’, which provides important insights into plant economy. Yet, whether this is true for fine roots and how root resource acquisition strategies change with forest succession remain unclear. We investigated the scaling relationship between fine‐root length (L) and mass (M) for 215 topsoil cores from 24 plots across four successional stages in tropical forests of Xishuangbanna, southwestern China. We also assessed the relative effects of edaphic conditions, leaf functional traits, tree species diversity and soil fungal factors on L versus M scaling relationship using hierarchical variation partitioning. Our results revealed the existence of diminishing returns in root length (L vs. M scaling exponent <1), and that the exponent was higher in late‐ than early‐successional forests, corresponding to a strategy shifting from ‘do‐it‐yourself’ in the late‐successional stage to ‘outsourcing’ resource uptake by soil fungi in the early‐successional stage. Soil fungal abundance was the main driver of changes in the L versus M scaling exponent across plots (explained 58% of variances), with root endophytic fungi the strongest predictor (22.11%), followed by mycorrhizal fungi (10.41%), while other factors (leaf functional traits, edaphic nutrient conditions and tree species diversity) exerted weak effects. Our results suggest that root endophytic and mycorrhizal fungi act as key modulators of root economy changes during forest succession, but the former has received less attention previously. L versus M scaling exponent may be a better indicator for shifts in root resource acquisition strategy than the commonly used specific root length. Read the free Plain Language Summary for this article on the Journal blog.

Root and biomass allocation traits predict changes in plant species and communities over four decades of global change.

Global change is affecting the distribution and population dynamics of plant species across the planet, leading to trends such as shifts in distribution toward the poles and to higher elevations. Yet, we poorly understand why individual species respond differently to warming and other environmental changes, or how the trait composition of communities responds. Here we ask two questions regarding plant species and community changes over 42 years of global change in a temperate montane forest in Québec, Canada: (1) How did the trait composition, alpha diversity, and beta diversity of understory vascular plant communities change between 1970 and 2010, a period over which the region experienced 1.5°C of warming and changes in nitrogen deposition? (2) Can traits predict shifts in species elevation and abundance over this time period? For 46 understory vascular species, we locally measured six aboveground traits, and for 36 of those (not including shrubs), we also measured five belowground traits. Collectively, they capture leading dimensions of phenotypic variation that are associated with climatic and resource niches. At the community level, the trait composition of high-elevation plots shifted, primarily for two root traits: specific root length decreased and rooting depth increased. The mean trait values of high-elevation plots shifted over time toward values initially associated with low-elevation plots. These changes led to trait homogenization across elevations. The community-level shifts in traits mirrored the taxonomic shifts reported elsewhere for this site. At the species level, two of the three traits predicting changes in species elevation and abundance were belowground traits (low mycorrhizal fraction and shallow rooting). These findings highlight the importance of root traits, which, along with leaf mass fraction, were associated with shifts in distribution and abundance over four decades. Community-level trait changes were largely similar across the elevational and temporal gradients. In contrast, traits typically associated with lower elevations at the community level did not predict differences among species in their shift in abundance or distribution, indicating a decoupling between species- and community-level responses. Overall, changes were consistent with some influence of both climate warming and increased nitrogen availability.

Coordination between water relations strategy and carbon investment in leaf and stem in six fruit tree species.

The water relation strategy is a key issue in climate change. Given the difficulty of determining water relations strategy, there is a need for simple traits with a solid theoretical basis to estimate it. Traits associated with resource allocation patterns along a 'fast-slow' plant economics spectrum are particularly compelling, reflecting trade-offs between growth rate and carbon allocation. Avocado (Persea americana ), fig tree (Ficus carica ), mandarin (Citrus reticulata ), olive (Olea europaea ), pomegranate (Punica granatum ), and grapevine (Vitis vinifera ) were characterised in terms of iso-anisohydric strategy through stomatal behaviour, water potential at the turgor loss point (TLP), and hydroscape area. Additionally, the association of these metrics with leaf mass per area (LMA) and wood density (WDen) was explored. We observed high coordination between LMA and WDen, and both traits were related to metrics of water relation strategy. More anisohydric species tended to invest more carbon per unit leaf area or unit stem volume, which has implications for hydraulic efficiency and water stress tolerance. WDen and TLP were the most powerful traits in estimating the water relation strategy for six fruit species. These traits are easy to measure, time-cost efficient, and appear central to coordinating multiple traits and behaviours along the water relations strategies.

Machine Learning Methods for Evaluation of Technical Factors of Spraying in Permanent Plantations

Considering the demand for the optimization of the technical factors of spraying for a greater area coverage and minimal drift, field tests were carried out to determine the interaction between the area coverage, number of droplets per cm2, droplet diameter, and drift. The studies were conducted with two different types of sprayers (axial and radial fan) in an apple orchard and a vineyard. The technical factors of the spraying interactions were nozzle type (ISO code 015, code 02, and code 03), working speed (6 and 8 km h−1), and spraying norm (250–400 L h−1). The airflow of both sprayers was adjusted to the plantation leaf mass and the working pressure was set for each repetition separately. A method using water-sensitive paper and a digital image analysis was used to collect data on coverage factors. The data from the field research were processed using four machine learning models: quantile random forest (QRF), support vector regression with radial basis function kernel (SVR), Bayesian Regularization for Feed-Forward Neural Networks (BRNN), and Ensemble Machine Learning (ENS). Nozzle type had the highest predictive value for the properties of number of droplets per cm2 (axial = 69.1%; radial = 66.0%), droplet diameter (axial = 30.6%; radial = 38.2%), and area coverage (axial = 24.6%; radial = 34.8%). Spraying norm had the greatest predictive value for area coverage (axial = 43.3%; radial = 26.9%) and drift (axial = 72.4%; radial = 62.3%). Greater coverage of the treated area and a greater number of droplets were achieved with the radial sprayer, as well as less drift. The accuracy of the machine learning model for the prediction of the treated surface showed a satisfactory accuracy for most properties (R2 = 0.694–0.984), except for the estimation of the droplet diameter for an axial sprayer (R2 = 0.437–0.503).

Seasonality in embolism resistance and hydraulic capacitance jointly mediate hydraulic safety in branches and leaves of oriental cork oak (Quercus variabilis Bl.).

Seasonality in temperate regions is prominent during the era of increased climatic variability. A hydraulic trait that can adjust to seasonally changing climatic conditions is crucial for tree safety. However, little attention has been paid to the intraspecific seasonality of drought-related traits and hydraulic safety of keystone forest trees. We examined seasonal variations in the key morphological and physiological traits as well as multiple hydraulic safety margins (SMs) at the branch and leaf levels in oriental cork oak (Quercus variabilis Bl.), which is predominant in Chinese temperate forests. Pneumatic measurements indicated that, as seasons progressed, the water potential at which 50% of branch embolisms occur (P50_branch) decreased from -3.34 to -4.23MPa, with a coefficient of variation (CV) of 9.08%. Sapwood capacitance ranged from 48.19 to 248.08kgm-3MPa-1, peaking in autumn and reaching minimum in winter (CV 60.58%). Rehydration kinetics confirmed higher leaf embolism vulnerability (P50_leaf) in spring and autumn than those in summer, with values ranging from -1.06 to -3.02MPa (CV 39.85%). All leaf pressure-volume (PV) traits shifted with growth, with CVs ranging from 6.95% to 46.69%. Sapwood density had significant negative correlations with P50_branch and hydraulic capacitance for elastic water storage, whereas leaf mass per area was linearly associated with PV traits but not with P50_leaf. Furthermore, the branch typical SMs (difference between branch midday water potential and P50_branch) were consistently >1.84MPa, and vulnerability segmentation was prevalent throughout, implying a plausible hydraulic foundation for the dominance of Q. variabilis. Diverse hydraulic response patterns existed across seasons, leading to positive SMs mediated by the aforementioned physiological traits. Although Q. variabilis exhibits a high level of hydraulic safety, its susceptibility to sudden summer droughts may increase due to global climate change.

Water Relations and Physiological Response to Water Deficit of ‘Hass’ Avocado Grafted on Two Rootstocks Tolerant to R. necatrix

Avocado (Persea americana Mill.) cultivation has spread to many countries from the tropics to the Mediterranean region, where avocado crops commonly face water shortages and diseases, such as white root rot (WRR) caused by Rosellinia necatrix. The use of drought- and WRR-tolerant rootstocks represents a potential solution to these constraints. In this research, water relations and the morpho-physiological response of avocado ‘Hass’ grafted on two selections of R. necatrix-tolerant rootstocks (BG48 and BG181) were evaluated under well-watered (WW) and at two soil-water-availability conditions (WS, ~50% and ~25% field capacity). Under WW, scion water use was markedly affected by the rootstock, with BG48 displaying a water-spender behavior, showing higher water consumption (~20%), plant transpiration rates (~30%; Eplant) and leaf photosynthetic rates (~30%; AN) than BG181, which exhibited a water-saving strategy based upon a trade-off between leaf-biomass allocation and tight stomatal control of transpiration. This strategy did not reduce biomass, with BG181 plants being more water use efficient. Under WS, BG48 and BG181 exhibited a drought-avoidance behavior based on distinct underlying mechanisms, but increases in leaf mass area (~18–12%; LMA), and decreases in Eplant (~50–65%), plant hydraulic conductance (~44–86%; Kh) and leaf water potential (~48–73%; Ψw) were observed in both rootstocks, which aligned with water stress severity. After rewatering, photosynthetic rates fully recovered, suggesting some ability of these rootstocks to withstand water stress, enabling the ‘Hass’ variety to adapt to region-specific constraints.

Plant functional types and tissue stoichiometry explain nutrient transfer in common arbuscular mycorrhizal networks of temperate grasslands

Abstract Plants and mycorrhizal fungi form mutualistic relationships that affect how resources flow between organisms and within ecosystems. Common mycorrhizal networks (CMNs) could facilitate preferential transfer of carbon and limiting nutrients, but this remains difficult to predict. Do CMNs favour fungal resource acquisition at the expense of plant resource demands (a fungi‐centric view), or are they passive channels through which plants regulate resource fluxes (a plant‐centric view)? We used stable isotope tracers (13CO2 and 15NH3), plant traits, and mycorrhizal DNA to quantify above‐ and below‐ground carbon and nitrogen transfer between 18 plant species along a 520‐km latitudinal gradient in the Pacific Northwest, USA. Plant functional type and tissue stoichiometry were the most important predictors of interspecific resource transfer. Of ‘donor’ plants, 98% were 13C‐enriched, but we detected transfer in only 2% of ‘receiver’ plants. However, all donors were 15N‐enriched and we detected transfer in 81% of receivers. Nitrogen was preferentially transferred to annuals (0.26 ± 0.50 mg N per g leaf mass) compared with perennials (0.13 ± 0.30 mg N per g leaf mass). This corresponded with tissue stoichiometry differences. Synthesis Our findings suggest that plants and fungi that are located closer together in space and with stronger demand for resources over time are more likely to receive larger amounts of those limiting resources. Read the free Plain Language Summary for this article on the Journal blog.

Carboxylation capacity is the main limitation of carbon assimilation in High Arctic shrubs.

Increases in shrub height, biomass and canopy cover are key whole-plant features of warming-induced vegetation change in tundra. We investigated leaf functional traits underlying photosynthetic capacity of Arctic shrub species, particularly its main limiting processes such as mesophyll conductance. In this nutrient-limited ecosystem, we expect leaf nitrogen concentration to be the main limiting factor for photosynthesis. We measured the net photosynthetic rate at saturated light (Asat) in three Salix species throughout a glacial valley in High-Arctic tundra and used a causal approach to test relationships between leaf stomatal and mesophyll conductances (gsc, gm), carboxylation capacity (Vcmax), nitrogen and phosphorus concentration (Narea, Parea) and leaf mass ratio (LMA). Arctic Salix species showed no difference in Asat compared to a global data set, while being characterized by higher Narea, Parea and LMA. Vcmax, gsc and gm independently increased Asat, with Vcmax as its main limitation. We highlighted a nitrogen-influenced pathway for increasing photosynthesis in the two prostrate mesic habitat species. In contrast, the erect wetland habitat Salix richardsonii mainly increased Asat with increasing gsc. Overall, our study revealed high photosynthetic capacities of Arctic Salix species but contrasting regulatory pathways that may influence shrub ability to respond to environmental changes in High Arctic tundra.

Caught between two states: The compromise in acclimation of photosynthesis, transpiration and mesophyll conductance to different amplitudes of fluctuating irradiance.

While dynamic regulation of photosynthesis in fluctuating light is increasingly recognized as an important driver of carbon uptake, acclimation to realistic irradiance fluctuations is still largely unexplored. We subjected Arabidopsis thaliana (L.) wild-type and jac1 mutants to irradiance fluctuations with distinct amplitudes and average irradiance. We examined how irradiance fluctuations affected leaf structure, pigments and physiology. A wider amplitude of fluctuations produced a stronger acclimation response. Large reductions of leaf mass per area under fluctuating irradiance framed our interpretation of changes in photosynthetic capacity and mesophyll conductance as measured by three separate methods, in that photosynthetic investment increased markedly on a mass basis, but only a little on an area basis. Moreover, thermal imagery showed that leaf transpiration was four times higher under fluctuating irradiance. Leaves growing under fluctuating irradiance, although thinner, maintained their photosynthetic capacity, as measured through light- and CO2-response curves; suggesting their photosynthesis may be more cost-efficient than those under steady light, but overall may incur increased maintenance costs. This is especially relevant for plant performance globally because naturally fluctuating irradiance creates conflicting acclimation cues for photosynthesis and transpiration that may hinder progress towards ensuring food security under climate-related extremes of water stress.

Leaf functional traits predict timing of nutrient resorption and carbon depletion in deciduous subarctic plants

Abstract Resorption of key elements promotes their conservation in plants in nutrient‐poor ecosystems. In seasonal environments, the timing of resorption is expected to influence resorption efficiency and plant fitness due to the trade‐off between maximizing photosynthetic carbon gain by late resorption and minimizing frost risks and nutrient loss by early resorption. Here, we hypothesize that (1) these alternative strategies with respect to the timing of element resorption both occur among summergreen species; (2) deciduous woody plants favour delayed resorption while herbaceous species benefit from gradual, early onset resorption; (3) this pattern is part of a more general relationship in which species with conservative resource economic traits have more delayed resorption. We measured nitrogen (N), phosphorus (P) and carbon (C) contents of mature, senescing and senesced leaves of 22 predominant plant species across four types of ecosystems in a subarctic region. We then calculated timing of resorption as the Julian calendar day of 50% of element resorption (T50), and examined its relationship with plant functional types and leaf resource economic traits (leaf mass per area [LMA], leaf C, N and P contents). The timing of N resorption in subarctic plants ranged from day 213 to 254, while the timing of P resorption ranged from day 211 to 261 and of C from day 214 to 260 across species. On average, the resorption of N and P and depletion of C were 13, 12 and 19 days respectively earlier in herbaceous plants than in woody ones. For all the three elements, T50 of plants decreased significantly with increasing acquisitive economic traits. Synthesis: As hypothesized, we found that (1) both “steady‐and‐slow” and “late‐and‐fast” strategies of resorption timing co‐occurred in a subarctic flora; consistent with these two strategies, herbaceous plants resorbed nutrients and carbon earlier than deciduous woody species; (2) relevant functional traits representing resource conservation were positively and linearly related to the timing of nutrient resorption and carbon depletion. These findings for element resorption timing have important implications for functional changes in the vegetation composition of seasonal regions in response to temperature fluctuations in a changing climate.

The space occupation and use by tree crowns explain variations of individual growth rates in an old-growth temperate forest in Japan

Relative growth rates (RGR), i.e., growth rates per unit biomass (ΔM/M, where M is plant mass and ΔM is the change in M over a period of time), reflect growth strategies of plant species. Partitioning of RGR to net assimilation rate (ΔM/leaf area) and leaf area ratio (leaf area/M) provides further insights into allocation strategies. To apply this analytical approach to large canopy tree species, we used crown area (Ac) as a proxy for leaf area to understand variations of RGR partitioned to space use efficiency (SUE, ΔM/Ac) and space occupation efficiency (SOE, Ac/M). With UAV imagery, we measured Ac of 226 co-occurring individuals of 14 canopy tree species in a 1-ha stand in a temperate old-growth mixed-forest in Japan, and analyzed how RGR was related to SUE and SOE. The results show that deciduous species exhibited higher SOE and lower SUE compared to evergreen species, even though their RGR values largely overlapped. Late successional species tended to have higher RGR through higher SUE than early-to-middle successional species. We also analyzed the relationship of absolute growth rates (AGR) with several functional traits including DBH (diameter at breast height), Ac, leaf- and stem traits. Both Ac and DBH were strong determinants of AGR across species. Low specific leaf area (SLA, leaf area per unit leaf mass) and high wood density positively contributed to AGR across species, offering long-term growth advantages for old-growth natural forest. The analytical framework introduced in this study may be useful to elucidate the variation of tree growth strategies of canopy trees in natural forest stands.

Effects of prescribed fire on planted oak growth and survival in restored savannas

Most oak savannas in the Midwestern United States have been lost to agriculture and habitat degradation. Because of their rarity and high plant and animal diversity, savannas are often a target for restoration, which frequently relies on the direct planting of oak seedlings to establish the necessary canopy. Returning fire to the system is critical to the herbaceous component, but with planted seedlings, managers risk damaging or killing trees if burning is introduced too soon. We studied the growth and physiological responses of three oak species (Quercus alba, Quercus macrocarpa, and Quercus velutina) to prescribed fire to determine impacts on planted trees. This study utilized two restored oak savanna units that were planted in 1995 and 1998, each with burned and unburned areas. We tracked trees ranging from 0.9 to 29.8 cm in diameter at breast height (DBH) to determine the size threshold above which top kill is unlikely and documented differences in leaf structure and extension growth between the burned and unburned areas. There was no mortality observed. Moreover, no trees larger than 4 cm DBH were top killed by the fire. Fire responses in leaf mass per unit area and chlorophyll content were small and inconsistent across species. However, all oak species grew more in burned areas than trees in adjacent unburned areas. Therefore, the addition of low‐intensity prescribed fire to an oak savanna planting may increase the growth rate of planted trees with minimal risk of mortality once trees have reached sufficient size.

The impact of biologically enhanced fertilisation systems on sweet potato (Ipomoеa batаtas) productivity and quality

The relevance of this research lies in determining the potential use of microbial preparations with varying functionalities to optimise the nutrition and stimulate the growth processes of sweet potato plants, as well as the synergistic effects of different preparations. The developed nutrient optimisation systems are designed to restore soil fertility, reduce the anthropogenic load on vegetable agroecosystems, produce high-quality yields, and increase sweet potato productivity without relying on energy-intensive production methods. This study aimed to investigate the impact of biological fertilisation systems on the biometric parameters, yield, and quality of sweet potato tubers. The research programme was implemented through field, statistical, computational-analytical, and laboratory methods. An increase in the number (7.33-9.83 per plant) and length (175.55-184.89 cm) of shoots was observed with the application of the biological preparations “Groundfix” + “Humifriend”, “Help-Rost for vegetables”, and “Mycofriend”. The use of foliar fertilisations in three terms of “Help-Rost for vegetables”, both in combination with “Mycofriend” during fertigation and with the foliar fertilisation “Humifriend”, resulted in maximal leaf mass formation on the plant (2.41-2.56 m2 /ha in the third decade of June and 23.12-27.45 m2 /ha in the third decade of August). Microbial preparations significantly increased net photosynthetic productivity by 28.9-63.9% during the period from the third decade of June to the third decade of July, especially when “Groundfix” and “Humifriend”, or “Humifriend” and “Help-Rost for vegetables” were combined. A substantial commercial yield of tubers (17.4 t/ha) was achieved by applying the mycorrhizal preparation “Humifriend” (1.5 L/ha) in the first fertigation and conducting three foliar applications of “Help-Rost for vegetables” at 2.0 L/ha. Treatments involving biological preparations demonstrated improvements in key biochemical parameters. The use of “Groundfix” + “Humifriend” and “Humifriend” + “Help-Rost for vegetables” resulted in a decrease in nitrate levels in the produce. The authors hypothesise that the optimal supply of micronutrients, particularly iron, manganese, and molybdenum, enhances the transformation of nitrates into organic matter. This research provides valuable insights for the rational application of biologically enhanced fertilisation systems to achieve high yields and quality of sweet potato tubers in various agricultural settings

The curvilinear responses of biomass accumulation and root morphology to a soil salt-nitrogen environment reflect the phytodesalination capability of the euhalophyte Suaeda salsa L.

Under the sufficient nitrogen supply, it is of great significance to investigate the law of biomass allocation, root morphological traits, and the salt absorption capacity of euhalophytes to evaluate their biological desalination in saline soil. Although the curvilinear responses of biomass accumulation and root morphology in response to soil salinity have been recognized, these perceptions are still confined to the descriptions of inter-treatment population changes and lack details on biomass allocation in organs at an individual level. In this study, Suaeda salsa was grown in root boxes across a range of soil salt levels. The study showed that their growth and development were significantly affected by soil soluble salts. The law of biomass allocation was described as follows: increased soil soluble salts significantly increased the leaf mass ratio and decreased the stem mass ratio, and slightly increased the root mass ratio among treatments. For individuals at each treatment, leaf mass ratio > stem mass ratio > root mass ratio, except in the control treatment at the flower bud and fruit stages. Biomass responses of the control treatment indicated that salt was not rigorously required for Suaeda salsa in the presence of an adequate nitrogen supply, as verified by the correlation between biomass, nitrogen, and soil soluble salt. Salt could significantly inhibit the growth of Suaeda salsa (P<0.01), whereas nitrogen could significantly promote its growth (P<0.01). Root morphology in response to soil soluble salts showed that salt acquisition by the root was highest at a salt level of 0.70%, which corresponds to light saline soil. Consequently, we conclude that phytodesalination by Suaeda salsa was optimal in the light saline soil, followed by moderate saline soil.