Key uncertainties remain in predicting carbon sequestration through enhanced weathering (EW), particularly regarding secondary mineral formation and interactions with the organic matter. We compared a coupled inorganic-organic geochemical model (PHREEQCENTURY) with soil measurements and CO2 efflux from a 389-day mesocosm experiment using soils amended with varying alkaline manure, basalt, and dunite inputs. Silicate amendments did not enhance dissolved inorganic C leaching or significantly increase pedogenic carbonate accumulation. PHREEQC simulations indicated that base cations preferentially precipitated as secondary clays rather than carbonates, inhibiting CO2 removal. Sequential extractions suggested that Al, Fe and base cations were mainly retained via adsorption to (hydr)oxides and organic matter, with additional retention in secondary clays indicated by models. Higher organic matter addition did not increase element release from basalt─and reduced leached K and Fe─while decreasing the reactive surface area of basalt, indicating a counteractive effect of manure on rock weathering. Alkaline manure addition also likely decreased weathering of pyroxene and olivine minerals. Cumulative soil CO2 efflux did not differ significantly among treatments, consistent with PHREEQCENTURY simulations, predicting limited treatment effects due to minor changes in soil pH, moisture and organic C stabilization as mineral-associated organic matter in this soil.

Spatio-temporal assessment of soil biogeochemical properties and CO2 efflux in a dry tropical watershed of India

Global warming is altering carbon (C) cycling in terrestrial and inland aquatic ecosystems. Yet it remains unclear how experimental warming and elevation (natural temperature gradient) jointly regulate priming effects (PEs) on organic matter decomposition in soils and sediments and thereby influence CO2 and CH4 emissions. We investigated temperature-dependent priming induced by 13C-labelled glucose additions across a soil-sediment continuum in the Rongbuk River Basin on the Tibetan Plateau (3759-4550 m a.s.l.). Soil and sediment samples were incubated under two temperatures (7°C and 17°C) to quantify PE for CO2 and CH4 (i.e., PE-CO2 and PE-CH₄). Labile C inputs induced consistently positive PE-CO2 in soils, with generally stronger responses in sediments. PE-CO2 ranged from 0.42 to 11 mg CO2 g-1 SOC in soils and from 0.41 to 15 mg CO2 g-1 SOC in sediments, whereas PE-CH4 ranged from -2.2 to 5.2 μg CH4 g-1 SOC in soils and from 0.14 to 7.9 μg CH4 g-1 SOC in sediments. Warming increased PE-CO2 but suppressed PE-CH4. Higher-elevation sites showed lower primed CO2 efflux but larger primed CH4 efflux than lower-elevation sites. This indicates that warming effects on priming depend on the balance between oxidative and reductive C processing. High-throughput amplicon sequencing targeting the 16S and ITS2 rDNA regions indicated specific effects on priming: bacterial community composition was closely correlated with rapid, substrate-driven CO2 priming, whereas fungal communities were indirectly linked to primed CH4 through their depolymerization of organic matter. Together, CO2 and CH4 released by priming of organic matter decomposition arise from distinct but coupled microbial pathways across soils and sediments, whereas sensitivity to temperature decreased along elevation. These findings highlight the need to explicitly account for oxidative and reductive priming related processes when predicting C turnover and greenhouse-gas feedbacks in high-elevation terrestrial-aquatic interface systems under climate change.

Photosynthetic activity in plant stems, particularly in woody plants and shrubs, is well known and documented. Nevertheless, our knowledge about the role of photochemical processes occurring in the stems of cultivated plants and their contribution to plant growth and development, including the root system, still remains unclear. Therefore, this study aims to determine the role of cells equipped with chloroplasts and located in the stems of tomato (Solanum lycopersicum L.) plants and whether changes in the activity of the photochemical processes affect the development of the plant's root system and aboveground organs. The described study was conducted on tomato plants with stems covered with a doubled agrotextile (DP) that absorb 99% of incident light and on plants growing without coverage (NDP). Stem darkening led to the changes in the intensity of photochemical processes in these organs - a decrease in both the maximum and actual photochemical efficiency [Fv/Fm and Y(II)], as well as an increase in energy dissipation, both controlled (NPQ - non-photochemical quenching) and uncontrolled [(Y(NO) - non-regulated energy dissipation in photosystem II] way. These changes correlate with alterations in the anatomy of the stem cross-section. Darkening led to an increase in stem surface conductance to water vapour but a decrease in stem CO2 efflux. The root length and dry mass of DP plants were significantly reduced compared to the roots of NDP plants. No significant differences were observed for the shoots (leaves + stems). The substantial changes in the structure of chloroplasts located in the stem cells of DP were also observed, with visible signs of ageing and disintegration of these organelles. In addition, the composition of the nitrogen forms in the soil where the plants were grown was different between DP and NDP. The soil from DP plants showed a higher total nitrogen content; however, unlike the ammonium and nitrate forms (NH4⁺ and NO3⁻), the nitrite form (NO2⁻) was present at a lower concentration in this substrate compared to that of the NDP plants. Darkening did not have a direct effect on the δ¹³C and δ¹⁵N composition between NDP and DP plants, nor on the carbon-to-nitrogen ratio in the leaves, roots, and stems. Nevertheless, based on the obtained results for δ¹³C, δ¹⁵N, and the nitrogen-to-carbon ratio, some general trends can be observed. The obtained results suggest that photochemical processes occurring in tomato stems have an important influence on the development of the tomato plant, especially on the root system. Limited light access to the stems restricts root system growth and development, but shows no visible negative effects on the above-ground parts of the tomato plants in this study. However, indirect effects on shoot growth and development cannot be excluded. Restricting light exposure to the stems likely reduces energy production in the form of energy carriers, such as ATP and NADPH, resulting in decreased efficiency of assimilate transport to the root. This disrupts the plant's nitrogen uptake and balance, and in turn limits root system development. Moreover, it can be assumed that the chloroplasts present in tomato stems differ structurally and, as a consequence, functionally from those in leaves, which are specialised for efficient photosynthesis. Because a well-developed root system is an important factor affecting plant growth and yield, the obtained results may suggest the possibility of agronomic practices aimed at increasing the efficiency of photochemical processes and photosynthesis in the stems, and consequently improving yields.

ABSTRACTSoil respiration (RS) represents a major process of release of carbon dioxide (CO2) from soil to atmospheric carbon pools. Measurements of soil respiration help to understand the dynamics of carbon in ecosystems. This study examines the soil respiration rate and the effect of environmental variables in different forests along elevation gradient. This study was conducted in three distinct montane forest types distributed along an elevational gradient in the middle mountain region of Nepal, namely Schima‐Castanopsis Forest, Oak Laurel Forest, and Evergreen Oak Forest. In each forest type, 10 circular chambers were installed for measuring soil respiration. Soil CO2 efflux was measured monthly for 1 year, using the “closed chamber method” with an infrared gas analyzer. Soil respiration rate was modeled as a function of soil temperature and moisture using a generalized linear model (GLM). Soil respiration rate varied significantly among the forest types, ranging from 274.7 to 352.4 mg CO2 m−2 h−1 and demonstrated seasonal changes with a summer peak. Soil respiration was significantly higher in Evergreen Oak Forest than Oak Laurel Forest and Schima‐Castanopsis Forest. Response of soil respiration to soil temperature and soil water content indicated a significant exponential relationship in all the forests. Soil respiration showed a strong correlation with soil temperature than soil water content. Temperature sensitivity (Q10) of soil respiration was higher in the forest of upper elevation (Evergreen Oak Forest, Q10 = 3.9) than in the lower elevation forests (Oak Laurel Forest, Q10 = 2.7; Schima Castanopsis Forest, Q10 = 2.5), indicating that soil respiration in the Evergreen Oak Forest is more responsive to temperature changes. Hence, forests at higher elevation are highly susceptible in the context of future climate warming due to enhanced efflux of soil CO2. This study highlights the necessity of incorporating belowground carbon processes into climate policy and sustainable forest management frameworks in Nepal.

A major constraint on modelling woody-tissue CO₂ efflux is the scarcity of datasets that adequately represent its variability and underlying drivers. We intensively sampled CO₂ efflux along the vertical profile of nine temperate broadleaf trees across three species and found substantial longitudinal variation. We partitioned the flux into growth and maintenance-associated components; accordingly we use ‘efflux’ for measurements and ‘respiration’ only for the derived components. Expressing efflux by wood volume, surface area and sapwood volume each offered insight into the underpinning of the flux. However, efflux was most strongly associated with surface area, particularly in medium and large branches, and across both growth and maintenance respiration. In small branches, where sapwood dominates, this surface area scaling weakens, suggesting maintenance respiration shifts from surface area- to volume-based scaling, while growth respiration remains associated with surface area. Sapwood depth, tree ring width and the relative contributions of growth and maintenance respiration explained much of the variation in efflux, though additional biological and physical factors, such as CO₂ diffusion from sap and variation in sapwood parenchyma, likely also contribute. These findings represent an important step towards reducing uncertainty in the spatial scaling of woody-tissue CO₂ efflux by linking within tree variation in respiration to underlying anatomical and growth-related controls.

Short-term recovery of urban soil functions after de-sealing in Palermo (Italy).

Cold acclimation of leaf respiration often increases respiration rates at a set temperature after temperature declines. Whether a similar response occurs in stems and contributes to frost tolerance remains unknown. We evaluated stem CO2 efflux (Es) and cold acclimation in dormant Quercus robur trees in a climate chamber with day/night air temperatures weekly changing from 20/10oC to 5/-10oC and back to 20/10oC over eleven weeks. Cold hardening was evidenced by lower cell damage at subfreezing temperatures compared to trees kept in a greenhouse at 21.5/18.5oC. A hysteresis between Es and stem temperature (Ts) evidenced a time lag between Es and metabolic activity during chilly and subfreezing weeks. Stem CO2 efflux was strongly related to Ts down to -10oC. At a standardized Ts of 5oC, Es_5 decreased the day after weekly temperatures declined, suggesting a rapid down-regulation of respiratory metabolism to enhance cryoprotection. Accordingly, soluble sugar concentrations increased with decreasing Ts. However, upon subsequent warming from subfreezing temperatures, stems continued dehydrating and did not recover previous respiration rates, suggesting freeze/thaw embolism and cell damage reduced stem apparent "respiratory capacity". Moderate frost tolerance in cold-hardened plants appears to depend on stem dehydration and SS accumulation, not increased stem metabolic activity.

The northern part of the state of Mato Grosso is located at the intersection of large-scale agricultural production and the Amazon, a tropical biome of great importance for ecosystem services and biodiversity. Agricultural production activities interact with natural capital, among other factors, in land use and in biogeochemical cycles of water and carbon. In this study, we sought to use remote sensing at the regional level to diagnose and spatialize the contribution of agricultural activity to dry areas. Using carbon dioxide orbital models, land use classification techniques, the Standardized Precipitation Index (SPI), and Pettitt and Mann–Kendall statistics, the variables were compared spatially for the biogeographic boundary of the Amazon in Mato Grosso in two distinct time frames: (i) over the crop years of the CO2 efflux model (2020 to 2023), and (ii) over the years 2008 to 2023, with consolidated data from the MODIS sensor system. The hot and cold spots analysis reinforces the correlation of carbon variables to land use; the drought index suggests a spatial correlation to forest loss, where more intense agricultural activity favors drought and inhibits moderate rainfall, and in turn is linked to the amount of forest in the context of intense continentality. Temporally, the statistical diagnosis highlights abrupt changes in 2011, 2013, and 2019, restate the complex relation of tropical forest and biogeochemical cycles, above all with carbon dioxide.

This study aimed to characterize the spatiotemporal dynamics of soil respiration (CO2 efflux), soil moisture, and soil temperature across different land-use systems in a semi-arid environment through in situ monthly monitoring and to evaluate the potential of UAV-based imagery combined with Random Forest modeling to spatialize these variables within the agroforestry system. The variables were monitored monthly using an Infrared Gas Analyzer (IRGA) over 9 months, and UAV imagery was acquired at two distinct time points. The 11-month experimental campaign enabled evaluation of seasonal and spatial variability and of soil physical and hydraulic properties. Soil CO2 efflux ranged from 1.0 to 6.7 μmol m−2 s−1, with higher values observed during the rainy period, closely following soil moisture dynamics. Soil moisture and temperature exhibited clear seasonal patterns driven by rainfall variability. The pasture system showed higher CO2 efflux in most months, while AFS2 presented more stable fluxes over time. In contrast, AFS1 exhibited lower CO2 efflux, likely associated with its soil characteristics. Despite these patterns, no significant differences were observed among land-use systems for most soil physical properties. UAV-derived data combined with machine learning techniques proved effective for modeling soil CO2 efflux, soil temperature, and soil moisture, demonstrating their potential for monitoring soil processes in semi-arid environments. Overall, agroforestry systems did not significantly differ from other land uses in terms of CO2 efflux, likely due to their early stage of development. These findings indicate that the effects of agroforestry systems on soil processes occur gradually and highlight the importance of long-term monitoring to fully capture system dynamics.

Spatial variability in soil carbon dynamics and related parameters in urbanization driven peri-urban region.

Abstract. Permafrost regions in subarctic and arctic areas harbor substantial carbon reserves, which are becoming increasingly vulnerable to microbial decomposition as soils warm. As the seasonally thawed active layer deepens and anthropogenic disturbances escalate, accurately predicting carbon fluxes from disturbed environments underlain by permafrost requires a comprehensive understanding of soil respiration dynamics. This study investigated the impact of surface disturbance on seasonal soil biological properties in a boreal forest ecosystem near Fairbanks, Alaska. Further, we sought to identify the key environmental and geochemical factors influencing soil biology in the undisturbed and disturbed soils. Our results revealed a substantial rise in soil respiration at the disturbed boreal forest site, which exhibited a 14.4 % overall increase in CO2 efflux compared to the undisturbed site. This effect was most pronounced during the summer, when the increase in CO2 efflux peaked at 20 %. This heightened respiratory activity was directly linked to significantly warmer soil conditions, with the mean annual soil temperature at the disturbed site measuring 0.60±0.16 °C, in stark contrast to the sub-zero temperatures of -0.37±0.08°C at the undisturbed site. Furthermore, the disturbed site had 30 % higher bacterial community richness, 1 % higher total mean C and 0.03 % higher total mean N concentration levels, and 11.9 % higher pH values in the subsoil layer, as well as a 147 % deeper maximum active thaw depth, suggesting potential controls underlying the variation in CO2 efflux. Our research underscores the essential importance of considering the rise in carbon emissions from anthropogenically disturbed soils underlain by permafrost, which are frequently neglected in assessments of the carbon cycle. This study contributes to a deeper understanding of the complex interactions governing soil respiration in disturbed permafrost environments, ultimately informing more accurate predictions of carbon fluxes in these ecosystems.

BackgroundChanges in global patterns can leave a lasting legacy in semiarid grasslands by reshaping microbial growth dynamics and carbon cycling during the first wet-up in the autumn—a period known for intense microbial activity and significant carbon emissions. To study the lasting impacts of decreased winter rain, we implemented two precipitation regimes (100% vs. 50% mean annual precipitation) in California Mediterranean-climate grassland field plots. After the dry season, soils were rewetted in the laboratory with H218O and sampled at 0 h, 3 h, 24 h, 48 h, 72 h, and 168 h post rewet. We quantified CO2 efflux, measured microbial growth and mortality via quantitative 18O stable isotope probing and 16S rRNA gene amplicon sequencing, and characterized the soil organic carbon chemical composition, metagenomes, and metatranscriptomes.ResultsWe found that reduced winter precipitation imposed a strong legacy effect on microbial turnover; despite maintaining similar respiration rates, microbial growth declined by ~1 order of magnitude, yielding decreased community growth efficiency (CGE = new biomass growth/respiration), and microbial mortality declined by ~2 orders of magnitude. Soil organic carbon also shifted from lipid-like, amino-sugar-like, and protein-like compounds (indicative of microbial necromass) to more oxidized lignin-like and tannin-like compounds (indicative of decomposing plant-derived compounds). Meta-omics revealed distinct metabolic strategies linked to CGE. At high-CGE, microbes appeared to consume more energetically favorable N-rich necromass (released via high microbial turnover); this allowed for increased amino acids and peptidoglycan biosynthesis and greater aromatic compound degradation, fueling further energy production and growth efficiency. At low CGE, communities had elevated carbohydrate metabolism and lipid turnover, consistent with increased investment in plant detritus degradation and membrane repair and maintenance rather than growth.ConclusionsTogether, our findings demonstrate that reduced winter rainfall decreases microbial turnover following rewetting without a concurrent reduction in CO2 emissions. This shift results in persistently lower CGE, which has the potential to increase soil carbon loss as CO2. If such conditions are maintained over multiple years, these changes could reshape soil organic carbon stocks and alter the balance of grassland ecosystems under future climate scenarios. While our data suggest that sustained reductions in CGE may drive SOC decline, the magnitude and persistence of these effects depend on long-term environmental dynamics and warrant further investigation.Video Supplementary InformationThe online version contains supplementary material available at 10.1186/s40168-026-02395-9.

Temporary reductions of stem CO2 efflux during rainfall events across tree species

ABSTRACTSoil microorganisms regulate carbon (C) cycling, and their growth and respiration are strongly dependent on temperature. Yet it remains unclear how warming alters microbial thermal traits, community structure, and the balance between microbial respiration and growth, particularly in subtropical ecosystems where high temperatures coincide with low soil moisture, potentially constraining microbial activity. In this study, we investigated soil microbial thermal traits for growth and respiration, and the microbial community composition in two subtropical land‐uses with contrasting microclimates: a cooler, moist pristine forest and a warmer, drier cropland. Using open top chambers (OTCs) or rain exclusion shelters over 1.5 years, we quantified how experimental warming and drought altered microbial functioning and upscaled these effects using field soil temperature and moisture records. Field warming increased the abundance of warm‐adapted bacterial and fungal taxa and led to shifts in microbial thermal trait distributions toward higher minimum temperature values for microbial growth, indicating community‐level thermal adaptation. These thermal trait adaptations resulted in a modeled 36% reduction in annual soil CO2 efflux in warmed plots. Overall, our results show that thermal trait adaptation, driven partly by community restructuring, buffers soil C losses under warming and may enhance soil C sequestration in subtropical ecosystems. These findings showcase the importance of integrating microbial thermal traits into soil C models to improve predictions of climate‐carbon feedbacks.

Research on greenhouse gas (GHG) fluxes has predominantly focused on subtropical soils, with far less attention given to emissions from tree stems. In particular, year-long simultaneous measurements of both soil and tree stem fluxes in these forests are lacking, and data on standing dead trees is exceptionally scarce. We determined the dynamics of standing dead and live tree stems, and soil CH4, N2O and CO2 fluxes in a subtropical forest. We determined GHG fluxes from standing dead and live tree stems with three different tree heights (10 cm, 50 cm and 150 cm) of Cunninghamia lanceolata from January 2023 to December 2024 and subjected to analysis by gas chromatography. Measurements of environmental parameters were conducted in tandem with those of fluxes and xylem sap flow. Live tree stems contributed less to the annual GHG dynamics than standing dead trees. Live and standing dead tree stems generally acted as net annual sources of CH4, N2O, and CO2. Tree stem GHG fluxes decreased with decreasing precipitation. Soil was a sink of CH4, but a net CO2 and N2O source. Isolated emission peaks dominated the temporal dynamics of stem CH4, N2O, and CO2 fluxes and significantly contributed to the net annual fluxes. The CH4, N2O, and CO2 efflux from both live and standing dead tree stems exhibited a similar seasonal trend. The status (live or dead) and height of the trees significantly influenced stem GHG dynamics. During the study, CH4 emissions from tree stems (across different heights and precipitation conditions) offset an estimated 55.61~60.03% of the soil's CH4 sink capacity. Here, we demonstrate for the first time a strong correlation between stem greenhouse gas fluxes and sap flow in subtropical forests. The stem fluxes of CH4 in live and standing dead trees represented a combination of soil-derived and stem-produced methane, whereas CO2 and N2O fluxes were primarily soil-derived.

Coastal wetlands are globally important natural carbon sinks but can also act as sources of greenhouse gas emissions. Despite recent progress in quantifying carbon sources and sinks in these ecosystems, uncertainties remain over the climate benefits of restoration, particularly where greenhouse gas emissions may offset carbon gains. Here, we present paired measurements of sediment and aquatic CO 2 and CH 4 effluxes comparing vegetated (mangrove and saltmarsh) and unvegetated (salt flat) wetlands, as well as tidally connected and tidally restricted wetlands, in tropical monsoonal northern Australia during the cool dry season of 2025. Sediment CO 2 and CH 4 effluxes were significantly higher in saltmarshes and mangroves than in salt flats, which likely reflects greater organic matter inputs, root-associated processes, and higher sediment moisture in vegetated habitats. In addition, tidally restricted wetlands exhibited substantially higher aquatic CH 4 effluxes than tidally connected systems, consistent with the observed salinity gradient. Sediment CH 4 efflux data from salt flats in this study (median: 0.013, range: 0.007-0.015 nmol CH 4 m -2 s -1 ) provide the first measurement of salt flat methane rates in Australia. These results fill emission factor gaps for tropical monsoonal coastal wetlands and reinforce the need to quantify both sediment- and water-air CO 2 and CH 4 fluxes in blue carbon assessments. More broadly, accounting for aquatic fluxes alongside sediment fluxes is essential for quantifying mitigation potential from restoring coastal wetlands and informing blue carbon management relevant to Australia’s Nationally Determined Contributions implementation. • Sediment properties and sediment–water GHG effluxes differ strongly among Australian tropical salt flats, saltmarshes, mangroves and tidally restricted wetlands. • Sediment CO 2 and CH 4 effluxes are significantly higher in coastal vegetated habitats than in unvegetated salt flats. • Salt flat CH 4 effluxes in this study (median: 0.013, range: 0.007-0.015 nmol CH 4 m -2 s -1 ) provide the first reported sediment CH 4 effluxes for Australian salt flats. • Tidally restricted wetlands exhibited substantially higher aquatic CH 4 effluxes than tidally connected systems. • Combined flux measurements highlight the equal importance of both sediment and aquatic components in blue carbon assessments.

Forest fire types, soil moisture extremes, and aspects and their interactions significantly affect soil CO2 effluxes in post-fire black pine forests

The climate impact of bivalve aquaculture remains inadequately quantified for China, the world’s dominant producer. Prevailing carbon footprint assessments often overlook the complexity of biological carbon flows and fail to capture effects that evolve across different timescales. To address these gaps, we developed a novel multi-temporal dual-carbon flow life cycle assessment framework that systematically quantifies both the anthropogenic (ACF) and biological (BCF) carbon footprints and evaluates the climate impacts across different time horizons. Applied to China’s largest mussel farm, the framework reveals the system’s total carbon footprint decreases from +261.7 kg CO2-eq/t under a conventional Cradle-to-Gate perspective to +84.6 kg CO2-eq/t over a centennial scale and further to +27.9 kg CO2-eq/t over a geological timescale. With the ACF constant across all timescales (+256.2 kg CO2-eq/t), the transition in total carbon footprint is driven entirely by the BCF. The BCF changes from a minor positive contribution during farming (+5.5 kg CO2-eq/t, from enhanced sea-to-air CO2 efflux) to a major net sink at centennial (–171.6 kg CO2-eq/t ) and geological (–228.3 kg CO2-eq/t) scales, primarily due to long-term carbon sequestration from shell removal, burial, and weathering. Consequently, the net carbon footprint is not a fixed attribute but a function of temporal perspective, controlled decisively by shell-waste management. Aligning the industry with climate goals thus requires not only reducing the ACF through material and energy efficiency during the production chain but, crucially, also diverting shells from incineration to burial or weathering pathways to secure their long-term sink potential.

Stem CO2 efflux varies in the vertical profile depending mostly on the variability in stem growth rate and the vertical pattern changes with tree age. Stem CO2 efflux (EA) from trees exhibits both temporal and vertical variability. EA is often measured only at the breast height, making it challenging to accurately upscale these measurements to represent the entire ecosystem. This study examines the potential drivers behind the EA vertical variability and evaluates the long-term changes in the EA ratio between two fixed heights. EA was monitored in two Norway spruce trees over eight growing seasons within a ten-year period (2005–2014). Measurements were carried out simultaneously at three heights (1.3, 3.2, and 4.5 m since 2005 till 2009 and 1.3, 4.5, and 7.5 m since 2011 till 2014) using an automated chamber system. Moreover, meteorological measurements and wood formation analyses were provided. Overall, EA generally increased with the height, though the pattern differed between trees. Assuming that EA at 1.3 m was representative of the whole stem resulted in underestimating the seasonal temperature-normalized EA by 5.3% in one tree and 16.6% in the other. Such variation makes it difficult to generalize the findings. A stem temperature gradient along the stem would contribute to a maximum increase in EA of 4.3%. Conversely, sap flow, which is understood to transport produced CO2 to the upper parts of the stem, had no apparent effect on the vertical variation of EA. Our findings suggest that the vertical variation in EA is primarily driven by the differences in stem growth, with the stem positions below the crown clearly distinguishable from those at the crown base and within the crown. Moreover, the differences in EA between 4.5 m and 1.3 m were not constant, showing a gradual decrease over time. This adds further uncertainty when generalizing observed vertical EA patterns over longer timescales.