Elevation gradients are generally characterized by a steady reduction in temperature with altitude, potentially leading to zonation of vegetation structure. A south-north transect across the central Himalayas spans from a tropical to alpine climates, offering an opportunity to investigate the relative roles of abiotic stress and competitive interactions in shaping plant community assembly. We hypothesise that vegetation composition and productivity shift from competition-driven realised niches at lower elevations, to stress-driven physiological niches at higher elevations. To investigate how these niche transitions influence community assembly and ecosystem processes, we used a dynamic vegetation model with regional plant functional types (PFTs) parameterised with trait data, including allometric relationships. The model captured spatial patterns in vegetation structure and productivity along the gradient. PFTs' establishment and performance depended on their climatic niche and the local competitive interactions, with persistence shaped by specific functional traits and adaptive strategies. At low elevations, where competitive interactions dominate, tropical shade-intolerant raingreen and tropical shade-tolerant evergreen PFTs dominated above-ground biomass production and vegetation cover. In contrast, shorter stature, evergreen, and cold-tolerant PFTs were favoured at high elevations, reflecting reduced competition and increasing temperature limitation. PFT functional diversity declined with elevation, while compositional evenness increased, with evidence of a mid-elevation diversity peak after accounting for stochasticity. Despite higher functional diversity at low elevations, vegetation structure and function – reflected in leaf-area index (LAI), foliar projective cover (FPC) and above-ground biomass – were dominated by a few competitively superior PFTs. Overall, these results indicate that vegetation dynamics along the elevation gradient are governed by a trade-off between competitive ability and stress tolerance. This trade-off drives shifts in structure, composition and productivity along the gradient, reflecting a transition from realised to physiological niche dominance mediated by environmental conditions and trait responses.

The capacity of nutrient-limited forests to enhance carbon (C) sequestration under elevated CO2 (eCO2) remains a critical uncertainty in C cycle modeling. While existing evidence suggests that low phosphorus (P) bioavailability may constrain CO2 fertilization effects on plant growth, the extent to which this limitation modulates ecosystem responses to eCO2 in forests adapted to P-deficient soils remains poorly understood. Here, using eight P-enabled models, we simulated the magnitudes and mechanisms through which P bioavailability interacts with eCO2, emulating an ecosystem-scale P enrichment experiment at a P-limited Eucalyptus forest undergoing long-term Free-Air CO2 Enrichment. While models predicted pronounced P effects on tree growth, P enrichment unexpectedly did not increase the CO2 effects on tree growth and ecosystem C sequestration. Models prioritized either CO2-driven or P-driven growth, but rarely both. This tradeoff emerged due to model-specific assumptions on 1) partitioning of the extra P in soil labile versus nonlabile pools; 2) plant photosynthetic acclimation to P deficiency; 3) C and nutrient use strategies regulating plant size and allocation; and 4) microbial-driven soil decomposition processes. By generating divergent yet biologically plausible outcomes, these predictions establish critical testable hypotheses for empirical research and highlight multiple P-related pathways that may influence the future land C sink.

Droughts have intensified under climate change, threatening ecosystem stability. While rising atmospheric CO2 concentrations may enhance vegetation drought resistance, the net effect remains uncertain amid concurrent warming. Here we combine ecological modeling with multi-source observations to investigate how CO2 and warming jointly regulate vegetation drought responses on the Qinghai-Tibetan Plateau, a sensitive alpine region exposed to escalating drought threats under changing precipitation regimes. Using factorial scenarios to isolate individual forcings, we show that 40-year CO2 rise mitigated drought-induced productivity losses by 5.7 +/- 0.9% under constant temperature. However, in the presence of warming, rising CO2 intensifies drought stress by 5.2 +/- 0.5%, reflecting increased plant water demand and disrupted regional water supply-demand balance. Permafrost areas experienced the strongest CO2-driven drought alleviation under constant temperature, but also the greatest warming-induced reversal. These findings reveal interacting CO2-warming impacts on alpine vegetation drought responses, highlighting ecological risks for the plateau and other permafrost-dominant regions under future warming.

Large-scale solar generation is critical for energy transitions. In Australia, increased solar production to meet emission targets means its land footprint increasingly competes with agricultural land. Understanding the scale and location of agricultural land use change and potential profitability losses from large-scale solar farms is essential for a sustainable transition, yet comprehensive spatial assessments are lacking. We quantified these potential trade-offs through spatially explicit modelling of 1568 scenarios that account for a range of uncertainties about utility-scale solar design, performance, land suitability and energy production targets. Our analysis considered siting strategies that either prioritised the highest solar yield or reduced the land use trade-off ratio of energy to agricultural profitability. The results show that meeting national utility-scale solar targets could convert up to 273,000 ha (0.28% of total agricultural land). While a yield-focused approach could result in annual agricultural profit losses of up to $29 million, adopting an approach that reduced opportunity costs on agricultural production can reduce these losses to $2.6 million for the same energy generation. Even the larger of these two figures represents less than 0.03% of Australia's farm-gate output. Impacts are primarily concentrated in grazing regions of Queensland, Western Australia and New South Wales. 'Agrisolar'-co-location of agriculture or grazing with solar development could help further mitigate agricultural production and regional impacts. These results show that while the overall national impact on agricultural land from large-scale solar expansion may be marginal, strategic spatial planning and agrisolar (where feasible) are crucial for mitigating adverse regional effects.

Societal Impact Statement People and nature need a renewable energy transition to help address the growing, and catastrophic, effects of climate change. A sustainable energy transition involves rigorously examining the potential impacts on nature – including plant life – and creating pathways for impact mitigation that strike a clear balance between energy production and biodiversity conservation. Given the critical roles that plants play in ecosystems, culture, wellbeing and prosperity, including for Indigenous people, their protection must be recognised, upheld and enhanced in the energy transition. This review seeks to chart a course for policymakers, proponents and practitioners to consider plants when planning, designing and implementing renewable energy infrastructure and projects. Summary A global scale renewable energy transition is now underway, bringing opportunities and challenges for nature, including plant life. Plants form the basis of terrestrial ecosystems and provision of essential ecosystem services; their protection and stewardship must be ensured during the renewable energy transition. Here, we provide a synthesis of the potential impacts of the energy transition on plants. We combine knowledge from research literature in plant ecology, plant biology, sustainability, conservation, spatial planning and social justice with that from policy documents, working papers and environmental assessments for existing renewable developments. The DPSIR method (Drivers, Pressures, State, Impacts, Responses) is used to organise the synthesis, including an examination of the utility of project life cycle assessment for anticipating impacts to plants. Where impacts may negatively affect plants or people, specific calls to action are offered. These include the need to tackle ‘plant blindness’ (i.e., the tendency to overlook, or undervalue plants, compared to animals) in the life cycle of renewable projects – from approval to decommissioning – and the need for Indigenous ownership and benefit sharing. Solutions which can accommodate and enhance plant biodiversity in conjunction with renewable energy projects, including closed‐loop or circular renewable design within the landscape, are discussed. Multiple global strategies call for the biodiversity and climate crises to be addressed in tandem (e.g., the Paris Accord, Global Biodiversity Framework, UN Sustainable Development Goals), underscoring the need for a nature‐based transition to renewable energy. Plant life must be recognised, valued and secured alongside wider biodiversity to achieve a sustainable future for Earth.

Phosphorus (P) limitation may constrain the capacity of forests to remove CO2 from the atmosphere under elevated CO2 (eCa). One key mechanism is that limited P availability requires plants to invest additional fixed carbon belowground, which then returns to the atmosphere via soil respiration. However, the extent and pathways of this response remain unclear. We quantified total soil respiration and inferred its component fluxes before and after alleviating P limitation via fertilization in an established eCa experiment in mature Eucalyptus woodland. eCa increased soil respiration by 22.5% regardless of P availability. Dependence of the stimulation on soil moisture indicated it was driven primarily by root-derived respiration rather than soil organic matter-derived heterotrophic respiration. Fine-root production was stimulated by eCa only after P addition, suggesting that P fertilization triggered a shift from rhizomicrobial respiration, associated with microbial use of root exudates and residues, to autotrophic respiration from root growth and metabolism. These findings indicate that within 9 months of P addition, EucFACE plants may have shifted P-acquisition strategies under eCa. As the first ecosystem-scale study on the interactive effect of eCa and P limitation, this research improves mechanistic understanding of short-term belowground responses and provides insight to motivate follow-up studies.

Drought-induced canopy browning and recovery dynamics threaten ecosystem stability worldwide, with Australia serving as a representative case. This study examined the 2019-2020 drought and subsequent recovery in Eucalyptus forests across two bioregions of the Australian state of New South Wales (NSW): the North Coast and South Eastern Highlands. Canopy browning and recovery were quantified using a 2010-2022 Sentinel-2 time series of Normalized Burn Ratio (NBR), which has been previously identified as the most effective spectral index for detecting drought-related declines in canopy greenness, and were validated with field-measured canopy health. Artificial neural networks were used to link NBR z-scores with climatic (precipitation, temperature, potential evapotranspiration), topographic (Topographic Wetness Index, aspect, slope), soil, and vegetation variables. Lagged and cumulative precipitation and temperature emerged as the dominant drivers of canopy browning, while recovery was influenced by potential evapotranspiration and temperature. Regional contrasts underscored the role of local climate, topography, and vegetation composition in shaping drought impacts and post-drought recovery trajectories.

Aim Allometric relationships, which describe plant growth patterns shaped by environmental conditions, reflect functional trade-offs and represent key functional traits that optimise adaptation, resource acquisition, stress tolerance and competition. Here, we assess how these allometric relationships and associated functional trade-offs drive ecosystem structure, functioning and competitive interactions between plant functional types (PFTs) in savanna ecosystems.Location Rainfall gradient, North Australian Tropical Transect (NATT), Australia.Time Period 1901-2022.Taxon Tree species of Northern Australia. Methods Using quantile regression, we established adaptive allometric relationships among diameter at breast height, tree height, crown radius and crown volume. These relationships were integrated into a dynamic vegetation model to simulate tree growth and competitive interactions in local patches across the broader savanna landscape. The model was validated using observed biomass, height, leaf area index and productivity data from six flux tower sites across the NATT. A neighbour removal experiment was conducted to analyse PFT performance under varying competitive pressure, expressed as a competitive index. Results The results demonstrate that incorporating adaptive allometric relationships improved the model's ability to represent vegetation dynamics and productivity. Tall Eucalyptus PFTs exhibited competitive dominance in high rainfall areas, while Acacia and other deciduous species thrived under drier conditions. The neighbour removal experiment revealed that competition strongly influenced PFT performance, with carbon mass production varying significantly between stand types. Tall Eucalyptus PFTs showed little response to neighbour removal, while other PFTs benefitted strongly from neighbour removal. The competitive index of PFTs increased significantly with rainfall, indicating stronger competition under wetter conditions. Main Conclusions Our findings suggest that savanna ecosystems are shaped by complex interactions between growth conditions, functional traits and adaptive strategies for coping with competition and stress. These interactions are reflected in allometric relationships and the associated trade-offs in plant growth strategies, which vary across different rainfall gradients.

Plants take up carbon dioxide (CO 2 ) through photosynthesis. How this will change with rising CO 2 concentrations in the atmosphere will strongly determine future climate change. An increase in the seasonal variations of atmospheric CO 2 in recent decades indicates a positive trend in photosynthetic carbon uptake. We combined data‐driven seasonal cycles of plant productivity with carbon sinks across the range predicted by current biospheric process models to explain the seasonal variations of CO 2 at high and low northern latitudes over the past 40 years. We find that increases in seasonal variations can only be explained by a larger gross primary productivity (GPP) of northern ecosystems than most current estimates and by an increase of GPP about proportional to the increase in atmospheric CO 2 , also larger than most current estimates. Our results provide an improved constraint to estimate the future behavior of the terrestrial carbon sink.

Environmental gradients affect vegetation structure and ecosystem productivity. Along the northern Australia tropical transect (NATT), which transitions from tropical moist conditions in the north to arid conditions in the south, vegetation composition and structure are closely tied to rainfall patterns. We hypothesise that biotic competition and abiotic stress exhibit opposing patterns along the NATT rainfall gradient and aim to disentangle these effects on vegetation structure and productivity. Using a trait-based dynamic vegetation model, we simulated vegetation responses to varying competition and stress along the NATT. The model successfully simulated spatial variations and temporal patterns in carbon and water fluxes, where evapotranspiration and gross primary productivity decrease with rainfall along the gradient. Simulation results showed that taller and medium-sized Eucalyptus had higher carbon mass, leaf area index, and foliar projective cover at the wet end of the gradient. In contrast, Acacia and grasses were dominant at the dry end. Crown coverage shows spatial and temporal variability with rainfall, with higher variability in tree plant functional types (PFTs) crown cover in the north and more uniform in the south, while grasses have maximum coverage during the wet season in the dry end of the gradient. These patterns suggest a shift in the importance of biotic versus abiotic factors, with competition playing a more significant role in the wet region and stress becoming more influential as aridity increases in the south. Overall, our study underscores water availability as a primary driver of vegetation structure and highlights the role of competition and stress in modulating ecosystem structure, composition, and productivity along the rainfall gradient.

Understanding plant responses to increasing CO2 is essential for predictions of plant productivity and of future climate (Walker et al. 2020). Isotope ratios (13C/12C and 2H/1H) have long been used in plant ecophysiology and for reconstruction of environmental variables. But it has also been known since decades that heavy isotopes are distributed unevenly WITHIN biological metabolites, i.e. that the abundances of 2H and 13C isotopomers vary. Because isotopomer variation is caused by enzyme isotope fractionation, it carries signals on the regulation of biochemical pathways. If such signals can be recovered from archives of plant material, they can report on plant-climate interactions on time scales from decades to millennia. We use NMR (nuclear magnetic resonance) to analyze isotopomers of the glucose units of plant archives, and I will describe the principles and practicalities of isotopomer measurements. First, in manipulation experiments we calibrate isotopomer responses to environmental drivers, in particular CO2 and T. Second, we analyse isotopomers in plant archives such as tree-ring series over previous decades of rising CO2, and use the calibrations from the manipulation experiments to deduce shifts in photosynthetic metabolism over decades. We will present results on 2H and 13C isotopomer variation and associated ecophysiological signals. We present data on 13C isotopomers in tree-ring cellulose and annual plants (Wieloch et al 2018). The results have implications for interpretation of the d13C of respired CO2. Furthermore, we show how 13C isotopomers give new insight into the pathways of C metabolism (Wieloch et al 2023). Photorespiration is a side reaction of photosynthesis that reduces C assimilation in most vegetation. Photorespiration is reduced by increasing CO2 yet exacerbated by rising T, so its evolution under climate change and implications for global C fluxes are highly uncertain. We present data showing how 2H isotopomers can be used to track photorespiration in response to CO2 and T. The opposing effects of CO2 and T on photorespiration will determine if forests will in the future be a sink or source of CO2 (Van der Sleen et al. 2015; Sperry et al. 2019). For select tree species, we compare results from FACE experiments and from decades-long tree ring series, to detect possible acclimation of gas exchange of broad-leaved trees over In summary, the presentation will describe how isotopomers can improve mechanistic understanding of plant function on long time scales, to be incorporated into Dynamic global vegetation models to improve predictions of C fluxes under climate change scenarios. References Walker et al., 2020 https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.16866. Van der Sleen et al., 2015. https://doi.org/10.1038/ngeo2313. Sperry et al., 2019. https://doi.org/10.1073/pnas.1913072116. Wieloch et al., 2018 https://www.nature.com/articles/s41598-018-23422-2 Wieloch et al., 2023 https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.18965

Droughts present a significant global challenge, particularly to forest ecosystems in regions such as eastern New South Wales, Australia, which is known for its dry climate and frequent, intense droughts. Recent studies have indicated a notable increase in tree mortality and canopy browning across this area, especially during the recent extreme drought period culminating in the Black Summer of 2019–2020. Our study investigates the impacts of drought on eucalypt forests by leveraging remote sensing and field observation data to detect and analyse vegetation health and stress indicators. Utilising data from Sentinel-2, alongside historical Landsat observations, we applied multiple spectral vegetation indices, namely the Normalized Difference Vegetation Index (NDVI), Normalized Difference Moisture Index (NDMI), Normalized Burn Ratio (NBR), and Tasseled Cap Transformation, to assess the extent of drought impacts. We found NBR to show the most consistent agreement with ground-based observations of drought-related tree mortality. Additionally, by integrating ground-based data from the “Dead Tree Detective” citizen science project, we were able to validate the remote sensing outcomes with a 90.22% consistency, providing confirmation of the extensive spatial distribution and severity of the inferred impacts. Our findings reveal that 13.16% of eucalypt forests and woodlands across eastern New South Wales experienced severe stress associated with drought during the 2019–2020 Black Summer drought. This study demonstrates the utility of satellite-derived drought indicators in monitoring forest health and highlights the necessity for continuous monitoring and research to understand the factors that trigger tree vitality loss.

The European spruce bark beetle (Ips typographus) is an insect species that causes significant damage to Norway spruce (Picea abies) forests across Europe. Infestation by bark beetles can profoundly impact forest ecosystems, affecting their structure and composition and affecting the carbon cycle and biodiversity, including a decrease in net primary productivity (NPP), a key indicator of forest health. The primary objective of this study is to enhance our understanding of the interplay among NPP, bark beetle infestation, land surface temperature (LST), and soil moisture content as key components influencing the effects of climate change-related events (e.g., drought) during and after a drought event in the Bavarian Forest National Park in southeastern Germany. Earth observation data, specifically Landsat-8 TIR and Sentinel-2, were used to retrieve LST and leaf area index (LAI), respectively. Furthermore, for the first time, we incorporated a time series of high-resolution (20 m) LAI as a remote sensing biodiversity product into a process-based ecological model (LPJ-GUESS) to accurately generate high-resolution (20 m) NPP products. The study found a gradual decline in NPP values over time due to drought, increased LST, low precipitation, and a high rate of bark beetle infestation. We observed significantly lower LST in healthy Norway spruce stands compared to those infested by bark beetles. Likewise, low soil moisture content was associated with minimal NPP value. Our results suggest synergistic effects between bark beetle infestations and elevated LST, leading to amplified reductions in NPP value. This study highlights the critical role of integrating high-resolution remote sensing data with

Nitrogen (N) transformation processes by soil microbes account for significant nitrous oxide (N2O) emissions from natural ecosystems and cropland. However, understanding and quantifying global soil N2O emissions and their responses to changing environmental conditions remain challenging. Here, we implemented a soil nitrification–denitrification module into the dynamic vegetation model LPJ-GUESS to estimate N2O emissions from global lands. The performance of this new development is examined using observed N2O fluxes from natural-soil and cropland field trials and independent global-scale estimates. LPJ-GUESS broadly reproduces the cumulative N2O emissions under different climate conditions and N fertilizer applications that are observed in the field experiments, with some deviations in emission seasonality. Globally, simulated soil N2O emissions from terrestrial ecosystems increase from 5.6±0.2 Tg N yr−1 in the 1960s to 9.9±0.3 Tg N yr−1 in the 2010s, with croplands contributing about two-thirds of the total increase. East Asia and South Asia show the fastest growth rates in N2O emissions over the study period due to the expansion of fertilized croplands. On a global scale, N fertilization (including synthetic fertilizer and manure use), atmospheric N deposition, and climate change contribute 58 %, 46 %, and 24 %, respectively, to the simulated soil N2O emissions in the 2010s. Rising CO2 levels in the atmosphere reduce the simulated emissions by 32 % through increased plant N uptake, whereas land use changes have varied spatial effects on emissions depending on N management intensity after land cover conversion. Our estimates only account for the direct soil N2O emissions, excluding those from fertilized pastures. This study highlights the importance of environmental factors in influencing global soil N2O emissions, particularly for assessing greenhouse gas mitigation potential in agricultural ecosystems.

The capacity for terrestrial ecosystems to sequester additional carbon (C) with rising CO2 concentrations depends on soil nutrient availability1,2. Previous evidence suggested that mature forests growing on phosphorus (P)-deprived soils had limited capacity to sequester extra biomass under elevated CO2 (refs. 3-6), but uncertainty about ecosystem P cycling and its CO2 response represents a crucial bottleneck for mechanistic prediction of the land C sink under climate change7. Here, by compiling the first comprehensive P budget for a P-limited mature forest exposed to elevated CO2, we show a high likelihood that P captured by soil microorganisms constrains ecosystem P recycling and availability for plant uptake. Trees used P efficiently, but microbial pre-emption of mineralized soil P seemed to limit the capacity of trees for increased P uptake and assimilation under elevated CO2 and, therefore, their capacity to sequester extra C. Plant strategies to stimulate microbial P cycling and plant P uptake, such as increasing rhizosphere C release to soil, will probably be necessary for P-limited forests to increase C capture into new biomass. Our results identify the key mechanisms by which P availability limits CO2 fertilization of tree growth and will guide the development of Earth system models to predict future long-term C storage.

Ecosystem restoration is a critical nature-based solution to mitigate climate change. However, the carbon sequestration potential of restoration, defined as the maximum achievable carbon storage, has likely been overestimated because previous studies have not adequately accounted for the competition between ecosystem water demands for maximizing carbon sequestration and human water needs. Here we used a comprehensive process-based model combined with extensive land-use data and evaporation recycling accounting for land-atmosphere feedback to estimate the water requirements associated with ecosystem restoration. We found that achieving the carbon sequestration potential of restoration would significantly reduce global water availability per capita by 26%, posing considerable risks to water security in water-stressed and highly populated regions. If human water use is safeguarded, the achievable carbon sequestration potential would be reduced by a third (from 396 PgC to 270 PgC). Brazil, the United States and Russia have the largest achievable potentials. Future projections accounting for changes in climate, atmospheric CO2, land use and human population under the shared socioeconomic pathway (SSP) scenarios SSP119, SSP245 and SSP585 suggest an increase in this achievable potential to 274-302 PgC by the end of the century, with China expected to have the largest potential. Our findings provide a nuanced understanding of the trade-offs and synergies between carbon sequestration goals and water security, offering an empirical framework to guide the sustainable implementation of ecosystem restoration strategies.

Drawing on collective experience from ten collaborative research projects focused on the Global South, we identify three major challenges that impede the translation of research on sustainability and resilience into better-informed choices by individuals and policy-makers that in turn can support transformation to a sustainable future. The three challenges comprise: (i) converting knowledge produced during research projects into successful knowledge application; (ii) scaling up knowledge in time when research projects are short-term and potential impacts are long-term; and (iii) scaling up knowledge across space, from local research sites to larger-scale or even global impact. Some potential pathways for funding agencies to overcome these challenges include providing targeted prolonged funding for dissemination and outreach, and facilitating collaboration and coordination across different sites, research teams, and partner organizations. By systematically documenting these challenges, we hope to pave the way for further innovations in the research cycle.

Globally, solar projects are being rapidly built or planned, particularly in high solar potential regions with high energy demand. However, their energy generation potential is highly related to the weather condition. Here we use state-of-the-art Earth system model simulations to investigate how large photovoltaic solar farms in the Sahara Desert could impact the global cloud cover and solar generation potential through disturbed atmospheric teleconnections. The results indicate negative impacts on solar potential in North Africa (locally), Middle East, Southern Europe, India, Eastern China, Japan, Eastern Australia, and Southwestern US, and positive impacts in Central and South America, the Caribbean, Central & Eastern US, Scandinavia and South Africa, reaching a magnitude of ±5% in remote regions seasonally. Diagnostics suggest that large-scale atmospheric circulation changes are responsible for the global impacts. International cooperation is essential to mitigate the potential risks of future large-scale solar projects in drylands, which could impact energy production.

Semi-arid ecosystems, common across the Australian continent, strongly influence the inter-annual variability and trend in the global terrestrial net carbon sink. Here we explore the future Australian terrestrial carbon cycle using the CMIP6 ensemble, and the dynamic global vegetation model LPJ-GUESS. Uncertainty in Australia’s carbon storage in vegetation ranged between 6 and 49 PgC at the end of the century and was strongly linked to biases in the meteorological forcing. Using LPJ-GUESS with bias-corrected meteorological forcing reduced uncertainty in the vegetation carbon storage to between 14 and 20 PgC, with the remaining range linked to model sensitivities to rising atmospheric CO2 concentration, temperature, and precipitation variability. Reducing this uncertainty will require improved terrestrial biosphere models, but also major improvements in the simulation of regional precipitation by Global Climate Models.