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Abstract. This paper aims to assess the spatial variability in the response of CO2 exchange to irradiance across the Arctic tundra during peak season using light response curve (LRC) parameters. This investigation allows us to better understand the future response of Arctic tundra under climatic change. Peak season data were collected during different years (between 1998 and 2010) using the micrometeorological eddy covariance technique from 12 circumpolar Arctic tundra sites, in the range of 64–74° N. The LRCs were generated for 14 days with peak net ecosystem exchange (NEE) using an NEE–irradiance model. Parameters from LRCs represent site-specific traits and characteristics describing the following: (a) NEE at light saturation (Fcsat), (b) dark respiration (Rd), (c) light use efficiency (α), (d) NEE when light is at 1000 μmol m−2 s−1 (Fc1000), (e) potential photosynthesis at light saturation (Psat) and (f) the light compensation point (LCP). Parameterization of LRCs was successful in predicting CO2 flux dynamics across the Arctic tundra. We did not find any trends in LRC parameters across the whole Arctic tundra but there were indications for temperature and latitudinal differences within sub-regions like Russia and Greenland. Together, leaf area index (LAI) and July temperature had a high explanatory power of the variance in assimilation parameters (Fcsat, Fc1000 and Psat, thus illustrating the potential for upscaling CO2 exchange for the whole Arctic tundra. Dark respiration was more variable and less correlated to environmental drivers than were assimilation parameters. This indicates the inherent need to include other parameters such as nutrient availability, substrate quantity and quality in flux monitoring activities.

AbstractData capturing multiple axes of tree size and shape, such as a tree's stem diameter, height and crown size, underpin a wide range of ecological research—from developing and testing theory on forest structure and dynamics, to estimating forest carbon stocks and their uncertainties, and integrating remote sensing imagery into forest monitoring programmes. However, these data can be surprisingly hard to come by, particularly for certain regions of the world and for specific taxonomic groups, posing a real barrier to progress in these fields. To overcome this challenge, we developed the Tallo database, a collection of 498,838 georeferenced and taxonomically standardized records of individual trees for which stem diameter, height and/or crown radius have been measured. These data were collected at 61,856 globally distributed sites, spanning all major forested and non‐forested biomes. The majority of trees in the database are identified to species (88%), and collectively Tallo includes data for 5163 species distributed across 1453 genera and 187 plant families. The database is publicly archived under a CC‐BY 4.0 licence and can be access from: https://doi.org/10.5281/zenodo.6637599. To demonstrate its value, here we present three case studies that highlight how the Tallo database can be used to address a range of theoretical and applied questions in ecology—from testing the predictions of metabolic scaling theory, to exploring the limits of tree allometric plasticity along environmental gradients and modelling global variation in maximum attainable tree height. In doing so, we provide a key resource for field ecologists, remote sensing researchers and the modelling community working together to better understand the role that trees play in regulating the terrestrial carbon cycle.

An interdisciplinary field investigation of historic glacial lake outburst floods (GLOFs) in the Kanchenjunga region of Nepal was conducted between April and May, 2019. Oral history and field measurements suggested that at least six major GLOFs have occurred in the region since 1921. A remote sensing analysis confirmed the occurrence of the six GLOFs mentioned by informants, including two smaller flood events not mentioned that had occurred at some point before 1962. A numerical simulation of the Nangama GLOF suggested that it was triggered by an ice/debris avalanche of some 800,000 m3 of material, causing a surge wave that breached the terminal moraine and released an estimated 11.2 × 106 m3 ± 1.4 × 106 m3 of water. Debris from the flood dammed the Pabuk Khola river 2 km below the lake to form what is today known as Chheche Pokhari lake. Some concern has been expressed for the possibility of a second GLOF from Nangama as the result of continued and growing landslide activity from its right lateral moraine. Regular monitoring of all lakes and glaciers is recommended to avoid and/or mitigate the occurrence of future GLOF events in the region. Collectively, the paper demonstrates the benefits and utility of interdisciplinary research approaches to achieving a better understanding of past and poorly documented GLOF events in remote, data-scarce high mountain environments.

Dans les forêts tropicales amazoniennes, des études récentes ont rapporté des augmentations de la biomasse aérienne et de la productivité primaire, ainsi que des changements dans la composition des espèces végétales favorisant les espèces à croissance rapide par rapport aux espèces à croissance lente. Cette altération omniprésente des forêts tropicales matures a été attribuée aux changements environnementaux mondiaux, tels qu'une augmentation de la concentration atmosphérique de CO2, des dépôts de nutriments, de la température, de la fréquence des sécheresses et/ou de l'irradiance. Nous avons utilisé des mesures standardisées et répétées de plus de 2 millions d'arbres dans dix grandes parcelles forestières (16 à 52 ha chacune) sur trois continents pour évaluer la généralité de ces résultats dans les forêts tropicales. La biomasse aérienne a augmenté dans sept de nos dix parcelles, de manière significative dans quatre parcelles, et a montré une forte diminution dans une seule parcelle. L'accumulation de carbone regroupée entre les sites était significative (+0,24 MgC ha(-1) y(-1), intervalles de confiance à 95 % [0,07, 0,39] MgC ha(-1) y(-1)), mais inférieure à celle rapportée précédemment pour l'Amazonie. Sur trois sites pour lesquels nous avions des données pour plusieurs intervalles de recensement, nous n'avons trouvé aucune augmentation concertée du gain de biomasse, en contradiction avec l'hypothèse de productivité accrue. Sur l'ensemble des dix parcelles, le quartile d'espèces à la croissance la plus rapide a gagné de la biomasse (+0,33 [0,09, 0,55] % y(-1)) par rapport à la communauté arboricole dans son ensemble (+0,15 % y(-1)) ; cependant, cette tendance significative était due à une seule parcelle. La biomasse des espèces à croissance lente a augmenté de manière significative lorsqu'elle a été calculée sur toutes les placettes (+0,21 [0,02, 0,37] % y(-1)), et dans la moitié de nos placettes lorsqu'elle a été calculée individuellement. Nos résultats ne corroborent pas l'hypothèse selon laquelle les espèces à croissance rapide sont de plus en plus dominantes dans les communautés d'arbres tropicaux. Au lieu de cela, ils suggèrent que nos parcelles peuvent se remettre simultanément des perturbations passées et être affectées par les changements dans la disponibilité des ressources. Des études à plus long terme sont nécessaires pour clarifier la contribution du changement global au fonctionnement des forêts tropicales. En los bosques tropicales amazónicos, estudios recientes han reportado aumentos en la biomasa aérea y en la productividad primaria, así como cambios en la composición de las especies de plantas que favorecen a las especies de rápido crecimiento sobre las de crecimiento lento. Esta alteración generalizada de los bosques tropicales maduros se atribuyó al cambio ambiental global, como un aumento en la concentración atmosférica de CO2, la deposición de nutrientes, la temperatura, la frecuencia de la sequía y/o la irradiancia. Utilizamos mediciones estandarizadas y repetidas de más de 2 millones de árboles en diez grandes parcelas forestales (16-52 ha cada una) en tres continentes para evaluar la generalidad de estos hallazgos en los bosques tropicales. La biomasa superficial aumentó en siete de nuestras diez parcelas, de manera significativa en cuatro parcelas, y mostró una gran disminución en una sola parcela. La acumulación de carbono agrupada en todos los sitios fue significativa (+0,24 MgC ha(-1) y(-1), intervalos de confianza del 95% [0,07, 0,39] MgC ha(-1) y(-1)), pero inferior a la informada anteriormente para la Amazonia. En tres sitios para los que teníamos datos para múltiples intervalos de censo, no encontramos un aumento concertado en la ganancia de biomasa, en conflicto con la hipótesis del aumento de la productividad. En las diez parcelas, el cuartil de especies de más rápido crecimiento ganó biomasa (+0,33 [0,09, 0,55] % y(-1)) en comparación con la comunidad arbórea en su conjunto (+0,15 % y(-1)); sin embargo, esta tendencia significativa se debió a una sola parcela. La biomasa de especies de crecimiento lento aumentó significativamente cuando se calculó en todas las parcelas (+0,21 [0,02, 0,37] % y(-1)), y en la mitad de nuestras parcelas cuando se calculó individualmente. Nuestros resultados no respaldan la hipótesis de que las especies de rápido crecimiento estén aumentando constantemente en dominio en las comunidades de árboles tropicales. En cambio, sugieren que nuestras parcelas pueden estar recuperándose simultáneamente de perturbaciones pasadas y verse afectadas por cambios en la disponibilidad de recursos. Se necesitan más estudios a largo plazo para aclarar la contribución del cambio global al funcionamiento de los bosques tropicales. In Amazonian tropical forests, recent studies have reported increases in aboveground biomass and in primary productivity, as well as shifts in plant species composition favouring fast-growing species over slow-growing ones. This pervasive alteration of mature tropical forests was attributed to global environmental change, such as an increase in atmospheric CO2 concentration, nutrient deposition, temperature, drought frequency, and/or irradiance. We used standardized, repeated measurements of over 2 million trees in ten large (16-52 ha each) forest plots on three continents to evaluate the generality of these findings across tropical forests. Aboveground biomass increased at seven of our ten plots, significantly so at four plots, and showed a large decrease at a single plot. Carbon accumulation pooled across sites was significant (+0.24 MgC ha(-1) y(-1), 95% confidence intervals [0.07, 0.39] MgC ha(-1) y(-1)), but lower than reported previously for Amazonia. At three sites for which we had data for multiple census intervals, we found no concerted increase in biomass gain, in conflict with the increased productivity hypothesis. Over all ten plots, the fastest-growing quartile of species gained biomass (+0.33 [0.09, 0.55] % y(-1)) compared with the tree community as a whole (+0.15 % y(-1)); however, this significant trend was due to a single plot. Biomass of slow-growing species increased significantly when calculated over all plots (+0.21 [0.02, 0.37] % y(-1)), and in half of our plots when calculated individually. Our results do not support the hypothesis that fast-growing species are consistently increasing in dominance in tropical tree communities. Instead, they suggest that our plots may be simultaneously recovering from past disturbances and affected by changes in resource availability. More long-term studies are necessary to clarify the contribution of global change to the functioning of tropical forests. في غابات الأمازون الاستوائية، أبلغت الدراسات الحديثة عن زيادات في الكتلة الحيوية فوق الأرض وفي الإنتاجية الأولية، فضلاً عن التحولات في تكوين الأنواع النباتية التي تفضل الأنواع سريعة النمو على الأنواع بطيئة النمو. ويعزى هذا التغيير المنتشر في الغابات الاستوائية الناضجة إلى التغير البيئي العالمي، مثل الزيادة في تركيز ثاني أكسيد الكربون في الغلاف الجوي، وترسب المغذيات، ودرجة الحرارة، وتواتر الجفاف، و/أو الإشعاع. استخدمنا قياسات موحدة ومتكررة لأكثر من مليوني شجرة في عشر قطع غابات كبيرة (16-52 هكتار لكل منها) في ثلاث قارات لتقييم عمومية هذه النتائج عبر الغابات الاستوائية. زادت الكتلة الحيوية فوق الأرض في سبع من قطعنا العشر، بشكل ملحوظ في أربع قطع، وأظهرت انخفاضًا كبيرًا في قطعة أرض واحدة. كان تراكم الكربون المجمع عبر المواقع كبيرًا (+0.24 MgC ha(-1) y(-1)، فواصل ثقة 95 ٪ [0.07، 0.39] MgC ha(-1) y(-1))، ولكنه أقل مما تم الإبلاغ عنه سابقًا في الأمازون. في ثلاثة مواقع كان لدينا بيانات عنها لفترات تعداد متعددة، لم نجد أي زيادة منسقة في كسب الكتلة الحيوية، بما يتعارض مع فرضية زيادة الإنتاجية. على جميع القطع العشر، اكتسب الربع الأسرع نموًا من الأنواع الكتلة الحيوية (+0.33 [0.09، 0.55 ]٪ y(-1)) مقارنة بمجتمع الأشجار ككل (+0.15 ٪ y(-1 ))؛ ومع ذلك، كان هذا الاتجاه الكبير بسبب قطعة أرض واحدة. زادت الكتلة الحيوية للأنواع بطيئة النمو بشكل كبير عند حسابها على جميع القطع (+0.21 [0.02، 0.37 ]٪ y(-1))، وفي نصف قطعنا عند حسابها بشكل فردي. لا تدعم نتائجنا الفرضية القائلة بأن الأنواع سريعة النمو تتزايد باستمرار في الهيمنة في مجتمعات الأشجار الاستوائية. وبدلاً من ذلك، يشيرون إلى أن قطع أراضينا قد تتعافى في وقت واحد من الاضطرابات السابقة وتتأثر بالتغيرات في توافر الموارد. من الضروري إجراء المزيد من الدراسات طويلة الأجل لتوضيح مساهمة التغير العالمي في عمل الغابات المدارية.

A transit ridership study is an essential part of sustainability, and can provide a deep understanding of people’s travel patterns for efficient transportation development and urbanization. However, there is a lack of empirical studies comparing subway and taxi services, and their interactions within a city, that is to say, the interdependent transportation networks. Incorporating new data, this study aims to examine the spatial variation of urban taxi ridership due to the impacts of a new subway line operation opened in 2014 in Wuxi, China. We examine the spatial patterns and interactions of ridership in Wuxi by integrating taxi trajectory from GPS data and subway data from continuously collected fare transactions. The results indicated that the demand for taxi and subway usage is quite elastic with respect to both location and time, and the new subway’s opening had more influence on areas adjacent to subway stations and urban center-suburban travel. Furthermore, increases in travel time and distance would increase the demand for subway, while taxi trips largely represented movements for those locations that the subway could not reach. This paper betters the understanding of travel patterns through large volumes of transportation data for sustainable urbanization policy design.

A novel asymmetric electrochemical capacitor (AEC) with high energy and power densities has been developed using a graphene oxide/cobalt(II)tetrapyrazinoporphyrazine composite (GO/CoTPyzPz) as the positive electrode and graphene oxide/carbon black (GO/CB) as the negative electrode in a neutral aqueous Na2SO4 electrolyte. The excellent specific capacitance, energy and power densities (∼500 F g−1, 44 W h kg−1 and 31 kW kg−1) coupled with long cycle life, excellent short response time, and low equivalent series resistance clearly indicate that this new material has great potential for the development of low-cost and ‘green’ aqueous AECs that operate at high energy and power densities. Interestingly, the energy density of the GO/CoTPyzPz//GOCB based AEC falls within the range usually observed for nickel metal hydride (NiMH) batteries (30–100 W h kg−1), but more importantly, shows better power performance than NiMH batteries (0.25–1 kW kg−1) widely used in hybrid vehicles such as Toyota Prius and Honda Insight.