• Energy Research

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.

Abstract Trees adjust their architecture to acclimate to various external stressors, which regulates ecological functions that are needed for growth, reproduction, and survival. Human activities, however, are fragmenting natural habitats apace and could affect tree architecture and allometry, but quantitative assessments remain lacking. Here, we leverage ground surveys of terrestrial LiDAR in Central Amazonia to comprehensively assess forest edge effects on tree architecture and allometry, and their associated impacts on the forest biomass 40 years after fragmentation. We found that young trees colonising the forest fragments have thicker branches and architectural traits that maximise light capture, and can produce 50% more wood than their counterparts of similar stem size and height in interior forests. Large trees that have survived disturbances arising from forest fragmentation are able to acclimate and maintain their wood production, but damages that reduce tree height near the edges can lead to a 30% decline of their woody volume. Despite the large wood production of colonising trees, changes in tree architecture lead to a net loss of 6.6 Mg ha-1 of the forest aboveground biomass, which account for 20% of all edge-related aboveground biomass losses of fragmented Amazonian forests (34.3 Mg ha-1). Our findings show a strong influence of edge effects on tree architecture and allometry, and reveal an additional unaccounted factor that exacerbates carbon losses in fragmented forests.

AbstractForests contribute to climate change mitigation through carbon storage and uptake, but the extent to which this carbon pool varies in space and time is still poorly known. Several Earth Observation missions have been specifically designed to address this issue, for example, NASA's GEDI, NASA‐ISRO's NISAR and ESA's BIOMASS. Yet, all these missions' products require independent and consistent validation. A permanent, global, in situ, site‐based forest biomass reference measurement system relying on ground data of the highest possible quality is therefore needed. Here, we have assembled a list of almost 200 high‐quality sites through an in‐depth review of the literature and expert knowledge. In this study, we explore how representative these sites are in terms of their coverage of environmental conditions, geographical space and biomass‐related forest structure, compared to those experienced by forests worldwide. This work also aims at identifying which sites are the most representative, and where to invest to improve the representativeness of the proposed system. We show that the environmental coverage of the system does not seem to improve after at least the 175 most representative sites are included, but geographical and structural coverages continue to improve as more sites are added. We highlight the areas of poor environmental, geographical, or structural coverage, including, but not limited to, Canada, the western half of the USA, Mexico, Patagonia, Angola, Zambia, eastern Russia, and tropical and subtropical highlands (e.g. in Colombia, the Himalayas, Borneo, Papua). For the proposed system to succeed, we stress that (1) data must be collected and processed applying the same standards across all countries and continents; (2) system establishment and management must be inclusive and equitable, with careful consideration of working conditions; and (3) training and site partner involvement in downstream activities should be mandatory.

La biomasse forestière est un indicateur essentiel pour la surveillance des écosystèmes et du climat de la Terre. Il s'agit d'une contribution essentielle à la comptabilisation des gaz à effet de serre, à l'estimation des pertes de carbone et de la dégradation des forêts, à l'évaluation du potentiel des énergies renouvelables et à l'élaboration de politiques d'atténuation du changement climatique telles que REDD+, entre autres. La cartographie mur à mur de la biomasse aérienne (AGB) est maintenant possible avec la télédétection par satellite (RS). Cependant, les méthodes RS nécessitent des données in situ existantes, à jour, fiables, représentatives et comparables pour l'étalonnage et la validation. Nous présentons ici l'initiative Forest Observation System (Fos), une coopération internationale visant à établir et à maintenir une base de données mondiale sur la biomasse forestière in situ. Les estimations de la hauteur de l'AGB et de la canopée avec leurs incertitudes associées sont dérivées à une échelle de 0,25 ha à partir de mesures sur le terrain effectuées dans des parcelles de recherche permanentes à travers les forêts du monde. Toutes les estimations des placettes sont géolocalisées et ont une taille qui permet une comparaison directe avec de nombreuses mesures RS. Le Fos offre le potentiel d'améliorer la précision des produits de la biomasse à base de RS tout en développant de nouvelles synergies entre la RS et les communautés de recherche sur les écosystèmes terrestres. La biomasa forestal es un indicador esencial para monitorear los ecosistemas y el clima de la Tierra. Es un insumo crítico para la contabilidad de gases de efecto invernadero, la estimación de las pérdidas de carbono y la degradación forestal, la evaluación del potencial de energía renovable y para el desarrollo de políticas de mitigación del cambio climático como REDD+, entre otras. El mapeo de pared a pared de la biomasa sobre el suelo (AGB) ahora es posible con la teledetección satelital (RS). Sin embargo, los métodos de RS requieren datos in situ existentes, actualizados, confiables, representativos y comparables para la calibración y validación. Aquí, presentamos la iniciativa del Sistema de Observación Forestal (FOS), una cooperación internacional para establecer y mantener una base de datos global de biomasa forestal in situ. Las estimaciones de altura de AGB y dosel con sus incertidumbres asociadas se derivan a una escala de 0,25 ha a partir de mediciones de campo realizadas en parcelas de investigación permanentes en los bosques del mundo. Todas las estimaciones de parcelas están geolocalizadas y tienen un tamaño que permite la comparación directa con muchas mediciones de RS. El FOS ofrece el potencial de mejorar la precisión de los productos de biomasa basados en RS al tiempo que desarrolla nuevas sinergias entre las comunidades de investigación de ecosistemas basados en RS y en tierra. Forest biomass is an essential indicator for monitoring the Earth's ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world's forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities. الكتلة الحيوية للغابات هي مؤشر أساسي لرصد النظم الإيكولوجية للأرض ومناخها. وهو مدخل حاسم في المحاسبة المتعلقة بغازات الدفيئة، وتقدير خسائر الكربون وتدهور الغابات، وتقييم إمكانات الطاقة المتجددة، ووضع سياسات للتخفيف من آثار تغير المناخ مثل المبادرة المعززة لخفض الانبعاثات الناجمة عن إزالة الغاباتوتدهورها، من بين أمور أخرى. أصبح من الممكن الآن رسم خرائط من الجدار إلى الجدار للكتلة الحيوية فوق الأرض (AGB) باستخدام الاستشعار عن بعد عبر الأقمار الصناعية (RS). ومع ذلك، تتطلب طرق RS بيانات موجودة وحديثة وموثوقة وتمثيلية وقابلة للمقارنة في الموقع للمعايرة والتحقق من الصحة. نقدم هنا مبادرة نظام مراقبة الغابات، وهو تعاون دولي لإنشاء وصيانة قاعدة بيانات عالمية للكتلة الحيوية للغابات في الموقع. يتم اشتقاق تقديرات ارتفاع AGB والمظلة مع أوجه عدم اليقين المرتبطة بها على مقياس 0.25 هكتار من القياسات الميدانية التي تم إجراؤها في قطع البحث الدائمة عبر غابات العالم. جميع تقديرات المخطط محددة جغرافيًا ولها حجم يسمح بالمقارنة المباشرة مع العديد من قياسات RS. يوفر نظام التشغيل الحر إمكانية تحسين دقة منتجات الكتلة الحيوية القائمة على RS مع تطوير أوجه تآزر جديدة بين RS ومجتمعات أبحاث النظام الإيكولوجي الأرضية.

Trees are an integral part in European landscapes, but only forest resources are systematically assessed by national inventories. The contribution of urban and agricultural trees to national-level carbon stocks remains largely unknown. Here we produced canopy cover, height and above-ground biomass maps from 3-meter resolution nanosatellite imagery across Europe. Our biomass estimates have a systematic bias of 7.6% (overestimation; R = 0.98) compared to national inventories of 30 countries, and our dataset is sufficiently highly resolved spatially to support the inclusion of tree biomass outside forests, which we quantify to 0.8 petagrams. Although this represents only 2% of the total tree biomass, large variations between countries are found (10% for UK) and trees in urban areas contribute substantially to national carbon stocks (8% for the Netherlands). The agreement with national inventory data, the scalability, and spatial details across landscapes, including trees outside forests, make our approach attractive for operational implementation to support national carbon stock inventory schemes.

Abstract The forest understory experiences temperature variations that are dampened compared to adjacent open areas, allowing the development of a forest microclimate and associated ecological conditions. It is however unclear to what extent forests will maintain this buffering effect under increasing global warming. Providing reliable projections of future forest microclimates is therefore crucial to anticipate climate change impacts on forest biodiversity, and to identify corresponding conservation strategies. Recent empirical studies suggest that the buffering of air temperature extremes in forest understory compared to open land could increase with global warming, albeit at a slower rate than macroclimate temperatures. Here, we investigate the trend of this temperature buffering effect in a high-emission global warming scenario, using the process-based Land Surface Model CLM5.1. We find biome-dependant buffering trends with strongest values in tropical forests where buffering increases for every degree of global warming by 0.1 ∘C for maximum soil temperature, and by 0.2 ∘C for maximum canopy air temperature. In boreal regions, forest microclimate exhibits a strong seasonality and the effect of global warming is more uncertain. Thus, our results highlight the importance of tropical forest canopies in particular, in maintaining hospitable conditions for understory species while increasing their climate debt under global warming. Our research also illustrates the potential and limitations of Land Surface Models to simulate forest microclimate, and calls for further collaborations between Earth system modelers and ecologists to jointly question climate and biosphere dynamics.

AbstractTropical forests are being deforested worldwide, and the remaining fragments are suffering from biomass and biodiversity erosion. Quantifying this erosion is challenging because ground data on tropical biodiversity and biomass are often sparse. Here, we use an unprecedented dataset of 1819 field surveys covering the entire Atlantic Forest biodiversity hotspot. We show that 83−85% of the surveys presented losses in forest biomass and tree species richness, functional traits, and conservation value. On average, forest fragments have 25−32% less biomass, 23−31% fewer species, and 33, 36, and 42% fewer individuals of late-successional, large-seeded, and endemic species, respectively. Biodiversity and biomass erosion are lower inside strictly protected conservation units, particularly in large ones. We estimate that biomass erosion across the Atlantic Forest remnants is equivalent to the loss of 55−70 thousand km2of forests or US$2.3−2.6 billion in carbon credits. These figures have direct implications on mechanisms of climate change mitigation.