• Energy Research

AbstractForest degradation accounts for ~70% of total carbon losses from tropical forests. Substantial emissions are from selective logging, a land‐use activity that decreases forest carbon density. To maintain carbon values in selectively logged forests, climate change mitigation policies and government agencies promote the adoption of reduced‐impact logging (RIL) practices. However, whetherRILwill maintain both carbon and timber values in managed tropical forests over time remains uncertain. In this study, we quantify the recovery of timber stocks and aboveground carbon at an experimental site where forests were subjected to different intensities ofRIL(4, 8, and 16 trees/ha). Our census data span 20 years postlogging and 17 years after the liberation of future crop trees from competition in a tropical forest on the Guiana Shield, a globally important forest carbon reservoir. We model recovery of timber and carbon with a breakpoint regression that allowed us to capture elevated tree mortality immediately after logging. Recovery rates of timber and carbon were governed by the presence of residual trees (i.e., trees that persisted through the first harvest). The liberation treatment stimulated faster recovery of timber albeit at a carbon cost. Model results suggest a threshold logging intensity beyond which forests managed for timber and carbon derive few benefits fromRIL, with recruitment and residual growth not sufficient to offset losses. Inclusion of the breakpoint at which carbon and timber gains outpaced postlogging mortality led to high predictive accuracy, including out‐of‐sampleR2values >90%, and enabled inference on demographic changes postlogging. Our modeling framework is broadly applicable to studies that aim to quantify impacts of logging on forest recovery. Overall, we demonstrate that initial mortality drives variation in recovery rates, that the second harvest depends on old growth wood, and that timber intensification lowers carbon stocks.

In most cases, when using wood from final felling directly for energy production, payback times could be many decades to more than a century, with substantial increases in net CO2 emissions, in the meantime. This is especially the case for many forests in Europe, because they are currently an effective carbon sink. Additional felling reduces average growth rates in these forests and thus the sequestration of carbon. The same is likely to be true for managed forests in other temperate regions. If wood from additional felling is used, it would be most effective to use it in products that stay in circulation for a long time, only to be used for energy at the end of its service life. An increase in wood demand may lead to an intensification of forest management, which may temporarily increase carbon sequestration rates and biomass yields. This would eventually reduce the payback times. However, it must be noted that it would still take a substantial amount of time for the intensification of forest management to become effective, especially when it includes drastic measures, such as converting natural forests into plantations.

Los registros de dióxido de carbono atmosférico indican que la superficie terrestre ha actuado como un fuerte sumidero de carbono global en las últimas décadas, y una fracción sustancial de este sumidero probablemente se encuentra en los trópicos, particularmente en la Amazonía. Sin embargo, no está claro cómo evolucionará el sumidero de carbono terrestre a medida que el clima y la composición atmosférica continúen cambiando. Aquí analizamos la evolución histórica de la dinámica de la biomasa de la selva amazónica a lo largo de tres décadas utilizando una red distribuida de 321 parcelas. Si bien este análisis confirma que los bosques amazónicos han actuado como un sumidero neto de biomasa a largo plazo, encontramos una tendencia decreciente a largo plazo de la acumulación de carbono. Las tasas de aumento neto de la biomasa superficial disminuyeron en un tercio durante la última década en comparación con la década de 1990. Esto es consecuencia de que los aumentos de la tasa de crecimiento se estabilizaron recientemente, mientras que la mortalidad por biomasa aumentó persistentemente en todo momento, lo que llevó a un acortamiento de los tiempos de residencia del carbono. Los posibles impulsores del aumento de la mortalidad incluyen una mayor variabilidad climática y retroalimentaciones de un crecimiento más rápido de la mortalidad, lo que resulta en una menor longevidad de los árboles. La disminución observada del sumidero amazónico difiere notablemente del reciente aumento de la absorción de carbono terrestre a escala global, y es contraria a las expectativas basadas en modelos. Les enregistrements atmosphériques de dioxyde de carbone indiquent que la surface terrestre a agi comme un puissant puits de carbone mondial au cours des dernières décennies, une fraction substantielle de ce puits étant probablement située sous les tropiques, en particulier en Amazonie. Néanmoins, on ne sait pas comment le puits de carbone terrestre évoluera à mesure que le climat et la composition atmosphérique continueront de changer. Nous analysons ici l'évolution historique de la dynamique de la biomasse de la forêt amazonienne sur trois décennies à l'aide d'un réseau distribué de 321 parcelles. Bien que cette analyse confirme que les forêts amazoniennes ont agi comme un puits de biomasse net à long terme, nous constatons une tendance à la baisse à long terme de l'accumulation de carbone. Les taux d'augmentation nette de la biomasse aérienne ont diminué d'un tiers au cours de la dernière décennie par rapport aux années 1990. C'est une conséquence de la stabilisation récente de l'augmentation du taux de croissance, tandis que la mortalité liée à la biomasse a constamment augmenté, ce qui a entraîné une réduction des temps de résidence du carbone. Les facteurs potentiels de l'augmentation de la mortalité comprennent une plus grande variabilité du climat et des rétroactions d'une croissance plus rapide sur la mortalité, entraînant une réduction de la longévité des arbres. Le déclin observé du puits amazonien s'écarte nettement de la récente augmentation de l'absorption terrestre de carbone à l'échelle mondiale, et est contraire aux attentes basées sur des modèles. Atmospheric carbon dioxide records indicate that the land surface has acted as a strong global carbon sink over recent decades, with a substantial fraction of this sink probably located in the tropics, particularly in the Amazon. Nevertheless, it is unclear how the terrestrial carbon sink will evolve as climate and atmospheric composition continue to change. Here we analyse the historical evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that Amazon forests have acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation. Rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while biomass mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortality increase include greater climate variability, and feedbacks of faster growth on mortality, resulting in shortened tree longevity. The observed decline of the Amazon sink diverges markedly from the recent increase in terrestrial carbon uptake at the global scale, and is contrary to expectations based on models. تشير سجلات ثاني أكسيد الكربون في الغلاف الجوي إلى أن سطح الأرض كان بمثابة حوض كربون عالمي قوي على مدى العقود الأخيرة، وربما يقع جزء كبير من هذا الحوض في المناطق المدارية، لا سيما في الأمازون. ومع ذلك، من غير الواضح كيف ستتطور بالوعة الكربون الأرضية مع استمرار تغير المناخ وتكوين الغلاف الجوي. نحلل هنا التطور التاريخي لديناميكيات الكتلة الحيوية لغابات الأمازون المطيرة على مدى ثلاثة عقود باستخدام شبكة موزعة من 321 قطعة أرض. في حين يؤكد هذا التحليل أن غابات الأمازون كانت بمثابة بالوعة صافية طويلة الأجل للكتلة الحيوية، فإننا نجد اتجاهًا تنازليًا طويل الأجل لتراكم الكربون. انخفضت معدلات الزيادة الصافية في الكتلة الحيوية فوق الأرض بمقدار الثلث خلال العقد الماضي مقارنة بالتسعينيات. وهذا نتيجة لاستقرار زيادات معدل النمو في الآونة الأخيرة، في حين زادت وفيات الكتلة الحيوية باستمرار طوال الوقت، مما أدى إلى تقصير أوقات بقاء الكربون. وتشمل الدوافع المحتملة لزيادة الوفيات زيادة تقلب المناخ، وردود الفعل على النمو الأسرع للوفيات، مما يؤدي إلى تقصير عمر الأشجار. يختلف الانخفاض الملحوظ في حوض الأمازون بشكل ملحوظ عن الزيادة الأخيرة في امتصاص الكربون الأرضي على النطاق العالمي، ويتعارض مع التوقعات القائمة على النماذج.

In het Energieakkoord is afgesproken dat meestook van biomassa in kolencentrales niet meer wordt dan 25 PetaJoule. Als onderdeel van de totale biomassa is zo’n 3,5 miljoen ton hout nodig. De mee te stoken biomassa zal aanvullend op de NTA8080-eisen moeten voldoen aan ‘duurzaamheidseisen voor koolstofschuld, indirecte landgebruikseffecten (ILUC) en duurzaam bosbeheer (FSC)’. In dit rapport wordt verkend, in hoeverre de duurzaamheidseisen genoemd in het Energieakkoord, risico’s op een carbon debt al uitsluiten en welke biomassa-stromen additioneel uitgesloten worden door een carbon debt eis. Ook zijn mogelijke procesrisico’s geïdentificeerd die discussie over carbon debt kan opleveren voor de verdere uitwerking van de afspraken uit het Energieakkoord.

In this report an overview of sustainability issues in Russian forestry is given, focusing on the European part of Russia and trade with the Netherlands. The present situation and developments in Russian forestry are described, taking into account the new Forest Code and increasing export tax on round wood. Trade of wood products between the Russian Federation and the Netherlands is quantified and put into an international perspective. Further sustainability issues, both from a Russian and Dutch perspective of the wood chain are assessed, including forest certification, illegal logging and stricter Dutch procurement regulations. It contains both policy recommendations and suggestions for further research.

AbstractUnderstanding the processes that determine above‐ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation models (DGVMs). AGB is determined by inputs from woody productivity [woody net primary productivity (NPP)] and the rate at which carbon is lost through tree mortality. Here, we test whether two direct metrics of tree mortality (the absolute rate of woody biomass loss and the rate of stem mortality) and/or woody NPP, control variation in AGB among 167 plots in intact forest across Amazonia. We then compare these relationships and the observed variation in AGB and woody NPP with the predictions of four DGVMs. The observations show that stem mortality rates, rather than absolute rates of woody biomass loss, are the most important predictor of AGB, which is consistent with the importance of stand size structure for determining spatial variation in AGB. The relationship between stem mortality rates and AGB varies among different regions of Amazonia, indicating that variation in wood density and height/diameter relationships also influences AGB. In contrast to previous findings, we find that woody NPP is not correlated with stem mortality rates and is weakly positively correlated with AGB. Across the four models, basin‐wide average AGB is similar to the mean of the observations. However, the models consistently overestimate woody NPP and poorly represent the spatial patterns of both AGB and woody NPP estimated using plot data. In marked contrast to the observations, DGVMs typically show strong positive relationships between woody NPP and AGB. Resolving these differences will require incorporating forest size structure, mechanistic models of stem mortality and variation in functional composition in DGVMs.