• Energy Research

To improve the estimate of greenhouse gas emissions (GHG) from tropical rangelands in sub-Saharan Africa, we measured GHG emissions from sheep excreta over two periods of 51 days on a Kenya rangeland. In addition, we measured GHG emissions from potential hotspots in the landscape linked to sheep grazing: overnight enclosures (“bomas”), where sheep are kept at night to protect them from theft and predators, the areas surrounding sheep bomas, and areas surrounding watering troughs. Results showed a short pulse of CO$_2$ fluxes after sheep urine application and a rapid increase of CH$_4$ fluxes following sheep dung application in both rainy and dry season. However, only small increases of N$_2$O fluxes were observed after dung and urine applications compared to controls without excreta. Elevated N$_2$O fluxes mainly coincided with heavy rainfall. Overall, N$_2$O emission factors (EFs) did not vary across excreta type or seasons, but mean N$_2$O EFs for dung (0.01%) and urine patches (0.02%) were only one tenth of the default EFs from the 2019 IPCC Refinement for dry climate. We did, however, find that bomas and watering troughs are sites of herd concentration that are important sources of GHG emissions in the landscape, and that emissions in these locations can remain elevated for months to years, especially when soil moisture is high. This study contributes to more robust estimates of GHG emissions from African livestock systems, which are fundamental to develop targeted mitigation strategies.

Abstract. For effective climate change mitigation strategies, adequate data on greenhouse gas (GHG) emissions from a wide range of land-use and land cover types area prerequisite. However, GHG field measurement data are still scarce for many land-use types in Africa, causing a high uncertainty in GHG budgets. To address this knowledge gap, we present in situ measurements of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions in the lowland part of southern Kenya. We conducted chamber measurements on gas exchange from four dominant land-use types (LUTs) and included (1) cropland, (2) grazed savanna, (3) bushland, and (4) conservation land. Between 29 November 2017 to 3 November 2018, eight measurement campaigns were conducted accounting for regional seasonality (including wet and dry seasons and transitions periods) in each LUT. Mean CO2 emissions for the whole observation period were significantly higher (p-value

Le sisal (Agave sisalana) est une culture résistante au climat cultivée dans de grandes exploitations agricoles situées dans des zones semi-arides. Cependant, aucune étude n'a étudié les flux de gaz à effet de serre du sol (GES : CO2, N2O et CH4) provenant de ces plantations et leur relation avec d'autres types de couverture terrestre. Nous avons examiné les flux de GES (Fs) dans une chronoséquence en sisal à Teita Sisal Estate dans le sud du Kenya. Les effets de l'âge du peuplement sur les F ont été examinés en utilisant des chambres statiques à GES et la chromatographie en phase gazeuse pendant une période d'un an dans sept peuplements : jeunes peuplements âgés de 1 à 3 ans, peuplements matures âgés de 7 à 8 ans et vieux peuplements âgés de 13 à 14 ans. Le bush adjacent a servi de site de contrôle représentant le type d'utilisation des terres environnantes. Les flux moyens de CO₂ étaient les plus élevés dans le peuplement le plus ancien (56 ± 3 mg C m-2 h-1) et les plus faibles dans le peuplement de 8 ans (38 ± 3 mg C m-2 h-1), ce que nous attribuons à la différence de respiration racinaire entre le peuplement. Tous les peuplements avaient des flux de CO₂ de 13 à 28 % plus élevés que ceux des broussailles (32 ± 3 mg C m-2 h-1). Les flux de CO2 pendant la saison humide étaient environ 70% plus élevés que la saison sèche dans tous les sites. Ils ont été influencés par la teneur en eau du sol (WS) et la phénologie de la végétation. Les flux moyens de N2O étaient très faibles (<5 µg N m-2 h-1) dans tous les sites en raison de la faible teneur en azote (N) du sol. Environ 89 % des flux de CH4 étaient inférieurs à la limite de détection (LOD ± 0,02 mg C m-2 h-1). Nos résultats impliquent que les plantations de sisal ont des émissions de CO2 dans le sol plus élevées que le type d'utilisation des terres environnantes, et que les émissions saisonnières étaient en grande partie dues au WS et à l'état de la végétation. Le méthane et le protoxyde d'azote sont d'importance mineure. Ainsi, les flux de GES du sol provenant des plantations de sisal sont un contributeur mineur aux émissions de GES agricoles au Kenya. El sisal (Agave sisalana) es un cultivo resistente al clima que se cultiva en granjas a gran escala en zonas semiáridas. Sin embargo, ningún estudio ha investigado los flujos de gases de efecto invernadero del suelo (GEI: CO2, N2O y CH4) de estas plantaciones y cómo se relacionan con otros tipos de cubierta terrestre. Examinamos los flujos de GEI (Fs) en una cronosecuencia de sisal en Teita Sisal Estate, en el sur de Kenia. Los efectos de la edad del pie en los F se examinaron utilizando cámaras estáticas de GEI y cromatografía de gases durante un período de un año en siete stands: stands jóvenes de 1 a 3 años, stands maduros de 7 a 8 años y stands viejos de 13 a 14 años. Los arbustos adyacentes sirvieron como sitio de control que representa el tipo de uso de la tierra circundante. Los flujos medios de CO₂ fueron más altos en el soporte más antiguo (56 ± 3 mg C m-2 h-1) y más bajos en el soporte de 8 años (38 ± 3 mg C m-2 h-1), lo que atribuimos a la diferencia en la respiración radicular entre el soporte. Todos los rodales tenían flujos de CO₂ un 13–28% más altos que los arbustos (32 ± 3 mg C m-2 h-1). Los flujos de CO2 en la estación húmeda fueron aproximadamente un 70% más altos que en la estación seca en todos los sitios. Fueron influenciados por el contenido de agua del suelo (WS) y la fenología de la vegetación. Los flujos medios de N2O fueron muy bajos (<5 µg N m-2 h-1) en todos los sitios debido al bajo contenido de nitrógeno (N) del suelo. Alrededor del 89% de los flujos de CH4 estaban por debajo del límite de detección (LOD ± 0.02 mg C m-2 h-1). Nuestros resultados implican que las plantaciones de sisal tienen mayores emisiones de CO2 del suelo que el tipo de uso de la tierra circundante, y las emisiones estacionales fueron impulsadas en gran medida por el WS y el estado de la vegetación. El metano y el óxido nitroso son de menor importancia. Por lo tanto, los flujos de GEI del suelo de las plantaciones de sisal son un contribuyente menor a las emisiones de GEI agrícolas en Kenia. السيزال (Agave sisalana) هو محصول مرن للمناخ يزرع في مزارع واسعة النطاق في المناطق شبه القاحلة. ومع ذلك، لم تحقق أي دراسات في تدفقات غازات الدفيئة في التربة (غازات الدفيئة: ثاني أكسيد الكربون وأكسيد النيتروز والميثان) من هذه المزارع وكيفية ارتباطها بأنواع الغطاء الأرضي الأخرى. قمنا بفحص تدفقات غازات الدفيئة (Fs) في تسلسل زمني للسيزال في Teita Sisal Estate في جنوب كينيا. تم فحص آثار عمر الوقوف على Fs باستخدام غرف غازات الدفيئة الثابتة واستشراب الغاز لمدة عام واحد في سبع حوامل: حوامل شابة تتراوح أعمارها بين 1–3 سنوات، وحوامل ناضجة تتراوح أعمارها بين 7–8 سنوات، وحوامل قديمة تتراوح أعمارها بين 13–14 عامًا. كانت الأدغال المجاورة بمثابة موقع تحكم يمثل نوع استخدام الأراضي المحيطة. كان متوسط تدفقات ثاني أكسيدالكربون أعلى في الحامل الأقدم (56 ± 3 ملغ C m -2 h -1) وأدنى في الحامل البالغ من العمر 8 سنوات (38 ± 3 ملغ C m -2 h -1)، والذي نعزوه إلى الاختلاف في تنفس الجذر بين الحامل. كانت جميع الحوامل تحتوي على تدفقات ثاني أكسيدالكربون أعلى بنسبة 13-28 ٪ من الأدغال (32 ± 3 ملغ C m -2 h -1). كانت تدفقات ثاني أكسيد الكربون في موسم الأمطار أعلى بحوالي 70 ٪ من موسم الجفاف في جميع المواقع. تأثرت بمحتوى مياه التربة (WS) والظواهر النباتية. كان متوسط تدفقات أكسيد النيتروز منخفضًا جدًا (<5 ميكروغرام نيوتن متر -2 ساعة -1) في جميع المواقع بسبب انخفاض محتوى نيتروجين التربة (N). كان حوالي 89 ٪ من تدفقات الميثان أقل من حد الكشف (LOD ± 0.02 mg C m -2 h -1). تشير نتائجنا إلى أن مزارع السيزال لديها انبعاثات أعلى من ثاني أكسيد الكربون في التربة مقارنة بنوع استخدام الأراضي المحيطة، وكانت الانبعاثات الموسمية مدفوعة إلى حد كبير بـ WS وحالة الغطاء النباتي. الميثان وأكسيد النيتروز لهما أهمية ثانوية. وبالتالي، فإن تدفقات غازات الدفيئة في التربة من مزارع السيزال هي مساهم ثانوي في انبعاثات غازات الدفيئة الزراعية في كينيا. Sisal (Agave sisalana) is a climate-resilient crop grown on large-scale farms in semi-arid areas. However, no studies have investigated soil greenhouse gas (GHGs: CO2, N2O and CH4) fluxes from these plantations and how they relate to other land cover types. We examined GHG fluxes (Fs) in a sisal chronosequence at Teita Sisal Estate in southern Kenya. The effects of stand age on Fs were examined using static GHG chambers and gas chromatography for a period of one year in seven stands: young stands aged 1–3 years, mature stands aged 7–8 years, and old stands aged 13–14 years. Adjacent bushland served as a control site representing the surrounding land use type. Mean CO₂ fluxes were highest in the oldest stand (56 ± 3 mg C m-2 h-1) and lowest in the 8-year old stand (38 ± 3 mg C m-2 h-1), which we attribute to difference in root respiration between the stand. All stands had 13–28% higher CO₂ fluxes than bushland (32 ± 3 mg C m-2 h-1). CO2 fluxes in the wet season were about 70% higher than dry season across all sites. They were influenced by soil water content (WS) and vegetation phenology. Mean N2O fluxes were very low (<5 µg N m-2 h-1) in all sites due to low soil nitrogen (N) content. About 89% of CH4 fluxes were below the detection limit (LOD ± 0.02 mg C m-2 h-1). Our results imply that sisal plantations have higher soil CO2 emissions than the surrounding land use type, and the seasonal emissions were largely driven by WS and the vegetation status. Methane and nitrous oxide are of minor importance. Thus, soil GHG fluxes from sisal plantations are a minor contributor to agricultural GHG emissions in Kenya.

Abstract CONTEXT Livestock are the primary source of greenhouse gas (GHG) emissions from agriculture in most African countries, but there is a paucity of baseline data and monitoring of GHG emissions from livestock in Africa, particularly for extreme or shock events. The COVID-19 pandemic represents a novels shock to livestock systems and may result in indirect effects on livestock emissions and other Sustainable Development Goals (SDGs). Due to the pandemic in 2020, extensive pastoralist livestock systems in Northern Kenya were subjected to restrictions on movement, increased costs of transportation, and closure of livestock markets. OBJECTIVE The objective of this study was to assess the indirect effects of the COVID-19 pandemic on GHG emissions from livestock systems in Northern Kenya using proxy data and a three-part framework based on changes in 1) herd size, 2) feed availability, and 3) livestock movement. METHODS We evaluated changes in GHG emissions from livestock systems in Northern Kenya due to the COVID-19 pandemic based on proxy data from crowd-sourced market data, household panel surveys, and remote sensing data on Normalized Difference Vegetation Index (NDVI). Proxy data were obtained before the pandemic in 2019 and after the pandemic in 2020 to compare between years and evaluate the indirect effects of the pandemic and associated restrictions on livestock GHG emissions using the three-part framework. RESULTS AND CONCLUSIONS Overall GHG emissions from livestock in Northern Kenya have decreased due to the pandemic and this was largely driven by reductions in herd size. This reduction in GHG emissions occurred despite an increase in GHG emissions from livestock associated with higher feed availability. Decreased livestock movement due to the pandemic contributed to reductions in GHG emissions from livestock, but such reductions were likely to be small due to limited need for livestock to travel longer distances under the prevailing conditions of high feed availability. SIGNIFICANCE This research shows that assessments of changes in GHG emissions from livestock systems due to shock events can be conducted successfully based on proxy data and the three-part framework developed here. We found that shock events, such as the COVID-19 pandemic, may lead to unexpected results with respect to the direction and magnitude of changes in livestock emissions depending on contextual factors and environmental conditions. Thus, we call for more spatially explicit and continued data collection to assess and monitor the consequences of shock events on GHG emissions from livestock and related SDGs in Africa.

AbstractGlobal population projections foresee the biggest increase to occur in Africa with most of the available uncultivated land to ensure food security remaining on the continent. Simultaneously, greenhouse gas emissions are expected to rise due to ongoing land use change, industrialisation, and transport amongst other reasons with Africa becoming a major emitter of greenhouse gases globally. However, distinct knowledge on greenhouse gas emissions sources and sinks as well as their variability remains largely unknown caused by its vast size and diversity and an according lack of observations across the continent. Thus, an environmental research infrastructure—as being setup in other regions—is more needed than ever. Here, we present the results of a design study that developed a blueprint for establishing such an environmental research infrastructure in Africa. The blueprint comprises an inventory of already existing observations, the spatial disaggregation of locations that will enable to reduce the uncertainty in climate forcing’s in Africa and globally as well as an overall estimated cost for such an endeavour of about 550 M€ over the next 30 years. We further highlight the importance of the development of an e-infrastructure, the necessity for capacity development and the inclusion of all stakeholders to ensure African ownership.

With climate change the occurrence of summer droughts is expected to increase in Central Europe. This could lead to increased nitrate (NO3-) leaching when water scarcity affects the N-uptake capacity of trees and increases soil N availability due to early leaf senescence and higher litter input. In the present study, we used 16 years of ecological monitoring data from the LTER research site "Zöbelboden" in Austria. The monitoring site is a mixed Spruce-Sycamore-Ash-Beech forest on karst, which is representative for many watersheds that supply drinking water in Austria. We found that in the year after a summer drought, NO3- leaching via soil water seepage was significantly elevated compared to the long-term mean. While in normal years, NO3- leaching was primarily affected by soil water seepage volume, after a summer drought these controls changed and NO3- leaching was controlled by NO3- input via precipitation, tree N uptake, and vapor-pressure deficit. Furthermore, higher aboveground litter input during dry years was correlated with increased NO3- leaching in the following year. Our findings show that NO3- leaching from temperate mountain forests on karst is susceptible to summer drought, which could affect drinking water quality in the Central European Alps in the future, especially in combination with forest disturbances like bark beetle outbreaks, which are often a direct consequence of drought damage to trees.