• Energy Research

AbstractGlobally, about 50% of all arable soils are classified as acidic. As crop and plant growth are significantly hampered under acidic soil conditions, many farmers, but increasingly as well forest managers, apply lime to raise the soil pH. Besides its direct effect on soil pH, liming also affects soil C and nutrient cycles and associated greenhouse gas (GHG) fluxes. In this meta‐analysis, we reviewed 1570 observations reported in 121 field‐based studies worldwide, to assess liming effects on soil GHG fluxes and plant productivity. We found that liming significantly increases crop yield by 36.3%. Also, soil organic C (SOC) stocks were found to increase by 4.51% annually, though soil respiration is stimulated too (7.57%). Moreover, liming was found to reduce soil N2O emission by 21.3%, yield‐scaled N2O emission by 21.5%, and CH4 emission and yield‐scaled CH4 emission from rice paddies by 19.0% and 12.4%, respectively. Assuming that all acid agricultural soils are limed periodically, liming results in a total GHG balance benefit of 633−749 Tg CO2‐eq year−1 due to reductions in soil N2O emissions (0.60−0.67 Tg N2O‐N year−1) and paddy soil CH4 emissions (1.75−2.21 Tg CH4 year−1) and increases in SOC stocks (65.7–110 Tg C year−1). However, this comes at the cost of an additional CO2 release (c. 624–656 Tg CO2 year−1) deriving from lime mining, transport and application, and lime dissolution, so that the overall GHG balance is likely neutral. Nevertheless, liming of acid agricultural soils will increase yields by at least 6.64 × 108 Mg year−1, covering the food supply of 876 million people. Overall, our study shows for the first time that a general strategy of liming of acid agricultural soils is likely to result in an increasing sustainability of global agricultural production, indicating the potential benefit of liming acid soils for climate change mitigation and food security.

A 3-year field experiment (October 2004-October 2007) was conducted to quantify N2O fluxes and determine the regulating factors from rain-fed, N fertilized wheat-maize rotation in the Sichuan Basin, China.

AbstractSalinity intrusion caused by land subsidence resulting from increasing groundwater abstraction, decreasing river sediment loads and increasing sea level because of climate change has caused widespread soil salinization in coastal ecosystems. Soil salinization may greatly alter nitrogen (N) cycling in coastal ecosystems. However, a comprehensive understanding of the effects of soil salinization on ecosystem N pools, cycling processes and fluxes is not available for coastal ecosystems. Therefore, we compiled data from 551 observations from 21 peer‐reviewed papers and conducted a meta‐analysis of experimental soil salinization effects on 19 variables related to N pools, cycling processes and fluxes in coastal ecosystems. Our results showed that the effects of soil salinization varied across different ecosystem types and salinity levels. Soil salinization increased plant N content (18%), soil NH4+ (12%) and soil total N (210%), although it decreased soil NO3− (2%) and soil microbial biomass N (74%). Increasing soil salinity stimulated soil N2O fluxes as well as hydrological NH4+ and NO2− fluxes more than threefold, although it decreased the hydrological dissolved organic nitrogen (DON) flux (59%). Soil salinization also increased the net N mineralization by 70%, although salinization effects were not observed on the net nitrification, denitrification and dissimilatory nitrate reduction to ammonium in this meta‐analysis. Overall, this meta‐analysis improves our understanding of the responses of ecosystem N cycling to soil salinization, identifies knowledge gaps and highlights the urgent need for studies on the effects of soil salinization on coastal agro‐ecosystem and microbial N immobilization. Additional increases in knowledge are critical for designing sustainable adaptation measures to the predicted intrusion of salinity intrusion so that the productivity of coastal agro‐ecosystems can be maintained or improved and the N losses and pollution of the natural environment can be minimized.

With an increasing interest in closing the nutrient loop in agroecosystems, organic amendments are highly recommended as a reliable resource for soil nutrient recycling. However, from a carbon sequestration perspective, not much has been reported on the contribution of different organic amendments to soil organic carbon (SOC), crop carbon (C) uptake, and soil carbon dioxide (CO2) emissions in wheat-maize cropping systems of sloppy upland soil. To fill the knowledge gap, a two-year lysimeter-field plots experiment was conducted in a sloppy upland purplish soil under wheat-maize cropping systems. The experiments were arranged in a complete random block design with five treatment plots, namely; fresh pig slurry as organic manure (OM), crop residues (CR), conventional mineral fertilizers (NPK) as the control, organic manure plus mineral fertilizers (OMNPK), and crop residues plus mineral fertilizers (CRNPK). Our results showed the leaf photosynthesis rate was not significantly increased by organic amendment application treatments compared to NPK treatment, and was within a range of 4.8 to 45.3 µmol m−2 s−1 for the wheat season and −20.1 to 40.4 µmol m−2 s−1 for the maize season across the five treatments and the measured growth stages. The soil CO2 emissions for the maize season (in the range of 203 to 362 g C m−2) were higher than for the wheat season (in the range of 118 to 252 g C m−2) on average across the different experimental treatments over the two-year experiment. The organic amendment application increased annual cumulative CO2 emissions from 30% to 51% compared to NPK treatment. Over the two years, the average crop C uptake ranged from 174 to 378 g C m−2 and from 287 to 488 g C m−2 for the wheat and maize seasons, respectively, and the organic amendment application increased the crop C uptake by 4% to 23% compared to NPK treatment. In the organic amendment treatments, the C balance ranged from −160 to 460 g C m−2 and from −301 to 334 g C m−2 for the wheat and the maize seasons, respectively, which were greater than those in the NPK treatment. Overall, the present study results suggest incorporation of organic amendments could be an effective strategy for increasing C sequestration and sustaining crop productivity in sloppy upland soil.

High nitrous oxide (N2O) emissions may occur during the non-rice growing season of Chinese rice-upland crop rotation systems. However, our understanding of N2O emission during this season is poor due to a scarcity of available field N2O measurements.

La structure des peuplements forestiers est non seulement un facteur crucial pour la régulation du fonctionnement des forêts, mais également un indicateur important de la gestion durable des forêts et des services écosystémiques. Bien qu'il existe quelques bases de données de structures nationales/mondiales pour les forêts naturelles, une base de données de structures synthétiques à l'échelle nationale pour les forêts de plantation sur la Chine, le plus grand acteur mondial dans les forêts de plantation, n'a pas été réalisée. Dans cette étude, nous avons construit une base de données sur la structure synthétique des stands à l'échelle nationale en examinant plus de 600 publications évaluées par des pairs. La base de données couvre les espèces d'arbres, l'âge moyen du peuplement, la hauteur moyenne des arbres, la densité du peuplement, la couverture de la canopée, le diamètre à hauteur de poitrine, ainsi que les propriétés topographiques et pédologiques auxiliaires associées in situ. Au total, 594 études publiées concernant divers paramètres de la structure du peuplement forestier ont été compilées pour 46 espèces d'arbres. Cette première synthèse pour la structure des peuplements des forêts de plantation sur la Chine soutient les études sur l'évolution/la santé des forêts de plantation en réponse au changement climatique rapide et aux perturbations intensifiées, et profite à la gestion durable des forêts à l'échelle nationale, au boisement futur ou à la planification du reboisement. Les utilisateurs potentiels comprennent ceux qui étudient la dynamique des communautés forestières, la croissance des arbres régionaux, la stabilité des écosystèmes et la santé, ainsi que ceux qui travaillent avec la conservation et la gestion durable. Cet ensemble de données est accessible gratuitement à l'adresse http://www.doi.org/10.11922/sciencedb.j00076.00091. La estructura de los rodales forestales no solo es un factor crucial para regular el funcionamiento de los bosques, sino también un indicador importante para la gestión forestal sostenible y los servicios ecosistémicos. Aunque existen algunas bases de datos de estructura nacional/global para bosques naturales, no se ha logrado una base de datos de estructura sintética en todo el país para bosques de plantación en China, el actor más grande del mundo en bosques de plantación. En este estudio, construimos una base de datos de estructura de stands sintéticos en todo el país mediante la encuesta de más de 600 publicaciones revisadas por pares. La base de datos cubre las especies de árboles, la edad media del rodal, la altura media del árbol, la densidad del rodal, la cobertura del dosel, el diámetro a la altura del pecho, así como las propiedades topográficas y del suelo in situ auxiliares asociadas. Se compilaron un total de 594 estudios publicados sobre diversos parámetros de estructura de rodales forestales para 46 especies de árboles. Esta primera síntesis para la estructura de rodales de los bosques de plantación sobre China respalda los estudios sobre la evolución/salud de los bosques de plantación en respuesta al rápido cambio climático y la intensificación de las perturbaciones, y beneficia la gestión forestal sostenible en todo el país, la forestación futura o la planificación de la reforestación. Los usuarios potenciales incluyen aquellos que estudian la dinámica de las comunidades forestales, el crecimiento regional de los árboles, la estabilidad de los ecosistemas y la salud, así como aquellos que trabajan con la protección y la gestión sostenible. Este conjunto de datos es de libre acceso en http://www.doi.org/10.11922/sciencedb.j00076.00091. Forest stand structure is not only a crucial factor for regulating forest functioning but also an important indicator for sustainable forest management and ecosystem services. Although there exists a few national/global structure databases for natural forests, a country-wide synthetic structure database for plantation forests over China, the world's largest player in plantation forests, has not been achieved. In this study, we built a country-wide synthetic stand structure database by surveying more than 600 peer-reviewed literature. The database covers tree species, mean stand age, mean tree height, stand density, canopy coverage, diameter at breast height, as well as the associated ancillary in-situ topographical and soil properties. A total of 594 published studies concerning diverse forest stand structure parameters were compiled for 46 tree species. This first synthesis for stand structure of plantation forests over China supports studies on the evolution/health of plantation forests in response to rapid climate change and intensified disturbances, and benefits country-wide sustainable forest management, future afforestation or reforestation planning. Potential users include those studying forest community dynamics, regional tree growth, ecosystem stability, and health, as well as those working with conservation and sustainable management. This dataset is freely accessible at http://www.doi.org/10.11922/sciencedb.j00076.00091. لا يعد هيكل الغابات عاملًا حاسمًا لتنظيم عمل الغابات فحسب، بل يعد أيضًا مؤشرًا مهمًا للإدارة المستدامة للغابات وخدمات النظام الإيكولوجي. على الرغم من وجود عدد قليل من قواعد بيانات البنية الوطنية/العالمية للغابات الطبيعية، إلا أنه لم يتم إنشاء قاعدة بيانات بنية تركيبية على مستوى الدولة لغابات المزارع في الصين، وهي أكبر جهة فاعلة في العالم في غابات المزارع. في هذه الدراسة، قمنا ببناء قاعدة بيانات لهيكل الحامل الاصطناعي على مستوى البلاد من خلال مسح أكثر من 600 من الأدبيات التي استعرضها الأقران. تغطي قاعدة البيانات أنواع الأشجار، ومتوسط عمر الحامل، ومتوسط ارتفاع الشجرة، وكثافة الحامل، وتغطية المظلة، والقطر عند ارتفاع الثدي، بالإضافة إلى الخصائص الطبوغرافية والتربة المساعدة في الموقع. تم تجميع ما مجموعه 594 دراسة منشورة تتعلق بمعايير هيكل الغابات المتنوعة لـ 46 نوعًا من الأشجار. يدعم هذا التوليف الأول لهيكل الحامل لغابات المزارع في الصين الدراسات حول تطور/صحة غابات المزارع استجابة لتغير المناخ السريع والاضطرابات المكثفة، ويفيد الإدارة المستدامة للغابات على مستوى البلاد أو التخطيط المستقبلي للتحريج أو إعادة التحريج. يشمل المستخدمون المحتملون أولئك الذين يدرسون ديناميكيات مجتمع الغابات، ونمو الأشجار الإقليمية، واستقرار النظام الإيكولوجي، والصحة، وكذلك أولئك الذين يعملون في مجال الحفظ والإدارة المستدامة. يمكن الوصول إلى مجموعة البيانات هذه مجانًا على http://www.doi.org/10.11922/sciencedb.j00076.00091.