• Energy Research

Understanding the variation in stomatal characteristics in relation to climatic gradients can reveal the adaptation strategies of plants, and help us to predict their responses to future climate changes. In this study, we investigated stomatal density (SD) and stomatal length (SL) in 150 plant species along an elevation gradient (540-2357 m) in Changbai Mountain, China, and explored the patterns and drivers of stomatal characteristics across species and plant functional types (PFTs: trees, shrubs, and herbs). The average values of SD and SL for all species combined were 156 mm(-2) and 35 µm, respectively. SD was higher in trees (224 mm(-2)) than in shrubs (156 mm(-2)) or herbs (124 mm(-2)), and SL was largest in herbs (37 µm). SD was negatively correlated with SL in all species and PFTs (P < 0.01). The relationship between stomatal characteristics and elevation differed among PFTs. In trees, SD decreased and SL increased with elevation; in shrubs and herbs, SD initially increased and then decreased. Elevation-related differences in SL were not significant. PFT explained 7.20-17.6% of the total variation in SD and SL; the contributions of CO2 partial pressure (P CO2), precipitation, and soil water content (SWC) were weak (0.02-2.28%). Our findings suggest that elevation-related patterns of stomatal characteristics in leaves are primarily a function of PFT, and highlight the importance of differences among PFTs in modeling gas exchange in terrestrial ecosystems under global climate change.

AbstractChinese forests cover most of the representative forest types in the Northern Hemisphere and function as a large carbon (C) sink in the global C cycle. The availability of long-term C dynamics observations is key to evaluating and understanding C sequestration of these forests. The Chinese Ecosystem Research Network has conducted normalized and systematic monitoring of the soil-biology-atmosphere-water cycle in Chinese forests since 2000. For the first time, a reference dataset of the decadal C cycle dynamics was produced for 10 typical Chinese forests after strict quality control, including biomass, leaf area index, litterfall, soil organic C, and the corresponding meteorological data. Based on these basic but time-discrete C-cycle elements, an assimilated dataset of key C cycle parameters and time-continuous C sequestration functions was generated via model-data fusion, including C allocation, turnover, and soil, vegetation, and ecosystem C storage. These reference data could be used as a benchmark for model development, evaluation and C cycle research under global climate change for typical forests in the Northern Hemisphere.

Les écosystèmes terrestres de la Chine jouent un rôle important dans le cycle mondial du carbone. Les contributions régionales à la variation interannuelle (IAV) du puits de carbone terrestre de la Chine et les attributions aux variations climatiques ne sont pas bien comprises. Ici, nous avons étudié comment les écosystèmes terrestres des quatre zones climatiques présentant diverses variabilités climatiques contribuent à la VAI de la productivité nette des écosystèmes terrestres (NEP) de la Chine à l'aide de données modélisées sur les flux de carbone provenant de six modèles d'écosystèmes. Les résultats du modèle montrent que la région moussoonale de la Chine domine la NEP IAV nationale avec une contribution de 86% (69%–96%) en moyenne. Les changements annuels des NEP nationaux sont principalement motivés par la productivité primaire brute IAV et la moitié de la variation annuelle résulte des changements des NEP en été. Les contributions régionales à l'IAV de la NEP en Chine sont cohérentes avec leurs contributions à l'ampleur de la NEP nationale. La variabilité des précipitations domine la variabilité annuelle du NEP en Chine. Les précipitations dans la zone climatique tempérée de la mousson contribuent le plus (23 %) à la VAI de la NEP en Chine en raison à la fois de la grande sensibilité de l'absorption du carbone par l'écosystème terrestre aux précipitations et de la grande fluctuation des précipitations causée par les anomalies de la mousson d'été en Asie de l'Est. Nos résultats suggèrent que l'IAV de la NEP peut être principalement attribuée aux écosystèmes avec une productivité et une réponse aux précipitations plus importantes, et soulignent l'importance des systèmes climatiques de mousson avec une forte variabilité saisonnière et interannuelle dans la variation interannuelle du puits de carbone terrestre. Los ecosistemas terrestres de China desempeñan un papel importante en el ciclo global del carbono. Las contribuciones regionales a la variación interanual (IAV) del sumidero de carbono terrestre de China y las atribuciones a las variaciones climáticas no se comprenden bien. Aquí hemos investigado cómo los ecosistemas terrestres en las cuatro zonas climáticas con diversas variabilidades climáticas contribuyen al IAV en la productividad neta de los ecosistemas terrestres (NEP) de China utilizando datos modelados de flujos de carbono de seis modelos de ecosistemas. Los resultados del modelo muestran que la región monzónica de China domina la NEP IAV nacional con una contribución del 86% (69%–96%) en promedio. Los cambios anuales de la NEP nacional son impulsados principalmente por el IAV de productividad primaria bruta y la mitad de los resultados de la variación anual de los cambios de la NEP en verano. Las contribuciones regionales a la NEP IAV en China son consistentes con sus contribuciones a la magnitud de la NEP nacional. La variabilidad de las precipitaciones domina la variabilidad anual de la NEP en China. La precipitación en la zona climática monzónica templada hace la mayor contribución (23%) al IAV de la NEP en China debido tanto a la alta sensibilidad de la absorción de carbono del ecosistema terrestre a la lluvia como a la gran fluctuación en la precipitación causada por las anomalías del monzón de verano de Asia oriental. Nuestros resultados sugieren que NEP IAV se puede atribuir principalmente a ecosistemas con mayor productividad y respuesta a las precipitaciones, y resaltan la importancia de los sistemas climáticos monzónicos con alta variabilidad estacional e interanual para impulsar la variación internanual en el sumidero de carbono terrestre. تلعب النظم الإيكولوجية الأرضية في الصين دورًا مهمًا في دورة الكربون العالمية. المساهمات الإقليمية في التباين بين السنوات (IAV) لمصارف الكربون الأرضية في الصين والعزو إلى التقلبات المناخية غير مفهومة جيدًا. لقد حققنا هنا في كيفية مساهمة النظم الإيكولوجية الأرضية في المناطق المناخية الأربع ذات المتغيرات المناخية المختلفة في المركبات المستقلة تحت الأرض في صافي إنتاجية النظم الإيكولوجية الأرضية في الصين باستخدام بيانات تدفقات الكربون المنمذجة من ستة نماذج للنظم الإيكولوجية. تُظهر نتائج النموذج أن المنطقة الموسمية في الصين تهيمن على المركبات المستقلة ذاتية القيادة الوطنية مع مساهمة بنسبة 86 ٪ (69٪ -96 ٪) في المتوسط. تكون التغييرات السنوية في السياسة الاقتصادية الوطنية مدفوعة في الغالب بإجمالي الإنتاجية الأولية، وينتج نصف التباين السنوي عن تغييرات السياسة الاقتصادية الوطنية في الصيف. تتسق المساهمات الإقليمية في برنامج التقييم الوطني للمركبات المستقلة في الصين مع مساهماتها في حجم السياسة الاقتصادية الوطنية. تهيمن تقلبات هطول الأمطار على التقلبات السنوية في السياسة الاقتصادية الجديدة في الصين. يمثل هطول الأمطار في المنطقة المناخية الموسمية المعتدلة أكبر مساهمة (23 ٪) في المركبات الجوية المستقلة في السياسة الاقتصادية الجديدة في الصين بسبب الحساسية العالية لامتصاص الكربون في النظام الإيكولوجي الأرضي لهطول الأمطار والتذبذب الكبير في هطول الأمطار الناجم عن شذوذ الرياح الموسمية الصيفية في شرق آسيا. تشير نتائجنا إلى أنه يمكن أن تعزى المركبات المستقلة الجديدة بشكل أساسي إلى النظم الإيكولوجية ذات الإنتاجية الأكبر والاستجابة لهطول الأمطار، وتسلط الضوء على أهمية أنظمة المناخ الموسمية ذات التباين الموسمي والسنوي العالي في دفع التباين السنوي في بالوعة الكربون الأرضية. China's terrestrial ecosystems play an important role in the global carbon cycle. Regional contributions to the interannual variation (IAV) of China's terrestrial carbon sink and the attributions to climate variations are not well understood. Here we have investigated how terrestrial ecosystems in the four climate zones with various climate variabilities contribute to the IAV in China's terrestrial net ecosystem productivity (NEP) using modeled carbon fluxes data from six ecosystems models. Model results show that the monsoonal region of China dominates national NEP IAV with a contribution of 86% (69%–96%) on average. Yearly national NEP changes are mostly driven by gross primary productivity IAV and half of the annual variation results from NEP changes in summer. Regional contributions to NEP IAV in China are consistent with their contributions to the magnitude of national NEP. Rainfall variability dominates the NEP annual variability in China. Precipitation in the temperate monsoon climate zone makes the largest contribution (23%) to the IAV of NEP in China because of both the high sensitivity of terrestrial ecosystem carbon uptake to rainfall and the large fluctuation in the precipitation caused by the East Asian summer monsoon anomalies. Our results suggest that NEP IAV can be mainly attributed to ecosystems with larger productivity and response to precipitation, and highlight the importance of monsoon climate systems with high seasonal and interannual variability in driving internannual variation in the land carbon sink.

Large-scale terrestrial ecosystem science research becomes an important research field with the promotion of meeting the scientific demand of biodiversity conservation, global climate change mitigation, regional eco-environment governance, and social sustainable development. It is developing rapidly under the guidance of China's ecological civilization construction strategy. Here, we systematically discussed the missions, theoretical foundation and methodology of large-scale terrestrial ecosystem science research and proposed a new theoretical foundation, conceptual system and logical framework for macroecosystem science research on the basis of macrosystem ecology theory. It elaborated the discipline connotation and application of the macroecosystem science to 1) deve-lop the conceptual network of ecosystem science based on the systematic characteristics of ecosystems; 2) develop the theoretical system of ecosystem state change analysis based on the ecosystem integrity and emergence characteristics; 3) develop the theoretical system of integrated research for ecosystem structure-process-function-service cascade relationship based on the attributes and state of ecosystems. We also discussed the methodology and technical system of regional and continental macroecosystem science research, and highlighted the urgency to construct a new generation of continental ecosystem observation and research network, and to develop the network observation-network experiment-numerical simulation-knowledge fusion four-in-one infrastructures.

Abstract The energy stored in biomass, a key component of global sustainable energy, is essential for achieving the United Nations Sustainable Development Goals, especially for climate change mitigation and energy security. However, it remains unknown how much energy is stored in the vegetation biomass of China's terrestrial ecosystems. Furthermore, the shortage of biomass has limited the development of China's bioeconomy and bioenergy industry, requiring us to seek more multi-source and sustainable biomass supplies. In view of this, through comprehensive investigations and systematic data integration (including biomass data, calorific value data, land cover data, climate data, etc.), we explored the gross biomass energy (BE) reserves and their spatiotemporal pattern based on a total of 14 vegetation types that account for 76.24% of China's land area. The theoretical potential of gross BE in China was estimated as 535.91 EJ in 2010, which was equivalent to 18.29 Gt standard coal. BE showed a trend of continuous increase from 1980 to 2060 and is expected to peak in 2030. Importantly, BE (per land area or per capita) was significantly negatively correlated with provincial development levels in China. Our findings indicate that China has abundant BE reserves, which have potential as feedstocks for the production of different forms of energy in the context of sustainable development. Furthermore, more advanced low-cost technologies, such as coal and biomass co-gasification, are expected to promote the transformation and upgradation of energy systems in China in the future.

Significance Previous estimations of carbon budgets in China’s terrestrial ecosystems varied greatly because of the multiplicity of data sources and the inconsistency of methodologies. By conducting a methodologically consistent field campaign across the country, we estimated that the total carbon pool in China’s forests, shrublands, grasslands, and croplands was 79.24 ± 2.42 Pg C. The carbon density exhibited a strong dependence on climate regime: it decreased with temperature but increased with precipitation. The country’s forests have a large potential of biomass carbon sequestration of 1.9–3.4 Pg C in the next 10 to 20 years assuming no removals. Our findings provide a benchmark to identify the effectiveness of the government’s natural protection policies.

AbstractGrazing exclusion (GE) is considered to be an effective approach to restore degraded grasslands and to improve their carbon (C) sequestration. However, the C dynamics and related controlling factors in grasslands withGEhave not been well characterized. This synthesis examines the dynamics of soil C content and vegetation biomass with the recovery age through synthesizing results of 51 sites in grasslands in China. The results illustrate increases in soil C content and vegetation biomass withGEat most sites. Generally, both soil C content and vegetation biomass arrive at steady state after 15 years ofGE. In comparison, the rates of increase in above‐ and belowground biomass declined exponentially with the age ofGE, whereas soil C content declined in a milder (linear) way, implying a lagged response of soil C to the inputs from plant biomass. Mean annual precipitation (MAP) and the rate of soil nitrogen (N) change were the main factors affecting the rate of soil C content change.MAPplayed a major role at the early stage, whereas the rate of soil N change was the major contributor at the middle and late stages. Our results imply that the national grassland restoration projects in China may be more beneficial for C sequestration in humid regions with highMAP. In addition, increased soil N supply to grasslands withGEat the latter recovery stage may enhance ecosystem C sequestration capacity.

AbstractTo explore grazing effects on carbon fluxes in alpine meadow ecosystems, we used a paired eddy-covariance (EC) system to measure carbon fluxes in adjacent fenced (FM) and grazed (GM) meadows on the Tibetan plateau. Gross primary productivity (GPP) and ecosystem respiration (Re) were greater at GM than FM for the first two years of fencing. In the third year, the productivity at FM increased to a level similar to the GM site. The higher productivity at GM was mainly caused by its higher photosynthetic capacity. Grazing exclusion did not increase carbon sequestration capacity for this alpine grassland system. The higher optimal photosynthetic temperature and the weakened ecosystem response to climatic factors at GM may help to facilitate the adaption of alpine meadow ecosystems to changing climate.