乡土阔叶树种在碳汇造林中的应用及优势分析

随着我国社会经济的发展,逐步暴露出了许多的生态环境问题。而为了维持生态的平衡,就要提高植树造林的力度,这其中碳汇造林就是植树造林工作的延伸。在碳汇造林中乡土阔叶树种发挥着重要作用,针对乡土阔叶树种在碳汇造林中的应用进行分析,对项目中出现的问题进行优化。     

内蒙古锡林郭勒盟典型草原固碳量及固碳潜力估算

为了评价不同放牧强度对草原固碳量及固碳潜力的影响，本研究采用系统动力学建模方法耦合CASA光合利用率模型、Shiyomi放牧模型、Raich土壤呼吸模型等模型，建立了基于系统动力学库-流思路的碳循环模型，该模型包含3个子系统、4个碳库。结果表明：1998至2015年，在内蒙古锡林郭勒盟的温度降低、降水量增加的背景下，净初级生产力呈现升高的趋势，典型草原土壤固碳量呈现下降趋势；放牧强度在3羊·公顷^-1下净生态系统初级生产力最低，固碳潜力最大，分别为-16.2 gC·m^-2和24.84 TgC。因此，建议内蒙古锡林郭勒盟典型草原西部（阿巴嘎旗、那仁宝力格站）的放牧强度不宜超过1.5羊·公顷^-1；东部（多伦县、东乌珠穆沁、西乌珠穆沁、锡林浩特站）不宜超过4.5羊·公顷^-1。     

Genetic bases of source-,sink-,and yield-related traits revealed by genome-wide association study in Xian rice

The source-sink relationship determines the ultimate grain yield.We investigated the genetic basis of the relationship between source and sink and yield potential in rice.In two environments,we identified quantitative trait loci(QTL)associated with sink capacity(total spikelet number per panicle and thousand-grain weight),source leaf(flag leaf length,flag leaf width and flag leaf area),source-sink relationship(total spikelet number to flag leaf area ratio)and yield-related traits(filled grain number per panicle,panicle number per plant,grain yield per plant,biomass per plant,and harvest index)by genome-wide association analysis using 272 Xian(indica)accessions.The panel showed substantial variation for all traits in the two environments and revealed complex phenotypic correlations.A total of 70 QTL influencing the 11 traits were identified using 469,377 high-quality SNP markers.Five QTL were detected consistently in four chromosomal regions in both environments.Five QTL clusters simultaneously affected source,sink,source–sink relationship,and grain yield traits,probably explaining the genetic basis of significant correlations of grain yield with source and sink traits.We selected 24 candidate genes in the four consistent QTL regions by identifying linkage disequilibrium(LD)blocks associated with significant SNPs and performing haplotype analysis.The genes included one cloned gene(NOG1)and three newly identified QTL(qHI6,qTGW7,and qFLA8).These results provide a theoretical basis for high-yield rice breeding by increasing and balancing source–sink relationships using marker-assisted selection.     

The role of lignin and cellulose in the carbon-cycling of degraded soils under semiarid climate and their relation to microbial biomass

A high level of biological degradation is usually observed in soils under semiarid climate where the low inputs of vegetal debris constraint the development of microbiota. Among vegetal inputs, cellulose and lignin are dominant substrates but their assimilation by the microbial community of semiarid soils is yet not understood. In the present study, ¹³C-labeled cellulose and ¹³C-labeled lignin (75 μg ¹³C g⁻¹ soil) were added to two semiarid soils with different properties and degradation level. Abanilla soil is a bare, highly degraded soil without plant cover growing on it and a total organic C content of 5.0 g kg⁻¹; Santomera soil is covered by plants (20% coverage) based on xerophytic shrubs and has a total organic C content of 12.0 g kg⁻¹. The fate of added carbon was evaluated by analysis of the carbon isotope signature of bulk soil-derived carbon and extractable carbon fractions (water and sodium-pyrophosphate extracts). At long-term (120 days), we observed that the stability of cellulose- and lignin-derived carbon was dependent on their chemical nature. The contribution of lignin-derived carbon to the pool of humic substances was higher than that of cellulose. However, at short-term (30 days), the mineralization of the added substrates was more related to the degradation level of soils (i.e. microbial biomass). Stable isotope probing (SIP) of phospholipid fatty acids (PLFA-SIP) analysis revealed that just a minor part of the microbial community assimilated the carbon derived from cellulose and lignin. Moreover, the relative contribution of each microbial group to the assimilation of lignin-derived carbon was different in each soil.     

Evaluation of direct and indirect phosphorus limitation of methanogenic pathways in a calcareous subtropical wetland soil

The effect of phosphorus (P) and carbon (C) on methanogenesis was investigated in a low-P (130 mg P kg⁻¹ soil) wetland within Everglades National Park. Soil was amended with C substrates (acetate, formate, butyrate, and glucose) with or without P, and CO₂ and CH₄ production was monitored. Production of CH₄ increased with P addition although no effect on CO₂ was observed. Methane production was stimulated by all C substrates except for butyrate. No effect of C on CO₂ production was observed except for stimulation following glucose addition. Production of CH₄ following formate addition was not affected by P, suggesting hydrogenotrophic methanogens may be substrate, not P, limited. Addition of P to all other C substrates heightened CH₄ production and lowered the CO₂–C:CH₄–C ratio relative to the corresponding C only treatment, suggesting that P may have limited acetoclastic methanogens and fermentation.     

中国草地固碳减排研究现状及其建议

随着经济的快速发展,温室气体的排放量不断增加,加之人类对自然资源的利用强度逐渐增加,导致全球生态系统的固碳能力减弱,大气中的温室气体浓度达到新高,所造成的温室效应已经成为国际社会普遍关注的重大全球性问题。中国草地碳汇资源得天独厚,发展草原碳汇经济成为履行国际承诺、打造碳汇新经济、建设美丽中国的重要载体。综述中国草地固碳减排现状及其影响因素,包括草地碳汇和家畜生产减排研究、气候变化背景下的草地碳汇、人工草地建设等方面,并提出中国草地固碳减排发展建议,以期为中国实现碳达峰、碳中和及草地固碳减排的贡献提供理论基础,为推动我国社会高质量发展、创造高品质生活提供坚实的技术支撑。     

Carbon stock and rate of carbon sequestration in Dipterocarpus forests of Manipur,Northeast India

We examined the carbon stock and rate of carbon sequestration in a tropical deciduous forest dominated by Dipterocarpus tuberculatus in Manipur,North East India.Estimation of aboveground biomass was determined by harvest method and multiplied with density of tree species.The aboveground biomass was between18.27–21.922 t ha-1and the carbon stock ranged from9.13 to 10.96 t C ha-1across forest stands.Aboveground biomass and carbon stock increased with the increase in tree girth.The rate of carbon sequestration varied from1.4722 to 4.64136 t ha-1year-1among the dominant tree species in forest stands in tropical deciduous forest area.The rate of carbon sequestration depends on species composition,the density of large trees in different girth classes,and anthropogenic disturbances in the present forest ecosystem.Further work is required to identify tree species having the highest potential to sequester CO2 from the atmosphere,which could lead to recommendations for tree plantations in a degraded ecosystem.     

Soil organic carbon fractions and humic substances are affected by land uses of Caatinga forest in Brazil

Caatinga is a Brazilian dry ecosystem that occupies around 1 million km² and is one of the largest tropical dry forests of the world. About 46% of the area that was originally covered has been deforested. Land use can cause pronounced reduction in soil carbon stocks that play a major role in the global carbon cycle. The objective of this study was to improve our understanding of the effect of land use on oxidizable carbon fractions, total carbon stocks and humic substances in different layers of soil in a Brazilian semi-arid region. We analyzed soils from tropical dry forest (TDF), forest succession with Anadenanthera falcata (ANA), with Tabebuia alba (TAB), secondary scrubby regeneration (SCR), and non-irrigated maize (MS). Forests showed larger fractions of more labile carbon, except for TDF. The most recalcitrant fraction of carbon stock, humin fraction stock, with the different land use decreased by 38–53% compared to TDF. Oxidizable carbon fractions, carbon stocks, and humic fraction stocks were able to differentiate the successional land uses and agricultural cover from TDF, mainly in the 0–5?cm layer. Our results show that changes in land use, especially with ANA forest succession, showed a larger labile carbon fraction, indicating easy decomposition and loss. Our results provide an alternative tool for the management of deforested areas in tropical dry caatinga ecosystems. This would contribute to the conservation of dry forest systems and could serve as guideline for sustainable management of agriculturally impacted caatinga areas.     

我国碳排放研究现状的文献计量分析

运用文献计量学方法考察1989~2010年公开发表在CNKI、维普和万方三大数据库的我国碳排放研究文献,较为系统地分析我国碳排放研究发文年度分布、期刊分布、高产作者及引文分布等问题,同时通过关键词统计分析,初步揭示出碳排放研究的新方向。