Carbon Fixation Capacity Research Articles

Changes in the metabolic potential of the sponge microbiome under ocean acidification

Anthropogenic CO2 emissions are causing ocean acidification, which can affect the physiology of marine organisms. Here we assess the possible effects of ocean acidification on the metabolic potential of sponge symbionts, inferred by metagenomic analyses of the microbiomes of two sponge species sampled at a shallow volcanic CO2 seep and a nearby control reef. When comparing microbial functions between the seep and control sites, the microbiome of the sponge Stylissa flabelliformis (which is more abundant at the control site) exhibits at the seep reduced potential for uptake of exogenous carbohydrates and amino acids, and for degradation of host-derived creatine, creatinine and taurine. The microbiome of Coelocarteria singaporensis (which is more abundant at the seep) exhibits reduced potential for carbohydrate import at the seep, but greater capacity for archaeal carbon fixation via the 3-hydroxypropionate/4-hydroxybutyrate pathway, as well as archaeal and bacterial urea production and ammonia assimilation from arginine and creatine catabolism. Together these metabolic features might contribute to enhanced tolerance of the sponge symbionts, and possibly their host, to ocean acidification.

Responses of soil organic carbon and microbial community structure to different tillage patterns and straw returning for multiple years.

Soil organic carbon is essential for maintaining terrestrial ecosystem function and mitigating soil degradation. Soil microorganisms participate in soil carbon cycling. They are affected by tillage methods and straw returning. A split-plot design was adopted in this experiment. The whole-plot treatment had two tillage methods, subsoil tillage (ST) and rotary tillage (RT). The split-plot treatment included full straw returning (F) and no straw returning (0). The microbial community structure and carbon sequestration genes were assessed by Illumina sequencing technique. Soil organic carbon contents were measured during 2012-2017. The results showed that 1) subsoil tillage and straw returning significantly increased pH, microbial biomass carbon, total nitrogen, silt content, and clay content, while significantly decreased sand content; 2) during the test period (2012-2017), soil organic carbon (SOC) content under all treatments showed an increasing trend, but the increment for average SOC content under straw returning and subsoiling treatments was significantly higher than that of no straw returning and rotary tillage by 33.2 % and 30.6%, respectively; 3) Proteobacteria was the most abundant type of bacteria in the soil, followed by Acidobacteria and Gemmatadanetes; 4) STF treatment maintained high microbial diversity; 5) Excepted for soil sand content, soil pH, microbial biomass carbon, total nitrogen, silt content and clay content all caused the variation of soil microbial community structure under the STF treatment in the direction of SOC accumulation; 6) in addition to the gene abundance in the di- and oligosaccharides metabolic pathway, the gene abundance in the metabolic pathways for CO2 fixation, central carbohydrate metabolism, fermentation, one-carbon metabolism, organic acids, sugar alcohols and glycoside hydrolases showed that subsoil tillage was significantly higher than rotary tillage, with posi-tively correlation with soil organic carbon content. Therefore, the combination of subsoil tillage and straw returning could improve basic soil properties, affect soil microbial community structure, and increase the capacity of soil carbon fixation, thus providing a realistic basis for solving soil degradation.

Detailed profiling of carbon fixation of in silico synthetic autotrophy with reductive tricarboxylic acid cycle and Calvin-Benson-Bassham cycle in Esherichia coli using hydrogen as an energy source

Carbon fixation is the main route of inorganic carbon in the form of CO2 into the biosphere. In nature, RuBisCO is the most abundant protein that photosynthetic organisms use to fix CO2 from the atmosphere through the Calvin-Benson-Bassham (CBB) cycle. However, the CBB cycle is limited by its low catalytic rate and low energy efficiency. In this work, we attempt to integrate the reductive tricarboxylic acid and CBB cycles in silico to further improve carbon fixation capacity. Key heterologous enzymes, mostly carboxylating enzymes, are inserted into the Esherichia coli core metabolic network to assimilate CO2 into biomass using hydrogen as energy source. Overall, such a strain shows enhanced growth yield with simultaneous running of dual carbon fixation cycles. Our key results include the following. (i) We identified two main growth states: carbon-limited and hydrogen-limited; (ii) we identified a hierarchy of carbon fixation usage when hydrogen supply is limited; and (iii) we identified the alternative sub-optimal growth mode while performing genetic perturbation. The results and modeling approach can guide bioengineering projects toward optimal production using such a strain as a microbial cell factory.

Fast acclimation of phytoplankton assemblies to acute salinity stress in the Jiulong River Estuary

Mixing of freshwater and seawater creates the well-known salinity gradients along the estuaries. In order to investigate how phytoplankton respond to the acute salinity changes, we exposed natural phytoplankton assemblies from the Jiulong River Estuary to differential saline field water while continuously monitoring their photosynthetic performances under both indoor- and outdoor-growth conditions. When the natural cell assemblies from salinity 30 field water were exposed to series low saline field water (salinity 25, 17, 13 and 7.5), the effective Photosystem II quantum yield (ΔF/Fm′) decreased sharply, e.g., to one-fifth of its initials after 5 min exposure to salinity 7.5 field water, and then increased fast during the following 40 min and almost completely recovered after 320 min. During such an exposure process, non-photochemical quenching (NPQ) sharply increased from 0 to 0.85 within 5 min, and then decreased to nearly 0 within the following 70 min. When these cells re-acclimated to salinity 7.5 field water were exposed to series high saline field water (salinity 13, 17, 25 and 30), a similar response pattern was observed, with the decreased ΔF/Fm′ accompanied with increased NPQ, and followed by the recovery-induced increase in ΔF/Fm′ and decrease in NPQ. A similar response pattern as ΔF/Fm′ to the acute osmotic stress was also observed in the photosynthetic carbon fixation capacity according to radiocarbon (14C) incorporation. Our results indicate that estuarine phytoplankton assemblies could rapidly recover from the acute osmotic stress, implying a potential cause for their frequent blooms in coastal-estuarine waters where despite drastically varying salinity, available nutrients are abundant due to the land-derived runoffs or mixing-caused relaxations from sediments.

Nitrogen Addition Increases the Sensitivity of Photosynthesis to Drought and Re-watering Differentially in C3 Versus C4 Grass Species.

Global change factors, such as variation in precipitation regimes and nitrogen (N) deposition, are likely to occur simultaneously and may have profound impacts on the relative abundance of grasses differing in functional traits, such as C3 and C4 species. We conducted an extreme drought and re-watering experiment to understand differences in the resistance and recovery abilities of C3 and C4 grasses under different N deposition scenarios. A C3 perennial grass (Leymus chinensis) and two C4 grasses (annual species Chloris virgata and perennial species Hemarthria altissima) that co-occur in Northeast China were selected as experimental plants. For both C3 and C4 grasses, N addition caused a strong increase in biomass and resulted in more severe drought stress, leading to a change in the dominant photosynthetic limitation during the drought periods. Although N addition increased antioxidant enzyme activities and protective solute concentrations, the carbon fixing capacity did not fully recover to pre-drought levels by the end of the re-watering period. N addition resulted in lower resilience under the drought conditions and lower resistance at the end of the re-watering. However, N addition led to faster recovery of photosynthesis, especially in the C3 grass, which indicate that the effect of N addition on photosynthesis during drought was asymmetric, especially in the plants with different photosynthetic nitrogen use efficiency (PNUE). These findings demonstrated that nitrogen deposition may significant alter the susceptibility of C3 and C4 grass species to drought stress and re-watering, highlighting the asymmetry between resistance and resilience and to improve our understanding about plant responses to climate change.

Decoupling light harvesting, electron transport and carbon fixation during prolonged darkness supports rapid recovery upon re-illumination in the Arctic diatom Chaetoceros neogracilis

During winter in the Arctic marine ecosystem, diatoms have to survive long periods of darkness caused by low sun elevations and the presence of sea ice covered by snow. To better understand how diatoms survive in the dark, we subjected cultures of the Arctic diatom Chaetoceros neogracilis to a prolonged period of darkness (1 month) and to light resupply. Chaetoceros neogracilis was not able to grow in the dark but cell biovolume remained constant after 1 month in darkness. Rapid resumption of photosynthesis and growth recovery was also found when the cells were transferred back to light at four different light levels ranging from 5 to 154 µmol photon m−2 s−1. This demonstrates the remarkable ability of this species to re-initiate growth over a wide range of irradiances even after a prolonged period in the dark with no apparent lag period or impact on survival. Such recovery was possible because C. neogracilis cells preserved their Chl a content and their light absorption capabilities. Carbon fixation capacity was down-regulated (ninefold dark decrease in $$P_{\text{m}}^{\text{C}}$$ ) much more than was the photochemistry in PSII (2.3-fold dark decrease in ETRm). Rubisco content, which remained unchanged after one month in the dark, was not responsible for the decrease in $$P_{\text{m}}^{\text{C}}$$ . The decrease in PSII activity was partially related to the induction of sustained non-photochemical quenching (NPQ) as we observed an increase in diatoxanthin content after one month in the dark.

Effects of NH4+-N and NO2−-N on carbon fixation in an anaerobic ammonium oxidation reactor

Inorganic carbon (IC) is used as a carbon source of the anaerobic ammonium oxidation (anammox) microorganisms during the anammox process. Meanwhile, anammox microorganisms possess a certain carbon fixation capacity. In this study, the effects of NH4+-N and NO2−-N on carbon fixation in an anammox reactor were investigated. The carbon fixation content had a positive correlation with the amount of NH4+-N and NO2−-N. A high carbon sequestration of 6.52 mg-C and relatively low CO2 emissions of 1.00 mg-C were caused by a high amount of influent nitrogen. The microbiology analysis showed that there was a significant relevance between the abundance of the cbbLR1 gene and the carbon fixation content. The results revealed that the Calvin cycle pathway for carbon fixation was used by the anammox bacteria, which may be uncultured Bacillus sp. clone TA_17 or uncultured Methylobacterium sp. clone LA8_13.

Photosynthetic carbon fixation capacity of black locust in rapid response to plantation thinning on the semiarid loess plateau in China

Photosynthetic carbon fixation capacity of black locust in rapid response to plantation thinning on the semiarid loess plateau in China

Controlling the nucleophilic properties of cobalt salen complexes for carbon dioxide capture.

The nucleophilic properties of cobalt salen complexes are examined using density functional theory to investigate its carbon fixing capacity. In particular, carbon dioxide attack on neutral and anionic cobalt salen molecules is considered. Carbon fixation occurs for the anionic cobalt salen complex and is due to the nucleophilic interaction between the cobalt center and carbon dioxide molecule in a Co dz2–CO2 π* interaction. A minimum energy path search by a nudged elastic band calculation reveals a lower forward activation energy for the anionic complex than the neutral complex, indicating that the formation of the anionic complex is thermodynamically and kinetically favored. In this case, the CO2 molecule is chemisorbed as partial charge transfer from the cobalt center to carbon dioxide is observed. Proposed reaction mechanisms explain how the Co–C bond energy of the CO2–cobalt salen complex can be tuned by appropriate substitutions of electron donating or withdrawing groups on the phenyl ring.

RcaE-Dependent Regulation of Carboxysome Structural Proteins Has a Central Role in Environmental Determination of Carboxysome Morphology and Abundance in Fremyella diplosiphon.

Carboxysomes are central to the carbon dioxide-concentrating mechanism (CCM) and carbon fixation in cyanobacteria. Although the structure is well understood, roles of environmental cues in the synthesis, positioning, and functional tuning of carboxysomes have not been systematically studied. Fremyella diplosiphon is a model cyanobacterium for assessing impacts of environmental light cues on photosynthetic pigmentation and tuning of photosynthetic efficiency during complementary chromatic acclimation (CCA), which is controlled by the photoreceptor RcaE. Given the central role of carboxysomes in photosynthesis, we investigated roles of light-dependent RcaE signaling in carboxysome structure and function. A ΔrcaE mutant exhibits altered carboxysome size and number, ccm gene expression, and carboxysome protein accumulation relative to the wild-type (WT) strain. Several Ccm proteins, including carboxysome shell proteins and core-nucleating factors, overaccumulate in ΔrcaE cells relative to WT cells. Additionally, levels of carboxysome cargo RuBisCO in the ΔrcaE mutant are lower than or unchanged from those in the WT strain. This shift in the ratios of carboxysome shell and nucleating components to the carboxysome cargo appears to drive carboxysome morphology and abundance dynamics. Carboxysomes are also occasionally mislocalized spatially to the periphery of spherical mutants within thylakoid membranes, suggesting that carboxysome positioning is impacted by cell shape. The RcaE photoreceptor links perception of external light cues to regulating carboxysome structure and function and, thus, to the cellular capacity for carbon fixation. IMPORTANCE Carboxysomes are proteinaceous subcellular compartments, or bacterial organelles, found in cyanobacteria that consist of a protein shell surrounding a core primarily composed of the enzyme ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCO) that is central to the carbon dioxide-concentrating mechanism (CCM) and carbon fixation. Whereas significant insights have been gained regarding the structure and synthesis of carboxysomes, limited attention has been given to how their size, abundance, and protein composition are regulated to ensure optimal carbon fixation in dynamic environments. Given the centrality of carboxysomes in photosynthesis, we provide an analysis of the role of a photoreceptor, RcaE, which functions in matching photosynthetic pigmentation to the external environment during complementary chromatic acclimation and thereby optimizing photosynthetic efficiency, in regulating carboxysome dynamics. Our data highlight a role for RcaE in perceiving external light cues and regulating carboxysome structure and function and, thus, in the cellular capacity for carbon fixation and organismal fitness.

In the lycophyte Selaginella martensii is the “extra-qT” related to energy spillover? Insights into photoprotection in ancestral vascular plants

Lycophytes are early diverging vascular plants, representing a minor group as compared to the dominating euphyllophytes, mostly angiosperms. Having maximally developed in a CO2-rich atmosphere, extant lycophytes are characterized by a low carbon fixing capacity, which is compensated by a marked ability to induce the non-photochemical quenching of chlorophyll fluorescence (NPQ). Different kinetic components contribute to NPQ, in particular the fast relaxing high-energy quenching qE, the middle relaxing qT, and the slowly relaxing qI. Unlike angiosperms, lycophytes enhance the qT component under high light, originating from an “extra-qT”. In this research, we analyze whether in Selaginella martensii the extra-qT can reflect a photosystem (PS) I-based quenching mechanism activated upon saturation of qE capacity. From comparative analyses of fluorescence quenching parameters, carbon fixation, in vivo low- and room-temperature fluorescence spectroscopy, and thylakoid protein phosphorylation, it is proposed that the extra-qT is not mechanistically separate from the ordinary qT. The results suggest a relationship between qT and photoprotective energy spillover to PSI, which is activated upon sensing the excitation energy pressure inside PSII and is possibly facilitated by phosphorylation of Lhcb6, a minor antenna protein of PSII. Energy spillover emphasizes 77K fluorescence emission from PSI core (F714) and becomes more relevant at irradiance levels corresponding to the CO2-limited, potentially photoinhibiting phase of photosynthesis. At the highest irradiances, when Lhcb6 phosphorylation potential has been saturated, the major LHCII increases in turn its phosphorylation level, probably leading to the full exploitation of PSI as a safe excitation sink. It is suggested that the low photosynthetic capacity of lycophytes could allow an easier experimental access to the use of PSI as a safe excitation quencher for PSII, a debated, emerging issue about thylakoid photoprotection in angiosperms.

Thinning effect on understory community and photosynthetic characteristics in a subtropical Pinus massoniana plantation

Thinning forest stands changes biotic and abiotic conditions, subsequently altering understory communities including their photosynthetic characteristics. We investigated the effects of thinning (25% basal area decrease) in a subtropical Pinus massoniana Lamb. plantation at two post-thinning times: 0.5 years (PT0.5) and 2.5 years (PT2.5). Thinning (PT0.5 and PT2.5) significantly increased understory density (+104.9% and +142.4%, respectively), aboveground biomass (+191.1% and +239.2%, respectively), the Shannon–Wiener index, and the Pielou index and decreased the Simpson index (p < 0.05). Species richness significantly increased at PT0.5 and decreased at PT2.5 (p < 0.05). Photosynthetic characteristics of new and old leaves of three dominant species (Woodwardia japonica (Linn. f.) Sm., Dryopteris championii (Benth.) C. Chr., and Dicranopteris dichotoma (Thunb.) Bernh.) showed different variations at 0.5 and 2.5 years after thinning, depending on their various adaptive strategies. Generally, thinning improved leaf carbon fixation capacity of these dominant plants (except W. japonica old leaves). Leaf photosynthetic characteristics of these species exhibited some common changes with respect to leaf morphological attributes and chlorophyll content. Thinning increased new-leaf length (or width) and reduced old-leaf chlorophyll b concentration at PT0.5 but reduced new-leaf length, specific leaf area, and all-leaf chlorophyll concentration at PT2.5. In conclusion, thinning is a useful tool for increasing understory abundance and carbon fixation capacity of some fern species.

近自然化改造对马尾松和杉木人工林生物量及其分配的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 近自然化改造对马尾松和杉木人工林生物量及其分配的影响 DOI: 10.5846/stxb201704030573 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中央级公益性科研院所基本科研业务费专项资金（CAFYBB2014QA033）；广西林业科技项目（桂林科字[2016]第37号）；广西自然科学基金项目（2014GXNSFBA118100） Effects of close-to-nature transformation on biomass and its allocation in Pinus massoniana and Cunninghamia lanceolata plantations Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:近自然化改造作为森林新增碳汇的最有希望的选择之一，将如何通过改变林分结构影响林分生物量和生产力进而影响林分固碳能力和潜力目前尚不清楚，因此，了解近自然化改造对人工林生物量及其分配的影响，对人工林生态系统碳管理具有重要意义。以马尾松近自然化改造林（P （CN））、马尾松未改造纯林（P （CK））、杉木近自然改造林（C （CN））和杉木未改造纯林（C （CK））4种人工林为研究对象，采用样方调查和生物量实测的方法，分析4种林分生物量差异，旨在揭示近自然化改造对马尾松和杉木人工林生物量及其分配的影响。结果表明：马尾松杉木人工林近自然化改造通过调整林分结构显著提升马尾松和杉木人工林生物量和生产力，8a后马尾松和杉木林分生物量分别增加46.71%和37.24%。乔木层生物量在林分生物量总量中占主导地位（95.48%-98.82%），并对林分生态系统总生物量变化起决定性作用。林分生物量和生产力的增加主要因为近自然化改造改变了林分群落结构，进而提高了乔木层生产力。研究结果表明，合理的经营措施不仅可以改善林分结构，提升林分生产力，并可为增强植被固碳能力创造有利条件。 Abstract:Close-to-nature transformation is considered one of the most promising options for creating new forest carbon sinks, but the mechanism by which it influences the biomass by changing the forest structure and thereby influencing the ability and potential of the forest for carbon sequestration remains unclear. Therefore, there is an urgent need to understand these key effects of close-to-nature transformation on the biomass for carbon management in plantation ecosystems. Based on a close-to-nature forest of Pinus massoniana plantation (P(CN)) and an unimproved pure stand of P. massoniana (P(CK)), and a close-to-nature stand of Cunninghamia lanceolata (C(CN)) and an unimproved pure stand of C. lanceolata (C(CK)) as the research objects, the biomass and allocation difference of the four forest types were studied using the method of quadrat sampling combined with biomass measurement, aiming to reveal the influence of close-to-nature transformation on forest biomass and its allocation patterns in P. massoniana and C. lanceolata plantation. The results indicated that the biomass and productivity of P. massoniana and C. lanceolata plantations can be significantly increased by close-to-nature transformation, and the biomass of P. massoniana and C. lanceolata forest stands can be increased by 46.71% and 37.24%, respectively, after 8 years. The biomass of the arborous layer dominates the total biomass (95.48%-98.82%), which plays a vital role in the overall change in forest stand ecosystem biomass. The increase in biomass and productivity in the forest is mainly due to the change in the forest stand community structure, which increases the productivity of the arborous layer. Taken together, the results indicate that reasonable management measures can not only improve stand structure and productivity, but also create favorable conditions that enhance vegetation carbon fixation capacity and potential. 参考文献 相似文献 引证文献

Carbon Storage Patterns of Caragana korshinskii in Areas of Reduced Environmental Moisture on the Loess Plateau, China.

Precipitation patterns are influenced by climate change and profoundly alter the carbon sequestration potential of ecosystems. Carbon uptake by shrubbery alone accounts for approximately one-third of the total carbon sink; however, whether such uptake is altered by reduced precipitation is unclear. In this study, five experimental sites characterised by gradual reductions in precipitation from south to north across the Loess Plateau were used to evaluate the Caragana korshinskii’s functional and physiological features, particularly its carbon fixation capacity, as well as the relationships among these features. We found the improved net CO2 assimilation rates and inhibited transpiration at the north leaf were caused by lower canopy stomatal conductance, which enhanced the instantaneous water use efficiency and promoted plant biomass as well as carbon accumulation. Regional-scale precipitation reductions over a certain range triggered a distinct increase in the shrub’s organic carbon storage with an inevitable decrease in the soil’s organic carbon storage. Our results confirm C. korshinskii is the optimal dominant species for the reconstruction of fragile dryland ecosystems. The patterns of organic carbon storage associated with this shrub occurred mostly in the soil at wetter sites, and in the branches and leaves at drier sites across the arid and semi-arid region.

Driving force and changing trends of vegetation phenology in the Loess Plateau of China from 2000 to 2010

Changes in vegetation phenology are key indicators of the response of ecosystems to climate change. Therefore, knowledge of growing seasons is essential to predict ecosystem changes, especially for regions with a fragile ecosystem such as the Loess Plateau. In this study, based on the normalized difference vegetation index (NDVI) data, we estimated and analyzed the vegetation phenology in the Loess Plateau from 2000 to 2010 for the beginning, length, and end of the growing season, measuring changes in trends and their relationship to climatic factors.The results show that for 54.84% of the vegetation, the trend was an advancement of the beginning of the growing season (BGS), while for 67.64% the trend was a delay in the end of the growing season (EGS). The length of the growing season (LGS) was extended for 66.28% of the vegetation in the plateau. While the temperature is important for the vegetation to begin the growing season in this region, warmer climate may lead to drought and can become a limiting factor for vegetation growth. We found that increased precipitation benefits the advancement of the BGS in this area. Areas with a delayed EGS indicated that the appropriate temperature and rainfall in autumn or winter enhanced photosynthesis and extended the growth process. A positive correlation with precipitation was found for 76.53% of the areas with an extended LGS, indicating that precipitation is one of the key factors in changes in the vegetation phenology in this water-limited region. Precipitation plays an important role in determining the phenological activities of the vegetation in arid and semiarid areas, such as the Loess Plateau. The extended growing season will significantly influence both the vegetation productivity and the carbon fixation capacity in this region.

Morpho-physiological response to drought of progenies of Pinus taeda L. contrasting in mean growth rate

Fil: Bulfe, Nardia Maria Lujan. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Misiones. Estacion Experimental Agropecuaria Montecarlo; Argentina

天山林区6种优势种灌木林生物量比较及估测模型

PDF HTML阅读 XML下载 导出引用 引用提醒 天山林区6种优势种灌木林生物量比较及估测模型 DOI: 10.5846/stxb201405130984 作者: 作者单位: 新疆林业科学院,新疆林业科学院,新疆林业科学院,新疆林业科学院,新疆林业科学院 作者简介: 通讯作者: 中图分类号: 基金项目: 自治区公益性科研院所基本科研业务费专项资金项目"天山中部灌木林生物量和生产力研究";新疆林业生态服务功能监测评估(xjlk(2013)001号);新疆阿尔泰山森林生态系统定位研究站开放基金 Biomass comparison and estimation models for six dominant species of woody shrubs in the forest zones of the Tianshan Mountains Author: Affiliation: Xinjiang Academy of Forestry Urumqi;China,Xinjiang Academy of Forestry Urumqi;China,Xinjiang Academy of Forestry Urumqi;China,Xinjiang Academy of Forestry Urumqi;China,Xinjiang Academy of Forestry Urumqi;China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用平均标准木收获法测定了天山东、中、西部林区6种优势种灌木,多刺蔷薇(Rosa spinosissima L.)、黑果小檗(Berberis heteropoda Schrenk.)、刚毛忍冬(Lonicera hispida Pall.)、天山绣线菊(Spiraea.tianschanica Pojark.)、新疆方枝柏(Juniperus pseudosabina Fisch. et Mey.)和黑果栒子(Cotoneaster melanocarpus Lodd.)的地上和地下生物量并构建基于D2H变量的个体生物量模型。结果表明:(1) 天山西部林区灌木林的总生物量大于中部和东部的;(2) 6种灌木的平均生物量大小排序为刚毛忍冬 > 黑果栒子 > 黑果小檗 > 新疆方枝柏 > 天山绣线菊 > 多刺蔷薇;(3) 6种灌木的生物量贡献主要源于根和枝生物量,不同器官生物量的大小排序根 > 枝 > 叶;6种灌木叶生物量的大小与枝的生物量之间呈极显著相关(P < 0.01);(4) 以D2H为自变量建立6种灌木不同器官及个体生物量估测模型24个,除黑果小檗和新疆方枝柏叶生物量模型达到显著水平(P < 0.05),其他各组成生物量模型均达到极显著水平(P < 0.01),模型模拟结果达到了较高的准确度,可用于推算灌木生物量。研究结果可为定量评估天山森林生态系统的固碳功能提供数据支撑,也可为深入开展森林生态系统服务功能评价提供依据。 Abstract:The woody shrub layer in the Tianshan Mountains comprises a large proportion of the plant biomass of the entire forest ecosystem, significantly affecting estimates of the total forest biomass. Therefore, using an average wood-harvesting method, this study measured both the aboveground and belowground biomasses of six species of dominant woody shrubs (Rosa spinosissima L., Berberis heteropoda Schrenk., Lonicera hispida Pall., Spiraea tianschanica Pojark, Juniperus pseudosabina Fisch. et Mey., and Cotoneaster melanocarpus Lodd.) in eastern, central, and western areas of the Tianshan Mountains. A series of individual biomass models inferred from the variable D2H were established. The results are as follows: (1) The total biomass of the forest in the western areas of the Tianshan Mountains was larger than that in the central and eastern areas. The average biomass of an individual plant of the six woody shrubs was in the order of Lonicera hispida > Cotoneaster melanocarpus > Berberis heteropoda > Juniperus pseudosabina > Spiraea tianschanica > Rosa spinosissima. (2) In the western areas of Tianshan Mountains, the ratio of aboveground biomass to belowground biomass was greater than 1 for all six species; in the central area, it was less than 1 for all species except R. spinosissima and L. hispida; and in the eastern area, it was less than 1 for all species except B. heteropoda. (3) In all species, roots and branches were the major contributors to the biomass. The plant organ biomass was in the order of root < branch < leaf. The biomass of different root sizes was in the order of thick root > large root > medium root > small root > fine root. The variation in biomass distribution among different nutritive organs and diameter-class roots reflects the strategies that species employed to adapt to selected habitats. (4) Twenty-four biomass estimation models, with D2H as an independent variable, were established to evaluate organ biomass and individual biomass in the six species. The established models included 10 linear models, eight power function models, four polynomial models, and two logarithmic models. Except for B. heteropoda and J. pseudosabina, which reached only the significant level, the biomass models for all species reached the extremely significant level. The results indicate that the models can provide highly accurate estimates that could be used to evaluate the biomass of woody shrubs. This study provides supporting data for quantitative assessment of carbon fixation capacity of the Tianshan Mountains forest ecosystem. In addition, it provides strong evidence for further evaluation of the service capacity of forest ecosystems. 参考文献 相似文献 引证文献

Triose phosphate use limitation of photosynthesis: short-term and long-term effects.

The triose phosphate use limitation was studied using long-term and short term changes in capacity. The TPU limitation caused increased proton motive force; long-term TPU limitation additionally reduced other photosynthetic components. Photosynthetic responses to CO2 can be interpreted primarily as being limited by the amount or activity of Rubisco or the capacity for ribulose bisphosphate regeneration, but at high rates of photosynthesis a third response is often seen. Photosynthesis becomes insensitive to CO2 or even declines with increasing CO2, and this behavior has been associated with a limitation of export of carbon from the Calvin-Benson cycle. It is often called the triose phosphate use (TPU) limitation. We studied the long-term consequences of this limitation using plants engineered to have reduced capacity for starch or sucrose synthesis. We studied short-term consequences using temperature as a method for changing the balance of carbon fixation capacity and TPU. A long-term and short-term TPU limitation resulted in an increase in proton motive force (PMF) in the thylakoids. Once a TPU limitation was reached, any further increases in CO2 was met with a further increase in the PMF but no increase or little increase in net assimilation of CO2. A long-term TPU limitation resulted in reduced Rubisco and RuBP regeneration capacity. We hypothesize that TPU, Rubisco activity, and RuBP regeneration are regulated so that TPU is normally in slight excess of what is required, and that this results in more effective regulation than if TPU were in large excess.

A comparative study on enzymatic hydrolysis of kenaf from two different harvest time-points, with- and without pretreatment

Kenaf biomass is potentially a valuable feedstock for bio-energy production due to fast growth of this plant, and its high capacity for carbon fixation and accumulation of carbohydrates. In this study, biomass productivity, chemical composition and physical properties of kenaf were investigated at two different harvest times. The average dry weight of early harvested biomass (EH, 109.0g/plant) was lower than that of late harvested biomass (LH, 132.3g/plant). However, the daily growth rates for EH and LH were 1.45 and 1.28g/d, respectively. There was no significant difference in carbohydrate content between EH- and LH-kenaf, while lignin content increased with higher S/G ratio in LH-kenaf. The enzymatic conversion rates of EH- and LH-kenaf with/without popping pretreatment were 90.4%/41.2% and 65.0%/27.5%, respectively. We suggest that early harvest has a positive impact on kenaf biomass, which had a lower lignin content and cellulose crystallinity.

Carbon sequestration of mature black locust stands on the Loess Plateau, China

In Northwestern China, the carbon fixing capacity of black locust ( Robinia pseudoacacia ) has been questioned because of its slow growth following the return of unproductive farmland to forest. To explore the effects of stand age on the carbon sequestration potential of R. pseudoacacia in a semi-arid, ecologically fragile area, parameters related to carbon fixation were investigated in plots of three stand ages (5, 10, and 25 years). Each plot was divided into four subsystems: R. pseudoacacia , understory vegetation, litter, and soil, and the carbon stored capacity of each subsystem was estimated. The organic carbon density of R. pseudoacacia , understory vegetation, and litter ranged from 3.4-16.8% and increased gradually with increasing stand age. Soil organic carbon increased with increasing stand age and accounted for 83.2-96.6% of the total carbon stored. Soil CaCO 3 content also increased with increasing soil depth and stand age. Because total plant and soil carbon storage increased with increasing age of R. pseudoacacia stands, the 25-year-old R. pseudoacacia community had the highest carbon fixation capacity, which was substantial even in this arid region.