土壤与植物生态化学计量学研究进展

生态化学计量学是一门新兴科学,主要研究生态作用和生态过程中能量平衡及碳、氮、磷等多重化学元素的平衡,有机统一了生物学不同层次(分子、细胞、个体、种群、生态系统以及全球尺度)的研究理论。陆地生态系统的生态化学计量学研究具有重要意义,土壤和植物的碳、氮、磷比例关系可以表征生态系统的养分限制状况以及有机质的分解程度及其对土壤肥力的潜在贡献等。主要综述了生态化学计量学的概念、起源及研究简史,重点概述了陆地生态系统(主要为草原生态系统)中土壤与植物碳、氮、磷的生态化学计量学特征及其对气候因子及人为干扰等因素的响应。     

Optimal nitrogen-to-phosphorus stoichiometry of phytoplankton

Redfield noted the similarity between the average nitrogen-to-phosphorus ratio in plankton (N:P = 16 by atoms) and in deep oceanic waters (N:P = 15; refs 1, 2). He argued that this was neither a coincidence, nor the result of the plankton adapting to the oceanic stoichiometry, but rather that phytoplankton adjust the N:P stoichiometry of the ocean to meet their requirements through nitrogen fixation, an idea supported by recent modelling studies. But what determines the N:P requirements of phytoplankton? Here we use a stoichiometrically explicit model of phytoplankton physiology and resource competition to derive from first principles the optimal phytoplankton stoichiometry under diverse ecological scenarios. Competitive equilibrium favours greater allocation to P-poor resource-acquisition machinery and therefore a higher N:P ratio; exponential growth favours greater allocation to P-rich assembly machinery and therefore a lower N:P ratio. P-limited environments favour slightly less allocation to assembly than N-limited or light-limited environments. The model predicts that optimal N:P ratios will vary from 8.2 to 45.0, depending on the ecological conditions. Our results show that the canonical Redfield N:P ratio of 16 is not a universal biochemical optimum, but instead represents an average of species-specific N:P ratios.     

The impact of surface-adsorbed phosphorus on phytoplankton Redfield stoichiometry

The Redfield ratio of 106 carbon:16 nitrogen:1 phosphorus in marine phytoplankton is one of the foundations of ocean biogeochemistry, with applications in algal physiology, palaeoclimatology and global climate change. However, this ratio varies substantially in response to changes in algal nutrient status and taxonomic affiliation. Here we report that Redfield ratios are also strongly affected by partitioning into surface-adsorbed and intracellular phosphorus pools. The C:N:surface-adsorbed P (80-105 C:15-18 N:1 P) and total (71-80 C:13-14 N:1 P) ratios in natural populations and cultures of Trichodesmium were close to Redfield values and not significantly different from each other. In contrast, intracellular ratios consistently exceeded the Redfield ratio (316-434 C:59-83 N:1 intracellular P). These high intracellular ratios were associated with reduced N2 fixation rates, suggestive of phosphorus deficiency. Other algal species also have substantial surface-adsorbed phosphorus pools, suggesting that our Trichodesmium results are generally applicable to all phytoplankton. Measurements of the distinct phytoplankton phosphorus pools may be required to assess nutrient limitation accurately from elemental composition. Deviations from Redfield stoichiometry may be attributable to surface adsorption of phosphorus rather than to biological processes, and this scavenging could affect the interpretation of marine nutrient inventories and ecosystem models.     

不同沼泽地对神农架大九湖湿地土壤—植被碳氮磷化学计量比的影响

湿地生态系统碳氮磷(C、N、P)生态化学计量比已成为当前探索群落生态动态过程的热点.然而,人类活动对沼泽湿地生态化学计量比的影响规律及其影响机制尚未明确.以神农架大九湖沼泽湿地为研究对象,探索植被—土壤碳氮磷生态化学计量比及其对人类活动的响应规律,以期为该区域湿地保护恢复提供决策支撑.研究表明:随着人类活动的影响,与泥...     

南方红豆杉人工林针叶C、N、P化学计量特征

【目的】 研究南方红豆杉人工林针叶C、N、P生态化学计量和养分重吸收特征,揭示南方红豆杉的养分限制格局和养分高效利用策略,为南方红豆杉人工林的高质量种植栽培提供理论依据。【方法】 以9年生南方红豆杉人工林为研究对象,通过测定其针叶碳(C)、氮(N)、磷(P)元素含量,分析针叶的生态化学计量、养分重吸收率及其相互关系。【结果】 南方红豆杉针叶C、N、P平均含量分别为479.67、22.52和2.21 g/kg,碳氮质量比(C:N)、碳磷质量比(C:P)、氮磷质量比(N:P)分别为21.74、226.25和10.55;N与P、C含量均呈极显著正相关,P与C含量呈显著正相关;生长季中,南方红豆杉针叶C含量最稳定,变异系数为3.90%,P含量的变异系数(22.43%)大于N(15.34%)。研究区南方红豆杉在生长季(6—11月)针叶C与N含量均表现为先平缓上升后显著下降趋势,8月达到高峰并持续到9月,C含量10月最低,N含量11月最低;P含量则表现为先显著上升后显著下降的趋势,在9月达到峰值,且显著大于其他各月份;针叶中C:N和N:P的变化比C:P更稳定,且P含量决定了C:P和N:P的动态变化。南方红豆杉针叶N重吸收率和P重吸收率分别为19.33%和22.16%,且P重吸收率与衰老叶P含量、C:P呈显著负相关,与N:P呈显著正相关。【结论】 研究区内,9年生南方红豆杉人工林针叶具备较好的C储存能力和养分资源竞争力,N、P重吸收率较低,养分在针叶中的驻留时间较长,生长未受到N、P限制。     

Efficient export of carbon to the deep ocean through dissolved organic matter

Oceanic dissolved organic carbon (DOC) constitutes one of the largest pools of reduced carbon in the biosphere. Estimated DOC export from the surface ocean represents 20% of total organic carbon flux to the deep ocean, which constitutes a primary control on atmospheric carbon dioxide levels. DOC is the carbon component of dissolved organic matter (DOM) and an accurate quantification of DOM pools, fluxes and their controls is therefore critical to understanding oceanic carbon cycling. DOC export is directly coupled with dissolved organic nitrogen and phosphorus export. However, the C:N:P stoichiometry (by atoms) of DOM dynamics is poorly understood. Here we study the stoichiometry of the DOM pool and of DOM decomposition in continental shelf, continental slope and central ocean gyre environments. We find that DOM is remineralized and produced with a C:N:P stoichiometry of 199:20:1 that is substantially lower than for bulk pools (typically >775:54:1), but greater than for particulate organic matter (106:16:1--the Redfield ratio). Thus for a given mass of new N and P introduced into surface water, more DOC can be exported than would occur at the Redfield ratio. This may contribute to the excess respiration estimated to occur in the interior ocean. Our results place an explicit constraint on global carbon export and elemental balance via advective pathways.     

Geochemical evidence for terrestrial ecosystems 2.6 billion years ago

Microorganisms have flourished in the oceans since at least 3.8 billion years (3.8 Gyr) ago, but it is not at present clear when they first colonized the land. Organic matter in some Au/U-rich conglomerates and ancient soils of 2.3-2.7 Gyr age has been suggested as remnants of terrestrial organisms. Some 2.7-Gyr-old stromatolites have also been suggested as structures created by terrestrial organisms. However, it has been disputed whether this organic matter is indigenous or exogenic, and whether these stromatolites formed in marine or fresh water. Consequently, the oldest undisputed remnants of terrestrial organisms are currently the 1.2-Gyr-old microfossils from Arizona, USA. Unusually carbonaceous ancient soils--palaeosols--have been found in the Mpumalanga Province (Eastern Transvaal) of South Africa. Here we report the occurrences, elemental ratios (C, H, N, P) and isotopic compositions of this organic matter and its host rocks. These data show that the organic matter very probably represents remnants of microbial mats that developed on the soil surface between 2.6 and 2.7 Gyr ago. This places the development of terrestrial biomass more than 1.4 billion years earlier than previously reported.     

安徽石台亚热带常绿阔叶林植物叶中 C、N、P特征分析

以安徽石台亚热带常绿阔叶林植物叶片为研究对象,分析了植物叶中C、N、P含量以及它们之间的化学计量关系,讨论了不同类型植物叶片的化学计量特征。结果显示:所研究的28种植物物种间差异明显,叶片中C含量为400.08～519.36 mg/g,N 为5.15～15.39 mg/g,P为0.30～0.97 mg/g,m(C):m(N)范围为29.99～92.25、m(C):m(P)的范围为467.01～1 443.81、m(N):m(P)的范围为10.01～29.29,且N与P、m(C):m(N)值与m(C):m(P)值之间呈现显著的正相关关系,m(N):m(P)的变化主要由P含量决定。不同生活型植物m(C):m(N)值从大到小表现为灌木(59.68)>乔木(51.56)>草本和藤本植物(44.50),草本和藤本植物与灌木之间m(C):m(N)差异显著; 不同植物m(C):m(P)值从大到小表现为灌木(1 043.4)>草本和藤本植物(818.78)>乔木(808.35),灌木与乔木、草本和藤本植物都存在显著差异。该地区灌木m(C):m(N)值和m(C):m(P)值均最高,说明灌木对N、P的利用效率最高。3种类型植物m(N):m(P)值均大于16,说明该地区常绿阔叶林主要受P限制。虽然植物受P限制,但其m(C):m(P)值含量较高,说明植物对其生长受限的元素利用效率会更高,这反映了植物对环境适应的一种对策。     

Ocean nutrient ratios governed by plankton biogeography

The major nutrients nitrate and phosphate have one of the strongest correlations in the sea, with a slope similar to the average nitrogen (N) to phosphorus (P) content of plankton biomass (N/P = 16:1). The processes through which this global relationship emerges despite the wide range of N/P ratios at the organism level are not known. Here we use an ocean circulation model and observed nutrient distributions to show that the N/P ratio of biological nutrient removal varies across latitude in Southern Ocean surface waters, from 12:1 in the polar ocean to 20:1 in the sub-Antarctic zone. These variations are governed by regional differences in the species composition of the plankton community. The covariation of dissolved nitrate and phosphate is maintained by ocean circulation, which mixes the shallow subsurface nutrients between distinct biogeographic provinces. Climate-driven shifts in these marine biomes may alter the mean N/P ratio and the associated carbon export by Southern Ocean ecosystems.     

炼山和套种绿肥对桉树人工林下植物和土壤C:N:P化学计量特征的影响

【目的】研究炼山和套种绿肥对桉树人工林林下植物和土壤C、N、P化学计量特征的影响,阐明炼山和套种绿肥条件下桉树人工林林下植物与土壤C、N、P的作用关系。【方法】在凭祥市热带林业实验中心青山试验场测定炼山和套种绿肥(山毛豆)处理下的桉树人工林林下植物与土壤C、N、P生态化学计量特征的变化规律。【结果】桉树人工林林下植物灌上(灌木层地上部分)有机碳、全氮含量最高,全磷含量最低;土壤有机碳和全氮含量随土壤层次的加深而递减,而土壤全磷则呈表层土的含量最高,随后减少再逐渐回升的趋势。炼山处理降低了林下植物中的有机碳、全氮含量,尤其是草上(草本层地上部分)和灌上(P0.05),却提高灌下(灌木层地下部分)的全磷含量(P0.05);炼山降低0～60cm土层的有机碳及全磷含量,降低0～10cm土层的全氮含量,提高10～60cm土层的全氮含量。套种绿肥后,林下植物有机碳含量降低,灌木层的全氮含量提高;显著降低草本层的全磷含量,而显著提高灌上的全磷含量;显著降低0～10cm的土壤有机碳及全磷含量(P0.05),小幅度降低0～10cm、10～20cm土层的全氮含量(P0.05)。炼山+套种绿肥处理,土壤表层0～10cm有机碳和全氮含量显著提高,林下植物草上全氮和全磷含量显著增加(P0.05);与单一的炼山或套种绿肥处理恰好相反。炼山提高林下植物生态化学计量比值,却降低土壤生态化学计量比值;套种绿肥总体上提高林下植物的N∶P和C∶P,降低林下植物的C∶N和土壤生态化学计量比值;炼山+套种绿肥对土壤生态化学计量比影响显著,总体降低林下植物的生态化学计量比,尤其是草上及灌上组分(P0.05)。林下草本和灌木层植物的地上部分与土壤的生态化学计量比呈负相关关系。【结论】炼山和套种绿肥对桉树人工林林下植物与土壤C∶N∶P化学计量特征有显著影响,炼山+套种绿肥比单一处理的方式更有利于提高土壤表层0～10cm有机碳和全氮含量以及林下草本植物地上部分全氮和全磷含量。     

Unusual stable isotope ratios in amino acid and carboxylic acid extracts from the Murchison meteorite

Much effort has been directed to analyses of organic compounds in carbonaceous chondrites because of their implications for organic chemical evolution and the origin of life. We have determined the isotopic composition of hydrogen, nitrogen and carbon in amino acid and monocarboxylic acid extracts from the Murchison meteorite. The unusually high D/H and 15N/14N ratios in the amino acid fraction (delta D = 1,370% after correction for isotope exchange; delta 15N = 90) are uniquely characteristic of known interstellar organic materials. The delta D value of the monocarboxylic acid fraction is lower (377%), but still consistent with an interstellar origin. These results confirm the extraterrestrial origin of both classes of compound, and provide the first evidence suggesting a direct relationship between the massive organo-synthesis occurring in interstellar clouds and the presence of pre-biotic compounds in primitive planetary bodies. The isotope data also bear on the historical problem of distinguishing indigenous material from terrestrial contaminants.     

Predator diversity dampens trophic cascades

Food web complexity is thought to weaken the strength of terrestrial trophic cascades in which strong impacts of natural enemies on herbivores cascade to influence primary production indirectly. Predator diversity can enhance food web complexity because predators may feed on each other and on shared prey. In such cases, theory suggests that the impact of predation on herbivores relaxes and cascading effects on basal resources are dampened. Despite this view, no empirical studies have explicitly investigated the role of predator diversity in mediating primary productivity in a natural terrestrial system. Here we compare, in a coastal marsh community, impacts of arthropod predators on herbivores and plant productivity between a simple food web with a single predator species and a complex food web with a diverse predator assemblage. We show that enhancing predator diversity dampens enemy effects on herbivores and weakens trophic cascades. Consequently, changes in diversity at higher trophic levels can significantly alter ecosystem function in natural systems.     

缓释肥N/P比及加载量对5种珍贵树种1年生苗生长和养分库构建的影响

【目的】 揭示不同缓释肥N与P₂O₅质量比(N/P比)及加载量对浙江楠等5种珍贵树种1年生容器苗生长、N与P素吸收利用及养分库构建的影响,以期为精细化培育珍贵树种容器苗提供科学指导。【方法】 采用4×4两因素析因设计,研究N/P比和加载量对浙江楠等5种珍贵树种1年生容器苗生长发育及N、P库构建的影响。【结果】 缓释肥N/P比、加载量对5树种1年生容器苗生长和干物质积累均有显著或极显著影响。随着N/P比提高,各树种的反应却不一致;当缓释肥加载量为F3(3.5 kg/m³)时, 5树种生长指标和干物质积累均达到最大值。浙江楠、浙江樟和木荷的叶N含量与缓释肥N/P比密切相关,但南方红豆杉和赤皮青冈叶N含量在各N/P比间差异不显著。除浙江楠外,其他4树种的叶P含量在不同N/P比下差异显著,但各树种叶N和P累积量却对N/P比响应均不敏感。较之于N/P比,缓释肥加载量对5种珍贵树种1年生容器苗N、P库构建的影响更明显,叶N、P含量及累积量均在较高的缓释肥加载量F3下达到最高。N、P含量在各树种器官内的变化规律基本一致,说明N、P吸收同步,但不同树种间N、P素在各器官的分配却不同。【结论】 浙江楠容器苗生长及其养分库构建均需高N缓释肥,浙江樟、赤皮青冈和木荷则需要相对高P缓释肥,而南方红豆杉容器苗生长对N/P比要求不严格,但其养分库构建需高N缓释肥;在考虑N/P比的同时,适量(3.5 kg/m³)增施缓释肥,可提高珍贵树种的容器苗质量。     

遮阴条件下杉木幼苗生长和C、N、P化学计量特征的变化

【目的】比较不同强度遮阴条件下杉木(Cunninghamia lanceolata)幼苗生长、生物量积累与分配,以及不同器官碳(C)、氮(N)、磷(P)积累、分配及化学计量特征的差异,探讨杉木幼苗在不同遮阴条件下的C、N、P元素积累及分配的响应策略,揭示遮阴处理对杉木幼苗C、N、P元素变化规律的影响,为杉木苗木繁育、林分光照环境调控管理等提供参考。【方法】选取当年生杉木幼苗为研究对象,通过人工遮阴方式设置5个遮阴梯度,即0%(对照,不遮阴)、遮阴强度40%(透光率60%)、60%(透光率40%)、85%(透光率15%)和95%(透光率5%),持续观测1 a。试验结束后测定幼苗株高与地径增量、各器官生物量、根冠比、各器官C、N、P含量、积累量,并分析C、N、P化学计量特征(以C/N、C/P,N/P表示元素质量比)等指标。【结果】①随遮阴强度的增大,杉木幼苗株高增量总体呈现上升趋势,而地径增量则显著降低(P<0.05)。根、茎、叶及总生物量、根生物量占比和根冠比降低,茎、叶生物量比增大;②根、茎、叶中及总的C、N、P积累量随遮阴强度的增大而降低。随着遮阴强度的增大,杉木地上部分(茎和叶)C和N分配比例增加,而地下部分(根)C和N分配比例则降低。③杉木幼苗C/N和C/P变化趋势相同,随着遮阴强度的增大先增加后减少。杉木幼苗各器官N/P低于14,表明杉木幼苗在不同遮阴下的生长受到N限制。【结论】杉木幼苗生长和生理特性对不同遮阴强度响应有差异,主要表现在随着遮阴强度的增加,株高生长加快,地径粗生长减缓,生物量分配倾向于地上部分,幼苗由“矮粗”逐渐转变为“细高”。但是过度遮阴不利于杉木幼苗的生长,导致幼苗生物量积累减少,C、N、P积累量降低。     

Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2

Terrestrial ecosystems in the humid tropics play a potentially important but presently ambiguous role in the global carbon cycle. Whereas global estimates of atmospheric CO2 exchange indicate that the tropics are near equilibrium or are a source with respect to carbon, ground-based estimates indicate that the amount of carbon that is being absorbed by mature rainforests is similar to or greater than that being released by tropical deforestation (about 1.6 Gt C yr-1). Estimates of the magnitude of carbon sequestration are uncertain, however, depending on whether they are derived from measurements of gas fluxes above forests or of biomass accumulation in vegetation and soils. It is also possible that methodological errors may overestimate rates of carbon uptake or that other loss processes have yet to be identified. Here we demonstrate that outgassing (evasion) of CO2 from rivers and wetlands of the central Amazon basin constitutes an important carbon loss process, equal to 1.2 +/- 0.3 Mg C ha-1 yr-1. This carbon probably originates from organic matter transported from upland and flooded forests, which is then respired and outgassed downstream. Extrapolated across the entire basin, this flux-at 0.5 Gt C yr-1-is an order of magnitude greater than fluvial export of organic carbon to the ocean. From these findings, we suggest that the overall carbon budget of rainforests, summed across terrestrial and aquatic environments, appears closer to being in balance than would be inferred from studies of uplands alone.     

林火对森林生态系统碳氮磷生态化学计量特征影响研究进展

林火可以改变森林生态系统元素的生态化学计量特征,反映火后森林生态系统环境中生物地球化学循环变化模式,阐明林火干扰下森林生态系统碳(C)氮(N)磷(P)生态化学计量特征,对于理解森林生态系统对林火干扰的响应机理至关重要。笔者通过查阅大量相关文献,总结与分析了林火干扰对森林生态系统C-N-P生态化学计量特征影响模式,以及林火干扰对植物C-N-P生态化学计量特征、凋落物C-N-P生态化学计量特征、土壤C-N-P生态化学计量特征的影响,认为森林生态系统C-N-P生态化学计量特征主要受到火烧因子(火烧强度、火烧频率、火烧后恢复时间)、植被类型及土壤性质3个方面的影响,针对林火对森林生态系统生态化学计量学研究亟待解决的科学问题,从林火干扰对植物生态化学计量内稳性的影响机制、林火干扰下多重元素生态化学计量学研究、建立林火干扰下植物-凋落物-土壤复合系统生态化学计量学关系等3个方面进行了展望,以期深入了解林火干扰下植物调控策略,明确林火干扰后多重化学元素间相互耦合机制,完善以植物-凋落物-土壤为复合整体的地上地下养分输入输出的关系,对于深刻理解全球气候变化背景下森林生态系统养分循环和平衡,以及合理制定林火管理措施具有重要作用。     

不同林龄榧树根、枝、叶的C、N、P化学计量及内稳性特征

目的 了解不同林龄榧树根、枝、叶的生态化学计量特征和内稳性特征的变化情况,为榧树的科学管理和保护提供基础数据。 方法 以浙江省诸暨市香榧国家森林公园0~100、≥100~300、≥300~500和≥500 a共4个林龄段的实生榧树为研究对象,通过野外采集榧树植株样品(根、枝、叶)和0~20 cm层土壤样品,分析不同林龄榧树根、枝、叶的碳(C)、氮(N)、磷(P)含量及其化学计量特征变化和榧树内稳性特征。结果 不同林龄榧树C、N、P含量及化学计量特征均无显著差异,根、枝、叶的C、N、P含量均以≥300~500 a的榧树表现最高,枝和叶的C、N含量以≥500 a的榧树最低,而根P含量以≥100~300 a的最低;不同林龄榧树叶的N/P(N、P质量比)均小于N限制的阈值(14);榧树根、枝、叶的C、N、P含量存在一定的变化趋势,整体上表现为叶>枝>根,叶和枝的C、P含量显著高于根的,叶N含量显著高于根和枝的,各器官N和P含量均为正相关关系,且枝中N、P相关性达到极显著水平(P <0.01);榧树根、枝、叶的化学计量特征存在差异,根和枝的C/N(C、N质量比)显著高于叶的,根的C/P(C、P质量比)显著高于枝、叶的; 内稳性指数H_N/P(20.00)>H_P(11.76),即内稳性以N/P大于P。结论榧树C、N、P化学计量特征随林龄增长未表现出差异,而榧树根、枝、叶的C、N、P含量及化学计量特征存在差异,并且榧树整个生长过程中均受到N素的限制,需要合理施N肥来促进榧树的生长。     

Ⅲ-Ⅴ族半导体微重力生长研究进展

空间微重力环境为理解被地面重力场掩盖的晶体生长现象与规律、探索新的晶体制备工艺提供了独一无二的平台.我国学者在过去的30多年里进行了Ⅲ-Ⅴ族半导体晶体的空间生长研究,主要进展有:在微重力条件下得到了器件级的半绝缘GaAs,基于其制备的低噪声场效应晶体管和模拟开关集成电路性能明显超过地基器件;通过抑制熔体静压力的作用,实现了GaSb及InSb两种材料的非接触Bridgman生长,并大幅降低了材料的位错密度;深入研究了浮力对流、Marangoni对流及旋转磁场驱动的强制对流对组分微观偏析的影响规律;将垂直梯度凝固法应用于半导体合金生长,获得了组分均匀分布的GaInSb材料.本综述回顾了以上方面的研究进展,并对半导体空间材料科学的未来挑战进行了展望.     

北京及周边地区植物叶的碳氮磷元素计量特征

通过测量北京及周边地区358种植物的叶碳、氮和磷(C,N,P)含量, 系统分析了该区域不同生长型植物的叶C,N,P的计量规律。结果显示, 本区植物叶C,N,P的几何均值分别是45.1%,2.61% 和0.20%(干重), 且叶片中C,N,P 含量分别是叶柄中相应元素含量的1.1,2.4 和1.8 倍, 反映了与器官功能相适应的元素计量分配关系。草本相比于木本植物具有高叶N(P) 低C 的特点, 而针叶树的叶N(C) 显著低于(高于)阔叶树, 但二者P含量没有显著差异。叶的C,N,P彼此显著相关, 其中C 和N(或P)负相关,N 和P正相关; 叶C∶N, C∶P 和N∶P 的几何均值是17.3, 242 和13.9。     

新疆胜利和田探区南部下二叠统烃源岩的有机地化研究

以下二叠统克孜里奇曼组（P1k)海相碳酸盐岩为主要研究对象,对新疆胜利和田探区南部的石炭－二叠系海相烃源岩开展了系统研究。有机岩石学分析表明,该套烃源岩具有陆源和海相有机质双重输入的特点,有机质呈现偏腐殖的特征,干酪根以Ⅲ,Ⅱ型为主,与碳酸盐岩通常具有的较好有机质类型存在一定差别。有机地化分析也支持上述结论,并且指示出沉积环境并非严格的强还原环境。分析认为造成有机质类型较差的原因主要有3种,即陆源有机质输入、宏观藻类的贡献以及沉积环境充氧造成的有机质氧化。根据以上有机岩石学和有机地化分析的结果,结合碳酸盐岩孔隙度低,排烃较晚的特点,确定该套烃源岩以生成轻质烃类为主。塔西南地区广泛发育有石炭－二叠系海相碳酸盐岩沉积,该套气源岩对于区内天然气的勘探具有一定的石油地质意义。