Implications of the Precambrian Non-stromatolitic Carbonate Succession Making up the Third Member of Mesoproterozoic Gaoyuzhuang Formation in Yanshan Area of North China

A particular non-stromatolitic carbonate succession making up the third member of the Mesoproterozoic Gaoyuzhuang （高于庄） Formation might demonstrate that a stromatolite decline of the Mesoproterozoic occurring at ca. 1 450 Ma besides other three events of the Proterozoic, respectively, occurred at ca. 2 000 Ma, ca. 1 000 Ma, and ca. 675 Ma. The forming duration of this non-stromatolitic carbonate succession can be generally correlative to that of a similar depositional succession in North America, i.e. a non-stromatolitic carbonate succession made up by the Helena Formation of the Belt Supergroup, which suggests that the stromatolite decline occurring at ca. 1 450 Ma may be a global event. This information endows the non-stromatolitic carbonate succession making up the third member of the Gaoyuzhuang Formation in the Yanshan （燕山） area with important significance for the further understanding of Precambrian sedimentology. The Mesoproterozoic Gaoyuzhuang Formation in Yanshan area is a set of more than 1 000 m thick carbonate strata that can be divided into four members （or subformations）. The first member （or the Guandi （官地） subformation） is marked by a set of stromatolitic dolomites overlying a set of transgressive sandstones; the second member （or the Sangshu＇an （桑树鞍） subformation） is a set of manganese dolomites with a few stromatolites; the third member （or the Zhangjiayu （张家峪） subformation） is chiefly made up of leiolite and laminite limestones and is characterized by the development of molar-tooth structures in leiolite limestone; the fourth member （or the Huanxiusi （环秀寺） subformation） is composed of a set of dolomites of stromatolitic reefs or lithoherms. Sequence-stratigraphic divisions at two sections, i.e. the Jixian （蓟县） Section in Tianjin （天津） and the Qiangou （千沟） Section of Yanqing （延庆） County in Beijing （北京）, demonstrate that a particularly non-stromatolitic succession making up the third member of the Mesoproterozoic Gaoyuzhuang Formation is developed in the Yanshan area of North China, in which lots of grotesque matground structures （wrinkle structures and palimpsest ripples） are developed in beds of leiolite limestone at the Qiangou Section and lots,of molar-tooth structures are developed in beds of leiolite limestone at the Jixian Section. The time scale of the Gaoyuzhuang Formation is deduced as 200 Ma （from 1 600 Ma to 1 400 Ma）. The duration of an obvious hiatus between the Gaoyuzhuang Formation and the underlying Dahongyu （大红） Formation is deduced as 50 Ma to 100 Ma, thus the forming duration of the Gaoyuzhuang Formation is thought as 100 Ma （1 500 Ma to 1 400 Ma）. Furthermore, the age of the subface of the third member of the Gaoyuzhuang Formation that is just in the mid position of the Gaoyuzhuang Formation can be deduced as about 1 450 Ma, which is the basis to infer a stromatolite decline of the Mesoproterozoic occurring at ca. 1 450 Ma. Importantly, several features of both the molar-tooth structure and the stromatolite, such as the particular forming environment, the important facies-indicative meaning, and the episodic distribution in the earth history, might express the evolutionary periodicity of the surface environment of the earth and can provide meaningful clues for the understanding of the Precambrian world, although their origin and forming mechanism is highly contentious. Therefore, like other three stromatolitic declines, respectively, occurring at ca. 675 Ma, ca. 1 000 Ma, and ca. 2 000 Ma, the identification of the stromatolite decline occurring at ca. 1 450 Ma during the Golden Age of stromatolites （2 800 Ma to 1 000 Ma） has important meaning for the further understanding of the evolving carbonate world of the Precambrian.

Sedimentary Features and Implications for the Precambrian Non-stromatolitic Carbonate Succession:A Case Study of the Mesoproterozoic Gaoyuzhuang Formation at the Qiangou Section in Yanqing County of Beijing

In the long Precambrian period, stromatolitic carbonate successions were very common. However, the non-stromatolitic carbonate succession that is marked by subtidal deposits shows a sharp contrast to the stromatolitic carbonate succession. Both the non-stromatolitic and the stromatolitic carbonate successions are important clues for the further understanding of the evolving carbonate world of the Precambrian. The Mesoproterozoic Gaoyuzhuang Formation at the Qiangou section in northwestern suburb of Beijing is a set of more than 1000 m-thick carbonate strata that can be divided into four members （or subformations）, in which a non-stromatolitic carbonate succession marked by the scarcity of stromatolites makes up the third member of the formation. This non-stromatolitic carbonate succession can further be subdivided into three third-order sequences that are marked by the regular succession of sedimentary facies. In third-order sequences, a lot of subtidal carbonate meter-scale cycles made up of medium-bedded leiolite limestones and thin-bedded marls constitute their transgressive system tracts （TSTs） and the early high-stand system tracts （EHSTs）, a lot of meter- scale cycles made up by thin-bedded limestones and marls constitute their condensed sections （CSs）, and thick-bedded to massive dolomitic limestones or lime dolomites make up the late high-stand system tracts （LHSTs）. The particularly non-stromatolitic carbonate succession making up the third member of the Mesoproterozoic Gaoyuzhuang Formation at the Qiangou section might be the representative of the non-stromatolitic carbonate succession of the Precambrian because of its special lithological features and particular sedimentary structures, and its general sedimentary features are helpful and meaningful for the further understanding of the evolution rules of the sophisticate and evolving carbonate world of the Precambrian. The time scale of the Gaoyuzhuang Formation is deduced as that from 1600 Ma to 1400 Ma; thus, the non-stromatolitic sedimentary succession making up the third member of the Gaoyuzhuang Formation may demonstrate a stromatolite decline event occurring at ca. 1450 Ma of the Proterozoic besides other three events that occurred respectively at ca. 2000 Ma, ca. 1000 Ma and ca. 675 Ma. The forming duration of this non-stromatolitic sedimentary succession of the third member of the Gaoyuzhuang Formation can be generally correlated with a similar sedimentary succession in North America, i.e. a non-stromatolitic sedimentary succession of the Helena Formation of the Belt Supergroup, which suggests that the stromatolite decline occurring at ca. 1450 Ma might be a global event. Therefore, the non-stromatolitic sedimentary succession discussed in the paper provides an important example for further understanding of carbonate sedimentology in the Precambrian.

Free Radicals in Organic Matter for Thermal History Reconstruction of Carbonate Succession

Geothermometer is one of the most useful methods to reconstruct the thermal history of sedimentary basins. This paper introduces the application of free radicals concentration of organic matter as a thermal indicator in the thermal history reconstruction of carbonate succession, based on anhydrous thermal simulation results of type I and H1 kerogen. A series of free radicals data are obtained under thermal simulation of different heating temperatures and times, and quantitative modds between free radical concentration （Ng） of organic matter and time-temperature index （TTI） for types I and type H1 kerogen are also obtained. This Ng.TTI relation was used to model the Ordovician thermal gradients of Well TZ12 in the Tarim Basin. The modeling result is corresponding to the results obtained by apatite fission track data and published data. This new method of thermal history reconstruction will be benefit to the hydrocarbon generation and accumulation study and resource assessment of carbonate succession.

Effects of degradation succession of alpine wetland on soil organic carbon and total nitrogen in the Yellow River source zone,west China

Wetland is an important carbon pool,and the degradation of wetlands causes the loss of organic carbon and total nitrogen.This study aims to explore how wetland degradation succession affects soil organic carbon(SOC)and total nitrogen(TN)contents in alpine wetland.A field survey of 180 soilsampling profiles was conducted in an alpine wetland that has been classified into three degradation succession stages.The SOC and TN contents of soil layers from 0 to 200 cm depth were studied,including their distribution characteristics and the relationship between microtopography.The results showed that SOC and TN of different degradation succession gradients followed the ranked order of Non Degradation(ND)>Light Degradation(LD)>Heavy Degradation(HD).SWC was positively correlated with SOC and TN(p<0.05).As the degree of degradation succession worsened,SOC and TN became more sensitive to the SWC.Microtopography was closely related to the degree of wetland degradation succession,SWC,SOC and TN,especially in the topsoil(0-30 cm).This result showed that SWC was an important indicator of SOC/TN in alpine wetland.It is highly recommended to strengthen water injection into the wetland as a means of effective restoration to reverse alpine meadow back to marsh alpine wetland.

The carbon fluxes in different successional stages:modelling the dynamics of tropical montane forests in South Ecuador

Background： Tropical forests play an important role in the global carbon（C） cycle.However, tropical montane forests have been studied less than tropical lowland forests, and their role in carbon storage is not well understood.Montane forests are highly endangered due to logging, land-use and climate change.Our objective was to analyse how the carbon balance changes during forest succession.Methods： In this study, we used a method to estimate local carbon balances that combined forest inventory data with process-based forest models.We utilised such a forest model to study the carbon balance of a tropical montane forest in South Ecuador, comparing two topographical slope positions（ravines and lower slopes vs upper slopes and ridges）.Results： The simulation results showed that the forest acts as a carbon sink with a maximum net ecosystem exchange（NEE） of 9.3 Mg C？（ha？yr）-1during its early successional stage（0–100 years）.In the late successional stage, the simulated NEE fluctuated around zero and had a variation of 0.77 Mg C？（ha？yr）–1.The simulated variability of the NEE was within the range of the field data.We discovered several forest attributes（e.g., basal area or the relative amount of pioneer trees） that can serve as predictors for NEE for young forest stands（0–100 years） but not for those in the late successional stage（500–1,000 years）.In case of young forest stands these correlations are high, especially between stand basal area and NEE.Conclusion： In this study, we used an Ecuadorian study site as an example of how to successfully link a forest model with forest inventory data, for estimating stem-diameter distributions, biomass and aboveground net primary productivity.To conclude, this study shows that process-based forest models can be used to investigate the carbon balance of tropical montane forests.With this model it is possible to find hidden relationships between forest attributes and forest carbon fluxes.These relationships promote a better understanding of the role of tropical montane forests in the context of global carbon cycle, which in future will become more relevant to a society under global change.

Ethylene Carbonate Ionic Liquid Catalyst Successfully Developed by Liaoyang Petrochemical Company

The Liaoyang Petrochemical Company has successfullydeveloped a novel ionic liquid catalyst for carbonylationof ethylene oxide with carbon dioxide to form ethylenecarbonate （EC）. This catalyst can achieve an 100 % conversionand a 98% selectivity at low temperature andunder low pressure, featuring high catalytic activity, goodstability, good adaptability to feedstocks and low productioncost.

Responses of soil nitrogen, phosphorous and organic matter to vegetation succession on the Loess Plateau of China

Revegetation is a traditional practice widely used for soil protection. We evaluated the effect of natural revegetation succession on soil chemical properties and carbon fractions （particulate organic carbon （POC）, humus carbon （HS-C）, humic acid carbon （HA-C） and fulvic acid carbon （FA-C）） on the Loess Plateau of China. The vegetation types, in order from the shortest to the longest enclosure duration, were： （a） abandoned overgrazed grassland （AbG3; 3 years）; （b） Hierochloe odorata Beauv. （HiO7; 7 years）; （c） Thymus mongoficus Ronnm （ThM15; 15 years）; （d） Artemisia sacrorum Ledeb （AtS25; 25 years）; （e） Stipa bungeana Trin Ledeb （StB36; 36 years） and （f） Stipa grandis P. Smirn （StG56; 56 years）. The results showed that the concentrations of soil organic carbon, total nitrogen and available phosphorus increased with the increase of restoration time except for ThM15. The concen- tration of NH4-N increased in the medium stage （for ThM15 and AtS25） and decreased in the later stage （for StB36 and StG56） of vegetation restoration. However, NO3-N concentration significantly increased in the later stage （for StB36 and StG56）. Carbon fractions had a similar increasing trend during natural vegetation restoration. The con- centrations of POC, HS-C, FA-C and HA-C accounted for 24.5%-49.1%, 10.6%-15.2%, 5.8%-9.1% and 4.6%-6.1% of total carbon, respectively. For AbG3, the relative changes of POC, HS-C and FA-C were significantly higher than that of total carbon during the process of revegetation restoration. The higher relative increases in POC, HS-C and FA-C confirmed that soil carbon induced by vegetation restoration was sequestrated by higher physical and chemical protection. The increases of soil C fractions could also result in higher ecological function in semiarid grassland ecosystems.

Carbon Accumulation and Distribution in Ecosystems of Taiwania flousiana Plantation and Successive Rotation Plantation of Cunninghamia lanceolata

The 23-year-old T. flousiana plantation and successive rotation plantation of C. lanceolata at Shankou Forest Farm of Nandan County, Guangxi were tested by the method of plot investigation combining with biomass measurement. Carbon storage and spatial distribution of different components in the two forests were analyzed. The results indicated that carbon content in different organs of T. flousiana ranged from 426.0 to 503.9 g/kg, and the order was bark 〉stem 〉 root 〉 branch 〉 leaf. The carbon contents in shrub, herb and litter layers were452.9 , 408.0 and 428.9 g/kg, respectively. Carbon content in the soil （0 -80 cm）was 16.59 g/kg. The carbon content in different organs of C. lanceolata ranged from 464.5 to 508.9 g/kg, and the order was bark 〉 stem 〉 branch 〉 root 〉 leaf. The carbon contents in shrub, herb and litter layers were 456.2, 416.3 and 468.1 g/kg, respectively. Carbon content in the soil （0 -80 cm）was 15.77 g/kg. Total carbon storage amounts of T. flousiana plantation and successive rotation plantation of C. lanceolata were 245.83 and 213.52 t/hm^2, respectively. The carbon storage order of different structure layers from T. flousiana plantation and successive rotation plantation of C. lanceolata was soil layer （0 -8 0 cm） 〉 vegetation layer 〉 litter layer. Annual net productivity in the arbor layers of T. flousiana plantation and successive rotation plantation of C. lanceolata plantations was 10.75 and 17.13 t/（hm^2 · a） ; annual net carbon fixation amounts were estimated as 5.05 and 3.47 t /（hm^2 · a） ; annual net absorption C02 amounts were 18.53 and 12.73 t/（hm^2 · a） respectively.

人工修复边坡植被演替初期有机碳组分及土壤生态化学计量特征

[目的]研究人工修复边坡演替初期土壤有机碳组分、碳氮磷含量及其化学计量比,揭示气候因子对人工修复边坡演替初期土壤有机碳组分、碳氮磷含量及其化学计量比的影响,以期为后期人工修复边坡的养护提供指导和建议,确保人工修复边坡的正向演替。[方法]在湛江、梧州、宜昌、南阳、焦作、潍坊、加查采集了初期基材配制相同、植物配制相近,修复年限为2~4年的植被混凝土人工修复边坡土样,通过实验获得土样有机碳组分、碳、氮、磷的数据,采用冗余分析,开展气候因子对人工修复边坡演替初期土壤有机碳组分、碳氮磷含量及其化学计量比的影响研究。[结果]人工修复边坡演替初期F_(1)含量的变化范围为1.10~3.64 g/kg;F_(2)含量的变化范围为1.33~3.04 g/kg;F_(3)含量的变化范围为2.02~3.34 g/kg;F_(4)含量的变化范围为10.86~15.24 g/kg;TOC含量变化范围为15.52~24.71 g/kg;TN含量变化范围为0.61~0.93 g/kg;TP含量的变化范围为0.81~1.22 g/kg;C∶N变化范围为23.55~27.95;C∶P变化范围为17.26~23.09;N∶P的变化范围为0.72~0.98;C∶N∶P的变化范围为17.26∶0.75∶1~24.81∶0.95∶1。[结论]演替初期人工修复边坡碳磷表现为中等及以上,氮表现为缺乏;有机碳组分以惰性有机碳为主且有机碳稳定性较强。有机碳组分的主要影响因子为年平均温度、物种丰富度和年平均降水;土壤碳氮磷含量及其化学计量比主要影响因子为年平均温度、物种丰富度、pH和容重。

黄土高原次生林演替对团聚体有机碳含量及化学稳定性的影响

次生林演替过程中土壤团聚体有机碳的积累机制和化学稳定性研究较少。为探明次生林演替对土壤团聚体有机碳含量及其化学组成稳定性的影响,选取黄土高原次生白桦林(演替初期),山杨辽东栎混交林(演替中期)和辽东栎林(演替后期)为研究对象,分析演替过程中不同粒径土壤团聚体有机碳含量变化特征。采用傅里叶红外光谱技术(FTRI)测定活性(AC)和非活性(IC)有机碳化学组成,以(IC/AC)作为有机碳化学组成稳定性指标,并分析其影响因素。结果表明:次生林演替过程中土壤团聚体有机碳含量表现出逐渐增加的趋势且各群落间差异显著(P<0.05),以演替后期的中等粒径团聚体为最高(37.63 g/kg)。土壤团聚体AC中多糖体有机碳含量最高(55.87%),而IC中芳香族有机碳含量最高(94.45%),演替过程中IC与AC总体变化趋势均呈现先降后增。IC/AC随着演替的进行呈先降低后升高的趋势,其中演替后期微团聚体有机碳化学组成稳定性最强达到了3.95。微团聚体含量(WM)与土壤全氮、全磷、全钾一起,显著促进了团聚体有机碳化学组成稳定性(P<0.05)。综上,次生林演替有利于促进土壤团聚体有机碳的积累以及有机碳化学稳定,其中微团聚体起到了关键性作用。

考虑用能经济性与用户满意度灵活协同的综合能源系统双层优化

在含氢能区域综合能源系统参与碳交易的能量协同优化过程中,用户经济性和满意度目标一致性动态变化,给含多决策变量的区域综合能源系统能量协同优化带来了挑战。为此,该文构建了包含氢能梯级利用的冷热电联产系统模型,提出了基于预测平均投票数指标的用户综合需求响应策略,具体地,以上层综合能源运营商为领导者和下层用户聚合商为跟随者构建了主从双层博弈均衡模型,并采用基于成功历史的自适应差分进化算法嵌套CPLEX求解双方收益均衡化的交互策略。仿真结果表明该文所提策略提升了双方收益,且该文采用基于成功历史的自适应差分进化算法的求解时间分别比差分进化算法、遗传算法、自适应遗传算法减少了15.6%,8.6%,4.8%。

鄱阳湖洲滩湿地植物演替对土壤微生物量的影响

湿地植物演替对土壤微生物量具有显著影响,但不同土壤理化环境下的植物演替对湿地土壤微生物量影响的具体差异还不清楚。以鄱阳湖土壤理化性质不同的4个碟形子湖(包括相对肥沃的东湖和白沙湖以及相对贫瘠的蚌湖和大湖池)为研究对象,运用空间代替时间的方法,在泥滩带、湿生植被带(苔草)和挺水植被带(南荻或芦苇)采集0~10 cm表层土壤,分析不同土壤理化性质条件下植物群落演替对土壤微生物量的影响。采用土壤微生物量碳(MBC)和微生物熵(qMB)指示土壤微生物量。蚌湖、大湖池、东湖和白沙湖洲滩湿地表层土壤MBC的平均值分别为1077.27、888.29、942.45和1162.46 mg/kg,土壤qMB的平均值分别为6.07%、6.17%、3.60%和3.79%。在泥滩—苔草—南荻植物演替洲滩,土壤MBC先增加后减少;但是在泥滩—苔草—芦苇植物演替洲滩,土壤MBC持续增加。植物演替没有显著改变土壤qMB。尽管植物的生长会增加所有洲滩湿地的土壤MBC,但增加的幅度在相对贫瘠的蚌湖和大湖池明显强于相对肥沃的东湖和白沙湖。蚌湖和大湖池的土壤qMB也显著高于东湖和白沙湖。在植被演替梯度上,洲滩湿地土壤MBC和qMB普遍受到土壤碳、氮、磷含量和pH的影响,但是不同洲滩湿地影响微生物量的关键元素并不相同。这些结果证明植物演替对湿地土壤微生物量的影响不仅与植物物种有关,还受土壤理化环境的影响。本研究将为认识湿地土壤微生物量的变化机制和科学管理长江中下游湖泊湿地提供依据。

Prospects,Challenges,and Recommendations for New Energy Development

Since nearly 200 parties to the United Nations Framework Convention on Climate Change reached the Paris Agreement at the UN Climate Change Conference in Paris in 2015,the parties have successively established goals to achieve carbon neutrality by the middle of the 21st century.Therefore,transforming from high-carbon-emitting fossil fuels to low-carbon or even zero-carbon-emitting renewable energy sources has become a crucial pathway for reducing carbon emissions and achieving carbon peak and neutrality.

海洋暗光层颗粒附着微生物的群落演替和生态功能

暗光层是各类元素到达更深水域或海底的必经通道,是海洋对颗粒有机物(particulate organic matter,POM)进行显著降解和生物利用的水层.微生物参与了暗光层中有机物的迁移转化过程,但对其群落演替和代谢活性知之甚少.研究总结了暗光层的环境特征及相关微生物类群的结构和功能,并结合不同海域暗光层上下界面垂直水层中的颗粒附着微生物的群落演替、碳源利用及潜在的生态功能,来解析微生物在暗光层中的空间动态变化,并反映该生态位中微生物对碳源的选择偏好.在未来全球变暖与海洋生物泵作用相对增强的背景下.今后的研究更需聚焦暗光层中的微生物类群,并统一POM粒级划分标准,来阐明暗光层中微型碳泵和深海碳沉降的调控及贡献.

阔叶红松林不同演替系列土壤可溶性有机碳含量及影响因素

为准确预测全球变化背景下中国小兴安岭地区森林生态系统碳汇动态、合理制定森林经营措施,以小兴安岭阔叶红松林不同演替系列典型群落为研究对象,采用时空替代法,探讨3个演替系列6种典型群落土壤可溶性有机碳含量及影响因素。结果表明,中生演替系列和旱生演替系列演替进程中土壤可溶性有机碳呈波动式趋势,0~10 cm层最大,10~20 cm层出现下降趋势,20~40 cm层后开始逐渐升高的趋势。湿生演替系列表现随土层的增加而降低的趋势。中生演替系列土壤可溶性有机碳积累与土壤毛管孔隙度呈正相关,与凋落物量呈显著正相关(P<0.05),与土壤全氮、全磷、全钾含量呈显著负相关(P<0.05)。湿生演替系列土壤可溶性有机碳与土壤含水率呈正相关,与土壤毛管孔隙度和凋落物量呈显著正相关(P<0.05),与土壤全氮含量呈显著负相关(P<0.05);旱生演替系列土壤可溶性有机碳与土壤毛管孔隙度、砂粒比、凋落物量、土壤全氮含量呈极显著负相关(P<0.01),与土壤全磷含量和土壤全钾含量呈极显著正相关(P<0.01)。

湖滨绿洲土壤有机碳含量的支持向量机估算模型

【目的】利用高光谱数据快速估算土壤有机碳含量,为干旱区湖滨绿洲合理开发土地资源提供科学依据。【方法】以新疆博斯腾湖北岸湖滨绿洲为研究区,将实测的土壤有机碳含量数据与高光谱数据相结合,对原始光谱进行SG平滑(SavitzkyGolay smoothing,SG)、连续统去除(Continuum Removal,CR)、连续小波变换(Continuous Wavelet Transform,CWT)预处理,采用连续投影算法(Successive Projections Algorithm,SPA)筛选特征波段;应用支持向量机(Support Vector Machines,SVM)模型估算土壤有机碳含量。【结果】(1)研究区土壤有机碳含量为0.69~50.32 g/kg,平均值为14.15 g/kg,标准差为9.51 g/kg,呈中等变异性,变异系数为67.20%。(2)土壤原始光谱反射率在350~750 nm,光谱反射率呈上升趋势,在750~2150 nm,光谱反射率呈相对平稳趋势,在2150~2500 nm,光谱反射率逐渐下降;连续小波变换对土壤原始光谱预处理后随着分解尺度的增加,光谱局部特征明显,吸收峰和反射峰越来越平滑;采用连续投影算法筛选的光谱特征波段集中于350~952 nm、1007~1742 nm、2082~2381 nm,且特征波段仅占可见光-近红外光谱波段的0.30%。(3)连续小波变换结合连续投影算法构建的SVM模型,其训练集和验证集分别R^(2)=0.76,RMSE=4.78和R^(2)=0.94,RMSE=3.30,RPD=2.50。【结论】CWT-SPA-SVM可有效估算研究区土壤有机碳含量。

考虑碳排放的煤矿掘进系统仿真探析

利用Anylogic仿真软件,应用系统动力学模型方法(System Dynamics,SD)综合考量碳排放等因素,建立了掘进效率模型。以某煤矿为例,根据该矿实际情况,通过调整掘进各工序的人员数量与人均支出,进行掘进效率优化。仿真结果表明,支护效率与平均无故障时间比较低,是影响煤矿巷道掘进的最主要因素;对于提升支护工序效率,增加人员数量的效果比对员工进行激励效果更好;对于提升巷道掘进效率,单一地增加员工数量与进行激励均无法满足要求,需要两种手段相结合。

Spatial-Temporal Changes of Soil Organic Carbon During Vegetation Recovery at Ziwuling, China

To probe the processes and mechanisms of soil organic carbon (SOC) changes during forest recovery, a 150-yearchronosequence study on SOC was conducted for various vegetation succession stages at the Ziwuling area, in the centralpart of the Loess Plateau, China. Results showed that during the 150 years of local vegetation rehabilitation SOC increasedsignificantly (P < 0.05) over time in the initial period of 55-59 years, but slightly decreased afterwards. Average SOCdensities for the 0-100 cm layer of farmland, grassland, shrubland and forest were 4.46, 5.05, 9.95, and 7.49 kg C m-3,respectively. The decrease in SOC from 60 to 150 years of abandonment implied that the soil carbon pool was a sink forCO2 before the shrubland stage and became a source in the later period. This change resulted from the spatially variedcomposition and structure of the vegetation. Vegetation recovery had a maximum effect on the surface (0-20 cm) SOCpool. It. was concluded that vegetation recovery on the Loess Plateau could result in significantly increased sequestrationof atmospheric CO2 in soil and vegetation, which was ecologically important for mitigating the increase of atmosphericconcentration of CO2 and for ameliorating the local eco-environment.

Reduced turnover rate of topsoil organic carbon in old-growth forests:a case study in subtropical China

Background:Old-growth forests are irreplaceable with respect to climate change mitigation and have considerable carbon(C)sink potential in soils.However,the relationship between the soil organic carbon(SOC)turnover rate and forest development is poorly understood,which hinders our ability to assess the C sequestration capacity of soil in old-growth forests.Methods:In this study,we evaluated the SOC turnover rate by calculating the isotopic enrichment factor β(defined as the slope of the regression between ^(13)C natural abundance and log-transformed C concentrations)along 0-30 cm soil profiles in three successional forests in subtropical China.A lower β(steeper slope)is associated with a higher turnover rate.The three forests were a 60-year-old P.massoniana forest(PF),a 100-year-old coniferous and broadleaved mixed forest(MF),and a 400-year-old monsoon evergreen broadleaved forest(BF).We also analyzed the soil physicochemical properties in these forests to examine the dynamics of SOC turnover during forest succession and the main regulators.Results:The β value for the upper 30-cm soils in the BF was significantly(p<0.05)higher than that in the PF,in addition to the SOC stock,although there were nonsignificant differences between the BF and MF.The β value was significantly(p<0.05)positively correlated with the soil recalcitrance index,total nitrogen,and available nitrogen contents but was significantly(p<0.01)negatively correlated with soil pH.Conclusions:Our results demonstrate that SOC has lower turnover rates in old-growth forests,accompanied by higher soil chemical recalcitrance,nitrogen status,and lower soil pH.This finding helps to elucidate the mechanism underlying C sequestration in old-growth forest soils,and emphasizes the important value of old-growth forests among global C sinks.

Effects of soil nitrate:ammonium ratio on plant carbon:nitrogen ratio and growth rate of Artemisia sphaerocephala seedlings

Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.