Tillage, <i>Desmodium intortum</i>, Fertilizer Rates for Carbon Stock, Soil Quality and Grain Yield in Northern Guinea Savanna of Nigeria

Northern Guinea Savanna of Nigeria soils are continuously and intensively cultivated, resulting in soil quality degradation, carbon stock depletion, accelerated soil erosion and soil nutrient depletion. Effects of land use change on soil carbon stocks (SOC) are of concern regarding greenhouse gas emissions mitigation and sustainable crop production, because there is a need for food sufficiency while conserving the environment. Also, managing soils under intensive use and restoring degraded soils are top priorities for a sustained agronomic production while conserving soil and water resources. Hence, this study;“Tillage, Desmodium intortum, fertilizer rates for carbon stock, soil quality and grain yield in Northern Guinea Savanna” is aimed at devising possible mitigating measures for soil quality degradation, carbon stock depletion and impoverished crop yields using Zea mays as test crop. The study was a Randomized Complete Block Design (RCBD) in split-split plot arrangement with four replicates. The four main tillage and Desmodium intortum combination treatments were: 1) Maize &#8722;without Desmodium + Conventional tillage (MC), 2) Maize + Desmodium live-mulch incorporated and relayed + Conservation tillage (MDIC), 3) Maize + Desmodium in no-tillage system (MDNT), 4) Maize + Desmodium in strip tillage (MDST). The main treatment plots were each divided to accommodate four (4) rates of N (60, 80, 100 and 120 kg·ha&#8722;1) as sub plots, while the N rate plots were further divided to accommodate three (3) rates of P (6.6, 13.2, and 26.4 kg·ha&#8722;1) as sub-subplots. Findings support that Desmodium intercrops with Maize treatments (MDIC, MDNT, and MDST) resulted in increased organic carbon contents in 2013, with MDNT resulting in significantly higher organic carbon content (7.37 g·kg&#8722;1 in 2012 and 8.37 g·kg&#8722;1 in 2013) than the other treatments. Also, zero tillage practice (MDNT) sequestered significantly higher carbon stock (18.06 t C ha&#8722;1), followed by minimum tillage (MDIC) that sequestered 15.99 t C ha&#8722;1 than the other treatments. Highest grain yield of 2.61 tha&#8722;1 under MDIC and MDNT was followed by MDST and least under MC. Total score of soil quality assessment gave least score values of 13 under MDIC and MDNT;thus best soil quality (SQ1) was ascribed to the minimum tillage with D. intortum intercrop and relayed (MDIC) and Zero tillage with D. intortum (MDNT) treatments. Maize Strip cropped with D. intortum treatment (MDST) was ranked SQ2.

Impacts of Land Cover Changes on Ecosystem Carbon Stocks Over the Transboundary Tumen River Basin in Northeast Asia

Understanding the effects of land cover changes on ecosystem carbon stocks is essential for ecosystem management and environmental protection, particularly in the transboundary region that has undergone marked changes. This study aimed to examine the impacts of land cover changes on ecosystem carbon stocks in the transboundary Tumen River Basin(TTRB). We extracted the spatial information from Landsat Thematic Imager(TM) and Operational Land Imager(OLI) images for the years 1990 and 2015 and obtained convincing estimates of terrestrial biomass and soil carbon stocks with the InVEST model. The results showed that forestland, cropland and built-up land increased by 57.5, 429.7 and 128.9 km2, respectively, while grassland, wetland and barren land declined by 24.9, 548.0 and 43.0 km2, respectively in the TTRB from 1990 to 2015. The total carbon stocks encompassing aboveground, belowground, soil and litter layer carbon storage pools have declined from 831.48 Tg C in 1990 to 831.42 Tg C in 2015 due to land cover changes. In detail, the carbon stocks decreased by 3.13 Tg C and 0.44 Tg C in Democratic People's Republic of Korea(North Korea) and Russia, respectively, while increased by 3.51 Tg C in China. Furthermore, economic development, and national policy accounted for most land cover changes in the TTRB. Our results imply that effective wetland and forestland protection policies among China, North Korea, and Russia are much needed for protecting the natural resources, promoting local ecosystem services and regional sustainable development in the transnational area.

Effect of Land Use Changes on Carbon Stock Dynamics in Major Land Use Sectors of Mizoram, Northeast India

Land use change activities have greatly affected the total ecosystem carbon stock (TECS) and also contribute to global change through emission of greenhouse gases. The present study assessed the change in vegetation biomass carbon stock (VBCS) and soil organic carbon stock (SOCS) following conversion in major land use sectors (agriculture, agroforestry, forest and plantation) in Mizoram, Northeast India. SOCS was the highest in agroforestry (50.85 Mg C ha-1) and the lowest in agriculture (33.99 Mg C ha-1). VBCS was the highest in plantation (131.66 Mg C ha-1) and the lowest in agriculture (7.44 Mg C ha-1). The highest positive TECS change rate was observed when agriculture was converted to plantation (6.61 Mg C ha-1·yr-1), while negative rate of change in carbon stock was observed following the establishment of agriculture from other land use. A positive rate of change was observed in both VBCS and SOCS with TECS rate of 3.58 Mg C ha-1·yr-1 when agriculture got converted to agroforestry. The absolute carbon stock change rates were higher in VBCS than SOCS signifying the importance to maintain tree based vegetation cover.

The M2 Money Supply, the Economy, and the National Debt: A Mathematical Approach

The United States dollar was tied to a finite standard dating back to 1792. The dollar has survived multiple wars, armed conflicts short of war, economic recessions, and the Great Depression. At the end of World War II, the dollar, by international agreement, effectively became the world’s reserve currency. Other currencies were fixed to the dollar and the dollar was in turn fixed to the gold standard, that is, the value of a dollar was fixed at thirty-five dollars per ounce of gold. In 1971, the United States government severed the dollar from the gold standard leaving the size of the money supply free of any finite limit. Since that time, the United States money supply, national debt, and stock market indices have experienced exponential growth. The purpose of this paper is to investigate mathematically and model the relationship among these key economic indicators. Our work in this paper allows us to gain some insight into how each of these economic indicators can influence one another while giving us a better idea of how the economy functions. We were allowed to collect data for each of the indicators over a certain period which allowed us to demonstrate that a strong correlation exists among these three indicators. After collecting our data and making some logical assumptions, we modeled the money supply as a function of time. In turn, we modeled the Dow Jones stock market index as a function of the money supply. Finally, we produced a model of the National Debt as a function of the Dow Jones stock market index. From the data, we collected and our economic indicator models, we derived a series of differential equations that would help us observe the exponential growth trend of each graphically. By showing a comparison from our collection of raw data versus our results from our model, we conclude that, under prevailing circumstances, it is reasonable to expect growth in all three indicators and increasing market volatility for some time to come. We have answered the question of whether the monetary and fiscal policies of the past half-century have been of some benefit. However, we question whether this trend is good for all Americans and whether it is sustainable in perpetuity. This paper concludes with possible areas of interest warranting additional investigation to enable us to better understand the economy and develop effective financial strategies.

The Importance of Involving Stakeholders and Scientists in the Management of Marine Fisheries

In recent years there has been increasing concern over the state of fish stocks,especially those that support key fisheries and supply food to many consumers.There is also concern over the state of aquatic environments,and the effects of climate change.Fisheries management is controlled by government agencies,often cooperating with similar agencies from other nations.This paper deals with the need for expert advice on fisheries,involving fishers as well as scientists.Mention is made of a Fisheries Partnership set up in Europe,bringing fishers and scientists together with other stakeholders to discuss the problems of managing fish stocks.The partnership was especially successful in improving relationships between fishers and scientists,and made significant improvements to some fish stock assessments.European Regional Advisory Councils were later established to play a similar role.They are providing significant advice on fisheries,but they do not yet play a key role in actual management.It is important to consider how stakeholders and scientists can become more actively involved in fisheries management.There is a crucial need to develop new,more participatory ways of managing fisheries.

Determining structural variation in a managed mixed stand in an old-growth forest, northern Iran

Numerous approaches have been developed to quantify forest structure modules.A variety has measured each as part of stand attributes.This study was carried out in managed mixed stands in northern Iran.The objective was to quantify stand structure and its variation before and after tree marking through the Gini index and structural triangle method.A full sampling inventory was taken in 2004 and 2014 at the beginning and end of a period,before and after tree marking operations in five stands.The results indicate that the Gini index was 39.5,62.2,43.0,82.0 and 74.0%forⅠ,Ⅱ,Ⅲ,ⅣandⅤstands respectively.Furthermore,approximate structural diameters were determined as a large category forⅠ,Ⅱ,ⅢandⅤstands while standⅡhad an intermediate-large class pre-tree marking to an intermediate-small class post-tree marking.The paired t-test results were not significant for tree numbers and growing stock changes for all species,and for beech,hornbeam,and velvet maple before and after tree harvesting in the whole stand.Therefore,the Gini index and the structural triangle method can be used for natural stand modeling,structural diversity designation,and for management practices in nature-oriented forestry strategies.

Estimation of Carbon Sequestration;Using Allometric Equations;in Azrou Cedar Forests (Cedrus atlantica Manetti) in the Central Middle Atlas of Morocco under Climate Change

The topic of carbon sequestration in forest ecosystems has recently taken a lot of attention due to concerns about global climate change. As a spontaneous species of the Central Middle Atlas, the Atlas Cedar was the subject of our study. Thus, a total of 30 sample trees were subjected to the weight measurements for the estimation of biomass and organic carbon stock in a logging lot in the Azrou forest. The amount of sequestered carbon was then extrapolated in all stand forests studied from the developed carbomass models. The results obtained show that the largest allocation of carbon stock (93%) is in the stem, followed by branches (5%) and foliage (2%). The average carbon storage in this cedar forest is 99.42 tC/ha (aboveground and belowground), or 364.58 t/ha of CO2, a value significantly higher than that found in other Moroccan forest ecosystems.

基于SDG15.3.1的土地利用变化对生态系统服务价值的影响

[目的]可持续发展目标15.3.1是表征土地退化的重要指标之一,探析土地利用变化和生态系统服务价值(ESV)对可持续发展目标15.3.1的影响是改进土地退化的关键因素。基于土地利用及碳储量变化对SDG15.3.1指标制定新的评价规则,并对SDG15.3.1完成情况进行评估。[方法]采用等效因子法计算生态系统服务价值,以定量分析土地利用变化对ESV的影响。[结果](1)研究区土地利用类型转换频繁,主要表现为高林地、水体和建设用地增加,耕地、草地和灌木林减少,未利用地基本保持不变。(2)ESV在空间上呈中间高、四周低,西部高、东部低的分布格局;2000-2020年总ESV损失7.32×10^(8)元。其中,2000-2010年,土地退化区域的ESV损失3.03×10^(9)元;2010-2020年,土地退化区域的ESV损失2.28×10^(9)元。(3)根据SDG15.3.1评估结果显示,2000-2010年和2010-2020年SDG15.3.1指标分别为5.22%和4.77%,而土地净恢复面积分别为-1.62×10^(5) hm 2和-2.4×10^(5) hm 2。SDG15.3.1指标的完成情况有所提高,但仍未实现土地退化零增长目标。[结论]研究结果为高原城市群在实现可持续发展目标15.3.1过程中土地利用变化对生态系统服务价值的影响提供参考。

高管变更对国有企业负债水平的影响研究

国有企业负债水平较高受到了较多的关注,研究国有企业高负债现象的成因和治理,对降低国有企业负债水平、保障经济平稳运行具有重要意义。以2013—2020年我国A股上市国有企业为研究样本,实证检验了地方政府领导干部更替、国有企业高管变更以及地方国有企业负债水平三者之间的关系。研究结果表明:在晋升压力的作用下,地方政府领导干部更替提高了国有企业的负债水平,其中国有企业高管变更发挥了中介传导作用。地方政府领导干部任期小于三年会给国有企业带来较大的不确定性,领导干部临近退休时对国有企业的干预意愿会降低。地方政府领导干部主要是通过增大短期负债的比重来提高国有企业的负债规模。国有企业的混合所有制程度越高,地方政府领导干部更替对国有企业负债水平的消极影响就越低。研究结论从微观政企关系角度完善了国有企业高负债的理论和动因基础,为国有企业的长期稳定发展提供了借鉴和参考。

基于PLUS和InVEST模型的乌鲁木齐市碳储量时空演变与预测

土地利用变化对陆地生态系统的碳储量变化有着重要影响,研究不同发展情景下陆地生态系用碳储量变化情况,有利于优化空间布局,协调土地利用与生态环境保护的关系。本研究结合PLUS和InVEST模型,通过多种驱动因素数据分析了2000—2020年乌鲁木齐市土地利用的变化特征,以此预测模拟2030年自然发展情景、生态保护优先情景和耕地保护优先情景下土地碳储量。结果表明:(1)2000—2020年乌鲁木齐市林地、水域、建设面积、未利用地数量增加,耕地、草地面积减少。(2)2030年,自然发展情景延续了以往发展模式,建设用地面积增幅为18.29%。生态保护优先情景下,建设用地的扩张速度得到有效控制,增幅已经减缓,为4.73%。耕地保护优先情景下耕地面积比自然发展情景下多了171 km^(2),耕地保护效果显著。(3)2000—2020年,碳储量呈下降趋势,共计减少8.5×10^(6)t。2030年自然发展情景下碳储量总量相较于2020年减少了4.065×10^(6)t,生态保护优先情景下比自然增长情景高7.519×10^(5)t,耕地保护优先情景比自然增长情景低1.979×10^(6)t。因此,在未来乌鲁木齐市发展规划中,应当落实耕地保护责任,控制建设用地向林地、草地等高碳密度用地的扩张,优化用地布局,提高区域碳储量水平。

中国科创板股票价格变动预测模型研究

为更好地预测中国科创板股票价格变动走势,使用随机森林和支持向量机两种机器学习算法对中国股票市场的历史数据进行分析,选择318支科创板股票作为样本数据集,并以华兴源创(688001.SH)为例,采用支持向量机和随机森林的原理和算法流程构建数据样本,比较基于昨日收盘价和基于前几日收盘价两种思路的预测效果。结果表明:当基于思路1预测时,随机森林模型的正确率为65.55%,支持向量机模型的正确率为70.59%;当基于思路2预测时,随机森林模型的正确率为43.70%,支持向量机模型的正确率为62.18%。在模型选择上,支持向量机对于股市预测水平更加切合,应更多地采用向量机模型实现对中国科创板股票的预测。在指标选取上,当日各项指标要比历史收盘价数据更加具有参考性,且未来结果不仅受到历史趋势的影响,还可能受到当日的各项指标影响。

关中平原城市群土地利用变化对碳储量时空格局的影响

生态系统碳储量的变化与土地利用的格局关系紧密,研究碳储量的变化对实现“双碳”目标具有重要意义。关中平原城市群是西部地区第二大城市群,国家战略的实施影响着土地利用类型,进而影响碳储量的时空分布。本文通过集成InVEST模型与PLUS模型,解析2000—2020年关中平原城市群土地利用类型和碳储量的时空演化特征,预测在自然增长、生态保护和经济发展3种情景下,2030年关中平原城市群土地利用和碳储量的变化。结果表明:1)2000—2020年关中平原城市群主要土地利用类型为耕地和林地,草地向耕地和林地转换以及耕地向建设用地转换是研究区土地利用类型转换的主要方式。2)2030年关中平原城市群在3种情景下,耕地面积均呈减少趋势。在自然增长、经济发展情景下,林地和草地面积呈减少趋势,建设用地存在显著式外延扩张;在生态保护情景下,林地和草地面积呈上升趋势,建设用地面积略有下降。3)2000—2020年,导致碳储量降低的主要原因是林地和草地面积的萎缩,碳储量累计减少7.02×10^(6)t。4)2030年在自然增长和经济发展情景下,关中平原地区建设用地和耕地扩张明显,碳储量明显降低;生态保护情景下建设用地扩张面积相对较小,在中部和东北部地区碳储量并无明显减小现象,总体碳储量呈散落增加。研究结果可为关中平原城市群未来的城市规划、国土空间管理提供科学依据。未来关中平原城市群可在生态保护情景的基础上进一步发展,在保护生态的同时限制建设用地的扩张。

放养密度对日本鳗鲡夏秋两季养殖水质及营养品质的影响

研究以日本鳗鲡(Anguilla japonica)为研究对象,分夏秋两季,调查并讨论了放养密度对养殖鱼水质和营养品质变化的影响。夏季低密度组放养密度分别为1.51(1号塘)、1.50(2号塘)和1.49 kg/m^(2)(3号塘),高密度组分别为2.17(4号塘)、2.14(5号塘)和2.13 kg/m^(2)(6号塘)。秋季低密度组放养密度分别为1.74(Ⅰ号塘)、1.72(Ⅱ号塘)和1.75 kg/m^(2)(Ⅲ号塘),高密度组分别为2.36(Ⅳ号塘)、2.34(Ⅴ号塘)和2.36 kg/m^(2)(Ⅵ号塘)。两次分别从每个养殖塘采集5份水样,每个密度组养殖塘随机采集4尾日本鳗鲡。结果显示:两季高密度塘水体透明度和溶氧显著低于低密度塘(P<0.05),总氮、总磷、氨氮、亚硝酸盐、COD、叶绿素a指标显著高于低密度塘(P<0.05),硅藻门、绿藻门、蓝藻门密度均大于低密度塘一个数量级,且经统计分析,夏季高密度组的蓝藻门密度显著高于低密度组(P<0.05)。此外,高密度塘水体菌群Shannon指数显著低于低密度塘,Simpson指数则相反(P<0.05)。在门水平上,经统计分析,夏秋两季高密度组放线菌门均显著低于低密度组(P<0.05);而夏季高密度组变形菌门极显著高于低密度组(P<0.01);秋季拟杆菌门显著高于低密度组(P<0.05)。在营养品质方面,日本鳗鲡肌肉的硬度、剪切力、咀嚼性、回复性参数及粗脂肪和粗蛋白含量均显著小于低密度塘(P<0.05);水分含量显著高于低密度塘(P<0.05)。综上,高密度与低密度塘相比,水质指标、藻类组成、菌群多样性及鱼体质构、营养成分等指标中大部分参数呈现一致性负面影响,共同构成日本鳗鲡品质与养殖环境的敏感参数。此外,夏季日本鳗鲡放养密度为2.13—2.17 kg/m^(2)水质呈现富营养化及轻度污染状态。

基于InVEST和PLUS模型的江西省土地利用碳储量时空变化与预测

土地利用变化是驱动碳储量变化的主要因素,评估土地利用变化对碳储量的影响对于碳平衡具有重要意义。以江西省为例,基于InVEST-PLUS模型,探究1990—2020年江西省土地利用变化和碳储量时空演变,测算2030年多情景碳储量。(1)江西省1990年、2000年、2010年和2020年的碳储量分别为12.7594、12.7600、12.6912、12.5800亿吨,总体呈现减少态势。林地的减少是造成碳储量损失的主要因素。地上生物量碳库和土壤碳库碳储量最多,占总碳储量的88.82%。(2)至2030年,较2020年,在自然发展与城镇发展情景下,碳储量分别减少380、1330万吨,在生态保护情景下则增加125万吨,表明采取生态保护措施,优化土地利用结构,能有效控制碳储量的减少。(3)碳储量明显较高的地区位于生态用地连片的赣南山区,而碳储量明显较低的地区位于碳密度值较低以及建设用地呈斑块状分布的赣北区域。研究结果将为江西省生态文明建设作出合理生态决策、实现高质量发展提供科学依据。

房价变动对家庭消费的影响研究——基于适度负债的调节效应

利用中国家庭金融调查(CHFS)2011年、2013年、2015年和2017年的数据,基于适度负债视角,构建非平衡面板模型,实证研究了房价变动对家庭消费的影响。研究发现:房价对家庭消费存在显著影响,且二者间的关系呈倒U型。随着房价升高,其对家庭消费的财富效应逐渐转变为挤出效应。而适度负债在房价变动与家庭消费的传导间起调节作用,当家庭利用适度债务杠杆时,房价变动对家庭消费的倒U型曲线拐点处于家庭消费的更高位置,这有利于净资产较高的家庭通过适度负债提高其边际消费倾向。基于此,政府应调控房价回归合理区间,充分发挥财富效应,对住房调控“因城施策”,以遏制房地产市场过度投机,鼓励居民合理利用适度负债,倡导“量入为出”。

债务违约风险的影响因素分析

选取2019—2020年沪深A股上市公司为研究样本,并根据以往文献选取可能影响债务违约风险的变量进行研究。主要的研究结果表明基本财务指标、股权结构、产品市场竞争、股价同步性均对债务违约风险有显著的影响。研究发现在非国有企业样本中,股权质押、第一大股东持股比例和利息保障倍数对债务违约风险的影响更为显著。进一步运用主成分分析将因子重新归为4类,并基于行业对影响因素进行K-均值聚类。所用的分析方法包括描述性检验、独立样本均值t检验、线性回归分析、因子分析、K-均值聚类分析。

Integrated Assessment of Forest Cover Change and Above-Ground Carbon Stock in Pugu and Kazimzumbwi Forest Reserves, Tanzania

A study was conducted to estimate the forest cover change, quantify and map tree above-ground carbon stock using Remote sensing and GIS techniques together with forest inventory. Landsat images of 1980, 1995 and 2010 acquired during dry season were used in the estimation of cover changes. Supervised image classification using Maximum Likeli-hood Classifier was performed in ERDAS Imagine software to analyze the images and further analysis was performed in Arc GIS 9.3 software. Stratified sampling procedure was used to select concentric inventory plots in Pugu Forest Reserve (PFR) and Kazimzumbwi Forest Reserve (KFR). Plots were laid according to NAFORMA, and the tree parameters in each sampling plot were collected. A Microsoft Excel spreadsheet was used to compute the above-ground bio- mass for each plot using an empirical equation relating wood basic density and tree height. The above-ground carbon was calculated using a conversion factor of 0.49. Geostatistical method in ArcGIS was used to analyze and map carbon. Results revealed that for the periods 1980-1995 and 1995-2010, Closed Forest in PFR decreased by 4.5% and 25.3% respectively, while for KFR, Closed Forest decreased by 11.9% and 31.3% respectively. The mean carbon density for PFR and KFR were respectively 5.72 tC/ha and 0.98 tC/ha while carbon stocks were 14 730.41 tC and 7 206.46 tC re- spectively. The revealed low carbon densities were attributable to decline in area under Closed Forest in the two Forest Reserves. The study recommends concerted efforts to enhance proper management of the forests so that the two forest reserves may contribute to REDD initiatives.

Temporal Variations in Carbon Stock of Pinus roxburghii Sargent Forests of Himachal Pradesh,India

The present study was conducted in Solan Forest Division of Himachal Pradesh covering an area of about 57,158 ha. The aim was to estimate and assess the temporal change in carbon stock of the Chil Working Circle, in two forest ranges of the Division, Solan and Dharampur, over the period of 1956-2011. The inventory data of the working plans of Solan Forest Division from 1956-1957, 1984-1985 and 2002-2003 were used in the present study while field data for biomass estimation was collected for the year 2011.The results showed a declining trend in carbon stock over 1956-1984 period, however, an increasing trend over 1984-2002 was observed, which showed a further increase for the period 2002-2011. These fluctuating trends in the forest carbon stock can be related to increasing anthropogenic pressure on forests and the subsequent introduction of a ban on green felling envisaging efficient forest management, both of which affect the forest carbon pool significantly.

Markov-Switching Time-Varying Copula Modeling of Dependence Structure between Oil and GCC Stock Markets

This paper proposes a Markov-switching copula model to examine the presence of regime change in the time-varying dependence structure between oil price changes and stock market returns in six GCC countries. The marginal distributions are assumed to follow a long-memory model while the copula parameters are supposed to evolve according to the Markov-switching process. Furthermore, we estimate the Value-at-Risk (VaR) based on the proposed approach. The empirical results provide evidence of three regime changes, representing precrisis, financial crisis and post-crisis, in the dependence structure between energy and GCC stock markets. In particular, in the pre- and post-crisis regimes, there is no dependence, while in the crisis regime, there is significant tail dependence. For OPEC countries, we find lower tail dependence whereas in non-OPEC countries, we see upper tail dependence. VaR experiments show that the Markov-switching time- varying copula model performs better than the time-varying copula model.